MB225-SP

NF30-SP MITSUBISHI | Alldatasheet

Document overview

• Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
• PDF pages: 105

Technical content

ADVANCED AND EVER ADVANCING MOULDED CASE CIRCUIT BREAKERS TECHNICAL NOTES A

1. CHARACTERISTICS AND

4.4 DC Tripping Characteristics of AC-Rated

6.5 I 2t Let-Through Characteristics and Current

6.7 Protective Coordination with

6.8 Coordination with Devices on the

1. SHORT-CIRCUIT CURRENT

9.3 Impedances and Equivalent Circuits of

CONTENTS

We have the pleasure of providing all our customers with the technical information for Mitsubishi moulded case circuit breakers. This indicates the fundamental data of our circuit breakers regarding the applicable standards, constructional principles, and operational performances. Please refer to the catalogue of our circuit breakers for details of specifications. Also please stand in need of the handling and maintenance manual for maintaning the circuit breakers in service continuously. We do hope they are available for all our customers to built more efficient systems.

1. INTRODUCTION Mitsubishi Advancing Technology Mitsubishi, the leading manufacturer of circuit break- ers, has been providing customers with a wide range of highly reliable and safe moulded case circuit break- ers (MCCB) and earth-leakage circuit breakers (ELCB), corresponding to the needs of the age. Since production began in 1933 many millions of Mitsubishi ACBs, MCCBs and MCBs have been sold throughout many countries. In 1985 a new design concept for controlling arc en- ergies within MCCBs – vapour jet control (VJC) – was introduced and significantly improved performance. It is provided the technological advance for a new ‘su- per series’ range of MCCBs and is used in all present ratings from 3 to 1600 amps. In 1995 Mitsubishi offers the new PSS (Progressive Super Series) breakers having ratings from 3 to 250 amps that concentrate the most advanced technolo- gies into a compact body. Their four major features are:

• New circuit-breaking technology ISTAC for a higher current-limiting performance, upgrading the circuit- breaking capability.
• Electronic circuit breakers with the Digital ETR pro- tecting the circuit accurately.
• One-frame, one-size design allowing efficient panel design.
• Cassette-type internal accessories that allow instal- lation by the user. Progressive Super Series, an integration of technol- ogy and know-how from this comprehensive electronic product manufacturer, will create its own fields of ap- plication with its excellent performance. A Brief Chronology

1933 Moulded case circuit breaker production

begins.

1952 Miniature circuit breaker production be-

gins.

1968 Manufacture commences of short-time-

delayed breakers.

1969 Production and sale of first residual cur-

rent circuit breakers. 1970 170kA breaking level ‘permanent power fuse’ integrated MCCBs is introduced.

1973 Introduction of first short-time delay and

current-limiting selectable breakers go on sale.

1974 First MELNIC solid-state electronic trip

unit MCCBs are introduced.

1975 ELCBs with solid-state integrated circuit

sensing devices are introduced. 1977-1979 Four new ranges of MCCBs are intro- duced – economy, standard, current lim- iting, ultra current limiting and motor rated designs – a comprehensive coverage of most application requirements.

1982 Compact ACBs with solid-state trip de-

vices and internally mounted accessories introduced. 1985-1989 Super series MCCBs with VJC and ETR are developed and launched – awarded the prestigious Japanese MInister of Con- struction Prize.

1990 New 200kA level U-series MCCBs super

current limiting breakers are introduced.

1991 Super-NV ELCBs and Super-AE ACBs

are introduced.

1995 Progressive Super Series 30~250 amps

are introduced.

1997 Progressive Super Series 400~800 amps

are introduced.

1. FEATURES – Advanced MCCB Design Technol- ogy & Performance

2.1 Arc-Extinguishing Device – ISTAC

Mitsubishi has developed an epoch-making ISTAC technology to realize an improved current-limiting and breaking performance within a smaller breaking space. Introduction of ISTAC technology upgrades the cur- rent-limiting, selective-breaking, and cascade-break- ing performance. The maximum peak let-through cur- rent Ip decreases to about 80% (compared with Mitsubishi’s 100AF). The passing energy I2t de- creases to about 65% (compared with MItsubishi’s 100AF). The smaller breaking space has led to an improved function, a smaller size, and a standardiza- tion of the breakers. Triple forces accelerating The triple forces generated by a newly designed cur- rent pass and theVapor Jet Control (VJC) insulat- ing materials which makes up a slot-type breaking construction accelerate the movable conductor, and separate the contacts faster than ever before in short- breaking. Electromagnetic attractive force which works between a current of the movable conductor and a current of the fixed upper conductor. Electromagnetic repulsive force which works between a current of the movable conductor and a current of the fixed lower conductor. Pressure which works on the movable conductor by gas generated in the slot. Lower, fixed-contact conductor Repulsive force Movable contact Attractive force Current A Current Current B Current C Upper, fixed-contact conductor Arc control by slot-breaking The VJC of the fixed contact incorporates newly de- veloped insulation made of ceramic fiber and metal hydroxide. The substantially improves the VJC effect. The arc-extinguishing gas energies to improve the capability of extinguishing the arc. The VJC suppresses the emergence of carbide prod- ucts in breaking a current and contribute to the recov- ery of insulation immediately thereafter. The VJCs on the fixed and movable contacts work together to forcefully reduce the arc spot and rapidly contract the total arc being extinguished. Fixed contact VJC Upper, fixed-contact conductor Lower, fixed-contact conductor Pressure Arc Movable contact Movable contact VJC Vapor jet control (VJC) Vapor Jet Controllers made of insulating material are arranged around the contacts where they control the arc as follows: 1. The arc spot is forcibly reduced by the arrange- ment of the insulating material. 2. The arc column is contracted. 3. Adiabatic expansion cools the arc. 4. The arc is transferred at the optimum moment to the arc-extinguishing chamber by the arrangement of the Vapor Jet Controllers.

2.2 Digital ETR (Electronic Trip Relay)

Mitsubishi’s electronic MCCBs are equipped with a digital ETR to enable fine protection. The digital ETR contains Mitsubishi’s original double IC (8 bit microcomputer and custom-IC). Digital detection of the effective value Electronic devices such as an inverter distort the cur- rent waveform. Mitsubishi’s PSS electronic breakers are designed to detect digitally the effective value of the current to minimize over-current tripping errors. This enables fine protection for the system. LSW : Long time-delay soft ware PSW : Pre-alarm soft ware WDT : Watch-dog timer circuit Power-source side terminal Load-side terminal Breaking mechanismRectifying circuit Test input Load-current indication LED (70%) Trip coil Custom IC I CV PSS WDT Microcomputer CPU Characteristics setting part A/D convertor SSW CT CT CT CT LSW PSW Input and output I : Instantaneous circuit CV : Constant voltage circuit Phase- selection sampling circuit Short time-delay soft ware Trigger circuit Over-current indication LED Pre-alarm indication LED Pre-alarm output Standard equipped pre-alarm system Mitsubishi’s PSS electronic breakers have a pre-alarm system as a standard. When the load current exceeds the set pre-alarm current, the breaker lights up an LED and outputs a pre-alarm signal. Load M 1×103 1×102 1×104 102 10310 Time (sec) 0.1 0.01 Ir IP Pre-alarm current Current setting TL Current (A) Is Ts Load current High-voltage fuse- Allowable short-time characteristics Short time-delay tripping current Short time-delay operating time Instantaneous tripping current Long time-delay operating time Current-Converted value on the high-voltage side Switch with fuse High voltage Low voltage Transformer MCCB (electronic) Ii Processing of the digital ETR Sampling and A/D conversion Calculating the digitally effective value Processing the long time-delay pre-alarm characteristics

2.3 Equipment of High Technology

l l l l l l l l l l l l l l l l l l l l l l l l l l l l l l ISTAC l l l l l l l l l l l l Digital-ETR l l l l l l l l l l l l l l l l l Analog-ETR l l l l

3.1 General

The primary components are: a switching mechanism, an automatic tripping device (and manual trip button), contacts, an arc-extinguishing device, terminals and a molded case. 3. CONSTRUCTION AND OPERATION Fig. 3.1 Type NF100-SP Construction Handle 1. Trip indication The automatically tripped condi- tion is indicated by the handle in the center position between ON and OFF, the yellow (or white) line cannot be seen in this posi- tion. 2. Resetting Resetting after tripping is per- formed by first moving the han- dle to the OFF position to en- gage the mechanism, then re- turning the handle to ON to re- close the circuit. 3. Trip-Free Even if the handle is held at ON, the breaker will trip if an overcurrent flows. 4. Contact On Mechanism Even in the worst case in which welding occurs owing to an overcurrent, the breaker will trip and the handle will maintain to ON, indicating the energizing state. ON OFF Trip Handle indication Arc-Extinguishing Device Mitsubishi MCCBs feature excel- lent arc-extinguishing perfor- mance by virtue of the optimum combination of grid gap, shape, and material. Trip Button (Push to Trip) Enables tripping mechanically from outside, for confirming the operation of the accessory switch- es and the manual resetting func- tion. Switching Mechanism The contacts open and close rap- idly, regardless of the moving speed of the handle, minimizing contact wear and ensuring safety. Rapidmovement Link-mechanism operation Magnetic flux Arc extinction Magnetic force Grid Arc Contact Molded case (Base) Terminal Molded case (Cover) Automatic tripping device ON OFF ON OFF

3.2 Switching Mechanism

The ON, OFF and TRIPPED conditions are shown in Fig. 3.2. In passing from ON to OFF, the handle ten- sion spring passes through alignment with the toggle link (“dead point” condition). In so doing, a positive, rapid contact-opening action is produced; the OFF to ON contact closing acts in a similar way (“quick make” and “quick break” actions). In both cases the action of the contacts is always rapid and positive, and inde- pendent of the human element – i.e., the force or speed of the handle. In auto tripping a rotation of the bracket releases the cradle and operates the toggle link to produce the contact-opening action described above. In the tripped condition the handle assumes the center position be- tween on and off, providing a visual indication of the tripped condition. Also, auto trip is “trip free,” so that the handle cannot be used to hold the breaker in the ON condition. The protective contact-opening func- tion cannot be defeated. In multipole breakers the poles are separated by integral barriers in the molded case. The moving con- tacts of the poles are attached to the central toggle link by a common-trip bar, however, so that tripping, opening and closing of all poles is always simulta- neous. This is the “common trip” feature, by which single phasing and similar unbalance malfunctions are effectively prevented. Spring tension line Toggle link Cradle BracketSpring a) On b) Off c) Tripped ON to OFF dead-point line OFF to ON dead-point line Handle centered; indicates tripped condition Fig. 3.2 Switching Mechanism Action

3.3 Automatic Tripping Device

There are three types of device, the thermal-magnetic type, the hydraulic-magnetic type and the electronic trip relay type.

n Automatic Tripping Devices l Thermal-Magnetic Type (100~800A Frame) 1. Time-Delay Operation An overcurrent heats and warps the bi- metal to actuate the trip bar. 2. Instantaneous Operation If the overcurrent is excessive, the amature is attracted and the trip bar ac- tuated. Fig. 3.3 l Thermal-Magnetic Type (1000~4000A Frame) 1. Time-Delay Operation An overcurrent heats and warps the bi- metal to actuate the trip bar. 2. Instantaneous Operation If the overcurrent is excessive, magneti- zation of the stationary core is strong enough to attract the armature and ac- tuate the trip bar. Fig. 3.4 l Hydraulic-Magnetic Type (30~60A Frame) 1. Time-Delay Operation At an overcurrent flow, the magnetic force of the coil overcomes the spring, the core closes to the pole piece, attracts the armature, and actuates the trip bar. The delay is obtained by the viscosity of silicon oil. 2. Instantaneous Operation If the overcurrent is excessive, the ar- mature is instantly attracted, without the influence of the moving core. Fig. 3.5 l Principle of Electronic Trip Relay (ETR) Operation 1. The current flowing in each phase is monitored by a current transformer (CT). 2. Each phase of the transformed current undergoes full-phase rectification in the rectifier circuit. 3. After rectification, each of the currents are converted by a peak-conversion and an effective-value conversion circuit. 4. The largest phase is selected from the converted currents. 5. Each time-delay circuit generates a time delay corresponding to the largest phase. 6. The trigger circuit outputs a trigger sig- nal. 7. The trip coil is excited, operating the switching mechanism. Fig. 3.6 Armature Trip bar Silicon oil Moving core Damping spring Pipe Coil Pole piece Bimetal Heater Armature Trip bar Latch Bimetal Latch Heater Stationary core Armature Trip bar Power-source side terminal Load-side terminal Breaking mechanismRectifying circuit Test input Load-current indication LED (70%) Trip coil Custom IC I CV PSS WDT Microcomputer CPU Characteristics setting part A/D convertor SSW LSW PSW Input and output Trigger circuit Trigger circuit Over-current indication LED Pre-alarm indication LED Pre-alarm output CT CT CT CT CT CT CT Power-supply side terminal Load-side terminal Test terminalsOvercurrent display LED (1000~1600A Frame)(100~800A Frame) Switching mechanism Trip coil Peak conversion and largest-phase selection Effective value conversion and largest-phase selection Test-signal generator circuit Long- delay circuit Short- delay circuit Instan- taneous circuit Special IC Rectifier circuit

Table 3.1 Comparison of Thermal-Magnetic, Hydraulic-Magnetic and Electronic Types Item Ambient temperature Frequency Mounting attitude Flexibility of operating characteristics Flexibility of rated current Thermal-magnetic type Operating current is affected by ambient temperature (bimetal responds to absolute temperature not temperature rise). Negligible effect up to several hundred Hz; above that the instantaneous trip is affect- ed due to increased iron losses. Negligible effect. Bimetal must provide adequate deflection force and desired temperature characteris- tic. Operating time range is limited. Units for small rated currents are physically impractical. Hydraulic-magnetic type Affected only to the extent that the damp- ing-oil viscosity is affected. Trip current increases with frequency, due to increased iron losses. Mounting attitude changes the effective weight of the magnetic core. Oil viscosity, cylinder, core and spring design, etc., allow a wide choice of operat- ing times. Coil winding can easily be designed to suit any ampere rating. Negligible effect up to 600A; Above that operating current decreases due to increase of a fever. IF distortion is big, minimum operating cur- rent increases. Distorted wave Electronic type Within the range of 50(60)~100% of rated current, any ampere rating are practical. Also, to lower the value of short-time delay or instantaneous trip can be easily done comparatively. Operating time can be easily shortened. To lengthen operating time is not. Negligible effect Tripping current of some types decrease due to CT or condition of operating circuit with high frequency, and others increase. Negligible effect For peak value detection, operating current drops. Operating time Current Operating time Current Operating time Ceiling HorizontalON ON OFF OFF Current Operating time Current Operating time High frequency Low frequency Current Operating time High frequency Low frequency Current Operating timeHigh temperature Low temperature Current Operating timeHigh temperature Standard temperature Low temperature Current Operating time Current Operating time Current Operating time Current Above 700A Operating time Current Small current width Current width Operating time Current Peak value detection Operating time Current Operating time Current

3.4 Contacts

A pair of contacts comprises a moving contact and a fixed contact. The instants of opening and closing impose the most severe duty. Contact materials must be selected with consideration to three major criteria: 1. Minimum contact resistance 2. Maximum resistance to wear 3. Maximum resistance to welding Silver or silver-alloy contacts are low in resistance, but wear rather easily. Tungsten, or majority-tungsten alloys are strong against wear due to arcing, but rather high in contact resistance. Where feasible, 60%+ sil- ver alloy (with tungsten carbide) is used for contacts primarily intended for current carrying, and 60%+ tung- sten alloy (with silver) is used for contacts primarily intended for arc interruption. Large-capacity MCCBs employ this arrangement, having multicontact pairs, with the current-carrying and arc-interruption duties separated.

3.5 Arc-Extinguishing Device

Arcing, an inevitable aspect of current interruption, must be extinguished rapidly and effectively, in nor- mal switching as well as protective tripping, to mini- mize deterioration of contacts and adjacent insulat- ing materials. In Mitsubishi MCCBs a simple, reliable, and highly effective “de-ion arc extinguisher,” consist- ing of shaped magnetic plates (grids) spaced apart in an insulating supporting frame, is used (Fig. 3.7). The arc (ionized-path current) induces a flux in the grids that attracts the arc, which tends to “lie down” on the grids, breaking up into a series of smaller arcs, and also being cooled by the grid heat conduction. The arc (being effectively longer) thus requires far more voltage to sustain it, and (being cooler) tends to lose ionization and extinguish. If these two effects do not extinguish the arc, as in a very large fault, the elevated temperature of the insulating frame will cause gas- sing-out of the frame material, to de-ionize the arc. Ac arcs are generally faster extinguishing due to the zero-voltage point at each half cycle.

3.6 Molded Case

The integral molded cases used in Mitsubishi MCCBs are constructed of the polyester resin containing glass fibers, the phenolic resin or glass reinforced nylon. They are designed to be suitably arc-, heat- and gas- resistant, and to provide the necessary insulating spacings and barriers, as well as the physical strength required for the purpose.

3.7 Terminals

These are constructed to assure electrical efficiency and reliability, with minimized possibility of localized heating. A wide variety of types are available for ease of mounting and connection. Compression-bonded types and bar types are most commonly used.

3.8 Trip Button

This is a pushbutton for external, mechanical tripping of the MCCB locally, without operating the external- accessory shunt trip or undervoltage trip, etc. It en- ables easy checking of breaker resetting, control-cir- cuit devices associated with alarm contacts, etc., and resetting by external handle. Supporting frame Grids Fig. 3.7 The De-Ion Arc Extinguisher Grid ArcAttraction force Induced flux Fig. 3.8 The Induced-Flux Effect

4.1 Overcurrent-Trip Characteristics (Delay

Tripping) Tripping times for overcurrents of 130 and 200% of rated current are given in Table 4.1, assuming ambi- ent temperatures of 40°C, a typical condition inside of panelboards. The figures reflect all poles tested to- gether for 130% tripping, and 105% non-tripping. Within the range of the long-delay-element (thermal or hydraulic) operation, tripping times are substan- tially linear, in inverse relationship to overcurrent mag- nitude. The tripping times are established to prevent ex- cessive conductor-temperature rise; although times may vary among MCCBs of different makers, the lower limit is restricted by the demands of typical loads: tung- sten-lamp inrush, starting motor, mercury-arc lamps, etc. The tripping characteristics of Mitsubishi MCCBs are established to best ensure protection against ab- normal currents, while avoiding nuisance tripping. 4.1.1Ambient Temperature and Thermal Tripping Fig. 4.1 is a typical ambient compensation curve (curves differ according to types and ratings), show- ing that an MCCB rated for 40°C ambient use must be derated to 90% if used in a 50°C environment. In an overcurrent condition, for the specified tripping time, tripping would occur at 180% rated current, not 200%. At 25°C, for the same tripping time, tripping would occur at 216%, not 200%.

4.1.2 Hot-State Tripping

The tripping characteristics described above reflect “cold-state tripping” – i.e., overloads increased from zero – and the MCCB stabilized at rated ambient. This is a practical parameter for most uses, but in intermit- tent operations, such as resistance welding, motor pulsing, etc., the “hot state” tripping characteristic must be specified, since over-loads are most likely to oc- cur with the MCCB in a heated state, while a certain load current is already flowing. Where the MCCB is assumed to be at 50% of rat- ing when the overload occurs, the parameter is called the 50% hot-state characteristic; if no percentage is specified, 100% is assumed. Hot-state ratings of 50% and 75% are common.

4.2 Short-Circuit Trip Characteristics (In-

stantaneous Tripping) For Mitsubishi MCCBs with thermal-magnetic trip units the instantaneous-trip current can be specified inde- pendently of the delay characteristic, and in many cases this parameter is adjustable offering consider- able advantage in coordination with other protection and control devices. For example, in coordination with motor starters, it is important to set the MCCB instan- taneous-trip element at a lower value than the fusing (destruction) current of the thermal overload relay (OLR) of the starter. For selective tripping, it must be remembered that even though the branch-MCCB tripping time may be shorter than the total tripping time of the main MCCB, in a fault condition the latter may also be tripped be- cause its latching curve overlaps the tripping curve of the former. The necessary data for establishing the required compatibility is provided in the Mitsubishi MCCB sales catalogues. The total clearing time for the “instantaneous” trip- ping feature is shown in Fig. 4.3; actual values differ for each MCCB type. Table 4.1 Overcurrent Tripping Times Rated current (A) 30 or less 31~63 64~100 101~250 251~400 401~630 631~800 801~1000 1001~1250 1251~1600 1601~2000 2001~4000 Tripping time (minutes, max.) 200% 8.5 8.5 130% 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 105% Non-Tripping time (minutes, max.) 20 25 Ambient temperature (:) % rating compensation 30 40 110 108 100 50 60 120 Fig. 4.1 Typical Temperature-Compensation Curve Cold state Operating time Current Hot state /CR Fig. 4.2 Hot-State-Tripping Curve 4. CHARACTERISTICS AND PERFORMANCE

(relay) time Electromagnet oparating time Time for contacts to open Arc- extinguishing time Mechanical delay time Arcing time Fig. 4.3 Instantaneous Tripping Sequence

4.3 Effects of Mounting Attitudes

Instantaneous tripping is negligibly affected by mount- ing attitude, for all types of MCCB. Delay tripping is also negligibly affected in the thermal types, but in the hydraulic-magnetic types the core-weight effect becomes a factor. Fig. 4.4 shows the effect, for verti- cal-surface mounting and for two styles of horizontal- surface mounting. (vertical plane) 100% 93% ON ON ON ON ON ON ON ON 90%110% 93%107% 107% 100% Fig. 4.5 Effects of Nonvertical-Plane Mounting on Current Rating

4.4 DC Tripping Characteristics of AC-Rated MCCBs

Table 4.2 DC Tripping Characteristics Trip unit Thermal magnetic Hydraulic magnetic Long delay No effect below 630A frame. Above this, AC types cannot be used for DC. DC minimum-trip values are 110~140% of AC values. Instantaneous DC inst.-trip current is approx. 130% of AC value. Tripping curve AC DC Overcurrent Tripping time AC DC Tripping time Overcurrent

4.5 Frequency Characteristics

At commercial frequencies the characteristics of Mitsubishi MCCBs of below 630A frame size are vir- tually constant at both 50Hz and 60Hz (except for the E Line models, the characteristics of MCCBs of 800A frame and above vary due to the CT used with the delay element). At high frequencies (e.g., 400Hz), both the current capacity and delay tripping curves will be reduced by skin effect and increased iron losses. Performance reduction will differ for different types; at 400Hz it will become 80% of the rating in breakers of maximum rated current for the frame size, and 90% of the rating in breakers of half of the maximum rating for the frame size. The instantaneous trip current will gradually in- crease with frequency, due to reverse excitation by eddy currents. The rise rate is not consistent, but around 400Hz it becomes about twice the value at 60Hz. Mitsubishi makes available MCCBs especially designed for 400Hz use. Apart from operating char- acteristics they are identical to standard MCCBs (S Line). Floor-mounted Overcurrent Tripping time Ceiling-mounted Wall-mounted (horiz. or vert. attitude) Fig. 4.4 Effect of Mounting Attitude on the Hydraulic- Magnetic MCCB Tripping Curves

4.6 Switching Characteristics

The MCCB, specifically designed for protective inter- ruption rather than switching, and requiring high-con- tact pressure and efficient arc-extinguishing capabil- ity, is expected to demonstrate inferior capability to that of a magnetic switch in terms of the number of operations per minute and operation life span. The specifications given in Table 4.3 are applicable where the MCCB is used as a switch for making and break- ing rated current. Electrical tripping endurance in MCCBs with shunt or undervoltage tripping devices is specified as 10% of the mechanical-endurance number of operations quoted in IEC standards. Shunt tripping or undervoltage tripping devices are intended as an emergency trip provision and should not be used for normal circuit-interruption purposes.

4.7 Dielectric Strength

In addition to the requirements of the various interna- tional standards, Mitsubishi MCCBs also have the impulse-voltage withstand capabilities given below (Table 4.4). The impulse voltage is defined as sub- Table 4.3 MCCB Switching Endurance Frame size 100 or less 225 400, 630 800 1000~2000 2500, 3000 3200, 4000 Operations per hour 120 120 Number of operations Without current 8500 7000 4000 2500 2500 1500 1500 With current 1500 1000 1000 500 500 500 500 Total 10000 8000 5000 3000 3000 2000 2000 stantially square-wave, with a crest length of 0.5~1.5µsec and a tail-length of 32~48µsec. The volt- age is applied between line and load terminals (MCCB off), and between live parts and ground (MCCB on). Table 4.4 MCCB Impulse Withstand Voltage (Uimp) Line Type Impulse-voltage (kA) MB NF S C U MB30-SP MB50-CP MB-50-SP MB100-SP MB225-SP NF30-CS NF400-CP NF630-CP NF800-CEP NF50-CP NF60-CP NF100-CP NF250-CP NF100-RP NF100-UP NF225-RP NF225-UP NF400-SP NF400-SEP NF400-HEP NF400-REP NF630-SP NF630-SEP NF630-HEP NF630-REP NF800-SEP NF800-HEP NF800-REP NF800-REP NF1000-SS NF1250-SS NF1600-SS MB30-CS 4 NF30-SP NF50-HP NF60-HP NF50-HRP NF100-SP NF100-HP NF100-SEP NF100-HEP NF160-SP NF160-HP NF250-SP NF250-HP NF250-SEP NF250-HEP NF400-UEP NF630-UEP NF800-UEP

1. CIRCUIT BREAKER SELECTION

5.1 Circuit Breaker Selection Table

Following Table shows various characteristics of each breaker to consider selection and coordination with upstream devices or loads. Characteristics Standard : Standard characteristics MCCBs Low-inst : Low-inst. MCCBs for Discrimination When a power fuse (PF) is used as a high-voltage protector, it must be coordinated with an MCCBs on the secondary side. Generator : Generator-Protection MCCBs These MCCBs have long-time-delay operation shorter than standard type and low instantaneous operation. Mag-Only : Magnetic trip only MCCBs These are standard MCCBs minus the thermal tripping device. They have no time- delay tripping characteristic, providing protection only against large-magnitude short- circuit faults. PF short-time tolerancs capacity Pf. Tr. MCCB1 MCCB2 Time MCCB operating characteristic curve Low-inst.MCCBs Current

Frame (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics CIRCUIT BREAKER SELECTION TABLE NF30-CS 3, 5, 10, 15, 20, 30 500 1.5/1.5 (415V) 1.5/1.5 (380V) 2.5/2 (240V) Hydraulic-magnetic Fixed ampere rating and instantaneous NF30-SP 3, 5, 10, 15, 20, 30 600 2.5/1 2.5/1 Magnetic Fixed ampere rating instantaneous 10, 15, 20, 30, 40, 50 600 2.5/1 2.5/1 Hydraulic-magnetic Fixed ampere rating and instantaneous Hydraulic-magnetic Fixed ampere rating and instantaneous – – Magnetic Fixed ampere rating instantaneous NF50-CP 33 0 ± 6 55 0 ± 10 10 100 ± 20 15 150 ± 30 20 200 ± 40 30 300 ± 60 33 9 ± 17 56 6 ± 28 10 132 ± 57 15 198 ± 86 20 265 ± 115 30 397 ± 172 33 3 ± 10 55 5 ± 17 10 110 ± 35 15 165 ± 52 20 220 ± 70 30 330 ± 105 10 110 ± 35 15 165 ± 52 20 220 ± 70 30 330 ± 105 40 440 ± 140 50 550 ± 175 10 100 ± 20 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 Type Rated current In (A) Rated insulation voltage Ui (V) AC

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Hydraulic-magnetic Fixed ampere rating and instantaneous Magnetic Fixed ampere rating and instantaneous NF50-HP 10, 15, 20, 30, 40, 50 600 7.5/4 234 234 NF60-CP 10, 15, 20, 30, 40, 50, 60 600 2.5/1 2.5/1 Hydraulic-magnetic Fixed ampere rating and instantaneous Magnetic Fixed ampere rating and instantaneous 10 110 ± 35 15 165 ± 52 20 220 ± 70 30 330 ± 105 40 440 ± 140 50 550 ± 175 10 110 ± 35 15 165 ± 52 20 220 ± 70 30 330 ± 105 40 440 ± 140 50 550 ± 175 60 660 ± 210 10 100 ± 20 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 10 100 ± 20 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 60 600 ± 120

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) NF60-HP 10, 15, 20, 30, 40, 50, 60 600 7.5/4 234 Magnetic Fixed ampere rating and instantaneous 100 Thermal, magnetic Fixed ampere rating and instantaneous Hydraulic-magnetic Fixed ampere rating and instantaneous Thermal, magnetic Fixed ampere rating and instantaneous 50 300 ± 60 60 360 ± 72 75 450 ± 90 100 600 ± 120 234 2 3 Magnetic Fixed ampere rating and instantaneous NF100-CP NF100-SP 15, 20, 30, 40, 50, 60, 75, 100 690 234 50, 60, 75, 100 600 7.5/4 Thermal, magnetic Fixed ampere rating and instantaneous 10 110 ± 35 15 165 ± 52 20 220 ± 70 30 330 ± 105 40 440 ± 140 50 550 ± 175 60 660 ± 210 50 750 ± 150 60 900 ± 180 75 1125 ± 225 100 1500 ± 300 10 100 ± 20 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 60 600 ± 120 50 500 ± 100 60 600 ± 120 75 750 ± 150 100 1000 ± 200 15 225 ± 45 20 300 ± 60 30 450 ± 90 40 600 ± 120 50 750 ± 150 60 900 ± 180 75 1125 ± 225 100 1500 ± 300 234 Thermal, magnetic Fixed ampere rating and instantaneous 15 90 ± 18 20 120 ± 24 30 180 ± 36 40 240 ± 48 50 300 ± 60 60 360 ± 72 75 450 ± 90 100 600 ± 120 234 Magnetic Fixed ampere rating and instantaneous 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 60 600 ± 120 75 750 ± 150 100 1000 ± 200

Frame (A) 100 NF100-CP T/A Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Rated insulation voltage Ui (V) AC Rated current In (A) 15 ~ 20 225 ± 45 20 ~ 25 300 ± 60 25 ~ 40 375 ± 75 40 ~ 63 600 ± 120 63 ~ 80 945 ± 189 80 ~ 100 1200 ± 240 NF50-HRP Thermal, magnetic Fixed ampere rating and instantaneous 15 225 ± 45 20 300 ± 60 30 450 ± 90 40 600 ± 120 50 750 ± 150 Magnetic Fixed ampere rating and instantaneous 100 NF100-SP T/A Thermal, magnetic Adjustable ampere rating and fixed instantaneous 600 7.5/4 15 ~ 20, 20 ~25, 25 ~40 40 ~ 63, 63 ~80, 80 ~10015, 20, 30, 40, 5015 ~ 20, 20 ~25, 25 ~40 40 ~ 63, 63 ~80, 80 ~100 690 2.5/1 690 23 4 Thermal, magnetic Adjustable ampere rating and fixed instantaneous 15 ~ 20 225 ± 45 20 ~ 25 300 ± 60 25 ~ 40 375 ± 75 40 ~ 63 600 ± 120 63 ~ 80 945 ± 189 80 ~ 100 1200 ± 240 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100

Frame (A) NF100-HP T/ANF100-HP Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Thermal, magnetic Fixed ampere rating and instantaneous 15 225 ± 45 20 300 ± 60 30 450 ± 90 40 600 ± 120 50 750 ± 150 60 900 ± 180 75 1125 ± 225 100 1500 ± 300 Magnetic Fixed ampere rating and instantaneous 23 4 Rated insulation voltage Ui (V) AC 234 690 15, 20, 30, 40, 50, 60, 75, 100Rated current In (A) 15 ~ 20, 20 ~25, 25 ~40 40 ~ 63, 63 ~80, 80 ~100 690 – (5/3) ] 23 4 Thermal, magnetic Adjustable ampere rating and fixed instantaneous NF100-RP 15, 20, 30, 40, 50, 60, 75, 100 690 Thermal, magnetic Fixed ampere rating and instantaneous 15 ~ 20 225 ± 45 20 ~ 25 300 ± 60 25 ~ 40 375 ± 75 40 ~ 63 600 ± 120 63 ~ 80 945 ± 189 80 ~ 100 1200 ± 240 15 225 ± 45 20 300 ± 60 30 450 ± 90 40 600 ± 120 50 750 ± 150 60 900 ± 180 75 1125 ± 225 100 1500 ± 300 100 15 150 ± 30 20 200 ± 40 30 300 ± 60 40 400 ± 80 50 500 ± 100 60 600 ± 120 75 750 ± 150 100 1000 ± 200 ] To be agreed soon.

I n (A) Rated insulation voltage Ui (V) AC Standard 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) I EC60947-2 I cu/ I cs Number of poles Automatic tripping device 100 15, 20, 30, 40, 50, 60, 75, 100 690 234 Thermal, magnetic Fixed ampere rating and instantaneous 30 ~ 50, 60 ~ 100 690 NF100-UP NF100-SEP Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Short time delay pick up current Variation is within 15% of setting current 2 to 10 I r 30 60-75-90-105-120-150- 180-210-240-300 40 80-100-120-140-160- 200-240-280-320-400 50 100-125-150-175-200- 250-300-350-400-500 60 120-150-180-210-240- 300-360-420-480-600 375-450-525-600-750 100 200-250-300-350-400- 500-600-700-800-1000 Instantaneous pick up current Variation is within 15% of setting current I n ~ I n 30 ~ 50 200 ~ 800 60 ~ 100 400 ~ 1600 Rating (A) and Inst. (A) 15 225 20 300 30 450 40 600 120 50 750 150 60 900 180 75 1125 225 100 1500 300 Low-inst Number of poles Automatic tripping device Rating (A) and Inst. (A) Generator Automatic tripping device Rating (A) and Inst. (A) Number of poles Mag-Only Number of poles Automatic tripping device Rating (A) and Inst. (A) NF100-HEP 30 ~ 50, 60 ~ 100 690 Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Short time delay pick up current Variation is within 15% of setting current 2 to 10 I r 30 60-75-90-105-120-150- 180-210-240-300 40 80-100-120-140-160- 200-240-280-320-400 50 100-125-150-175-200- 250-300-350-400-500 60 120-150-180-210-240- 300-360-420-480-600 375-450-525-600-750 100 200-250-300-350-400- 500-600-700-800-1000 Instantaneous pick up current Variation is within 15% of setting current I n ~ I n 30 ~ 50 200 ~ 800 60 ~ 100 400 ~ 1600 Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Rating:30 ~ 50A, 60 ~ 100A Inst.: Operating characteristics must be adjusted as follows. STD ≤ 3 ( I s setting) LTD : minimum setting L = 12sec setting) Rating:30 ~ 50A, 60 ~ 100A Inst.: Operating characteristics must be adjusted as follows. STD ≤ 3 ( I s setting) LTD : minimum setting L = 12sec setting)

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 160 NF160-SP 125, 150, 160 690 234 Thermal, magnetic Fixed ampere rating and instantaneous Magnetic Fixed ampere rating and instantaneous 125 1250 ± 250 160 1600 ± 320 NF160-SP T/A 100 ~125, 125 ~160 690 234 Thermal, magnetic Adjustable ampere rating and fixed instantaneous NF160-HP 125, 150, 160 690 23 4 Thermal, magnetic Fixed ampere rating and instantaneous 125 1750 ± 350 150 2100 ± 420 160 2240 ± 448 100 ~ 125 1400 ± 280 125 ~ 160 1400 ± 280 125 1750 ± 350 150 2100 ± 420 160 2240 ± 448 2 34 234 Magnetic Fixed ampere rating and instantaneous 125 1250 ± 250 160 1600 ± 320

Frame (A) 160 NF160-HP T/A 250 NF250-CP Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V AC Breaking capacity (kA rms) I EC60947-2 I cu/ I cs Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Thermal, magnetic Adjustable ampere rating and fixed instantaneous Thermal, magnetic Fixed ampere rating and instantaneous 125 1750 350 150 2100 420 175 2450 490 200 2800 560 225 3150 630 250 2500 500 Thermal, magnetic Fixed ampere rating and instantaneous I I n 125 750 150 500 100 150 900 180 600 120 175 1050 210 700 140 200 1200 240 800 160 225 1350 270 900 180 250 1500 300 1000 200 Magnetic Fixed ampere rating and instantaneous 125 1250 250 150 1500 300 175 1750 350 200 2000 400 225 2250 450 250 2250 450 690 – (10/5) ] 30/8 (30/15) ] 50/13 (50/25) ] 50/13 (50/25) ] 100/25(100/50) ] 23 4 600 Rated insulation voltage Ui (V) AC Rated current I n (A) NF250-CP T/A 100 125, 125 160 150 200, 200 250 125, 150, 175, 200, 225, 250 100 125, 125 160 600 Thermal, magnetic Adjustable ampere rating and fixed instantaneous 100 125 1400 280 125 160 1400 280 100 125 1400 280 125 160 1400 280 150 200 2100 420 200 250 2500 500 ] To be agreed soon. n

Frame (A) 250 NF250-SP Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 234 Thermal, magnetic Fixed ampere rating and instantaneous

6 In4 In

125 750 ± 150 500 ± 100 150 900 ± 180 600 ± 120 175 1050 ± 210 700 ± 140 200 1200 ± 240 800 ± 160 225 1350 ± 270 900 ± 180 250 1500 ± 300 1000 ± 200 Magnetic Fixed ampere rating and instantaneous 125 1250 ± 250 150 1500 ± 300 175 1750 ± 350 200 2000 ± 400 225 2250 ± 450 250 2250 ± 450 Rated insulation voltage Ui (V) AC Rated current In (A) 690 234 125, 150, 175, 200, 225, 250 NF250-SP T/A 100 125, 125 160 150 200, 200 250 690 234 Thermal, magnetic Fixed ampere rating and instantaneous Thermal, magnetic Adjustable ampere rating and fixed instantaneous 125 1750 ± 350 150 2100 ± 420 175 2450 ± 490 200 2800 ± 560 225 3150 ± 630 250 2500 ± 500 NF250-HP 125, 150, 175, 200, 225, 250 690 23 4 Thermal, magnetic Fixed ampere rating and instantaneous 100 125 1400 ± 280 125 160 1400 ± 280 150 200 2100 ± 420 200 250 2500 ± 500 234 23 4 Magnetic Fixed ampere rating and instantaneous 125 1750 ± 350 150 2100 ± 420 175 2450 ± 490 200 2800 ± 560 225 3150 ± 630 250 2500 ± 500 125 1250 ± 250 150 1500 ± 300 175 1750 ± 350 200 2000 ± 400 225 2250 ± 450 250 2250 ± 450 ~ ~

Frame (A) 250 Low-inst Standard Mag-Only Generator 690V 500V 440V 400V 230V AC Breaking capacity (kA rms) I EC60947-2 I cu/ I cs Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Rated insulation voltage Ui (V) AC Rated current I n (A) 100 125, 125 160 150 200, 200 250 690 – (10/5) ] 30/8 (30/15) ] 50/13 (50/25) ] 50/13 (50/25) ] 100/25(100/50) ] 234 Thermal, magnetic Adjustable ampere rating and fixed instantaneous 100 125 1400 280 125 160 1400 280 150 200 2100 420 200 250 2500 500 NF225-RP NF250-HP T/A 125, 150, 175, 200, 225 690 Thermal, magnetic Fixed ampere rating and instantaneous Thermal, magnetic Fixed ampere rating and instantaneous 125 1750 350 150 2100 420 175 2450 490 200 2800 560 225 3150 630 125 1750 350 150 2100 420 175 2450 490 200 2800 560 225 3150 630 690 23 4 125, 150, 175, 200, 225 NF225-UP 225 ] To be agreed soon.

I n (A) Rated insulation voltage Ui (V) AC Standard 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) I EC60947-2 I cu/ I cs Number of poles Automatic tripping device Rating (A) and Inst. (A) Low-inst Number of poles Automatic tripping device Rating (A) and Inst. (A) 250 Automatic tripping device Rating (A) and Inst. (A) Generator Number of poles Mag-Only Number of poles Automatic tripping device Rating (A) and Inst. (A) Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Short time delay pick up current Variation is within 15% of setting current 2 to 10 I r 125 250-312.5-375-437.5-500- 625-750-875-1000-1250 150 300-375-450-525-600- 750-900-1050-1200-1500 175 350-437.5-525-612.5-700- 875-1050-1225-1400-1750 200 400-500-600-700-800-1000- 1200-1400-1600-2000 225 450-562.5-675-787.5-900- 1125-1350-1575-1800-2250 250 500-625-750-875-1000- 1250-1500-1750-2000-2500 Instantaneous pick up current Variation is within 15% of setting current I n 125 250 1000 3500 NF250-HEP 125-250 690 Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Short time delay pick up current Variation is within 15% of setting current 2 to 10 I r 125 250-312.5-375-437.5-500- 625-750-875-1000-1250 150 300-375-450-525-600- 750-900-1050-1200-1500 175 350-437.5-525-612.5-700- 875-1050-1225-1400-1750 200 400-500-600-700-800-1000- 1200-1400-1600-2000 225 450-562.5-675-787.5-900- 1125-1350-1575-1800-2250 250 500-625-750-875-1000- 1250-1500-1750-2000-2500 Instantaneous pick up current Variation is within 15% of setting current I n 125 250 1000 3500 NF250-SEP 125-250 690 Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up, and instantaneous Rating:125 250A Inst.: Operating characteristics must be adjusted as follows. STD ≤ 3 ( I s setting) LTD : minimum setting L = 12sec setting) Rating:125 250A Inst.: Operating characteristics must be adjusted as follows. STD ≤ 3 ( I s setting) LTD : minimum setting L = 12sec setting)

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 400A NF400-SEP 200 400 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 200 400-500-600-700-800- 1000-1200-1400-1600- 2000 225 450-562.5-675-787.5- 900-1125-1200-1500- 1800-1350-1575-1800- 2250 250 500-625-750-875-1000- 1250-1500-1750-2000- 2500 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 Instantaneous pick up current Variation is within ±15% of setting current

4 In 16 In

Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF400-CP Thermal, magnetic Fixed ampere rating and instantaneous 250, 300, 350, 400 600 250 2500 ± 500 300 3000 ± 600 350 3500 ± 700 400 4000 ± 800 Thermal, magnetic Fixed ampere rating and instantaneous 250 1500± 300 1000± 200 300 1800± 360 1200± 240 350 2100± 420 1400± 280 400 2400± 480 1600± 320 Magnetic Fixed ampere rating and instantaneous 250 2500 ± 500 300 3000 ± 600 350 3500 ± 700 400 4000 ± 800 NF400-SP 234 Thermal, magnetic Fixed ampere rating and instantaneous 250, 300, 350, 400 690 250 3500 ± 700 300 4200 ± 840 350 4900 ± 980 400 5600 ± 1120 23 4 Magnetic Fixed ampere rating and instantaneous 250 2500 ± 500 300 3000 ± 600 350 3500 ± 700 400 4000 ± 800

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 400A NF400-UEP Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF400-HEP NF400-REP 200 400 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 200 400-500-600-700-800- 1000-1200-1400-1600- 2000 225 450-562.5-675-787.5- 900-1125-1200-1500- 1800-1350-1575-1800- 2250 250 500-625-750-875-1000- 1250-1500-1750-2000- 2500 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 200 400-500-600-700-800- 1000-1200-1400-1600- 2000 225 450-562.5-675-787.5- 900-1125-1200-1500- 1800-1350-1575-1800- 2250 250 500-625-750-875-1000- 1250-1500-1750-2000- 2500 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 200 400-500-600-700-800- 1000-1200-1400-1600- 2000 225 450-562.5-675-787.5- 900-1125-1200-1500- 1800-1350-1575-1800- 2250 250 500-625-750-875-1000- 1250-1500-1750-2000- 2500 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 Instantaneous pick up current Variation is within ±15% of setting current ~ ~ ~

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 630A NF630-SEP Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF630-CP NF630-SP 300 630 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 630 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current

4 In 15 In

500, 600, 630 23 4 Thermal, magnetic adjustable ampere rating and fixed instantaneous

500 Lo 2500 ± 500

Hi 7000 ± 1400

600 Lo 3000 ± 600

Hi 8400 ± 1680

630 Lo 3150 ± 630

Hi 8820 ± 1764 690 500, 600, 630 Thermal, magnetic Fixed ampere rating and instantaneous 500 5000 ± 1000 600 6000 ± 1200 630 6300 ± 1260 600 Magnetic Fixed ampere rating and instantaneous 500 5000 ± 1000 600 6000 ± 1200 630 6300 ± 1260 234 Thermal, magnetic adjustable ampere rating and fixed instantaneous

500 Lo 2000 ± 400

Hi 5000 ± 1000

600 Lo 2400 ± 480

Hi 6000 ± 1200

630 Lo 2520 ± 504

Hi 6300 ± 1260

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 630A Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF630-UEP 300 630 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 630 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 630 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 300 600-750-900-1050-1200- 1500-1800-2100-2400- 3000 350 700-875-1050-1225- 1400-1750-2100-2450- 2800-3500 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 630 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current ~ ~ ~

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 800A Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF800-HEP 400 800 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 450 900-1150-1350-1575- 1800-2250-2700-3150- 3600-4500 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 700 1400-1750-2100-2450- 2800-3500-4200-4900- 5600-6300 800 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current

4 In 12 In

Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 450 900-1150-1350-1575- 1800-2250-2700-3150- 3600-4500 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 700 1400-1750-2100-2450- 2800-3500-4200-4900- 5600-6300 800 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 450 900-1150-1350-1575- 1800-2250-2700-3150- 3600-4500 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 700 1400-1750-2100-2450- 2800-3500-4200-4900- 5600-6300 800 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current Adjustable ampere rating, instantaneous pick up current Instantaneous pick up current Variation is within ±15% of setting current 2 to 10 Ir ~ ~ ~

(Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) Rated insulation voltage Ui (V) AC Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 800A Rated current In (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics NF800-UEP 400 800 adjustable Electronic trip relay Adjustable ampere rating Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 450 900-1150-1350-1575- 1800-2250-2700-3150- 3600-4500 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 700 1400-1750-2100-2450- 2800-3500-4200-4900- 5600-6300 800 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current Adjustable long time delay operating time, short time delay pick up and instantaneous Short time delay pick up current Variation is within ±15% of setting current 2 to 10 Ir 400 800-1000-1200-1400- 1600-2000-2400-2800- 3200-4000 450 900-1150-1350-1575- 1800-2250-2700-3150- 3600-4500 500 1000-1250-1500-1750- 2000-2500-3000-3500- 4000-5000 600 1200-1500-1800-2100- 2400-3000-3600-4200- 4800-6000 700 1400-1750-2100-2450- 2800-3500-4200-4900- 5600-6300 800 1260-1575-1890-2205- 2520-3150-3780-4410- 5040-6300 Instantaneous pick up current Variation is within ±15% of setting current ~ ~

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only (Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Solid-state Adjustable ampere rating Adjustable short time delay pick up Fixed instantaneous pick up Short time delay pick up current Variation is within ±10% of the setting current 5-7.5-10 In 500 2500-3750-5000 600 3000-4500-6000 700 3500-5250-7000 800 4000-6000-8000 900 4500-6750-9000 1000 5000-7500-10000 Instantaneous pick up current 20000 NF1000-SS 1000 500-600-700-800-900-1000 690 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 500 2500-3750-5000 1500-2250-3000 1000-1500-2000 600 3000-4500-6000 1800-2700-3600 1200-1800-2400 700 3500-5250-7000 2100-3150-4200 1400-2100-2800 800 4000-6000-8000 2400-3600-4800 1600-2400-3200 900 4500-6750-9000 2700-4050-5400 1800-2700-3600 1000 5000-7500-10000 3000-4500-6000 2000-3000-4000 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 500 1500-2250-3000 1000-1500-2000 600 1800-2700-3600 1200-1800-2400 700 2100-3150-4200 1400-2100-2800 800 2400-3600-4800 1600-2400-3200 900 2700-4050-5400 1800-2700-3600 1000 3000-4500-6000 2000-3000-4000 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 5-7.5-10 In 500 2500-3750-5000 600 3000-4500-6000 700 3500-5250-7000 800 4000-6000-8000 900 4500-6750-9000 1000 5000-7500-10000 +4000 –2000

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only (Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Solid-state Adjustable ampere rating Adjustable short time delay pick up Fixed instantaneous pick up Short time delay pick up current Variation is within ±10% of the setting current 5-7.5-10 In 600 3000-4500-6000 700 3500-5250-7000 800 4000-6000-8000 1000 5000-7500-10000 1200 6000-9000-12000 1250 6250-9375-12500 Instantaneous pick up current 20000 NF1250-SS 1250 600-700-800-1000-1200-1250 690 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 600 3000-4500-6000 1800-2700-3600 1200-1800-2400 700 3500-5250-7000 2100-3150-4200 1400-2100-2800 800 4000-6000-8000 2400-3600-4800 1600-2400-3200 1000 5000-7500-10000 3000-4500-6000 2000-3000-4000 1200 6000-9000-12000 3600-5400-7200 2400-3600-4800 1250 6250-9375-12500 3750-5625-7500 2500-3750-5000 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 600 1800-2700-3600 1200-1800-2400 700 2100-3150-4200 1400-2100-2800 800 2400-3600-4800 1600-2400-3200 1000 3000-4500-6000 2000-3000-4000 1200 3600-5400-7200 2400-3600-4800 1250 3750-5625-7500 2500-3750-5000 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 5-7.5-10 In 600 3000-4500-6000 700 3500-5250-7000 800 4000-6000-8000 1000 5000-7500-10000 1200 6000-9000-12000 1250 6250-9375-12500 +4000 –2000

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only (Inst trip only) Generator 690V 500V 440V 400V 240V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Solid-state Adjustable ampere rating Adjustable short time delay pick up Fixed instantaneous pick up Short time delay pick up current Variation is within ±10% of the setting current 5-7.5-10 In 600 3000-4500-6000 700 3500-5250-7000 800 4000-6000-8000 1000 5000-7500-10000 1200 6000-9000-12000 1250 6250-9375-12500 Instantaneous pick up current 20000 NF1250-UR 1250 600-700-800-1000-1200-1250 690 +4000 –2000

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only (Inst trip only) Generator 690V 500V 440V 400V 230V Frame (A) AC Breaking capacity (kA rms) IEC60947-2 Icu/Ics Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) Solid-state Adjustable ampere rating Adjustable short time delay pick up Fixed instantaneous pick up Short time delay pick up current Variation is within ±10% of the setting current 3-4.5-6 In 800 2400-3600-4800 1000 3000-4500-6000 1200 3600-5400-7200 1400 4200-6300-8400 1500 4500-6750-9000 1600 4800-7200-9600 Instantaneous pick up current 20000 NF1600-SS 1600 800-1000-1200-1400-1500-1600 690 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 800 2400-3600-4800 1600-2400-3200 1000 3000-4500-6000 2000-3000-4000 1200 3600-5400-7200 2400-3600-4800 1400 4200-6300-8400 2800-4200-5600 1500 4500-6750-9000 3000-4500-6000 1600 4800-7200-9600 3200-4800-6400 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 800 2400-3600-4800 1600-2400-3200 1000 3000-4500-6000 2000-3000-4000 1200 3600-5400-7200 2400-3600-4800 1400 4200-6300-8400 2800-4200-5600 1500 4500-6750-9000 3000-4500-6000 1600 4800-7200-9600 3200-4800-6400 Solid-state Adjustable ampere rating Adjustable instantaneous pick up Variation is within ±10% of the setting current 3-4.5-6 In 800 2400-3600-4800 1000 3000-4500-6000 1200 3600-5400-7200 1400 4200-6300-8400 1500 4500-6750-9000 1600 4800-7200-9600 +4000 –2000

Rated current In (A) Rated insulation voltage Ui (V) AC Low-inst Standard Mag-Only Generator 600V 500V 415V 380V 240V Frame (A) AC Interrupting capacity (kA rms) IEC157-1 P1/P2 Number of poles Automatic tripping device Rating (A) and Inst. (A) Automatic tripping device Rating (A) and Inst. (A) Number of poles Number of poles Automatic tripping device Rating (A) and Inst. (A) Number of poles Automatic tripping device Rating (A) and Inst. (A) 2000 Thermal, adjustable-magnetic Fixed ampere rating and adjustable instantaneous Adjustable-magnetic Fixed ampere rating and adjustable instantaneous NF2000-S NFE2000-S 1800, 2000 600 h 1200-1400-1600-1800-2000 600 Solid-state Adjustable ampere rating, adjustable short time delay pick up and fixed instantaneous pick up 2500 NF2500-S 2500 600 h Thermal, adjustable-magnetic Fixed ampere rating and adjustable instantaneous Adjustable-magnetic Fixed ampere rating and adjustable instantaneous Variation is within ±10% of the Hi setting current Lo 1 2 3 1800 3200-4000-4800-5600-

45 H i

Variation is within ±10% of the Hi setting current Lo 1 2 3 2500 4000-5000-6000-7000- Variation is within ±10% of the Hi setting current Lo 1 2 3 2000 3200-4000-4800-5600- Variation is within ±10% of the Hi setting current Lo 1 2 3 2500 4000-5000-6000-7000- Short time delay pick up current Variation is within ±10% of the setting current 3-4.5-6 In 1200 3600-5400-7200 1400 4200-6300-8400 1600 4800-7200-9600 1800 5400-8100-10800 2000 6000-9000-12000 Instantaneous pick up current 30000 ± 3000

Rated current In (A) Rated insulation voltage Ui (V) AC Standard 600V 500V 415V 380V 240V Frame (A) AC Interrupting capacity (kA rms) IEC157-1 P1/P2 Number of poles Automatic tripping device Rating (A) and Inst. (A) 3000 (3200) NF3200-S 2800, 3000, 3200 600 h Thermal, adjustable-magnetic Fixed ampere rating and adjustable instantaneous Low-inst Number of poles Automatic tripping device Rating (A) and Inst. (A) Generator Automatic tripping device Rating (A) and Inst. (A) Number of poles – Mag-Only Number of poles Automatic tripping device Rating (A) and Inst. (A) NFE3000-S 1800-2000-2500-3000 600 Adjustable-magnetic Fixed ampere rating and adjustable instantaneous Short time delay pick up current Variation is within ±10% of the setting current 2-3-4 In 1800 3600-5400-7200 2000 4000-6000-8000 2500 5000-7500-10000 3000 6000-9000-12000 Instantaneous pick up current 30000 ± 3000 Solid-state Adjustable ampere rating, adjustable short time delay pick up and fixed instantaneous pick up Variation is within ±10% of the Hi setting current Lo 1 2 3 4 5 H i 2800 5000-6600-8300-10000-11600-13300-15000 3000 5000-6600-8300-10000-11600-13300-15000 3200 5000-6600-8300-10000-11600-13300-15000 Variation is within ±10% of the Hi setting current Lo 1 2 3 4 5 H i 3000 5000-6600-8300-10000-11600-13300-15000 3200 5000-6600-8300-10000-11600-13300-15000 h Specifty frequency

Rated current In (A) Rated insulation voltage Ui (V) AC Standard 600V 500V 415V 380V 240V Frame (A) AC Interrupting capacity (kA rms) IEC157-1 P1/P2 Number of poles Automatic tripping device Rating (A) and Inst. (A) 4000 NF4000-S 3600, 4000 600 h Thermal, adjustable-magnetic Fixed ampere rating and adjustable instantaneous Low-inst Number of poles Automatic tripping device Rating (A) and Inst. (A) Generator Automatic tripping device Rating (A) and Inst. (A) Number of poles – Mag-Only Number of poles Automatic tripping device Rating (A) and Inst. (A) NFE4000-S 2500-3000-3500-4000 600 Adjustable-magnetic Fixed ampere rating and adjustable instantaneous Variation is within ±10% of the Hi setting current Lo 1 2 3 H i 4000 8300-10000-11600-13300-15000 Solid-state Adjustable ampere rating, adjustable short time delay pick up and fixed instantaneous pick up Variation is within ±10% of the Hi setting current Lo 1 2 3 H i 3600 8300-10000-11600-13300-15000 4000 8300-10000-11600-13300-15000 h Specifty frequency Short time delay pick up current Variation is within ±10% of the setting current 2-3-4 In 2500 5000-7500-10000 3000 6000-9000-12000 3500 7000-10500-14000 4000 8000-12000-16000 Instantaneous pick up current 35000 ± 3500

1. PROTECTIVE CO-ORDINATION

6.1 General

The primary purpose of a circuit protection system is to prevent damage to series connected equipment and to minimise the area and duration of power loss. The first consideration is whether an air circuit breaker or moul- ded case circuit breaker is most suitable. The next is the type of system to be used. The three major types are: Fully Rated, Selective and Cascade Back-Up. Fully Rated This system is highly reliable, as all of the breakers are rated for the maximum fault level at the point of their installation. Discrimination (selective interruption) can be incorporated in some cases. The disadvantage is that high cost branch breakers may be necessary. Selective-Interruption(Discrimination) Selective Interruption requires that in the event of a fault, only the device directly before the fault will trip, and that other branch circuits of the same or higher level will not be affected. The range of selective Interruption of the main breaker varies considerably depending on the breaker used. Cascade Back-Up Protection This is an economical approach to the use of circuit breakers, whereby only the main (upstream) breaker has adequate interrupting capacity for the maximum available fault current. The mccb’s downstream cannot handle this maximum fault current and rely on the opening of the upstream breaker for protection. The advantage of the cascade back-up approach is that it facilitates the use of low cost, low fault level breakers downstream, thereby offering savings in both the cost and size of equipment. As Mitsubishi mccb’s have a very considerable current limiting effect, they can be used to provide this ‘cascade back-up’ protection for downstream circuit breakers.

6.2 Interrupting Capacity Consideration

50·60 100 400 630 800 30 or less 50~75 100 150~300 20 or less 30~50 75 100~150 200~500 – 2.5 5 10 15 25 30 35 50 85 100 125 170 200 NF30- CS NF50-CP NF60-CP NF50-HP, NF60-HP NF50-HRP NF100-CP NF250-CP NF400-CP NF630-CP NF800-CEP NF160-SP NF250-SP NF250-SEP NF400-SP, NF400-SEP NF100-HP NF100-HEP NF160-HP NF250-HP NF250-HEP NF100-UP NF225-UP 30 or less 50~100 150~300 500~1000 1500~2000 2500~5000 400 50·60 630 800 2.5 12585655035307.5 10 15 18 25 Table 2 440VAC 100 NF250-CP NF400-CP NF1000-SS~NF1600-SS, NF2000-S~NF4000-S NFE2000-S, NFE3000-S, NFE4000-S NF800-SEP NF800-REP NF225-UP NF630-REPNF630-CP NF800-CEP NF225-RP 200 NF30- SP 3ph trans. capacity (kVA) Interrupting capacity (kA)(sym) 1ph trans. capacity (kVA) NF100-SP NF100-SEP NF1000-SS~NF1600-SS, NF2000-S~NF4000-S NFE2000-S, NFE3000-S, NFE4000-S NF800-SEP NF800-UEP NF630-UEP NF400-UEP 2000~3000500~1500 160 250 Trans. capacity (kVA) Interrupting capacity (kA)(sym) NF50-CP NF60-CP NF50-HP NF60-HP NF50-HRP NF630-SP, NF630-SEP NF100-CP NF160-HP NF250-HP NF250-HEP NF160-SP NF250-SP NF250-SEP NF100-RPNF100-HP NF100-HEP NF100-SP NF100-SEP Frame (A) 1000 4000 160 250 1000 4000 NF1250- UR NF100- RP NF225- RP NF1250- UR NF630-SP, NF630-SEP Frame (A) NF100-UP C Series S Series 1.5 NF30-SPNF30-CS NF400-SP, NF400-SEP NF400-REP NF400 -HEP NF400 -REP NF630 -HEP NF630 -REP NF800 -HEP NF800 -REP NF800 -HEP NF630 -HEP NF400 -HEP NF800-UEP NF630-UEP NF400-UEP

<How to see the table> Example 1 All rated current of branch breaker, type NF30-SP can fully discriminate with all rated current of main breaker, type NF400-SEP up to the fault levels, 5kA that is the interrupting capacity of type NF30-SP. Example 3 Some rated current of branch breaker, type NF100-CP having low-inst. trip can discriminate with some rated current of main breaker, type NF400-SEP as shown by a deep color up to the fault levels, 7.5kA. 6 denotes that the short time delay pick up current of the main breaker, type NF400-SEP is set at 6 5 Ir notch or higher. Example 2 Some rated current of branch breaker, type NF160- SP can discriminate with some rated current of main breaker, type NF630-SEP as shown by a deep color up up to the fault levels, 10kA. 6 denotes that the short-time delay pick up current of the main breaker, type NF630-SEP is set at 6 5 Ir notch or higher.

6.3 Selective-Interruption (Discrimination)

6.3.1 Selective-Interruption Combination

Following tables show combinations of main-circuit selective coordination breakers and branch breakers and the available selective tripping current at the set- ting points at the branch-circuits. Icu (kA) Rated current (A) Type Icu(kA) NF400-SEP 200 225 250 300 350 400 Main Breaker Selective limit current NF30-SP Type Branch Breaker Short-circuit point Continuous supply Healthy circuit Main breaker Branch breaker Type 125 150 160 Icu (kA) Rated current (A) Type Icu(kA) NF630-SEP 300 350 400 500 600 630 Main Breaker Selective limit current 25NF160-SP Branch Breaker 3.5 Type Branch Breaker NF100-CP Icu (kA) Rated current (A) Type Icu(kA) NF400-SEP 200 225 250 300 350 400 Main Breaker 100 7.5 Selective limit current 440VAC 440VAC 3.5 3.5 2.5 3.5 Selection Conditions 1. The main breaker rated current, STD operating time and INST pickup current are to be set to the maxi- mum values. 2. When selecting the over-current range, also check the conformity using the other characteristic curves. Main breaker STD pick up current. Set up STD operating time in the maximum value. Set up inst pick up current in the maximum value. Branch breaker 230VAC

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP 50 50 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 Icu: Rated breaking capacity Selective limit current BH-D6 Type B 6 2.5 3.5 2.5 3 2.5 0.8 1.6 3.5 3.5 2.5 2.5 2.5 3.5 2.5 Selective limit current BH-D6 Type C 6 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3 2.5 0.8 1.6 10 7 3.5 3.5 2.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3 2.5 2.5 Selective limit current BH-D10 Type B 10 2.5 3.5 2.5 3 2.5 0.8 1.6 3.5 3.5 2.5 2.5 2.5 3.5 2.5 Selective limit current BH-D10 Type C 10 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3 2.5 0.8 1.6 10 7 3.5 3.5 2.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3 2.5 2.5

I cu(kA) Type Main Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 50 50 85 85 Type I cu(kA) 125 150 175 200 225 250 30 40 50 60 75 100 300 350 400 500 600 630 200 225 250 300 350 400 Selective limit current NF30-SP 5 2.5 3.5 2.5 2.5 3.5 0.8 1.6 3 2.5 3.5 5 5 Selective limit current NF50-CP 5 2.5 3.5 2.5 2.5 3.5 0.8 1.6 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 2.5 Selective limit current NF50-HP 25 2.5 3.5 2.5 2.5 3.5 0.8 1.6 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 2.5 10 20 Selective limit current NF60-CP 60 10 7 1.6 654 3.5 33 3.5 3.5 3 3 2.5 2.5 Selective limit current NF60-HP 60 10 7 1.6 654 3.5 33 3.5 3.5 3 3 2.5 2.5 Selective limit current NF100-CP 25 50 100 3.5 3.5 3.5 2.5 3.5 7.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.5 2.5 Selective limit current NF100-SP 50 100 2.5 2.5 2.5 3.5 2.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.5 2.5 Selective limit current NF100-SP T/A 15 2020 100 2.5 2.5 3.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 3.5 2.5 2.5 3.5 7.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 Selective limit current NF100-HP 100 100 2.5 2.5 2.5 3.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.5 2.5 Selective limit current NF100-HP T/A 100 15 2020 100 2.5 2.5 3.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 3.5 2.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 I cu: Rated breaking capacity

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 50 85 125 125 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 125 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 55 555 Selective limit current 55 555 Selective limit current 20 20 25 25 25 Selective limit current 55 5 5 5 Selective limit current 20 20 25 25 25 100 Selective limit current 2.5 2.5 3.5 2.5 3 2.5 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 15 2525 25 Selective limit current 100 2.5 2.5 3.5 2.5 3 2.5 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 15 50 50 50 Selective limit current 20 25 15 20 25 40 40 63 63 80 80 100 2.5 3.5 2.5 3 2.5 2.5 2.5 3.5 2.5 2.5 2.5 15 50 50 50 Selective limit current 100 2.5 2.5 3.5 2.5 3 2.5 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 25 100 100 100 Selective limit current 20 25 15 20 25 40 40 63 63 80 80 100 2.5 3.5 2.5 3 2.5 2.5 2.5 3.5 2.5 2.5 2.5 25 100 100 100 Branch Breaker Main Breaker Type Icu(kA) NF30-SP 5 NF50-CP 5 NF50-HP 25 NF60-CP 5 NF60-HP 25 NF100-CP 25 NF100-SP 50 NF100-SP T/A 50 NF100-HP 100 NF100-HP T/A 100 Icu: Rated breaking capacity

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 50 50 85 85 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 300 350 400 500 600 630200 225 250 300 350 400 Selective limit current NF100-SEP 50 100 2.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 3.5 2.5 7.5 2.5 3.5 2.5 3 3 2.5 Selective limit current NF100-HEP 100 100 2.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3 3 2.5 Selective limit current NF160-SP 50 125 150 160 10 10 8 3.5 10 10 8 6.4 3.5 Selective limit current NF160-SP T/A 50 100 125 125 160 3.5 6.4 2.5 2.5 Selective limit current NF160-HP 100 125 150 160 10 10 8 3.5 10 10 8 6.4 3.5 Icu: Rated breaking capacity Selective limit current NF160-HP T/A 100 100 125 125 160 3.5 6.4 2.5 2.5 Selective limit current NF250-CP 30 125 150 175 200 225 250 10 10 8 6.4 3.5 7.5 Selective limit current NF250-CP T/A 30 100 125 125 160 150 200 200 250 6.4 2.5 2.5 2.5 2.5 3.5 7.5 Selective limit current NF250-SP 50 125 150 175 200 225 250 10 10 8 6.4 3.5 Selective limit current NF250-SP T/A 50 100 125 125 160 150 200 200 250 6.4 2.5 2.5 2.5 2.5 3.5 Selective limit current NF250-HP 100 125 150 175 200 225 250 10 10 8 6.4 3.5 3.5 Selective limit current NF250-HP T/A 100 100 125 125 160 150 200 200 250 6.4 2.5 2.5 2.5 2.5 3.5

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 50 85 125 125 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 125 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 100 3 2.5 2.5 3 2.5 2.5 18 50 50 50 Selective limit current 100 3 2.5 2.5 3 2.5 2.5 35 100 100 100 Selective limit current 125 150 160 3.5 3.5 2.5 3.5 3.5 2.5 7.5 7.5 4.5 4.5 5050 Selective limit current 100 125 125 160 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 2.5 2.5 10 50 50 50 Selective limit current 125 150 160 3.5 3.5 2.5 3.5 3.5 2.5 7.5 7.5 4.5 4.5 5050 Selective limit current 100 125 125 160 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 2.5 2.5 10 50 50 50 Selective limit current 125 150 175 200 225 250 3.5 2.5 3.5 3.5 7.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 7.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 7.5 2525 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 2.5 3.5 3.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 10 5050 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 2.5 3.5 3.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 10 5050 4.5 4.5 4.5 Branch Breaker Main Breaker Type Icu(kA) NF100-SEP 50 NF100-HEP 100 NF160-SP 50 NF160-SP T/A 50 NF160-HP 100 NF160-HP T/A 100 NF250-CP 30 NF250-CP T/A 30 NF250-SP 50 NF250-SP T/A 50 NF250-HP 100 NF250-HP T/A 100 Icu: Rated breaking capacity

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 50 50 85 85 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 300 350 400 500 600 630 200 225 250 300 350 400 Selective limit current NF250-SEP 50 125 150 175 200 225 250 3.5 6.4 3.5 3.5 2.5 3.5 2.5 3.5 Selective limit current NF250-HEP 100 125 150 175 200 225 250 3.5 6.4 3.5 3.5 2.5 3.5 2.5 3.5 Selective limit current NF400-CP 50 250 300 350 400 10 8 9.5 Selective limit current NF400-SP 85 250 300 350 400 10 8 9.5 Selective limit current NF400-SEP 85 200 225 250 300 350 400 3.5 3.5 9.5 Selective limit current NF400-HEP 100 200 225 250 300 350 400 3.5 3.5 9.5 Selective limit current NF630-CP 50 500 600 630 Selective limit current NF630-SP 50 500 600 630 Selective limit current NF630-SEP 85 300 350 400 500 600 630 Selective limit current NF630-HEP 100 300 350 400 500 600 630 Icu: Rated breaking capacity

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 50 85 125 125 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 125 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 125 150 175 200 225 250 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 250 300 350 400 Selective limit current 3.5 3.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 250 300 350 400 Selective limit current 10 8 10 8 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 6 6 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Selective limit current 200 225 250 300 350 400 3.5 3.5 3.5 3.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 Selective limit current 200 225 250 300 350 400 3.5 3.5 3.5 3.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 Selective limit current 500 600 630 10 8 9.6 10 8 9.6 4.5 4.5 Selective limit current 500 600 630 9.6 9.6 Selective limit current 300 350 400 500 600 630 9.6 9.6 Selective limit current 300 350 400 500 600 630 9.6 9.6 Branch Breaker Main Breaker Type Icu(kA) NF250-SEP 50 NF250-HEP 100 NF400-CP 50 NF400-SP 85 NF400-SEP 85 NF400-HEP 100 NF630-CP 50 NF630-SP 50 NF630-SEP 85 NF630-HEP 100 Icu: Rated breaking capacity

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 30 50 50 50 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 300 350 400 500 600 630200 225 250 300 350 400 Selective limit current NF30-SP 5 2.5 3.5 2.5 2.5 3.5 0.8 1.6 3 2.5 3.5 2.5 2.5 Selective limit current NF50-CP 5 2.5 3.5 2.5 2.5 3.5 0.8 1.6 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 2.5 2.5 2.5 Selective limit current NF50-HP 10 2.5 3.5 2.5 2.5 3.5 0.8 1.6 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 2.5 7.5 10 Selective limit current NF60-CP 5 60 10 7 1.6 654 3.5 33 3.5 3.5 3 3 2.5 2.5 2.5 2.5 Selective limit current NF60-HP 10 60 10 7 1.6 654 3.5 33 3.5 3.5 3 3 2.5 7.5 2.5 Selective limit current NF100-CP 10 50 100 3.5 3.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.5 2.5 Selective limit current NF100-SP 30 100 2.5 2.5 2.5 3.5 2.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.52.5 Selective limit current NF100-SP T/A 30 15 20 20 25 25 40 40 63 63 80 80 100 2.5 2.5 3.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 3.5 2.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 Selective limit current NF100-HP 50 100 2.5 2.5 2.5 3.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 2.5 2.5 2.5 3.5 2.5 2.5 3 2.52.5 Selective limit current NF100-HP T/A 50 15 20 20 25 25 40 40 63 63 80 80 100 2.5 2.5 3.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 3.5 2.5 2.5 3.5 7.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 Icu: Rated breaking capacity

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 36 42 85 85 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 2.5 2.5 5 5 5 Selective limit current 2.5 2.5 5 5 5 Selective limit current 10 10 10 10 10 Selective limit current 2.5 2.5 5 5 5 Selective limit current 10 10 10 10 10 100 Selective limit current 2.5 3.5 2.5 3 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 10 1010 10 Selective limit current 100 2.5 3.5 2.5 3 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 10 22 22 22 Selective limit current 15 20 20 25 25 40 40 63 63 80 80 100 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 10 22 22 22 Selective limit current 100 2.5 3.5 2.5 3 2.5 2.5 2.5 3.5 2.5 3 2.5 2.5 18 50 50 50 Selective limit current 15 20 20 25 25 40 40 63 63 80 80 100 2.5 3.5 2.5 3 2.5 2.5 3.5 2.5 3 2.5 18 50 50 50 Branch Breaker Main Breaker Type Icu(kA) NF30-SP 5 NF50-CP 5 NF50-HP 10 NF60-CP 5 NF60-HP 10 NF100-CP 10 NF100-SP 30 NF100-SP T/A 30 NF100-HP 50 NF100-HP T/A 50 Icu: Rated breaking capacity

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 30 50 50 50 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 300 350 400 500 600 630200 225 250 300 350 400 Selective limit current NF100-SEP 25 100 2.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 3.5 2.5 2.5 3.5 2.5 3 3 2.5 Selective limit current NF100-HEP 50 100 2.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 2.5 3.5 2.5 2.5 2.5 3.5 2.5 3.5 2.5 7.5 2.5 3.5 2.5 3 3 2.5 Selective limit current NF160-SP 25 125 150 160 10 10 8 3.5 3.5 Selective limit current NF160-SP T/A 25 100 125 125 160 3.5 2.5 2.5 2.5 2.5 Selective limit current NF160-HP 50 125 150 160 10 10 8 3.5 3.5 Icu: Rated breaking capacity Selective limit current NF160-HP T/A 50 100 125 125 160 3.5 2.5 2.5 2.5 2.5 Selective limit current NF250-CP 15 125 150 175 200 225 250 3.5 7.5 Selective limit current NF250-CP T/A 15 100 125 125 160 150 200 200 250 2.5 2.5 2.5 2.5 3.5 7.5 Selective limit current NF250-SP 25 125 150 175 200 225 250 3.5 Selective limit current NF250-SP T/A 25 100 125 125 160 150 200 200 250 2.5 2.5 2.5 2.5 3.5 Selective limit current NF250-HP 50 125 150 175 200 225 250 3.5 Selective limit current NF250-HP T/A 50 100 125 125 160 150 200 200 250 2.5 2.5 2.5 2.5 3.5

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 36 42 85 85 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 100 3 2.5 2.5 3 2.5 2.5 10 22 22 22 Selective limit current 100 3 2.5 2.5 3 2.5 2.5 18 50 50 50 Selective limit current 125 150 160 3.5 3.5 2.5 3.5 3.5 2.5 7.5 7.5 4.5 4.5 2222 Selective limit current 100 125 125 160 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 10 22 22 22 Selective limit current 125 150 160 3.5 3.5 3.5 2.5 3.5 3.5 3.5 2.5 7.5 7.5 4.5 4.5 2222 Selective limit current 100 125 125 160 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 2.5 2.5 2.5 2.5 10 22 22 22 Selective limit current 125 150 175 200 225 250 3.5 2.5 3.5 3.5 7.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 7.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 7.5 1515 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 3.5 2.5 3.5 3.5 3.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 10 2222 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 3.5 2.5 3.5 3.5 3.5 3.5 2.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 100 125 125 160 150 200 200 250 Selective limit current 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 3.5 3.5 2.5 2.5 2.5 2.5 3.5 3.5 10 2222 4.5 4.5 4.5 Branch Breaker Main Breaker Type Icu(kA) NF100-SEP 25 NF100-HEP 50 NF160-SP 25 NF160-SP T/A 25 NF160-HP 50 NF160-HP T/A 50 NF250-CP 15 NF250-CP T/A 15 NF250-SP 25 NF250-SP T/A 25 NF250-HP 50 NF250-HP T/A 50 Icu: Rated breaking capacity

Branch Breaker Icu(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) NF100-SEP NF250-SEP NF400-SEP NF630-SEP 50 50 85 85 Type Icu(kA) 125 150 175 200 225 25030 40 50 60 75 100 300 350 400 500 600 630 200 225 250 300 350 400 Selective limit current NF250-SEP 25 125 150 175 200 225 250 3.5 3.5 2.5 3.5 2.5 2.5 3.5 Selective limit current NF250-HEP 50 125 150 175 200 225 250 3.5 3.5 2.5 3.5 2.5 2.5 3.5 Selective limit current NF400-CP 25 250 300 350 400 10 8 9.5 Selective limit current NF400-SP 42 250 300 350 400 10 8 9.5 Selective limit current NF400-SEP 42 200 225 250 300 350 400 3.5 3.5 9.5 Selective limit current NF400-HEP 65 200 225 250 300 350 400 3.5 3.5 9.5 Selective limit current NF630-CP 36 500 600 630 Selective limit current NF630-SP 42 500 600 630 Selective limit current NF630-SEP 42 300 350 400 500 600 630 Selective limit current NF630-HEP 65 300 350 400 500 600 630 Icu: Rated breaking capacity

Icu(kA) Type Rated current (A) NF800-CEP NF800-SEP NF1000-SS NF1250-SS 36 42 85 85 400 450 500 600 700 800400 450 500 600 700 800 600 700 800 1000 1200 1250 NF1600-SS 800 1000 1200 1400 1500 1600500 600 700 800 900 1000 Selective limit current 125 150 175 200 225 250 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Selective limit current 125 150 175 200 225 250 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 3.5 3.5 2.5 3.5 2.5 3.5 2.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 250 300 350 400 Selective limit current 3.5 3.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 250 300 350 400 Selective limit current 10 8 10 8 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Selective limit current 200 225 250 300 350 400 3.5 3.5 3.5 3.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 Selective limit current 200 225 250 300 350 400 3.5 3.5 3.5 3.5 3.5 3.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 Selective limit current 500 600 630 10 8 10 8 4.5 4.5 Selective limit current 500 600 630 Selective limit current 300 350 400 500 600 630 Selective limit current 300 350 400 500 600 630 Branch Breaker Main Breaker Type Icu(kA) NF250-SEP 25 NF250-HEP 50 NF400-CP 25 NF400-SP 42 NF400-SEP 42 NF400-HEP 65 NF630-CP 36 NF630-SP 42 NF630-SEP 42 NF630-HEP 65 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600625 750 875 1000 1125 1250 Selective limit current NF100-CP 25 60 100 333 433 3 Selective limit current NF100-SP 50 60 100 333 433 3 Selective limit current T/A 50 63 80 80 100 Selective limit current NF100-HP 100 60 100 333 433 3 Selective limit current T/A 100 63 80 80 100 Selective limit current NF100-SEP 50 60 100 333333 Selective limit current NF100-HEP 100 60 100 333333 Selective limit current NF160-SP 50 125 150 160 Selective limit current T/A 50 100 125 125 160 Selective limit current NF160-HP 100 125 150 160 Selective limit current T/A 100 100 125 125 160 Selective limit current NF250-CP 30 125 150 175 200 225 250 Selective limit current NF250-CP T/A 30 100 125 125 160 150 200 200 250 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 40001600 1920 2240 2560 28803200 Selective limit current 100 Selective limit current 100 Selective limit current 63 80 80 100 Selective limit current 100 Selective limit current 63 80 80 100 Selective limit current 100 Selective limit current 100 Selective limit current 125 150 160 Selective limit current 100 125 125 160 Selective limit current 125 150 160 Selective limit current 100 125 125 160 Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Branch Breaker Main Breaker Type Icu(kA) NF100-CP 25 NF100-SP 50 NF100-SP T/A 50 NF100-HP 100 NF100-HP T/A 100 NF100-SEP 50 NF100-HEP 100 NF160-SP 50 NF160-SP T/A 50 NF160-HP 100 NF160-HP T/A 100 NF250-CP 30 NF250-CP T/A 30 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600625 750 875 1000 1125 1250 Selective limit current NF250-SP 50 125 150 175 200 225 250 Selective limit current NF250-SP T/A 50 100 125 125 160 150 200 200 250 Selective limit current NF250-HP 100 125 150 175 200 225 250 Selective limit current NF250-HP T/A 100 100 125 125 160 150 200 200 250 Selective limit current NF250-SEP 50 125 150 175 200 225 250 Selective limit current NF250-HEP 100 125 150 175 200 225 250 Selective limit current NF400-CP 50 250 300 350 400 Selective limit current NF400-SP 85 250 300 350 400 Selective limit current NF400-SEP 85 200 225 250 300 350 400 Selective limit current NF400-HEP 100 200 225 250 300 350 400 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 40001600 1920 2240 2560 28803200 Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Selective limit current 125 150 175 200 225 250 Selective limit current 125 150 175 200 225 250 250 300 350 400 Selective limit current 333 250 300 350 400 Selective limit current 333 Selective limit current 200 225 250 300 350 400 Selective limit current 200 225 250 300 350 400 Branch Breaker Main Breaker Type Icu(kA) NF250-SP 50 NF250-SP T/A 50 NF250-HP 100 NF250-HP T/A 100 NF250-SEP 50 NF250-HEP 100 NF400-CP 50 NF400-SP 85 NF400-SEP 85 NF400-HEP 100 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 230VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600 625 750 875 1000 1125 1250 Selective limit current NF630-CP 50 500 600 630 Selective limit current NF630-SP 50 500 600 630 88 1 0 88 Selective limit current NF630-SEP 85 300 350 400 500 600 630 Selective limit current NF630-HEP 100 300 350 400 500 600 630 Selective limit current NF800-CEP 50 400 450 500 600 700 800 Selective limit current NF800-SEP 85 400 450 500 600 700 800 Selective limit current NF800-HEP 100 400 450 500 600 700 800 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 4000 1600 1920 2240 2560 28803200 Selective limit current 500 600 630 Selective limit current 500 600 630 Selective limit current 300 350 400 500 600 630 Selective limit current 300 350 400 500 600 630 Selective limit current 400 450 500 600 700 800 Selective limit current 400 450 500 600 700 800 Selective limit current 400 450 500 600 700 800 Branch Breaker Main Breaker Type Icu(kA) NF630-CP 50 NF630-SP 50 NF630-SEP 85 NF630-HEP 100 NF800-CEP 50 NF800-SEP 85 NF800-HEP 100 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600625 750 875 1000 1125 1250 Selective limit current NF100-CP 10 60 100 333 433 3 Selective limit current NF100-SP 30 60 100 333 433 3 Selective limit current T/A 30 63 80 80 100 Selective limit current NF100-HP 50 60 100 333 433 3 Selective limit current T/A 50 63 80 80 100 Selective limit current NF100-SEP 25 60 100 333333 Selective limit current NF100-HEP 50 60 100 333333 Selective limit current NF160-SP 25 125 150 160 Selective limit current T/A 25 100 125 125 160 Selective limit current NF160-HP 50 125 150 160 Selective limit current T/A 50 100 125 125 160 Selective limit current NC250-CP 15 125 150 175 200 225 250 Selective limit current NF250-CP T/A 15 100 125 125 160 150 200 200 250 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 40001600 1920 2240 2560 28803200 Selective limit current 100 Selective limit current 100 Selective limit current 63 80 80 100 Selective limit current 100 Selective limit current 63 80 80 100 Selective limit current 100 Selective limit current 100 Selective limit current 125 150 160 Selective limit current 100 125 125 160 Selective limit current 125 150 160 Selective limit current 100 125 125 160 Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Branch Breaker Main Breaker Type Icu(kA) NF100-CP 10 NF100-SP 30 NF100-SP T/A 30 NF100-HP 50 NF100-HP T/A 50 NF100-SEP 25 NF100-HEP 50 NF160-SP 25 NF160-SP T/A 25 NF160-HP 50 NF160-HP T/A 50 NC250-CP 15 NF250-CP T/A 15 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600625 750 875 1000 1125 1250 Selective limit current NF250-SP 25 125 150 175 200 225 250 Selective limit current NF250-SP T/A 25 100 125 125 160 150 200 200 250 Selective limit current NF250-HP 50 125 150 175 200 225 250 Selective limit current NF250-HP T/A 50 100 125 125 160 150 200 200 250 Selective limit current NF250-SEP 25 125 150 175 200 225 250 Selective limit current NF250-HEP 50 125 150 175 200 225 250 Selective limit current NF400-CP 25 250 300 350 400 Selective limit current NF400-SP 42 250 300 350 400 Selective limit current NF400-SEP 42 200 225 250 300 350 400 Selective limit current NF400-HEP 65 200 225 250 300 350 400 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 40001600 1920 2240 2560 28803200 Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Selective limit current 125 150 175 200 225 250 100 125 125 160 150 200 200 250 Selective limit current Selective limit current 125 150 175 200 225 250 Selective limit current 125 150 175 200 225 250 250 300 350 400 Selective limit current 333 250 300 350 400 Selective limit current 333 Selective limit current 200 225 250 300 350 400 Selective limit current 200 225 250 300 350 400 Branch Breaker Main Breaker Type Icu(kA) NF250-SP 25 NF250-SP T/A 25 NF250-HP 50 NF250-HP T/A 50 NF250-SEP 25 NF250-HEP 50 NF400-CP 25 NF400-SP 42 NF400-SEP 42 NF400-HEP 65 Icu: Rated breaking capacity

Branch Breaker Ics(kA) TypeMain Breaker SELECTIVE-INTERRUPTION COMBINATIONS (DISCRIMINATION) 440VAC (Sym. kA) Rated current (A) AE630-SS AE1000-SS AE1250-SS AE1600-SS 65 65 65 65 Type Icu(kA) 500 600 700 800 900 1000315 378 441 504 567 630 800 960 1120 1280 1440 1600 625 750 875 1000 1125 1250 Selective limit current NF630-CP 50 500 600 630 Selective limit current NF630-SP 50 500 600 630 88 1 0 88 Selective limit current NF630-SEP 85 300 350 400 500 600 630 Selective limit current NF630-HEP 100 300 350 400 500 600 630 Selective limit current NF800-CEP 50 400 450 500 600 700 800 Selective limit current NF800-SEP 85 400 450 500 600 700 800 Selective limit current NF800-HEP 100 400 450 500 600 700 800 Icu: Rated breaking capacity

Ics(kA) Type Rated current (A) AE2000-SS AE2500-SS AE3200-SS AE4000-SSC 85 85 85 85 1250 1500 1750 2000 2250 25001000 1200 1400 1600 1800 2000 3200 3600 4000 1600 1920 2240 2560 28803200 Selective limit current 500 600 630 Selective limit current 500 600 630 Selective limit current 300 350 400 500 600 630 Selective limit current 300 350 400 500 600 630 Selective limit current 400 450 500 600 700 800 Selective limit current 400 450 500 600 700 800 Selective limit current 400 450 500 600 700 800 Branch Breaker Main Breaker Type Icu(kA) NF630-CP 50 NF630-SP 50 NF630-SEP 85 NF630-HEP 100 NF800-CEP 50 NF800-SEP 85 NF800-HEP 100 Icu: Rated breaking capacity

6.4 Cascade Back-up Protection

6.4.1Cascade Back-up Combinations Following tables show the available MCCB combina- tions for cascade interruption and their interrupting capacity. Fault point Branch breaker Branch breaker Main breaker Main MCCB S C NF30-SP MB30-SP MB50-CP MB50-SP NF50-HP NF60-HP NF50-HRP NF100-SP MB100-SP NF100-HP NF160-SP NF160-HP NF250-SP MB225-SP NF250-HP NF400-SP NF400-SEP NF630-SP NF630-SEP NF50-CP NF60-CP NF630-CP NF250-CP NF100-CP NF400-CP 2.5 10 14 5555 125 35 50 14 20 15 10 15 10 15 10 10 10 10 10 10 10 10 10 10 10 125 50 50 10 10 10 10 20 30 18 15 15 15 14 14 14 125 125 50 50 125 200 125 200 200 85 85 42 35 35 35 35 35 35 35 35 35 30 125 200 125 200 50 50 35 30 65 65 65 65 65 65 125 200 125 200 200 85 85 65 35 50 50 50 35 50 50 35 50 50 125 200 85 85 85 65 65 65 65 65 65 65 125 200 200 200 200 35 50 50 35 50 50 35 50 50 125 200 85 85 85 65 65 65 65 65 65 125 200 200 200 200 65 65 65 65 65 65 200 200 200 65 65 65 65 200 200 10 14 5555 125 35 50 5 20 30 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 14 125 200 125 14 14 14 14 25 25 25 25 30 30 30 25 25 25 20 20 20 20 20 20 18 18 18 125 200 50 30 25 20 35 35 35 35 35 35 35 35 35 30 30 30 50 50 50 30 42 50 50 42 50 50 42 42 42 200 200 25 50 25 50 25 50 50 65 125 50 65 125 50 65 125 85 85 85 15 25 35 35 125 200 125 200 200 200 200 125 7.5 2.5 Branch MCCB 440VAC Interrupting capacity (kA) NF100-SP NF100-HP NF160-SP NF160-HP NF250-SP NF250-HP NF400-SP NF400-HEP NF400-REP NF630-SP NF630-HEP NF630-REP NF800-SEP NF800-HEP NF800-REP NF400-CP NF630-CP NF225-RP NF225-UP NF400-UEP NF630-UEP NF800-CEP NF100-RP NF100-UP NF800-UEP NF1250-UR NF1000-SS, NF1250-SS, NF1600-SS NF2000-S, NF2500-S NF3200-S, NF4000-S NF250-CP S C U

S C NF30-SP MB30-SP MB50-CP MB50-SP NF50-HP NF60-HP NF50-HRP NF100-SP MB100-SP NF100-HP NF160-SP NF160-HP NF250-SP MB225-SP NF250-HP NF400-SP NF400-SEP NF630-SP NF630-SEP NF50-CP NF60-CP NF630-CP NF250-CP NF100-CP NF400-CP 5 425 01 01 01 01 0 7.5 125 200 35 50 42 85 35 35 35 35 30 30 30 30 30 30 25 14 14 125 200 125 100 50 50 50 50 50 50 50 50 50 50 30 30 125 200 125 125 200 125 200 200 125 125 100 85 85 85 85 85 85 85 125 200 125 200 200 125 125 125 200 125 200 200 125 125 85 85 85 85 85 85 85 70 70 70 70 125 200 200 125 125 125 200 200 200 200 85 85 85 85 85 85 85 70 70 70 70 125 200 200 125 125 125 200 200 200 200 100 100 100 200 200 200 100 100 100 100 200 200 100 35 50 10 10 10 10 7.5 125 200 35 50 35 85 50 50 50 50 50 50 50 50 50 50 30 30 125 200 125 50 50 50 50 50 50 50 50 50 50 50 50 35 35 125 200 200 50 50 85 85 85 85 85 85 85 85 85 85 85 85 200 200 200 85 85 85 85 85 85 85 85 85 200 200 100 100 100 100 125 100 125 100 125 125 125 125 30 50 50 50 125 200 125 200 200 200 200 170 100 100 100 Branch MCCB 230VAC Interrupting capacity (kA) NF100-SP NF100-HP NF160-SP NF160-HP NF250-SP NF250-HP NF400-SP NF400-HEP NF400-REP NF630-SP NF630-HEP NF630-REP NF800-SEP NF800-HEP NF800-REP NF400-CP NF630-CP NF225-RP NF225-UP NF400-UEP NF630-UEP NF800-CEP NF100-RP NF100-UP NF800-UEP NF1250-UR NF1000-SS, NF1250-SS, NF1600-SS NF2000-S, NF2500-S NF3200-S, NF4000-S NF250-CP S C U

6.5 I2t let-Through and Current Limiting Characteristics

I2t let-through characteristics Current limiting characteristics NF100-HP,NF250-HP short-circuit current,sym.r.m.s.(kA) 1 2 4 10 20 40 60 80 10086 100 Max. Iet-through current(kA) NF250-HP NF100-HP(30A) NF100-HP(20A) NF100-HP(15A) NF100-HP (40~100A) Prospective short-circuit current,asym.peak NF400-UEP,NF630-UEP,NF800-UEP short-circuit current,sym.r.m.s.(kA) 1 2 4 10 20 40 60 80100 20086 100 200 400 Max. Iet-through current(kA) NF630-UEP NF800-UEP NF400-UEP Prospective short-circuit current,asym.peak NF100-RP,NF100-UP,NF225-RP,NF225-UP short-circuit current,sym.r.m.s.(kA) 3 10 20 50 100 200 100 200 Max. Iet-through current(kA) NF225-UP NF225-RP NF100-UP NF100-RP Prospective short-circuit current,asym.peak NF100-RP,NF100-UP,NF225-RP,NF225-UP Max. I2t (A2-sec) ( 106) short-circuit current,sym.r.m.s.(kA) 3 10 20 50 100 200 5.0 2.0 1.0 0.5 0.2 0.1 0.05 NF225-UP NF225-RP NF100-UP NF100-RP NF400-UEP,NF630-UEP,NF800-UEP Max. I2t (A2-sec) ( 106) short-circuit current,sym.r.m.s.(kA) 1 2 4 10 20 40 60 80100 20086 0.8 0.6 0.4 0.2 0.1 NF630-UEP NF800-UEP NF400-UEP NF100-HP,NF250-HP short-circuit current,sym.r.m.s.(kA) 1 2 4 10 20 40 60 80 10086 0.8 0.6 0.4 0.2 0.1 Max. I2t (A2-sec) NF250-HP NF100-HP (30A) NF100-HP (20A) NF100-HP (15A) NF100-HP (40~100A) ( 106)5

Table 6.4 Allowable Fault Conditions in Conductors

6.6 Protective Coordination with Wiring

6.6.1 General Considerations

If it is assumed that the heat generated by a large current passing through a wire is entirely dissipated within the wire, the following expression is applicable (for copper wires): I t=5.055 10 log e 234+T 234+To) I : Current(A, rms) S : Wire cross-sectional area(mm2) t : Current let-through time(sec) T : Wire temperature due to short circuit(°C) To : Wire temperature before short circuit(°C) Assume that short-circuit current occurs in a wire car- rying its rated current (hot state To=60°C). If 150°C is the allowable temperature T, the following expression is applicable (see also Fig. 6.13): Is Allowable short-circuit current accoeding to I2t kA, sym. (PF) 1.5 2.5 120 150 185 240 Allowable I A25 sec S Wire size mm 2 Notes: 1.Allowable I2t is calculated assuming that all heat energy is dissipated in the conductor, conductor allowable maximum temperature exceeds 150°C, and hot start is applied, at 60°C. 2. I s is an asym. value of allowable short- circuit current reduced to below the allowable I 2t, assuming half cycle interruption for 16mm2 or less and one cycle interruption for 25mm2 or more. Allowable I2t=14000S2 Considering let-through energy (∫i2dt) in a fault where the protector has no current-limiting capability, if short- circuit occurs when let-through current is max., ∫i 2dt is: where current le is the effective value of the AC com- ponent. Half-cycle interruption is applied to wire of up to 14mm 2, and one-cycle interruption to larger wires. Table 6.4 is restrictive in that, e.g., in a circuit of fault capacity of 5000A or more, 2.5mm 2 wires would not be permitted. In practice, the impedance of the con- ductor itself presents a limiting factor, as does the in- herent impedance of the MCCB, giving finite let- through I 2t and Ip values that determine the actual fault-current flow. 6.6.2 600V Vinyl-Insulated Wire (Overcurrent) Japanese Electrical Installations Technical Standards (domestic) specify vinyl-insulated wire operating tem- perature as 60°C max., being a 30°C rise over a 30°C ambient temperature. This is to offset aging deterio- ration attendant on elevated temperatures over long periods. Criteria for elevated temperatures over short periods have been presented in a study by B. W. Jones and J. A. Scott (“Short-Time Current Ratings for Air- craft Wire and Cable,” AIEE Transactions), which pro- poses 150°C for periods of up to 2 seconds, and 100°C for periods in the order of 20 seconds. These criteria can be transposed to currents for different wire sizes by the curves given in Fig. 6.14. Such figures, how- ever, must be further compensated for the difference between vinyl materials used for aircraft and for 0.0145 10 0.0325 106 0.0885 106 0.2245 106 0.5045 106 1.405 106 3.585 106 8.755 106 17.25 106 35.05 106 68.65 106 1265 106 2025 106 3155 106 4795 106 8065 106 1.17 (0.9) 1.76 (0.9) 2.93 (0.9) 4.68 (0.9) 6.79 (0.8) 10.5 (0.6) 16.0 (0.5) 17.3 (0.3) 24.2 (0.3) 34.5 (0.3) 48.3 (0.3) 65.6 (0.3) 82.8 (0.3) 103 (0.3) 128 (0.3) 166 (0.3) Fig. 6.13 Temperature Rises Due to Current Flow in Copper Wires ×103 ×104 Temperature rise(°C) 1000 700 500 300 200 100 12 2 33 44 5 6 7 856 1 (A/mm 2) 2·sec Approx. 71 Ie (A ·sec) in 1 cycle interruption (Power factor is 0.5.) Approx. 34 Ie (A ·sec) in 1 cycle interruption (Power factor is 0.3.)

Fig. 6.14 Relation of Let-through Current to Time until 600V Vinyl-Insulated Wire Reaches a 70°C Temperature Rise. (In a Start from No Load State at Ambient Temperature of 30°C) Fig. 6.15 MCCBs and Wiring Sizes 100 125 150 175 200 225 250 300 350 400 Wire size (mm MCCB rating(A) 1.5 2.5 120 185 240 Unprotected region Protected region Fig. 6.16 Wire Derating Method, for Conduit Routing Current (×102A) Time (sec) 1000 800 600 500 100 200 300 400 630 1851501209570503525 6.0 4.0 2.5 1.51.0 500400300240 Wire sizes (mm2) =Correction factor Time. !2 !1 !1 Current Open wiring Routed in conduit ground use; ultimately, the temperature figure of 75°C is derived (100°C per Jones and Scott, compensated) as a suitable short-time limitation for wiring with heat- proof vinyl or styrene-butadene-rubber insulation. Current transpositions for the range of wire sizes are not presented, being non-standard ; however, Fig. 6.15 gives MCCB ratings for temperature limitations of 30°C in normal operation, and 75°C for periods of up to 20 seconds. The apparent disparity of the ambient ratings of 30°C for wiring against 40°C for MCCBs, is reconcilable in that wiring, for the most part, is externally routed, while MCCBs are housed in panelboards or the like. The two figures can be used compatibly, without modifi- cation. It is further noted that, where MCCBs with long- delay elements of the thermal type are employed, the effect of increased ambient, which would normally derate the wiring, is adequately compensated by the attendant decrease in thermal-region tripping time of the MCCB. The curves in Fig. 6.17 show the comparison of the delay regions of MCCB tripping with allowable cur- rents in open-routed wiring. Fig. 6.16 shows the method required by the Japanese standards referred to above, for derating wiring to be routed in conduit.

Fig. 6.17 600V Wire and MCCB Protection Compatibility 2000 1000 100 200 300 400 600 800 0.8 10 100 1000 10000 Current (A) a) 50A-fream MCCB Tripping time (sec) 0.6 0.5 2000 1000 100 200 300 400 600 800 0.8 10 100 1000 10000 Current (A) c) 225A-fream MCCB Tripping time (sec) 0.6 0.5 2000 1000 100 200 300 400 600 800 0.8 100 1000 10000 100000 Current (A) d) 400A-fream MCCB Tripping time (sec) 0.6 0.5 2000 1000 100 200 300 400 600 800 0.8 10 100 1000 10000 Current (A) b) 100A-fream MCCB Tripping time (sec) 0.6 0.5 MCCB rating 15A MCCB rating 125A MCCB rating 250A 300A 350A 400A 150A 175A 200A 225A 20A 30A 40A 50A Wire size 1.0mm 2 Wire size 16mm 2 Wire size 50mm 2 70mm 2 95mm 2 120mm 2 150mm 2 25mm 2 35mm 2 50mm 2 70mm 2 MCCB rating 60A 75A 100A Wire size 10mm 2 16mm 2 25mm 2 1.5mm 2 2.5mm 2 4.0mm 2 6.0mm 2

6.7 Protective Coordination with Motor Starters

Motor starters comprise a magnetic contactor and a thermal overload relay, providing the nesessary switching function for control of the motor, plus an automatic cutout function for overload protection. Mitsubishi Electric’s excellent line of motor starters are available for a wide range of motor applications and are compatible with Mitsubishi MCCBs. Magnetic contactors are rugged switching devices required to perform under severe load conditions with- out adverse affect. They are divided into Classes A through D (by capacity); Class A, e.g., must be able to perform 5 cycles of closing and opening of 10 times rated current, followed by 100 closing operations of the same current after grinding off 3/4 of the contact thickness. Current ratings of contactors usually differ according to the circuit rated voltage, since voltage determines arc energy, which limits current-handling capability. Thermal overload relays (OLRs) employ bimetal ele- ments (adjustable) similar to those of MCCBs. For compatibility with the magnetic contactor, the OLR must be capable of interrupting 10 times the motor 6.7.2Levels of Protection (Short Circuit) In some cases it may be advantageous to allow the starter to be damaged in the event of a short circuit, provided that the fault is interrupted and the load side is properly protected. IEC standards defines 2 types of coordination, sum- marized as: 1. Type “1” coordination requires that, under short- circuit conditions, the contactor or starter shall cause no danger to persons or installation and may not be suitable for further service without re- pair and replacement of parts. 2. Type “2” coordination requires that, under short- circuit conditions, the contactor or starter shall cause no danger to persons or installation and shall be suitable for further use. The risk of con- tact welding is recognized, in which case the manufacturer shall indicate the measures to be taken as regards the maintenance of the equip- ment. Fig. 6.18 Protective Coordination; MCCBs and Motor Starters MCCB Magnetic contactor and thermal overload relay Protection function MCCB Starter combination Protects the motor against overcurrents up to 10 times rating. Protects circuit wiring' control devices' and OLR against fusion. Motor normal starting current OLR-MCCB curve intersection Transient peak of motor current Time Motor overheat/burnout curve MCCB trip. curve OLR trip. curve Current-time limitations of motor wiring Intersection of MCCB and OLR trip curves OLR heater fusion Current-time limitations of MCCB-to-starter wiring 23 4 5 6 Current Key MCCB inst. trip current Protection limit; the possible short-circuit at the motor terminals must be less than this value. MCCB rated interruption capacity Motor starting current Fig. 6.19Protection Coordination Criteria for MCCBs and Motor Starters full-load current without destruction of its heater ele- ment. Mitsubishi Type TH OLRs are normally capable of handing 12 to 20 times rated current; in addition there is available a unique saturable reactor for par- allel connection to the heaters of some types, giving a fusion-proofing effect of 40~50 times. 6.7.1Basic Criteria for Coordination It is necessary to ensure that the MCCB does not trip due to the normal starting current, but that the OLR cutout curve intersects the MCCB thermal delay-trip- ping curve between normal starting current and 10 times full-load current. The MCCB instantaneous-trip- ping setting should be low enough to protect the OLR heater element from fusion, in a short-circuit condi- tion. The above criteria should ensure that either the MCCB or the OLR will interrupt an overload, to protect the motor and circuit wiring, etc. In practice it is desirable for the MCCB instantaneous tripping to be set for about 15 times full-load current as a margin against tran- sients, such as in reclosing after power failure, Y-delta switching, inching, etc. 1. 4.

6.7.3 Motors with Long Starting Times

The usual approach is to select a starter with a larger current rating, but this method, of course, involves a degree of sacrifice of protection. Mitsubishi provides a unique solution to this problem in the form of a satu- rable reactor added to the OLR heater element. The effect is to change the high-current characteristics, so that nuisance tripping in starting is eliminated, with- out loss of overload protection. Mitsubishi saturable reactors are adjusted to allow around 25~30 seconds of continuous starting current. 6.7.4Motor Breakers (M Line MCCBs) and Magnetic Contactors M Line MCCBs are provided with trip curves espe- cially suitable for motor protection, with ratings based on motor full-load currents. They provide overcurrent and short-circuit protection, and are normally used with magnetic contactors. The need for protective coordi- nation (as with a regular MCCB plus a starter) is elimi- nated, and the reliability of protection in a short-cir- cuit condition is far higher than that of the heater of a starter OLR. Where the motor starting time is long, the MCCB tripping curve must be checked carefully, since tripping times are rather short in the delay-trip range. Care must also be taken with respect to surge conditions such as inching, reversing, restart, Y-delta starting, etc.

6.7.5 Motor Thermal Characteristics

Overload currents in motors can lead to burnout, or insulation damage resulting in shock or fire hazard; the basic approaches to protection are (summarized from Japanese standards): 1. MCCB + magnetic contactor + OLR 2. Motor breaker + magnetic contactor 3. Motor breaker alone In 1, the OLR is the primary interrupter of overload, and being adjustable, can be set for the true load re- quirement. Large overcurrent or short-circuit fault con- ditions are interrupted by the MCCB instantaneous trip. In 2, the motor breaker is the protector for both overload and short-circuit, and not being adjustable must be selected carefully, for best coordination with the load concerned. In 3, since the MCCB is relied on not only for all protective functions but also for switch- ing, this arrangement should be reserved for applica- tions requiring infrequent motor starting and stopping.

6.7.6 Motor Starting Current

Motor starting times of up to 15 seconds are generally considered safe; more than this is considered undesirable; more than 30 seconds is considered dangerous and should be avoided wherever possible. For instantaneous tripping considerations, the MCCB is normally set to 600% of the motor full-load current, for trouble-free line-starting of an induction motor. More detailed consideration is required where short- time inrush effects (current magnification) are involved, such as in Y-delta switching, running restart, etc. Two basic causations are as follows: 1. Superimposed DC Transient (Low Power-Factor Effect) Fig. 6.20 shows that the power factor is about 0.3 at starting, causing a significant DC component, so that the total transient inrush current may reach about twice the value of the AC component, even though the latter is of constant amplitude. Peak in- rush current (lt) of 1.4 x normal starting current (lo) must be allowed for, in selecting the MCCB instanta- neous-trip setting. 2. Residual Voltage (Running Restart) If residual (regenerative) voltages appearing at the motor terminals are out of phase with the supply volt- age (at the time of reclosing after being interrupted, before the motor speed is substantially reduced), the cumulative effect of the line voltage and the residual voltage is equivalent to the motor being directly sub- jected to a large line overvoltage, with a resulting ab- normal inrush current of: Residual+source V Source V 5 Normal starting inrush current This is a current magnification effect, which may be as much as 2 x in direct restarting, and 1+ ( ) x in Y- delta-switching restarting. When the DC-transient fac- tor (§1 above) is added, the magnification becomes 2.4 in the case of direct restarting, and 1.9 for Y-delta restarting. Fig. 6.21 Peak Inrush-Current Measurements Fig. 6.20 Transient DC Component 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 It 2 Io It Power factor (lag) Io Current magnification Motor output (kW) b) Test results a) Test connections Contactor Backup MCCB CT Motor breaker Oscillo- graph Direct (line) starting Inching duty Reversing duty -delta switching M

Fig. 6.23 Coordinated PF and MCCB Characteristics 6.8.2Electronic MCCBs and HV PF A basic requirement is that the deteriorated short-de- lay curve of the PF, and the short-delay trip curve of Electronic MCCB, which is shifted +10% along the current axis, do not overlap. To facilitate matching, the rated current of the PF should be as large as possible; however, there is an upper limit, as seen from the following criteria: 1.The rated current should be 1.5~2 times the load current. 2. To ensure protection in the event of a short circuit, the PF must interrupt a current of 25 times the trans- former rating within 2 seconds. 3.To ensure that the PF neither deteriorates nor fuses as a result of the transformer excitation surge current, the short-delay deterioration curve of the PF must be more than 0.1 seconds, at a current of 10 times the transformer rating. The “10 times” factor becomes “15 times” in the case of a single- phase transformer. Thus, if normal starting current is assumed as 600% of full-load current, the peak inrush becomes 1200% in Y-delta restarting and 1600% in direct restarting. The MCCB instantaneous-trip setting must be selected at larger than these values. Fig. 6.21 shows test date with respect to four condi- tions of transient inrush current, expressed as magni- fications of full-load current, measured on motors rated from 0.2~30kW. The MCCB was used for line-start- ing switching, and the contactor for the other switch- ing duties. Phase matching between the line and re- sidual voltages was uncontrolled. The oscillographs taken showed that the peak inrush currents persist for about one-half cycle, followed by a rapid decrease to normal starting-current level. From the curves it can be concluded that peak inrush mag- nifications vary greatly depending on the duty involved; for reversing duty, the MCCB instantaneous trip set- tings must be selected from 1600 ~3400% of full- load current. For line starting and Y-delta starting, the range spans from 1000~2000%.

6.8 Coordination with Devices on the High-

Voltage Circuit.

6.8.1 High-Voltage Power Fuse

The MCCB on the secondary (low-voltage) side of a power transformer must have tripping characteristics that provide protective coordination with the power fuse (PF) on the high-voltage side (Fig. 6.22). The MCCB must always trip in response to overcurrent, to ensure that the PF does not fuse or deteriorate by elevated temperature aging. Fig. 6.23 shows the MCCB curve in relationship to the deteriorated PF curve (if this is unavailable, the average fusing curve reduced by 20% can usually be assumed). The PF characteristic can be converted to the secondary side, or the MCCB characteristic to the primary side; the curves must not overlap in the overcurrent region. Where the MCCB instantaneous-tripping current of the MCCB is adjustable, difficulties in matching the curves can be overcome as shown, but a 10% mar- gin must be included to allow for the tolerance of the MCCB tripping setting. The shaded area in Fig. 6.23 belong to overcurrent region, the overcurrent generally occur at the lower circuit of MCCB2. Thus, it may in some cases be better to accept a co- ordination between the PF and MCCB2, permitting a mismatch between the PF and MCCB1. Fig. 6.22 Protective Coordination of MCCBs and HV-Side PF PF Tr MCCB 1 MCCB 2 Time MCCB tripping curve Minimum setting of inst,-trip current Short-delay fusing of PF (deteriorated) Overcurrent

6.8.3 MCCBs and HV-Side OCR

An overcurrent-relay remote tripping device (OCR) on the HV side of the circuit must be coordinated with the MCCBs on the LV side. The OCR setting must take into consideration the coordination with the OCR at the power-utility substation and, at the same time, the following: 1. The setting of an OCR with an instantaneous-trip element must be at least 10 times the transformer current rating, to ensure that the excitation surge of the latter does not trip the OCR. 2. To ensure short-circuit protection, the OCR must operate within 2 seconds, at 25 times the transformer rated current. Figs. 6.26 and 6.27 show the setup, and the coordinat- ed characteristics converted to the low-voltage side. The turns ratio of the CT is 150:5, to match the rated primary current of 87.5A. Considering cooperation of the OCR with the upper-ranking substation OCR, the OCR dial is normally set to 0.2 or less, or 1 second max. if it has an instantaneous trip element. On the Mitsubishi Type MOC-E general-purpose relay this is equivalent to dial setting No. 2. Latching-curve over- lap, shown by the broken lines in Fig. 6.27, must be allowed for. The instantaneous trip is set to 30A, in accordance with §1, above. For setting the Electronic MCCBs (800 and 600A ver- sions of Type NF800-SEP), the short-delay tripping currents of both are set to MIN. NF800-SEP have neg- ligible latching inertia, so that the reset characteris- tics (except in the instantaneous-trip region) can be regarded as the same as the tripping characteristics. Further, there is very little tolerance variation between units; thus, the tripping characteristics can be shown as a single line. If the NF800-SEP short-delay trip current is set at MAX (where MIN and MAX respectively correspond to 2 and 10 times rated current), a 600A rating setting will correspond to 6000A tripping, and an 800A set- ting will correspond to 8000A tripping. In this case (at MAX setting), short-delay latching of the NF800-SEP will overlap the OCR latching (4710A, secondary con- version). But if the NF800-SEP and the OCR are all set to MIN, so that the latching values do not exceed 4710A, good coordination will be achieved. As the OCR has an instantaneous-trip element, set at 30A (secondary conversion 28.3kA), the region of selective interruption between the OCR and the NF800-SEP will extend to this value. Considering the coordination of the Electronic MCCBs with the lower-level MCCBs (NF250-CP), it NF250-CP NF800-SEP 800A setting CT ratio CT Tr OCR CB or S Type MOC-E 5A tap dial < 2 NF800-SEP 600A setting 6.6kV/210V 3f1000 kVA Electronic MCCB PF Tr Fig. 6.25 Coordinated PF and Electronic MCCB Characteristics 3 hours 1 hour40 10 min6 1 min 3020 10 sec 1 sec 0.6 0.4 0.2 0.1 0.06 0.02 0.01 0.006 0.004 0.002 Short-delay tripping current setting range Electronic MCCB characteristic curve Deteriorated curve of PF 150 200 300 400 600 800 1,000 2,000 4,000 6,000 20,000 150,000 10,000 40,000 Current (A rms) Time Fig. 6.24 Protective Coordination of Electorinic MCCBs and PF Fig. 6.26 Electronic MCCBs in Coordination with an HV- Side OCR

Fig. 6.27 Coordinated OCR and Electronic MCCB Characteristics can be seen from Fig. 6.27 that the maximum trip curve (tolerance) of the C Line units matches well with the NF800-SEP curves, with no danger of overlap. 3 hours 1 hours 10 min 0.6 0.4 0.2 0.1 0.06 0.02 0.01 0.006 0.004 0.002 1 min 10 sec 1 sec Time 150 300 600 1,000 4,000 10,000 40,000 80,000 200 400 800 6,000 20,000 60,0002,000 Current (A, rms) NF800-SEP 800A setting Max. MOC-E tripping curve CT ratio 150/5 Tap 5 Dial #2 Latching curveInst. trip setting 30A NF250-CP 175A Min. Max. Min.

7.SELECTION In selecting MCCBs for a particular application, in addition to purely electrical aspects of load and distri- bution conductor systems, physical factors such as panelboard configuration, installation environment, ambient-temperature variations, vibration, etc. must also be considered. MCCBs are rated for an ambient of 40°C, and where panelboard internal temperatures may exceed this, the MCCBs installed should be derated in accor- dance with Table 7.1. 1.Actual load currents may exceed the nominal-val- ues. 2.Load currents may increase with time, due to dete- rioration of load devices (i.e., friction in motors). 3.Source voltage and frequency may vary.

7.1 Motor Branch Circuits

The following discussion assumes single motors and cold-start operation. 7.1.1General Considerations The starting current (IMS ) and time (TMS ) for the mo- tor, and its full-load current, dictate the rated current, long-delay trip and instantaneous-trip curves for the MCCB as shown in Fig. 7.2. A safety-margin of up to 50% should be considered for the starting time, to allow for voltage variations and increase in load fric- tion. The instantaneous-trip curve should be at least 1.4 x normal starting current to allow for the effect of the DC component attendant to the low power factor (about 0.3) of the starting current. For -delta start- ing the unphased-switching allowance increases the 1.4 margin to 1.9. For running restarting the unphased- switching allowance increases the factor to 2.4. Rated currents MCCB trip curve Starting current and long-delay trip Inrush and inst. trip Motor starting current TMS IMS Current Time Fig. 7.2 MCCB and Motor Starting 7.1.2Motor Breaker Where starting times are relatively short and currents are small, the Mitsubishi M Line motor breakers can be used without the need for a motor starter.

7.2 For Lighting and Heating Branch Cir-

In such circuits, switching-surge magnitudes and times are normally not sufficient to cause spurious tripping problems; however, in some cases, such as mercury- arc lamps or other large starting-current equipment, the methods presented in §7.1 above should be con- sidered. In general, branch MCCBs should be selected so that the total of ratings of the connected loads is not more than 80% of the MCCB rating. Fig. 7.1 MCCB Selection Consideration Table 7.1MCCB Deratings Due to Installation Factors Panelboard max. internal temp. (°C) Load allowable, due to panelboard temp. (%) Supply system Ambient temperature Main,submain or branch use Ambient conditions Wire connection Load current Operation conditions Load Short circuit Installation and connection style Service purpose Regulations

7.3 For Main Circuits

7.3.1For Motor Loads The method of “synthesized motors” is recommended – that is, the branch-circuit loads to be connected are divided into groups of motors to be started simulta- neously (assumed), and then each group is regarded as a single motor having a full-load current of the total of the individual motors in the group. The groups are regarded as being sequentially started. The rating of the branch MCCB for the largest syn- thesized motor is designated IB max., those of the subsequent synthesized motors as I1, I2, ...In-1. The rating of the main MCCB becomes: IMAIN = IB max + (I1 + I2 +...In-1) x D where D is the demand factor (assumed as 1 if inde- terminate). 7.3.2For Lighting and Heating, and Mixed Loads For lighting and heating loads the rating of the main MCCB is given as the total of the branch MCCB rat- ings times the demand factor. For cases where both motor-load branches and lighting and heating branches are served by a common main MCCB, the summation procedures are handled separately, as described in the foregoing, then grand-totalized to give the main MCCB rating.

7.4 For Welding Circuits

7.4.1Spot Welders A spot welder is characterized by a short, heavy in- termittent load, switched on the transformer primary side. The following points must be considered in MCCB selection: 1.The intermittent load must be calculated in terms of an equivalent continuous current. 2.The excitation transient surge due to the breaker being on the transformer primary side must be al- lowed for. MCCB Welder Weld workpiece Control timer Supply Fig. 7.3 Spot-Welder Circuit The temperature rise of the MCCB and wiring de- pends on the thermal-equivalent continuous current. To convert the welder intermittent current into a ther- mal-equivalent continuous value (Ie), consider the current waveform (Fig. 7.4); load resistance (R) gives power dissipation: W = I12 Rt1 and average heat produced: t1 + t2 W = t1 + t2 I Rt1 = I12 Rβ = R(I1 β )2 where β is the duty factor, defined as total conduction time total time This is equivalent to heating by a continuous current of I1 β . In the example of Fig. 7.4: Ie = I1 β = 1200 x 0.0625 = 300 (A) i.e., a continuous current of 300A will produce the average temperature. In practice, however, the instan- taneous temperature will fluctuate as shown in Fig. 7.5 and the maximum value (Tm ) will be greater than the average (Te) that would be produced by a con- tinuous current of 300A. The operation of an MCCB thermal element depends on the maximum rather than the average temperature, so it must be selected not to trip at Tm ; in other words, it is necessary to ensure that its hot-start trip delay is at least as great as the interval of current flow in the circuit. The rated current of a “mag-only” MCCB (which does not incorporate a thermal trip function) can be selected based on the thermal equivalent current of the load, allowing a margin of approximately 15% to the calculated value to accommodate supply-voltage fluctuations, equip- ment tolerance, etc. Thus: IMCCB = Ie x 1.15 = 300 x 1.15 = 345 (A) The MCCB selected becomes the nearest standard value above 345A. I1 1200A Time (Duty factor β = 0.0625) Current t1 t2 (3sec.) (45sec.) 3 +45 Fig. 7.4 Welder Intermittent Current Time Te Tm Temperature Fig. 7.5 Temperature Due to Intermittent Current For practical considerations, rather than basing selection on welding conditions, the MCCB should be selected to accommodate the maximum possible duty, based on the capacity and specifications of the welder. If the welder rated capacity, voltage and duty fac- tor in Fig. 7.3 are 85kVA, 200V and 50% respectively, the thermal-equivalent continuous current (Ie) be-

comes: rated voltage rated capacityIe = x duty factor = 200 85 + 103 x 0.5 = 300A Hence, the MCCB rated current becomes: IMCCB = Ie x 1.15 = 300 x 1.15 = 345A (i.e., the next higher standard value). The relationship between the duty factor, which does not exceed the working limitations, and the maxi- mum permissible input I β at the above duty factor is: β IeI = β 300=β If the total period is taken as 60 seconds and the duty factor is converted into the actual period during which current flows, the above relationship can be expressed graphically as in Fig. 7.6. Thus, although the thermal equivalent current is 300A, the maximum permissible input current for a duty factor of 50% (30 seconds current flow) is 425A. For a duty factor of 6.25% (3.75 sec current flow) it is 1200A. Even if the secondary circuit of the welder were short circuited, however, the resultant primary current would only in- crease by about 30% over the standard maximum welding current. If this is 400kVA, the maximum pri- mary current I βmax is: primary voltage standard maximum inputI max = x 1.3 200 400 x 103 x 1.3 = 2600A= β Hence the maximum input current Iβ should be re- stricted to 2600A. The 75% hot-start characteristic of the 350A Type NF400-SP breaker is shown by the broken line in Fig. 7.6, and the temperature-rise characteristics up to the upper limit of the welder, by the solid line. To ensure protection of the welder from burnout, the delay-trip characteristic is selected at higher than the solid line; however, to establish MCCB protection criteria, it is necessary to look at each welder individually. Operating time (sec) 3.75 0.6 425 Primary input current (A) Type NF400-SP·350A 75% hot start 10" 300026001200 Fig. 7.6 Welder Temperature Rise and MCCB Trip Curve

7.4.2 MCCB Instantaneous Trip and Trans-

When a welding-transformer primary circuit is closed, depending upon the phase angle at the instant of clo- sure, a transient surge current will flow, due to the super-imposed DC component and the saturation of the transformer core. In order to prevent spurious tripping of protective devices resulting from such surges, and also to main- tain constant welding conditions, almost all welders currently available are provided with a synchronized switch-on function, with or without wave-peak con- trol. With synchronized switch-on, the measured ratio between the RMS value of the primary current under normal conditions and the maximum peak transient current ranges from √ 2 ~ 2. For nonsynchronized soft-starting-type welders the measured ratio is a maximum of 4. Maximum instantaneous transient surge excitation currents for various starting methods are as follows: Synchronized switch-on welders with wave peak con- trol: I max = 2 x I maxβ Synchronized switch-on welders without wave peak control: Imax = 2 x Iβmax Nonsynchronized switch-on welders with soft start: Imax = 4 x Iβmax Nonsynchronized switch-on welders without soft start: Imax = 20 x Iβmax If synchronized switch-on is employed, the tran- sient surge excitation currents are relatively consis- tent, so that the relationship I max = 2 Iβmax is suffi- cient. For a synchronized switch-on type welder of maxi- mum primary input (Iβmax ) = 2600A Imax = 2 x Iβmax = 2 x 2600 = 5200A Since MCCB instantaneous trip currents are speci- fied in terms of RMS value, Iinst is as follows: ImaxIinst = = 3680A 2 5200= The MCCB should be selected so that Iinst is smaller than the lower tolerance limit, of the instantaneous trip current.

7.4.3 Arc Welders

An arc welder is an intermittent load specified. The MCCB rating can by selected by converting the load current into thermal-equivalent continuous current. If this is taken as the rated current, however, the cur- rent duration per cycle will become relatively long, with the attendant danger of thermal tripping of the MCCB. In the total period of 10 minutes, if the duty factor is 50%, a 141% overload exists for 5 minutes; if the duty factor is 40%, a 158% overload exists for 4 minutes; and if the duty factor is 20%, a 224% overload exists

for 2 minutes. Thus: E 1.2 x P x 103 IMCCB ≥ where 1.2:Allowance for random variations in arc-welder current, and supply-volt- age fluctuations P: Welder rated capacity (kVA) E: Supply voltage (V) The switching transient in the arc welder is mea- sured as 8~9 times the primary current. Consequently, using 1.2 allowance, it is necessary to select instan- taneous-trip characteristics such that the MCCB does not trip with a current of 11 times the primary current.

7.5 MCCBs for Transformer-Primary Use

Transformer excitation surge current may possibly exceed 10 times rated current, with a danger of nui- sance tripping of the MCCB. The excitation surge current will vary depending upon the supply phase angle at the time of switching, and also on the level of core residual magnetism. The maximum is as shown for switching-point P in Fig. 7.7. During the half cycle following switch-on the core flux will reach the sum of the residual flux f r, plus the switching-surge flux 2fm . The total, 2fm +fr, represents an excitation current in excess of the saturation value. The decay-time con- stant of this tends to be larger for larger transformer capacities. Table 7.2 shows typical values of excita- tion surge current, but as these do not take circuit impedance into account, the actual values will be larger. If both the primary leakage impedance and cir- cuit impedance are known, the surge current may be derived by considering the transformer as an air core reactor; otherwise the values in Table 7.2 should be used. This table gives maximum values, however, that are based on the application of rated voltages to rated taps; it should be noted that supply overvoltage will result in even larger surges. Since it is the instantaneous-trip function of the MCCB that responds to the transient current, ther- mal-magnetic MCCBs, which can more easily be manufactured to handle high instantaneous-trip cur- rents, are advantageous over completely electromag- netic types, where the instantaneous-trip current is a relatively small multiple of the rated current. Table 7.2 Transformer Excitation Surge Currents Capacity (kVA) 100 150 200 300 500 Decay time constant (Hz) First 1/2-cycle peak (multiple) Decay time constant (Hz) First 1/2-cycle peak (multiple) 1ph transformer 3ph transformer Table 7.3 Transformer Capacities and Primary-Side MCCBs Tran. kVA 7.5 100 150 200 300 500 3 phase 400V NF30-SP ( 30) NF50-SP ( 40) NF50-SP ( 50) NF100-SP ( 50) NF100-SP ( 60) NF100-SP ( 100) NF250-SP ( 150) NF250-SP ( 175) NF250-SP ( 225) NF400-SP ( 300) NF400-SP ( 350) NF630-SP ( 600) NF1000-SS ( 900) MCCB Type (rated current (A)) 1 phase 230V NF100-SP ( 75) NF100-SP ( 100) NF250-SP ( 150) NF250-SP ( 200) NF400-SP ( 300) NF400-SP ( 400) NF630-SEP ( 600) NF1000-SS ( 500) NF1000-SS ( 500) NF1000-SS ( 800) NFE2000-S (1200) NFE2000-S (1500) 1 phase 400V NF100-SP ( 40) NF100-SP ( 60) NF100-SP ( 75) NF250-SP ( 125) NF250-SP ( 150) NF250-SP ( 225) NF400-SP ( 400) NF630-SP ( 500) NF630-SP ( 630) NF1000-SS ( 500) NF1000-SS ( 600) NF1000-SS ( 900) NFE2000-S (1400) 3 phase 230V NF50-SP ( 50) NF100-SP ( 40) NF100-SP ( 60) NF100-SP ( 100) NF250-SP ( 125) NF250-SP ( 175) NF400-SP ( 250) NF400-SP ( 300) NF400-SP ( 400) NF630-SP ( 500) NF630-SP ( 600) NF1000-SS ( 900) NF1600-SS (1400) Note: 1 “Multiple” means the first 1/2-cycle peak as a multiple of the rated-current peak.

φr P Normal flux Transient flux Surge current Voltage 2φm φR Fig. 7.7 Excitation Surge Effects In MC CB selection for 400V, 50kVA transformer- primary used, rated RMS current is: 3 x Voltage (V) Capacity (kVA) x 103 I = = 72.2A3 x 400 50 x 103 From Table 7.2, the peak value of the excitation surge current Iφ is 23 times that of the rated current, hence: Iφ =23 x 2 I = 23 x 2 x 72.2A = 2348A Thus the MCCB selected should have instantaneous trip current of no less than 2348A. The Type NF250- SP 150A MCCB, with: Iinst = 2 x 150 x 11.2 = 2376A satisfies the above condition. Thus the 3-pole version of this type is suitable for this application. Examples of MCCBs selected in this way are shown in Table 7.3; it is necessary to confirm that the short- circuit capacities of the breakers given are adequate for the possible primary-side short-circuit current in each case.

7.6 MCCBs for Use in Capacitor (PF Cor-

rection) Circuits The major surge tendency results from circuit open- ing due to the leading current. If the capacitor circuit of Fig. 7.8 is opened at time t1 in Fig. 7.8, arc extinc- tion will occur at time t2, the zero-point of the leading current (i). Subsequently the supply-side voltage (Vt) will vary normally, but the load-side voltage (Vc) will be maintained at the capacitor charge value. The po- tential difference (Vc-Vt) will appear across the MCCB contacts and at time t3, approximately 1/2-cycle after t2, will become about twice the peak value of the sup- ply voltage (Em ). If the MCCB contacts are not suffi- ciently open, an arc will reappear across the gap, re- sulting in an oscillatory capacitor discharge (at a fre- quency determined by the circuit reactance, includ- ing the capacitor) to an initial peak-to-peak amplitude of 4Em . When the arc extinguishes, Vc will once again be maintained at a potential of –Em and the potential difference across the MCCB contacts will increase again. This cycle will repeat until the gap between the contacts becomes too great, and the interruption will be completed. Since Mitsubishi MCCBs exhibit extremely rapid contact separation, repetitive arcing is virtually non- existent; however, some MCCBs do not make and break so rapidly, and in such cases, if the load ca- pacitance is large enough, they will not discharge quickly, and if the arc extinguishes near the peak of the reverse-going oscillation voltage, the capacitor voltage will be maintained in the region of –3Em by the first restriking of the arc; at the second restrike it will become 5Em , on the third –7Em , etc., ultimately leading to breakdown of the capacitor. Thus, rapid switching is essential in leading power-factor circuits. In selecting an MCCB, first consider the surge cur- rent. If the supply voltage is V volts, the capacitor C farads, the frequency f Hertz and the current Ι amp, the kVA rating (P) becomes: For a three-phase system:

1000 P = 3 VI = 2πfCV2

For a single-phase system:

1000 P = VI = 2πfCV2

Fig. 7.8 Capacitor Circuit Vt VcVc i Vct1 t2 Em Em Fig. 7.9 Circuit-Opening Conditions VtVc = Em Vc = – 3Em Vc = – 7Em Vc = 5Em Circuit opening Fig. 7.10 Accumulative Capacitor Charge When the switch (Fig. 7.11) is closed, a charge (q=CV) must be instantaneously supplied to equal the

instantaneous supply voltage (V), according to the phase angle at the instant of circuit closure. This charge results in a large surge current. If the circuit is closed at the peak (E m ) of the supply voltage (V), the surge current (i), according to transient phenomena theory, is:

2 Emi =

ε C 4L – R2 2Lsin tC 4L – R2 From Fig. 7.12, the maximum value (im ) is: Emim = ε C L Rarctan C C 4L – R2 4L – R2 and appears at time t = t0 where: 2Lt0 = Rarctan C C 4L – R2 4L – R2 Although V is not constant, τ0 is extremely small, so that V = Em can be assumed for the transient dura- tion; similarly, the conduction time can be assumed as 2τ 0. Thus, an MCCB for use in a capacitive circuit must have an instantaneous-trip current of greater than i m x 2τ0. Example: MCCB selection for a 3-phase 230V 50Hz 150 kVA capacitor circuit. From Table 7.4, C = 0.9026 x 10–2 (F) and I = 377(A). The values of R and L in the circuit must be esti- mated, and for this purpose it is assumed that the short-circuit current is approximately 100 times the circuit capacity – i.e., 50,000A. Z = R2 + (2πfL)2 ∴ 50,000 = 3 Z V thus: Z = = 2.66 x 10 –3 3 x 50,000 230 since: Em = obtained from their respective formulas as, V = 188, im and τ0 can be 3 and assuming: then: 2πfL = 2.60 x 10–3 Ω thus: R = 5.21 x 10–4 Ω L = 8.29 x 10–6 (H) = 5R 2πfL im =6200A Since current-flow duration is approximately 2τ0, an MCCB is selected with a latching time of 0.001 seconds at 6200A. The Type NF630-SP is suitable, having a latching time of 0.0029 seconds at 10,000A. Even with a shorter latching time, tripping is unlikely under the application of the above current, but selec- tion of an MCCB with an instantaneous-trip current of greater than 6200 = 4400A is recommended for an adequate safety margin. Such an MCCB will be rated at 600A. Accordingly, in this example the Type NF630- SP, rated at 600A, is selected. Table 7.4 is a basis for selection, but since, in cases where the short-circuit capacity of the circuit is considerably higher than that of the MCCB, spurious tripping due to the switching surge may occur, it is also necessary to make calcu- lations along the lines of the above example. Em Vc iL R C Fig. 7.11 PF Correction Capacitor Vc i im τo FIg. 7.12 Currents and Voltages

7.7 MCCBs for Thyristor Circuits

Both overcurrent and overvoltage protection must be provided for these elements. MCCBs can be used effectively for overcurrent, although application de- mands vary widely, and selection must be made care- fully in each case. Overvoltage protection must be provided separately; devices currently in use include lightning arresters, dischargers, RC filters and oth- ers. 1. MCCB Rated Currents A primary factor determining the rated current of the MCCB to be used is the question of AC-side or DC- side installation. AC-side installation permits a lower rating, which is a considerable advantage. Fig. 7.13 shows both AC and DC installation (MCCBs 1 and 2); Table 7.5 gives a selection of circuit formats and cur- rent configurations; using this table it is possible to determine the MCCB rating for either MCCB 1 or 2, as required. The current curve of the thyristor (aver- age current is usually given) and the tripping curve of the MCCB should be rechecked to ensure that there is no possibility of overlap. When an overcurrent is due to a fault in the load, causing a danger of thermal destruction of the circuit elements, either AC or DC protection is adequate, provided the parameters are properly chosen. When

Table 7.4 MCCB Selection for Circuits with PF-Correction a) 230V, 50Hz Circuit Capacitor rating kVA 100 150 200 300 400 µF 301 602 903 1203 1504 1805 2407 3009 4513 6017 9026 12034 18052 24069 Single-phase circuit Capacitor rated current (A) 21.7 43.5 65.2 87.0 108.7 130.4 173.9 217.4 326.1 434.8 652.2 869.6 1304.3 1739.1 MCCB rated current (A) 100 125 175 200 250 350 500 700 1000 1400 2000 2500 Three-phase circuit Capacitor rated current (A) 12.6 25.1 37.7 50.2 62.8 75.3 100.4 125.5 188.3 251.0 376.5 502.0 753.1 1004.1 MCCB rated current (A) 100 125 150 200 300 400 600 800 1200 1500 b) 230V, 60Hz Circuit Capacitor rating kVA 100 150 200 300 400 µF 251 501 752 1003 1254 1504 2006 2507 3761 5014 7522 10029 15043 20057 Single-phase circuit Capacitor rated current (A) 21.7 43.5 65.2 87.0 108.7 130.4 173.9 217.4 326.1 434.8 652.2 869.6 1304.3 1739.1 MCCB rated current (A) 100 125 175 200 250 350 500 700 1000 1400 2000 2500 Three-phase circuit Capacitor rated current (A) 12.6 25.1 37.7 50.2 62.8 75.3 100.4 125.5 188.3 251.0 376.5 502.0 753.1 1004.1 MCCB rated current (A) 100 125 150 200 300 400 600 800 1200 1500 Capacitor rating kVA 100 150 200 300 400 µF 199 298 398 497 597 796 995 1492 1989 2984 3979 5968 7958 Single-phase circuit Capacitor rated current (A) 12.5 25.0 37.5 50.0 62.5 75.0 100.0 125.0 187.5 250.0 375.0 500.0 750.0 1000.0 MCCB rated current (A) 100 125 150 200 300 400 600 800 1200 1500 Three-phase circuit Capacitor rated current (A) 7.2 14.4 21.7 28.9 36.1 43.3 57.7 72.2 108.3 144.3 216.5 288.7 433.0 577.4 MCCB rated current (A) 100 125 175 225 350 500 700 900 c) 400V, 50Hz Circuit Basically, overcurrent leads to excessive tempera- ture rise of the thyristor junction, resulting in loss of the control function, and thermal destruction. A fault, therefore, must be interrupted as quickly as possible, before the junction temperature rises above its speci- fied limit. In the overcurrent region, designated on the current-surge withstand curves of the circuit element, the element can usually withstand the surge for at least one cycle. The current-surge withstand, gener- ally specified as a peak value, must be converted to RMS, to select a suitable MCCB. An overload of short-circuit proportion, either ex- ternal or in a bridge-circuit thyristor element, necessi- d) 400V, 60Hz Circuit Capacitor rating kVA 100 150 200 300 400 µF 166 249 332 414 497 663 829 1243 1658 2487 3316 4974 6631 Single-phase circuit Capacitor rated current (A) 12.5 25.0 37.5 50.0 62.5 75.0 100.0 125.0 187.5 250.0 375.0 500.0 750.0 1000.0 MCCB rated current (A) 100 125 150 200 300 400 600 800 1200 1500 Three-phase circuit Capacitor rated current (A) 7.2 14.4 21.7 28.9 36.1 43.3 57.7 72.2 108.3 144.3 216.5 288.7 433.0 577.4 MCCB rated current (A) 100 125 175 225 350 500 700 900 the fault is in one of the thyristor elements, resulting in reverse current, the result is often that other circuit elements will be destroyed (see Fig. 7.14) if the cir- cuit is not interrupted immediately. In this case AC- side protection or protection in series with each ele- ment is necessary. 2. Tyristor Overcurrent Protection Total protection of each element is possible in theory, but in practice overall coordination and the best com- promise for economy are usually demanded. Where elements are critical, complex combinations of pro- tective devices can be employed, at proportionally higher cost. Notes: 1. The MCCB rated current should be approx. 150% of the capacitor rated current. 2. The MCCB short-circuit capacity should be adequate for the circuit short-circuit capacity.

Note: Load is assumed resistive, with elements conductive through 180°. Table 7.5Thyristor Circuits and Current Formats Fig. 7.13 AC- and DC-side Protectors for Thyristors Fig. 7.14 Fault-Current Flow Circuit No. I Circuit No. II Circuit No. III Circuit No. IV Element average current IF (A) Element RMS current Ie (A) Average DC current ID (A) RMS current IB (A) RMS current IB (A) Current waveform Current waveform Circuit diagramCurrent flow MCCB1MCCB2 π IP IP IP IP π IP π IP π IP 6 + (6 0.552 IP) IP 3 + (6 2.45 IF) IFπ 1 3 + (6 0.817 ID ) ID π IF or 2IF 2IF 3IF π IF π ID or π IF π ID or π IF (6 2.22 IF) 2M2 π ID (6 1.11 ID ) or 2 + IF 6 3IFπ 1 3M3 2 + ID 6 ID π 3M3 or Ie π ID or π IF 2M2 π ID or π IF 2M2 π ID or Load MCCB1 MCCB1 MCCB2 Load MCCB1 MCCB2 Load MCCB1 MCCB2 Load IP IP IP IP IP IP IP IP Load MCCB1 MCCB2 LoadFault element

protection (MCCB1, Fig. 7.15) is presented, but the DC-protection case (MCCB2) can be plotted in the same way. Region 2 in Fig. 7.17 is the area of overcurrent for which protection is effected by the MCCB. For pro- tection of region 1, an overload relay is effective, and for region 2, inductance L must be relied on to limit the fault-current rise rate, or a high-speed current-lim- iting fuse must be used. Practical considerations, in- cluding economy and the actual likelihood of faults in the regions concerned, may dictate the omission of the protective devices for regions 1 and 3, in many cases. The lower the instantaneous-trip setting of the MCCB, the wider the region 2 coverage becomes. MCCB2 MCCB1 L Smoothing inductance R E Short circuit Load Fig. 7.15 Thyristor Short Circuit MCCB Short-circuit current Trip current q Arc voltage Circuit voltage t1 t3 t2 t4 tT t1 : Time to MCCB latching t2 : MCCB opening time t3 : Time from contact parting to current peak value t 4 : Arc duration tT : Total interruption time q : Current-rise rate Fig. 7.16 Thyristor Short-Circuit Interruption tates rapid interruption of the circuit. Normally, such interruption takes place within one cycle; thus, from the point of view of element thermal destruction, the time integral of the current squared must be consid- ered. Quantitatively, the permissible ei 2dt of the ele- ment must be greater than the ei2dt of the MCCB cur- rent through interruption, converted to apply to the element. The latter is influenced by the short-circuit current magnitude, the interruption time, and the cur- rent-limiting capability of the MCCB. It is important to note that the MCCB interruption time will be considerably influenced by the short-cir- cuit current rise rate, di/dt, on the load side. In the short circuit of Figs. 7.15 and 7.16, the current is: i = (1 – ε )R E –tL R and the current rise rate di/dt is: ( )t=0 =dt di L E Thus, the inductance of the line, and the smoothing inductance significantly affect di/dt. Where the poten- tial short-circuit current is very large, the inductance should be increased, to inhibit the rise rate and assist the MCCB to interrupt the circuit in safe time. This is The MCCB current during total time (t T) is ei2 dt, which, converted to the ei2 dt applied to the circuit element, must be within the limit specified. Having determined the circuit constants, testing is preferable to calculation for confirmation of this relationship. Assuming a large current-rise rate, with an AC-side short-circuit current i = I pssin ω t, and an MCCB inter- ruption time of one cycle, the ei2 dt applied to the thy- ristor is as follows: 1. For circuits I, II and III of Table 7.10: ei2dt = e Ip2 sin2 ω tdt = Ip2 12f (A2sec) 2. For circuit IV: ei2dt = 2e Ip2 sin2 ω tdt = ( )+( A 2sec)f Ip2 33f where Ip is the peak value of the element current and f is the supply frequency. If the ei2 dt of the circuit element is known, the per- missible ei2dt for the MCCB can be determined, us- ing the last two equations given above. Provided that the interruption time is not greater than one cycle, the MCCB current will be the same as the element cur- rent for circuits I and II, and twice that for circuits III and IV. This means that the MCCB ei 2dt through the interruption time should be within twice the permis- sible ei 2dt of the element. Diodes are generally stronger against overcurrent than thyristors, and since diodes can handle larger I 2·t, protection is easier. Fig. 7.17 shows the protection coordination situa- tion of a selection of devices, plotted together with the thyristor current-surge withstand curve. AC-side

1. Element Breakdown in Thyristor-Leonard Systems In this system of DC motor control, if power outage or commutation failure due to a thyristor control-circuit fault occurs during inversion (while motor regenera- tive power is being returned to the AC supply), the DC motor, acting as a generator while coasting, will be connected to a short-circuit path, as in Fig. 7.18. For thyristor protection, MCCBs must be placed in the DC side, as shown. A Mag-Only MCCB with a tripping current of about 3 times the rated current is employed, either 3- or 4- pole, series-connected as shown in Fig. 7.20. Since the element short-circuit current is the same as the MCCB current, circuit protection is effected provided that the ei 2dt limit for the element is larger than that for the MCCB interruption duration. This must be es- tablished by test. Fig. 7.19 High-Speed Fuses for Thyristor-Circuit Protection Fig. 7.20 Series Connection of MCCB Poles Fig. 7.18 Ward-Leonard Thyristor Protection /,/, /,/, 3-Phase Fullwave Rectification MCCB : Mag-Only Tripping time Hrs Min Sec 100 14108 0.5 0.2 0.1 0.05 0.02 0.01 125 200 300 400 500 600 700 1000 1500 2000 3000 4000 Current (% of rating) Region 1 Region 2 Region 3 Thyristor current-surge withstand MCCB tripping High-speed current-limiting fuse Overcurrent-relay Fig. 7.17 Thyristor and Protector Operating Curves M Short-circuit path in a commutation element failure Short-circuit path in a power outage Commutation element failure AC supply High-speed fuses M M M b) 4-pole MCCB a) 3-pole MCCB

Fig. 7.19 shows connection of high-speed fuses for protection against thyristor breakdown that would otherwise result in short-circuit flow from the AC sup- ply side. 4. MCCBs for Lamp Mercury-Lamp Circuits The ballasts (stabilizers) used in this type of lamp cover a variety of types and characteristics. For 200V applications (typical), choke-coil ballasts are used. For 100V applications a leakage-transformer ballast is employed. Normal ballasts come in low power-factor versions and high power-factor versions, with correc- tion capacitors. More sophisticated types include the constant-power (or constant-output) type, which main- tains constant lamp current both in starting and nor- mal running, and flickerless types, which minimize the flicker attendant on the supply frequency. In selecting an MCCB where normal (high or low PF) ballasts are to be used, the determining factor is the starting current, which is about 170% of the stable running current. In the cases of constant-power or flickerless types, the determining factor is the normal running current, which is higher than the starting cur- rent. For MCCB selection, the latter types can be re- garded as lighting and heating general loads, as pre- viously discussed. For selection of MCCBs for regular ballasts, the 170% starting current is assumed to endure for a maximum of 5 minutes. MCCBs of 100A or less frame size have a tripping value very close to rating for over- loads of duration of this order, so that the MCCB rat- ing should be the nearest standard value above 170% of the stable running current. MCCBs of above 100A frame size can handle a current of around 120% of the rating for 5 minutes without tripping; thus the near- est standard MCCB rating above 1.2 1.7 = 1.4 times the stable-running current of the lamp load is the suitable protector. As an example, consider MCCB selection for 10 units of 100W, 100V, 50Hz general-purpose high power-factor mercury lamps. The stable-running cur- rent per lamp is 1.35A. Thus: 1.35 x 10 x 1.7 = 23A, and the selection becomes NF30-SP, 30A rated.

Fig. 7.22 MDU Breaker Circuit Diagram (without voltage and electric power measurement)

7.8 MDU Breaker

The MDU breaker is a circuit breaker equipped with the MDU (Measuring Display Unit) which measures and digitally displays electric circuit information. Combining the circuit breaker, CT, VT and measuring display unit, saves space and wiring, allows monitoring of various electric circuits and the energy load conditions.

7.8.1 Measurement

(a) Motion As shown in Fig. 7.21, the electric current of each phase is transformed by the primary CT and inputted into the overload relay circuit for an electronic NFB. The electric current is transformed by the secondary CT and sent to the measuring display unit, MDU. Line voltage is converted to a signal in proportion to the voltage signal by resistance, transformed by the VT equivalent CT and inputted into the MDU. The MDU measures and displays by the electric current and voltage signals. Fig. 7.22 shows the internal block diagram of a model without voltage/electric power measuring functions. The frequency detection circuit provides an electric circuit fre- quency for measurement calculation. MDU converts the electric current and volt- age signals from CT and VT into the volt- age signal through the I/V conversion sec- tion. This signal is selected by a multiplexer and digitized at an A/D conversion section for digital calculation by a microcomputer. The CPU performs effective value calcula- tion, demand calculation, electric power cal- culation, electric energy accumulation and harmonic calculation, etc. The items to be measured are load current, line voltage, electric power, electric energy and harmonic current (3rd, 5th, 7th and ALL). It allows easy confirmation of electric circuit conditions and precise and efficient Fig. 7.23 MDU Block Diagram Fig. 7.21 MDU Breaker Circuit Diagram PAL Close-open working part Line side terminal Trip coil VT equivalent CT Open protection circuit Secondary CT Overload relay circuit Overload signal MDU circuit Alarm display section B/NET transmission circuit Fault event cause signalPrimary CT Measuring display operation section MDU power circuit MA MB FG Control power Transmission line D N S Load side terminal PAL Close-open working part Line side terminal Trip coil Secondary CT Overload relay circuit Overload signal MDU circuit Frequency detecting circuit Alarm display section B/NET transmission circuit Fault event cause signal Primary CT Measuring display operation section MDU power circuit MA MB FG Control power Transmission line D N S Load side terminal Open protection circuit I/V conversion section Constant voltage circuit Control power Current input Voltage input Alarm I/V conversion section I/V conversion section I/V conversion section I/V conversion section I/V conversion section I/V conversion section Input section Multiplexer MA MB Operation/setup section Microcomputer Segment LED display section Alarm LED display section CPU A/D conversion section

(b) Measurement precision The precision (allowance) of a measurement unit means the rate of errors against measurement range expressed as a percentage. The preci- sion of electric current and voltage, etc. for MDU is equivalent to JISC1111 and it is the rate of errors against the rated current and voltage of measurement expressed as a percentage. Also, the precision of the electric power and electric energy is shown as a rate of errors against the rated current and voltage of measurement. Table 7.6Measurement Item List Fig. 7.24 Example of the NF600-SEP 3P MDU Display Fig. 7.25 Mounting (c) External appearance and mounting of MDU An example of the external appearance of MDU is shown in Fig. 7.24 and Fig. 7.25 showing the mounting structure. energy management.Table 7.6 shows all the items. Sampling for measurement of voltage, electric current and electric power takes place once every several seconds, and the measured values are subject to calculation of the measure- ment values, such as the present values and average value, etc. Since the average value and electric energy are calculated from the sampling value measured once every several seconds, care should be taken when there is a breaking load such as a resistance welder. Electric en- ergy cannot be used to provide data for con- tracts or verification. *1 Confomts to JISC1111. *2 It is not a power average/supply value obtained by Measurement Method. *3 B/NET transmission and electric energy accumulated pulse output cannot be mounted simultaneously. Item Applicable models NF600-SEP NF600-HEP NF400-SEP NF400-HEP Power provided NF400-SEP NF400-HEP NF800-SEP NF800-HEP Load current of each phase, precision ±2.5%* Present value, average value, maximum average value Line voltage, precision ±2.5%* Present value, average value, maximum average value Harmonic load current 3rd, 5th, 7th and ALL Precision ±2.5%* Present value, maximum value, average value, maximum average value Electric power, precision ±2.5%* Present value, average value, maximum average value Electric energy accumulated, precision ±2.5%* Fault event current/fault event cause Maximum measuring current Control power Electric energy accumulated pulse output(option) B/NET transmission(option) Alarm(LED Indication) Maximum measuring voltage Measuring rated current Measuring rated voltage PAL OVER Load current of each phase, line voltage, electric power, electric energy, ALL harmonic current, fault event current/fault event cause Alarm PAL Solid straight relay no voltage contact a DC24V/AC100 • 200V 20mA Pulse range 0.35 to 0.45sec Pulse unit 1,10,100,1000,10000, kWh=/Pulse AC100-240V 50/60Hz DC100V 200V 12VA

• ••
• •••
• ••
• ••
• •••
• •• 400A 400A 600A 800A 440V 440V 440V 440V 800A 800A 1200A 1600A 690V 690V 690V 690V Measured value display Outline of main unit mounting Outline of panel mounting A m k A V W Wh V W Wh RR-S Display selection Phaseselection ALARMFunction Measured value selection SS-T TT-R PRESENT MAX DEMAND TIME CLEAR EPAL Pulse unit PAL OVER EPAL ECA Alarm reset switch Alarm keep DEMAND N TRIP LA PF DISP PHASE MODE FUNC SET Function switch Measured value selection switch Phase selection switch Display selection switch Set switch HARM Measuring display unit

7.8.2Maintenance function In the fault event of a circuit breaker trip, the MDU breaker measures the fault event cause and the fault event current that is load current, and records them in a non-volatile memory device in order to identify the cause of the fault event and make a prompt recovery. Also, since it records the maximum values of demand current and hourly electric energy, etc. in a non-volatile memory device, it is useful for understanding the condition of power consumption. The fault event cause indicates either an overload or a short circuit. 7.8.3Alarm output function A circuit breaker monitors various alarm outputs and turns on an alarm LED. The alarms are the PAL, the load current pre-alarm and OVER, the overload alarm. 7.8.4Transmission function The measured data is transmitted through B/NET, MITSUBISHI distribution control network (option). It can obtain the unit management data for energy saving and automatically collect the electric equipment operation data for preventive maintenance. Furthermore, electric energy accumulated can output as a pulse output (op- tion). It enables the direct input into a sequencer realizing labor saving of power consumption control by the sequencer. Fig.7.26 Demand Characteristics An average value is a value close to an average within the demand time limits. Also, demand time limit ( t0 ) means a period until measuring display value ( I 0 ) indicates 95% of input ( I ) when a certain input ( I ) is continuously turned on. It takes about three times as long as the time limit ( t0 ) until it indicates 100% of input ( I ) ( Fig. 7.26 ). Withstand Voltage and Insulation Resistance Tests As VT is connected between the poles on the load side of a circuit breaker, voltage resistance tests be- tween the electrodes on the load side cannot be con- ducted (shown as 5 in Table 7.7.) Although an insu- lation resistance test at DC500V does not result in damage to the circuit breaker, the insulation resistance value measured by the test will be low (shown as There is no problem regarding the voltage and insu- lation resistance tests between the circuit breaker main circuit and earth. Table 7.7 Places for Withstand Voltage and Insulation Resistance Tests Measured Point/test Insulation resistance measurement Withstand voltage test Between line part and earth State of handle Between left and middle poles Between middle and right poles Between left and right poles Between middle and neutral poles Between left and middle poles Between middle and right poles Between left and right poles Between middle and neutral poles Between line and load side terminal Load side Line side Between different poles ON OFF ON OFF I 0.95 I I Measuring display value (Time limit) t0 Time t

x 100 100% or less

7.9 Selection of MCCBs in inverter circuit

7.9.1Cause of distorted-wave current Distorted-wave current is caused by factors such as the CVCF device of a computer power unit, various recti- fiers, induction motor control VVVF device corresponding to more recent energy-saving techniques, etc, wherein thyristor and transistor are used. Any of these devices generates DC power utilizing the switching function of a semiconductor and, in addition, transforms the generated DC power into intended AC power. Generally, a large capacity capacitor is connected on its downstream side from the rectification circuit for smoothing the rectifica- tion, so that the charged current for the capacitor flows in pulse form into the power circuit. Because voltage is chopped at high frequency in AC to DC transforming process, load current to which high frequency current was superimposed by chopping basic frequency flows into the load line. This paragraph describes the VVVF in- verter, of these devices, which will develop further as main control methods for induction motors currently in broad use in various fields . Fig. 7.27 illustrates an example of MCCBs application to inverter circuit. Two control methods of PAM (Pulse Amplitude Modulation) and PWM (Pulse Wide Modulation) are available for the VVVF inverter and generating higher harmonic wave components differs depending on the difference between the control methods. As seen from Tables 7.9 and 7.10, this harmonic wave component of input current can be made smaller (improved) by inputting DC reactor (DCL) or AC reactor (ACL). Further, in the case of the output current waveform in Fig. 7.29, the PWM generates higher harmonic wave components than that of the PAM. This table is subject to the current which meets the following requirements. Fig.7.27 Example of MCCBs Application to Inverter Circuit Notes: 1.The characteristics of perfect solenoid type MCCBs vary significantly depending on wave distortion. Therefore, use of thermal acting solenoid type MCCBs is recommended. 2.NF2000-S, NF2500-S, NF3200-S, NF4000-S 3.NFE2000-S, NFE3000-S, NFE4000-S Table 7.8 Reduction Rate q Distortion percent Real value of total harmonic wave component Real value of basic frequency w Peak factor = Peak value Real value 3 or less e Higher harmonic wave components are mainly No.7 or a lower harmonic wave. MCCBs tripping system Thermalacting solenoid type (bimetal system) 1.4 1.4 1.4 (Note 2) Thermal acting solenoid type (CT system) (Note 1) Perfect solenoid type Electronic type (Real value detection) (Note 3) Electronic type (Peak value detection) Reduction rate K 7.9.2Selection of MCCBs MCCBs characteristic variations and temperature rises dependent on distortion of the current wave must be considered when selecting MCCBs for application to an inverter circuit (power circuit). The relation of rated current I NFB to load current I of MCCBs is selected as follows from the MCCBs tripping system. Thermal acting solenoid type (bimetal system) and electronic type (real value detection) are both real current detection systems which enable exact overload protection even under distorted-wave current. Due to the above explanation, it is advantageous to select real current detection type MCCBs. I NFB K x I NFB M Inverter Induction motor

High harmonic wave current content (%) P W M No ACL (Standard) Basic 3.7 81.6 49.6 27.4 7.6 6.7 2.5 83.6 48.3 23.7 6.2 4.7 97.0 21.9 7.1 3.9 2.8 97.2 21.7 7.0 3.7 2.6 With power factor modifying ACL With power factor modifying ACLWith standard ACL P A M Power factor = (DC voltage x DC) /( 3 x AC effective voltage x AC effective current) Waveform factor = (Effective value) /(Mean value) Peak factor = (Max value) /(Effective value) Circuitwith ACL Large ACL Small With DCL Input current Power factor Below 58.7 58.7% 58.7–83.5% 83.5% 83.5–95.3% 95.3% 1.23 1.28 Above 1.99 1.99 1.99–1.27 1.27 1.27–1.23 Above 2.16 2.16 2.16–1.71 1.71 1.71–1.28 Waveform factor Peak factor Waveform (half wave portion) t I ACL V Ed DCL V Ed Table 7.9 Data of High Harmonic Wave CurrentContent in Inverter Power Circuit (Example) Table 7.10Peak Factor of Inverter Input Current Note: No DCL Output frequency 60Hz , subject to 100% load Fig.7.28 Inverter Input Current Fig.7.29 Inverter Output Current (a) PAM system (b) PWM system (a) PAM system (b) Equal-value PWM system

1. ENVIRONMENTAL CHARACTERISTICS High temperature Low temperature High humidity High altitude Dirt and dust Corrosive gas, salt air Environment Trouble Countermeasures 1. Nuisance tripping 2. Insulation deterioration 1. Condensation and freezing 2. Low-temperature fragility in shipping (around –40˚C) 1. Insulation resistance loss 2. Corrosion 1. Reduced temperature, otherwise no problem up to 2,000m 1. Contact discontinuity 2. Impaired mechanism movement 3. Insulation resistance loss 1. Corrosion 1. Reduce load current (derate). 2. Avoid ambients above 60˚C. 1. Install heater for defrosting and drying. 2. Ship tripped, or if not possible, OFF. 1. Use MCCB enclosure such as Type W. 2. Inspect frequently, or install high- corrosion-resistant MCCBs. 1. See “Low temperature”, above. 1. Use Type I MCCB enclosure. 1. Use Type W MCCB enclosure or install high-corrosion-resistant MCCBs. Table 8.1 Abnormal Environments, and Countermeasures

8.1 Atmospheric Environment

Abnormal environments may adversely affect perfor- mance, service life, insulation and other aspects of MCCB quality. Where service conditions differ sub- stantially from the specified range as below, derating of performance levels may result. Ambient temperature range–10˚C~+40˚C (Average temperature for 24 hours, however, shall not be higher than 35˚C.) 2. Relative humidity 85% max. with no dewing 3. Altitude 2,000m max. 4. Ambient No excessive water or oil vapour, smoke, dust, salt content, corrosive sub- stance, vibration, and im- pact Expected service life (MTTF) under the above conditions is 15 years.

8.1.1 High Temperature Application

To comply with relevant standards, all circuit break- ers are calibrated at 40˚C. If the circuit breaker is to be used in an environment where the ambient tem- perature is likely to exceed 40˚C please apply the de- rating factor shown in table 8.2. For example: To select a circuit breaker for use on a system where the full load current is 70A in an ambi- ent temperature at 50˚C then from table 8.2 0.9 70A = 77.8A Select a circuit breaker with a trip unit adjustable from 80-100A or fixed at 100A. Table 8.2 MCCB Derating Ambient Temperature (°C) Derating factor 0.9 0.8 0.7

8.1.2 Low Temperature Application

In conditions where temperatures reach as low as –5˚C special MCCBs are usually required. Mitsubishi, however, have tested their standard MCCBs to tem- peratures as low as –10°C without any detrimental effects. For conditions where temperatures drop below –10˚C special MCCBs must be used. If standard MCCBs experience a sudden change from high temperature, high humidity conditions to low temperature conditions, there is a possibility of ice forming inside the mechanism. In such conditions we recommend that some form of heating be made avail- able to prevent mal-operation. In conditions of low temperature MCCBs should be stored in either the tripped or OFF position. Low Temperature MCCBs Special low temperature MCCBs are available that can withstand conditions where temperatures fall to as low as –40˚C. These special MCCBs are available in sizes up to 1200A in the standard series and above 50A in the compact series.

8.1.3 High Humidity

In conditions of high humidity the insulation resistance to earth will be reduced as will the electrical life. For applications where the relative humidity ex- ceeds 85% the MCCB must be specially prepared or special enclosures used. Special preparation includes plating all metal parts to avoid corrosion and special painting of insulating parts to avoid the build up of mildew. There are two degrees of tropicalisation: Treatment 1- painting of insulating material to avoid build up of mildew plus special plating of metal parts to avoid corrosion. Treatment 2- painting of insulating material to avoid build up of mildew only.

8.1.4 Corrosive Atmospheres

In the environment containing much corrosive gas, it is advisable to use MCCB of added corrosion resis- tive specifications. For the breakers of added corrosionproof type, corrosion-proof plating is applied to the metal parts. Where concentration of corrosive gas exceeds the level stated below, it is necessary to use MCCB of added corrosion resistive type being enclosed in a water-proof type enclosure or in any enclosure of pro- tective structure. Allowable containment for corrosive gas. H 2S 0.01ppm SO 2 0.05ppm NH 3 1ppm

8.1.5 Affecting of Altitude

When MCCBs are used at altitudes exceeding 2000m above sea level, the effects of a drop in pressure and drop in temperature will affect the operating perfor- mance of the MCCBs. At an altitude of 2200m, the air pressure will drop to 80% and it drops to 50% at 5500m, however interrupting capacity is unaffected. The derating factors that are applicable for high alti- tude applications are shown in table 8.3. (According to ANSI C 37.29-1970) Table 8.3 Derating Factors for High Altitude Appli- cations Altitude 3000m 4000m 5000m 6000m Rated current 0.98 0.96 0.94 0.92 Rated voltage 0.91 0.82 0.73 0.65 For example: NF800-SEP on 4000m 1. Voltage The rated operating voltage is AC690V. You should derate by 690x0.82=565.8V. It means that you can use this NF800-SEP up to AC565.8V rated voltage. 2. Current The rated current is 800A. You should derate by 800x0.96=768A. It means that you can use this NF800-SEP up to 768A rated current.

8.2 Vibration-Withstand Characteristics

8.2.1 The Condition of Test

1. Installation position and Direction of vibration

• Every vertical and horizontal at vertical installed (as shown in Fig. 8.1) 2. The position of MCCBs and vibration time Forty minutes in each position (ON, OFF and TRIP) 3. Vibration criteria
• Frequency 5~100Hz
• Vibration acceleration 2.2g
• Period 10min./cycle

8.2.2 The Result of Test

The samples must show no damage and no change of operating characteristic (200% release), and must not be tripped or switched off by the vibration. Vertical Wire connection Horizontal Fig. 8.1 Applied Vibration

8.3 Shock-Withstand Characteristics

8.3.1 The Condition of Test

1. MCCBs are drop-tested, as described in Fig. 8.2. The arrows show the drop direction. 2. The samples are set to ON, with no current flow- ing. 8.3.2 The Result of Test (as Shown in Table 8.4) The samples must show no physical damage, and the switched condition must not be changed by the drop in any of the drop-attitudes tested. The judgment of failure:

• A case the switched condition changed from ON to OFF
• A case the switched condition changed from ON to Trip
• A case the sample shows physical damage Table 8.4 Shock-Withstand Characteristics of Mitsubishi MCCB Type BH-K BH-P, BH-S, BH-PS, BH-D MB30-CS MB30-SP MB50-CP MB50-SP MB100-SP MB225-SP NF30-SP NF50-HP NF50-HRP NF60-HP NF100-SP NF100-SEP NF100-HP NF100-HEP NF160-SP NF160-HP NF250-SP NF250-SEP NF250-HP NF250-HEP NF400-SP NF400-SEP NF400-HEP NF400-REP NF630-SP NF630-SEP NF630-HEP NF630-REP NF800-SDP NF800-SEP NF800-HEP NF800-REP NF1000-SS NF1250-SS NF1600-SS NF2000-S NF2500-S NF3200-S NF4000-S NFE2000-S NFE3000-S NFE4000-S NF30-CS NF50-CP NF60-CP NF100-CP NF250-CP NF400-CP NF630-CP NF800-CEP NF100-UP NF100-RP NF225-UP NF225-RP NF400-UEP NF630-UEP NF800-UEP NF1250-UR No tripped (G) No damage (G) Series BH MB NF S C U ∗: 1G = 980cm/s2 Line terminals Line terminals Fig. 8.2 Drop-Test Attitudes

9.1 Purpose

Japanese and international standards require, in sum- mary, that an overcurrent protector must be capable of interrupting the short-circuit current that may flow at the location of the protector. Thus it is necessary to establish practical methods for calculating short-cir- cuit currents for various circuit configurations in low- voltage systems.

9.2 Definitions

1. % Impedance The voltage drop resulting from the reference current, as a percentage of the reference voltage (used for short-circuit current calculations by the % impedance method). reference voltage voltage drop at capacity load% impedance = x 100 (%) (Reference voltage: 3-phase – phase voltage) 2. Reference Capacity The capacity determined from the rated current and voltage used for computing the % impedance (nor- mally 1000kVA is used). 3. Per-Unit Impedance The % impedance expressed as a decimal (used for short-circuit current calculations by the per-unit method). 4. Power Supply Short-Circuit Capacity 3-phase supply (MVA) =kl3 x rated voltage (kV) x short circuit current (kA) 5. Power Supply Impedance Impedance computed from the short-circuit capacity of the supply (normally indicated by the electric power company; if not known, it is defined, together with the X/R ratio, as 1000MVA and X/R=25 for a 3-phase supply (from NEMA.AB1). 6. Motor contribution Current While a motor is rotating it acts as generator; in the event of a short circuit it contributes to increase the total short-circuit current. (Motor current contribution must be included when measuring 3-phase circuit short-circuit current). 7. Motor Impedance The internal impedance of a contributing motor. (A contributing motor equal to the capacity of the trans- former is assumed to be in the same position as the transformer, and its % impedance and X/R value are assumed as 25% and 6 (from NEMA.AB1). 8. Power Supply Overall Impedance The impedance vector sum of the supply (Z L), the transformer (ZT) and the motor (ZM ). Overall impedance of 3-phase supply ZL + ZT + ZM (ZL + ZT) • ZM(Zs) = (%Ω ) 9. Short-Circuit Current Measurement Locations In determining the interruption capacity required of the MCCB, generally, the short-circuit current is cal- culated from the impedance on the supply side of the breaker. Fig. 9.1 represents a summary of Japanese standards.

In computing low-voltage short-circuit current, all im- pedances from the generator (motor) to the short-cir- cuit point must be included; also, the current contrib- uted by the motor operating as a load. The method is outlined below.

9.3.1 Impedances

1. Power Supply Impedance (Z The impedance from the power supply to the trans- former-primary terminals can be calculated from the short-circuit capacity specified by the power company, if known. Otherwise it should be defined, together with X/R, as 1000MVA and X/R=25 for a 3-phase supply. Note that it can be ignored completely if significantly smaller than the remaining circuit impedance. 2. Transformer Impedance (Z Together with the line impedance, this is the largest factor in determining the short-circuit current magni- tude. Transformer impedance is designated as a per- centage for the transformer capacity; thus it must be converted into a reference-capacity value (or if using Ohm’s law, into an ohmic value). Tables 9.1 show typical impedance values for trans- formers, which can be used when the transformer impedance is not known. 3. Motor Contribution Current and Impedance (Z M ) The additional current contributed by one or more motors must be included, in considering the total 3- phase short-circuit current. Motor impedance depends on the type and capacity, etc.; however, for typical induction motors, % impedance can be taken as 25% and X/R as 6. The short-circuit current will thus in- crease according to the motor capacity, and the im- pedance up to the short-circuit point. The following assumptions can normally be made. a. The total current contribution can be considered as a single motor, positioned at the transformer location. b. The total input (VA) of motor contribution can be considered as equal to the capacity of the trans- former (even though in practice it is usually larger). Also, both the power factor and efficiency can be assumed to be 0.9; thus the resultant motor contri- bution output is approximately 80% of the trans- former capacity. c. The % impedance of the single motor can be con- sidered as 25% and the X/R as 6. 9. SHORT-CIRCUIT CURRENT CALCULATIONS

Reactance(mW/m) Load Supply side MCCB load terminals in the case of bare line (the line impedance on the MCCB load side may not be added). MCCB Load terminal in the case of insulated line (the line impedance on the MCCB load side can be added.) Fig. 9.1 Short-Circuit Locations for Current Calculations Table 9.1 Impedances of 3-Phase Transformers 1.81 1.78 1.73 1.61 1.63 1.50 1.25 1.31 1.17 1.23 1.13 Transformer capacity (kVA) 100 150 200 300 500 750 1000 1500 2000 Impedance (%) 1.31 1.73 1.74 1.91 2.60 2.82 4.06 4.92 4.94 5.41 5.89 4. Line and Bus-Duct Impedance (ZW , ZB) Table 9.2 gives unit impedances for various configu- rations of wiring, and Table 9.3 gives values for duct- ing. Since the tables give ohmic values, they must be con- verted, if the %-impedance method is employed. 5. Other Impedances Other impedances in the path to the short-circuit point include such items as CTs, MCCBs, control devices, and so on. Where known, these are taken into con- sideration, but generally they are small enough to be ignored.

9.3.2 Equivalent Circuits

1. Three-Phase Based on the foregoing assumptions for motors, the equivalent circuits of Fig. 9.2 can be used for calcu- lating 3-phase short-circuit current. The motor imped- ance (Z M ) can be considered as shunting the series string consisting of the supply (ZL) and transformer (ZT) impedances, by busbars of infinite short-circuit capacity. When the three impedances are summed, the total impedance and the resistive and reactive components are given as: Cable size (mm 2) Resistance (mΩ /m) 2-or 3-core cables 1-core cables (close-spaced) 1-core cables (6cm-spaced) 2-or 3-core cables 1-core cables (close-spaced) 1-core cables (6cm-spaced) 1.5 2.5 4.0 6.0 10.0 16.0 25.0 35.0 50.0 70.0 95.0 120.0 150.0 185.0 240.0 300.0 400.0 500.0 630.0 12.10 7.41 4.61 3.08 1.83 1.15 0.727 0.524 0.387 0.268 0.193 0.153 0.124 0.0991 0.0754 0.0601 0.0470 0.0366 0.0283 0.1076 0.1032 0.0992 0.0935 0.0873 0.0799 0.0793 0.0762 0.0760 0.0737 0.0735 0.0720 0.0721 0.0720 0.0716 0.0712 0.1576 0.1496 0.1390 0.1299 0.1211 0.1043 0.1014 0.0964 0.0924 0.0893 0.0867 0.0838 0.0797 0.0806 0.0818 0.0790 0.0777 0.0702 0.0691 0.2963 0.2803 0.2656 0.2527 0.2369 0.2138 0.2000 0.1879 0.1774 0.1669 0.1573 0.1498 0.1427 0.1356 0.1275 0.1195 0.1116 0.1043 0.0964 0.1292 0.1238 0.1191 0.1122 0.1048 0.0959 0.0952 0.0915 0.0912 0.0884 0.0882 0.0864 0.0865 0.0864 0.0859 0.0854 0.1891 0.1796 0.1668 0.1559 0.1453 0.1251 0.1217 0.1157 0.1109 0.1072 0.1040 0.1006 0.0956 0.0967 0.0982 0.0948 0.0932 0.0843 0.0829 0.3555 0.3363 0.3187 0.3033 0.2843 0.2565 0.2400 0.2254 0.2129 0.2001 0.1888 0.1798 0.1712 0.1627 0.1530 0.1434 0.1339 0.1252 0.1157 Notes: 1. Resistance values per IEC 228 Reactance per the equation: L(mH/km) = 0.05 + 0.4605log10D/r(D=core separation, r=conductor radius) 3. Close-spaced reactance values are used. Table 9.2 Wiring Impedance Table 9.3 Bus-Duct Impedance Rated current (A) 400 600 800 1000 1200 1500 2000 2500 3000 Resistance (mΩ /m) at 20°C 0.125 0.114 0.0839 0.0637 0.0397 0.0328 0.0244 0.0192 0.0162 Reactance (mΩ /m) 50Hz 0.0250 0.0231 0.0179 0.0139 0.0191 0.0158 0.0118 0.0092 0.0077 60Hz 0.0300 0.0278 0.0215 0.0167 0.0230 0.0190 0.0141 0.0110 0.0092

ZS = = R S + j XS ZL + ZT + ZM (ZL + ZT) · ZM R S = (RL + RT + RM )2 + (XL + XT + XM )2 (RL + RT + RM ) {RM (RL + RT) – XM (XL + XT)} + (XL + XT + XM ) {XM (RL + RT) + RM (XL + XT)}[ XS = (RL + RT + RM )2 + (XL + XT + XM )2 (RL + RT + RM ) {XM (RL + RT) + RM (XL + XT)} – (XL + XT + XM ) {RM (RL + RT) – XM (XL + XT)}[ Thus, when calculating the short-circuit current at various points in a load system, if the value ZS is first computed, it is a simple matter to add the various wire or bus-duct impedances. Table 9.4 gives values of total supply impedance (Z S), using transformer imped- ance per Table 9.1, power-supply short-circuit capacity of 1000MVA, and X/R of 25. ZM ZB ZW ZL L T B W Short- circuit point M Z T ZB ZM ZL ZW ZT ZB ZW Z ZS Fig. 9.2 3-Phase Equivalent Circuits Table 9.4 Total Impedances for 3-Phase Power Supplies 100 150 200 300 500 750 1000 1500 2000 Impedance based on 1000kVA(%) Ohmic value (mΩ )Transformer capacity (kA) Notes: 1. Total power-supply impedance ZS =ZL + ZT + ZM (ZL + ZT)ZM 2. For line voltages (E') other than 200V, multiply the ohmic value by ()200 2E' 33.182 +j 26.482 21.229 +j 22.583 15.473 +j 17.109 9.56 +j 12.389 6.977 +j 12.15 4.306 +j 8.795 2.089 +j 7.27 1.427 +j 5.736 0.969 +j 4.336 0.671 +j 3.142 0.467 +j 2.544 230V 17.553 +j 14.009 11.230 +j 11.946 8.185 +j 9.051 5.057 +j 6.554 3.691 +j 6.427 2.278 +j 4.653 1.105 +j 3.846 0.755 +j 3.034 0.513 +j 2.294 0.355 +j 1.662 0.247 +j 1.346 440V 64.240 +j 51.269 41.099 +j 43.720 29.956 +j 33.123 18.508 +j 23.985 13.507 +j 23.522 8.336 +j 17.027 4.044 +j 14.074 2.763 +j 11.104 1.876 +j 8.394 1.299 +j 6.083 0.904 +j 4.925

Ias = Is · { 1 + 2e e + 2 1 + } = Is · K3x 2πR– x 2πR– that is: K3 = { 1 + 2e e + 2 1 + }x 2πR– x 2πR– K3 is the asymmetrical coefficient, derived from the symmetrical value and the circuit power factor. 3. Peak Value of Asymmetrical Short-Circuit Current This value (I p in Fig. 9.3) depends upon the phase angle at short circuit closing and on the circuit power factor; it is maximum when θ = 0. It will reach peak value in each case, ω t = 2 π + ϕ after the short circuit occurrence. It can be computed as before, by means of the circuit power factor and the symmetrical short- circuit current. Ip = Is [1 + sinϕ·e ] = Is · Kp2 π x R–( + ϕ)· thus: Kp = 2 [1 + sinϕ·e ]2 π x R–( + ϕ)· Kp, the peak asymmetrical short-circuit current coeffi- cient, is also known as the closing-capacity coefficient, since I p is called the closing capacity. Thus, in each case, the asymmetrical coefficients can be derived from the symmetrical values and the circuit power fac- tor. These coefficients are shown Fig. 9.4. As As 1/2 Cycle Ip Ad Fig. 9.3 Short-Circuit Current

9.4 Classification of Short-Circuit Current

A DC current (Fig. 9.3) of magnitude determined by the voltage phase angle at the instant of short circuit and-the circuit power factor will be superimposed on the AC short-circuit current. This DC component will rapidly decay; however, where a high-speed circuit-interruption device such as an MCCB or fuse is employed, the DC component must be considered. Further, the mechanical stress of the electric circuit will be affected by the maximum instantaneous short-circuit current; hence, the short- circuit current is divided, as below. 1. RMS Symmetrical Short-Circuit Current (I This is the value exclusive of the DC component; it is As/M2 of Fig. 9.3. 2. RMS Asymmetrical Short-Circuit Current (Ias) This value includes the DC component. It is defined as: AsIas = )2 + Ad2( Accordingly, when the DC component becomes maxi- mum (i.e., θ – ϕ = ± 2 π , where the voltage phase angle at short circuit is θ, and the circuit power factor is cosϕ), Ias will also become maximum 2 1 cycle after the short circuit occurs, as follows: Ias = Is · 1 + 2e = Is · K1, that is: K1 = 1 + 2ex 2πR– x 2πR– where K1 is the single-phase maximum asymmetrical coefficient, and Ias can be calculated from the asym- metrical value and the circuit power factor. In a 3- phase circuit, since the voltage phase angle at switch- on differs between phases, I as will do the same. If the average of these values is taken 2 1 cycle later, to give the 3-phase average asymmetrical short-circuit cur- rent, the following relationship is obtained: Kp 3.0 2.0 1.0 K1 K3 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.0 20 10 8 7 6 5 4 3 2.5 2 1.5 1 0.5 K1: Single-phase maximum asymmetrical coefficient K 3: 3-phase asymmetrical coefficient Kp: Closing capacity coefficient Power factor R X Kp Fig. 9.4 Short-Circuit Current Coefficients

9.5 Calculation Procedures

Table 9.5Necessary Equations 9.5.1Computation Methods Regardless of method, the aim is to obtain the total impedance to the short-circuit point. One of two com- mon methods is used, depending upon whether a percentage or ohmic value is required. 1.Percentage Impedance Method This method is convenient in that the total can be derived by simply adding the individual impedances, without the necessity of conversion when a voltage transformer is used. Since impedance is not an absolute value, being based on reference capacity, the reference value must first be determined. The reference capacity is normally taken as 1000kVA; thus, the percentage impedance at the transformer capacity, the percentage imped- ance derived from the power supply short-circuit ca- pacity, and also the motor impedance must be con- verted into values based on 1000kVA (Eqs. 13 and 14). Also, the wiring and bus-duct impedances that are given in ohmic values must be converted into per- centage impedances (Eq. 12). 2.Ohmic Method In calculating short-circuit currents for a number of points in a system, since the wire and bus-duct im- pedances will be different in each case, it is conve- nient to use Ohm’s law, in that if, for example, the total supply impedance (Z s ) is derived as an ohmic value, the total impedance up to the short-circuit point can be obtained by simply adding this value to the wire and bus-duct impedances, which are in series with the supply. For total 3-phase supply impedance s ), refer to Table 9.4 (which shows calculations of Z s based on standard transformers) to eliminate troublesome calculations attendant to the motor im- pedance being in parallel with Z s 9.5.2Calculation Examples 1.3-phase Circuit For the short circuit at point S in Fig. 9.5, the equiva- lent circuit will be as shown in Fig. 9.6. The 3-phase short-circuit current can be obtained by either the %- impedance method or Ohm’s law, as given in Table 9.6. 3-phase Impedance Ohmic method % impedance method Remarks I as = K I s Key I s V Z I as P I B K 3-phase short-circuit current (A, sym) Line-line voltage (V) Circuit impedance (1-phase component) 3-phase short-circuit current (A, asym.) Reference capacity (3-phase component, VA) % impedance of circuit (single-phase component, %) Reference current (A) 3-phase asymmetrical coefficient Conversion from percentage value to ohmic value Where P is the capacity at which %Z was derived. Power supply impedance seen from primary side Supply impedance seen from second- ary side Conversion from ohmic value to per- centage value Eq. 2 is derived from Eqs. 1, 1' and 2'. Eq. 3 is derived from Eqs. 1 and 1'. Because Eq. 1 can be obtained from Eqs. 2 and 12, it can be seen that I s of the % impedance method is not affect- ed by the selection of the reference ca- pacity. The single-phase short-circuit current in a 3-phase circuit is M 3/2 times the 3- phase short-circuit current. Conse- quently, a 3-phase circuit can be exam- ined via the 3-phase short-circuit current. Eqs. 9 and 12 are derived from Eqs. 1' and 2', and Eqs. 3' and 4'. As the supply impedance is defined as 100% at short circuit capacity, for Eq. 13 conversion to reference capacity is made. When the supply short-circuit capacity is unknown, the impedance is taken as 0.0040+j0.0999 (%) for 3-phase sup- ply, and 0.0080+j0.1998 (%) for a 1- phase supply (see Table 9.6). The motor and transformer impedanc- es are converted from %Z at their equipment capacities into %Z at refer- ence capacity, using Eq. 14. Eq. 14 for motor impedance becomes Transformer impedance, motor im - pedance: Conversion to %Z at reference capac- ity Power-supply impedance: I S M 3 · Z V Z = · %Z x 10 Ω P V V P reference capacity %Z = x equipment capacity reference capacity %Z at equip- ment capacity (4.11 + j24.66) x (For details see Table 9.6.) equipment capacity reference capacity short-circuit capacity (primary voltages) Z = primary-side power supply x impedance primary voltage secondary voltages I S M 3 · V · %Z P V/ M I B

• Z P = M 3 · V · I B I B K 1 + 2e e + 2 1 + x π R x π R

Table 9.6 Calculation Example: 3-Phase Short-Circuit Current Fig. 9.6 Equivalent CircuitFig. 9.5 Circuit Configuration ZL = x 100 = 0.1 (%)1000 x 106 1000 x 103 1500 x 103 1000 x 103 1500 x 103 x 0.8 1000 x 103 ZS = ZL + ZT + ZM (ZL + ZT)ZM Ohmic method% impedance method Power supply impedance ZL Transformer impedance ZT Motor impedance ZM Total power supply impedance ZS Line impedance ZW Total impedance Z 3-phase short-circuit symmetrical current 123Is The supply short-circuit capacity, being unknown, is defined as 1000MVA with XL/RL = 25. From Eq. 13, at the 1000kVA reference capacity: since XL/RL = 25, The total motor capacity, being unknown, is assumed equal to the transformer capacity, with: %Z M = 25(%) XM /RM = 6 From Eq. 14, at reference capacity, 1000kVA: From Table 9.1: ZT = 1.23 + j5.41 From Eq. 14, after conversion to reference capacity, 1000kVA: Z W = (0.0601 + j0.079) x 10 –3 x 10 x 100 4402 1000 x 103 Multiplying the value from Table 9.2 by a wire length of 10M, and converting to the 1000kVA reference, from Eq. 12: Z = Z S + ZW From Eq. 2: (R and X are calculated, per §9.3.2.) 0.1 = RL2 + (25RL)2 = 25.02RL ZL = RL + jXL = 0.0040 + j0.0999 (%) Is = = 35.622 (A) x 100M3 x 440 x3.683 1000 x 103 ZL = = 0.0436 ( Ω )1000 x 106 (6600)2 ZL = (1.741 + j43.525) x ( )6600 440 ZL = x 100 x 10–2 x 103 = 0.1936 (mΩ )1000 x 106 4402 = 1.2906 + j6.9825 (mΩ ) 1500 x 103 4402 = 6.6294 + j39.7847 (mΩ ) 1500 x 103 x 0.8 4402 ZS = ZL + ZT + ZM (ZL + ZT)ZM The supply short-circuit capacity, being unknown, is defined as 1000MVA with XL/RL = 25. From Eq. 10, the supply impedance seen from the primary sicde: and since X L/RL = 25: ZL = 1.741 + j43.525 (mΩ ) From Eq. 11, supply impedance converted to the secondary side is: and since XL/RL = 25, ZL = 0.0069 + j0.1721 (mΩ ) Note: The supply ohmic impedance can more simply be derived: since it is 100% at short-circuit ca- pacity, Z L is obtained from Eq. 9, after percent- age to ohmic conversion: The total motor capacity, being unknown, is assumed equal to the transformer capacity, with: From Eq. 9, after percentage to ohmic conversion: ZW = (0.0601 + j0.079) x 10 Multiplying the value from Table 9.2 by a wire length of 10M. Z = ZS + ZW From Eq. 1 (R and X are calculated, per §9.3.2.) = 0.00773 + j0.1934 (mΩ ) From Table 9.1: From Eq. 9, after percentage to ohmic conversion. Is = = 35.622 (A) M3 x 7.1307x10–3 440 Short-circuit point S 3ph 50Hz 6.6kV/440V 1500kVA 10mWire 300mm 2 M Short-circuit point S Z L ZM ZW ZT

MOULDED CASE CIRCUIT BREAKERS HEAD OFFICE: MITSUBISHI DENKI BLDG., MARUNOUCHI, TOKYO 100-8310. TELEX: J24532 CABLE: MELCO TOKYO Y-0525-C 9909 (ROD) Printed in Japan Made from recycled paper New publication, effective DEC. 1998 Specifications subject to change without notice. Be sure to read the instruction manual fully before using this product.Safety Tips :