CB as Per IEC60947

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International standard

IEC 60947-2Low voltage switchgear

Part 2: Circuit-breakers

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Standard IEC 60947-2 Contents

I. General 3

2. Definitions 8

3. Circuit-breaker characteristics 10

4. Constructional requirements 14

5. Specific points (appendices) 21

6. Tests 27

7. Conclusion 34

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Standard IEC 60947-2


Came into f orce in 1999

Takes into account the circuit-br eaker main technological upgr ades


Is internationally r ecognized and approved

and is applied in the majority of countries (> 100)

General

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IEC

IEC

UL

CSAIEC

JIS/IEC

IEC

IEC

IEC

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Standard IEC 60947-2 General

The scope« Standard IEC 60947-2 applies to circuit-breakers, the main contacts

of which are intended to be connected to circuits, the rated voltage of

which does not in exceed 1000 V AC or 1500 DC; « »

The standard applies to circuit-breakers intended for use by

experienced operators.

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The scopeStandard IEC 60947-2 contains additional specifications for:

Circuit-br eaker s suitable f or isolation

Residual curr ent devices (appendix B)

Circuit-br eaker s with electronic protection (appendices J and F)

Circuit-br eaker s f or IT systems (appendix H)

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Standard IEC 60947-2 defines

The circuit-br eaker classification

accor ding to utilization category A or B

accor ding to design type

air circuit-br eaker, moulded case circuit-br eaker

The circuit-br eaker mechanical and electr ical data:

size, tr ip unit, etc.

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Standard IEC 60947-2 Definitions

Circuit-breaker classification

Utilization category A Utilization category B

Circuit-br eaker not specifically intended Circuit-br eaker specifically intended

f or discr imination f or discr imination:

Without an intentional short-time delay With intentional short-time delay

(adjustable)

Without short time withstand curr ent With short time withstand curr ent

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Extract from appendix K of standard IEC 60947-2

Characteristics Ue Rated oper ational voltage

voltage Ui Rated insulation voltage

Uimp Rated impulse withstand voltage

curr ent In Rated curr ent

Ith Conventional f r ee-air ther mal curr entIthe Conventional enclosed ther mal curr ent

Icm Rated short-circuit making capacity

short-circuit Icu Rated ultimate short-circuit br eaking capacity

Ics Rated service short-circuit br eaking capacity

Icw Rated short-time withstand curr ent

Ir Adjustable overload setting curr ent

1.05 x Ir Conventional non-tr ipping curr enttr ip unit 1.30 x Ir Conventional tr ipping curr ent

Isd Short time delay tr ipping setting curr ent

Ii Instantaneous tr ipping setting curr ent

Definitions

Terminology / Vocabulary

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Standard IEC 60947-2 Circuit-breaker characteristics

Overload withstandIn (in A rms) = rated current

Maximum uninterrupted curr ent

withstood at ambient

temper atur e, given without

abnor mal temper atur e r ise

Ir (in A rms) = adjustable

overload setting current

Ir depends on In

Ir char acter izes the

overload protection

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Short-circuit withstandIcu (kA rms) = rated ultimate

short-circuit breaking capacity

This per f or mance expr esses

the maximum value of the

short-circuit curr ent that can

be broken by the circuit-br eaker

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Short-circuit withstand

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Standard IEC 60947-2 introduces a

new important performance

Ics (as a % of Icu) = rated service

short-circuit breaking capacity

This per f or mance expr esses

the suitability of a circuit-br eaker toensur e f ully nor mal service af ter

br eaking this curr ent 3 times

Nor mal r atio between Ics and Icu

Utilization category A Utilization category B% of Icu % of Icu

2550 50

75 75

100 100

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Standard IEC 60947-2Safety in use: breaking capacity tests simulate

those encountered in "real life"

Prospective short circuit curr ent (Isc) & ultimate short circuit br eaking capacity(Icu)

when designing an installation, the wor st case of short circuit curr ent is calculated : we call this

the "prospective short circuit curr ent".

prospective Isc: theor etical thr ee phase short circuit at the ter minals of the

circuit br eaker

"bolted" short circuit (without arc and impedance)

the circuit br eaker must be capable of interrupting this short circuit (a fault very unlikely to

occur except dur ing commissioning).

ultimate short circuit breaking capacity (Icu):

maximum short circuit curr ent that the br eaker can interrupt.

is the only short circuit breaking capacity that needs tobe considered when selecting a breaker.

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Safety in use: breaking capacity tests

simulate those encountered in "real life"

prospective short circuit level (Isc) & service br eaking capacity (Ics)

in pr actice, short circuit curr ents ar e much lower than the calculated prospective short

circuit level because they ar e strongly limited by :

the impedance of cables and connections

the electr ic arc (within the br eaker) its type : phase-neutr al or between two phase.

r educed short circuits ar e mor e probable as they ar e gener ally some distance away

f rom the tr ansf or mer .

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Short-circuit withstandStandard IEC 60947-2 introduces anew performance for category B circuit-breakers

Icw (in kA rms) = rated short-timewithstand current

Icw is the maximum short-circuitcurr ent that a circuit-br eaker can

withstand f or a short dur ation(t without deter ior ation of these char acter istics

ICW must be at least equal to12 In or 5 kA f or In e 2500 A30 kA f or I

n

> 2500 A

The standar dized delay time (tis: 0.05 - 0.1 - 0.25 - 0.5 -or 1s

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Standard IEC 60947-2 Constructional requirements

Isolation co-ordinationThe circuit-breaker, as a safety device, must be able to withstand

Networ k overvoltages

this suitability is char acter ized by the withstand to the conventional

dielectr ic test at 2 Ui + 1000 - 1 min at power f r equency

Impulse voltages ( «lightning stroke» simulation)

this suitability is char acter ized by the withstand to the1.2/ 50 Qs impulse voltage test of value Uimp

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Standard IEC 60947-2 Constructional requirements

Isolation co-ordinationUimp (kV peak) = rated impulse withstand voltage

Characterization of Uimp

Depends on the LV networ k voltage

Depends on the position of the circuit-br eaker in the LV networ k

Depends on altitude: Uimp must be valid up to 2000 m

tests carr ied out at +23 % of value

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Characterization of Uimp

Nominal Applications

installation voltage

at the or igin of the on the distr ibution and at loadinstallation/MSB final circuits level

230 /400 V 6 4 2.5

400 /690 V 8 6 4

Constructional requirements

Isolation co-ordination

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Constructional requirements

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Industrial circuit-breaker Uimp = 8 kV

Tests to be consider ed

Uimp + 23 % = 9.8 kV

standar d industr ial circuit-br eaker s and those suitable f or isolation

Application of Impulse voltage value

impulse voltage Breakers Disconnector Breakers

Phase-to-phase 9.8 kV 9.8 kV

Up-to-downstr eam 12.3 kV (*)

contacts open

Phase-to-earth 9.8 kV 9.8 kV

(*) 14.7 kV f or f ront face class II circuit-br eaker as per IEC 61 140

Test between upstr eam

and downstr eam

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Standard IEC 60947-2 Constructional requirementsCircuit-breaker suitable for isolation

Test of isolation suitability

3 tests designed to ensur e user s that a device

«suitable f or isolation» is not dangerous

in open position...

- even af ter having eliminated a short-circuit up to Icu

- even in the event of overvoltage on the networ k ...

or in closed position

cannot be declar ed «open» and/or « padlockable »

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Standard IEC 60947-2 Constructional requirementsCircuit-breaker suitable for isolation

Leakage current measurement test

at 110 % of maximum utilization voltage Ue

New device, leakage curr ent < 0.5 mA per pole,

Af ter br eaking at Ics, leakage curr ent < 2 mA per pole,

Af ter dur ability tests, leakage curr ent < 2 mA per pole,

Af ter br eaking at Icu, leakage curr ent < 6 mA per pole

Impulse voltage withstand

Uimp = 12 kV (instead of 9.8 kV) between the inlet and the outlet of the

open device

(*) 14.7 kV f or f ront face class II circuit-br eaker as per IEC 61 140

Mechanical ruggedness test

Circuit-br eaker with a pole held in closed position must not be indicated

«open» and/or «lockable» by padlock.

Padlockable in « open » position

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Class ll

enclosur e

Class ll

f ront face

Front face class ll

Mechanical ruggedness

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Standard IEC 60947-2 Constructional requirementsCircuit-breaker /isolator

Marking

A circuit-br eaker that is «suitable for isolation» will display the circuit-

br eaker/isolator symbol on its f ront face

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Standard IEC 60947-2 Specific points (appendix A)

Cascading Discr imination

Standard IEC 60947-2 recognizes and defines circuit-breaker

co-ordination

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Standard IEC 60947-2 Specific points (appendix B)Residual current device

Standard IEC 60947-2 appendix B defines

The char acter istics of the r esidual curr ent devices

The tests and ver ifications that must be per f or med on a r esidual curr ent

device

in or der to guar antee the safety of the r esidual curr ent f unction

in or der to guar antee the quality of the r esidual curr ent f unction

(malf unctioning)

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Tests and verifications

Quality of the r esidual curr ent f unction

no nuisance tr ipping in the event of:

- single-phase overcurr ent (standar dized tests)

- curr ent waves gener ated by impulse voltage

- networ k capacitance load

- in event of an insulation fault with a DC component

(class A),

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Class A cycle

I fault

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Tests and verifications

Safety of the r esidual curr ent f unction

af ter br eaking at Icu and Ics, no deter ior ation of the earth leakage

protection units,

corr ect oper ation of the f unction:- in har sh environmental conditions

(damp heat 28-day cycle)0 12 14h30

Hygro (%)

100

90

55

25

t

(°C)

dur ation

(h)

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Standard IEC 60947-2 Specific points (appendix F)Circuit-breaker with electronic trip unit

Standard IEC 60947-2 appendices F defines

The additional specificationsf or circuit-br eaker s withelectronic tr ip unit

The tests r equir ed to guar anteetheir corr ect oper ation in

r estr ictive industr ialenvironments

EMC tests: immunity todisturbances,

EMC tests: ver ification of r adiated emission level,

(very har sh) environmental

tests, dry and damp heat,temper atur e var iationsAfter each test,verification of proper trip unit operation

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Standard IEC 60947-2 Specific points (appendix H)

Circuit-breaker suitable for IT


Defines this br eaking type

(with a single pole at phase-to-phase voltage)

Stipulates a specific test

the devices not suitable f or use with the IT system ar e mar kedwith the symbol IT

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PIM

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Standard IEC 60947-2 Tests

Standard IEC 60947-2 makes provision for complete device testing

Cumulative tests grouped into sequences

One sample undergoes all the sequence tests

5 Test Sequences + 1 Combined test sequence

All the f unctions and char acter istics ar e tested

Specific tests

Circuit-br eaker suitable f or isolation

Residual curr ent device,

Circuit-br eaker with electronic tr ip unit,

EMC Tests

etc.

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Test sequencesCategoryA Category B

Ics < Icu Icw = Ics = Icu

Sequence 1Gener al oper ating

char acter istics

Sequence 2Service br eaking

capacity Ics

Sequence3Ultimate br eaking

capacity Icu

Sequence 4Rated short time

withstand curr ent Icw

Combinedtest sequence

Example NS630b to 1000 L NS630b to 1600 N-HNS100 to NS630 NS1600b to 3200 N-H Masterpact + Multi 9 Masterpact H2-H3-L1 N1-H1

Tests

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Example Sequence 1 and 2Test Circuit-breaker type Tests to be performed in turn Additional tests for sequences Cat. A Cat. B on the same circuit-breaker circuit-breakers declared

Icw Icw Icw suitable for isolation< Ics = Ics = Ics

= Icu

Sequence 1 1. Ver ification of tr ipping thr esholds 1. DittoGener al 2. Dielectr ic properties 2. Dielectr ic propertiesoper ating 2.1 If an Uimp is declar ed by the Uimp withstand compulsory:

char acter istics Manufactur er : Uimp Test phase-to ditto opposite plus between phase, phase-to-earth Inlet and Outlet: Uimp + 25 %

2.2 If no Uimp is declar ed and leakage curr ent testDielectr ic test 50 Hz at 2Ui + 1000 (< 0.5 mA per pole at 110 % Ue)

3. Mechanical dur ability 3. Ditto4. Electr ical dur ability 4. Ditto5. Oper ation in overload at 6 In 5. Ditto6. Dielectr ic withstand at 2 Ue (min. 1000 V) 6. Ditto + leakage curr ent test

(< 2 mA per pole at 110 % Ue)7. Temper atur e r ise at In 7. Ditto8. Ver ification of non-dr if t of 8. Ditto

overload tr ip units

Sequence 2 1. Thr ee successive curr ent br eakings Ics 1. DittoService as per cycle O - 3 mm - CO - 3 mm - CO

br eaking 2. Ver ification of suitability f or 2. Dittocapacity Ics oper ation, achievement of 5 %

of electr ical dur ability3. Dielectr ic withstand at 2 Ue (50 Hz-1 mm) 3. Ditto + leakage test curr ent

(e 2 mA per pole at 110 % Ue)4. Temper atur e r ise at In 4. Ditto5. Ver ification of non-dr if t of 5. Ditto

overload tr ip units

Test sequences

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Standard IEC 60947-2 Tests

Tripping curves

all the important points

on the tr ipping curve

ar e tested

essential featur es ar e tested in r eal

and the har dest conditions

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In «sequence 3» of standardized tests

O - t - CO test

Verifications

Dielectr ic at 2 Ui (minimum 1000 V) f or 1 minute,

NB: f or circuit-br eaker suitable f or isolation test of leakage I = < 6 mA at 110 % Ue

Ver ification of overload tr ip units at 2 Ir

Standard IEC 60947-2 clarifies the definition of circuit-breaker

breaking capacity

The circuit-breaker must not be dangerous » after 2 breakings at Icu

Tests Icu

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Standard IEC 60947-2 Tests Ics

In « sequence 2 » of standardized tests

O - t - CO - t - CO test

Verifications

Dielectr ic at 2 Ui (minimum 1000 V) f or 1 minute,

NB: f or circuit-br eaker suitable f or isolation test of leakage I e 2 mA at 110 % Ue

Of suitability to br eak its nominal curr ent by achieving 5% of electr ical

dur ability

Of temper atur e r ise at In,

Ver ification of overload tr ip units at Ir

The circuit-breaker must be suitable for operation after a short circuit

at Ics. This performance is guaranteed 3 times.

The Ics performance represents a practical » breaking capacity.

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In « sequence 4 » of standardized tests

Category B circuit-breaker

Verifications

Device withstand at Icw and (t indicated by the manufactur er

Of temper atur e r ise at In, af ter O - t - CO cycleat Icw at maximum voltage

Dielectr ic at 2 U 1(minimum 1000 V) f or 1 minute,

Overload tr ip units at 2 Ir

The circuit-breaker must be suitable for operation after a short-circuit at Icw

Tests Icw

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Standard IEC 60947-2 Conclusion


A standard that adheres to reality

Simple, clear choice of circuit-breakers

In and Icu ar e sufficient to deter mine the circuit-br eaker,

New recognized, defined and tested characteristics / functions

Suitability f or isolation,

Residual curr ent device,

Circuit-br eaker s with electronic tr ip unit

Tests representative of the real stresses exerted on a circuit-breaker

Ics, etc.

Cumulative tests in sequences, Tests of all the design char acter istics

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A standard that adheres to reality

Examples

probable Isc very close to probable Isc less than

prospective Isc: Ics = 100 % Icu prospective Isc: Ics = 50 % Icu

NS160N is optimized C60L is optimized

Conclusion

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1250 kVA

Isc = 29 kA

28 kA

160 A

MSB

Sub-distributionboard

18 kA

8.5 kA

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Standard IEC 60947-2 Conclusion

A circuit-breaker certified according to Standard IEC 60947-2

guarantees a quality device with durable performance of all its safety

functions.

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Documents

Transcript of CB as Per IEC60947