Standard Guidelines 60947 vs 60898 2015

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© ABB GroupOctober 14, 2015 | Slide 1

Generalrequirements forLV apparatuses

Basics of StandardsStandards guidelines IEC 60947 and60898


Contents

§ IEC 60947 Standard, for industrial application– Definitions for MCCBs and ACBs

– Choice criteria based on rated and limit values

§ IEC 60898 Standard, for domestic application

– Definitions for MCBs

– Choice criteria based on rated and limit values

§ Comparison between prescription of IEC 60947 and 60898


– International Standard IEC 60947

– European Standard EN 60947

§ IEC 947-1 Part 1: General rules

§ IEC 947-2 Part 2: Circuit breakers

§ IEC 947-3 Part 3: Switch disconnectors

§ IEC 947-4 Part 4: Contactors

§ IEC 947-5 Part 5: Control circuit devices

§ IEC 947-6 Part 6: Multifunction devices

§ IEC 947-7 Part 7: Auxiliary materials

Standard for LV apparatus

§ IEC 60947 Standard for industrial application

Ø TIÊU CHUẨN QUỐC GIA TCVN 6592-4-1:2009 (IEC 60947-4-1 : 2002) VỀ THIẾT BỊĐÓNG CẮT VÀ ĐIỀU KHIỂN HẠ ÁP

Ø TCVN 7447-5-51: 2010 hoàn toàntương đương với IEC 60364-5-51:2005

Ø TIÊU CHUẨN QUỐC GIA TCVN 6434-1:2008 (IEC 60898-1 : 2003) VỀ KHÍ CỤĐIỆN - ÁPTÔMÁT BẢO VỆ QUÁ DÒNGDÙNG TRONG GIA ĐÌNH VÀ CÁC HỆTHỐNG LẮP ĐẶT TƯƠNG TỰ


Standard for LV apparatus

The Standards IEC 60947 part 1 and part 2 gives the requirement forCBs, that are able to be connected in circuits with a rated voltage

< 1000V ac and < 1500V dcThis Standard is applicable whatever may be:- the rated currents of the CBs;- the method of construction of the CBs;- the possible application of the CBs.

The main objects of part 1 are:definition of electrical parameters;definition of working, mounting and transport condition.

The main objects of part 2 are referred to the prescriptionand parameters for working and test of the CBs

§ IEC 60947 Standard

IEC 60947-1

IEC 60947-2


IEC Standard definitions


A mechanical switching device capable of breaking, carrying and makingcurrents under normal circuit conditions and also making, carrying, for aspecified time, and breaking currents under specified abnormal circuitconditions such as those of short-circuit

§ BREAKING Breaking Capacity ( Icu, Ics)

§ WITHSTAND Short time withstand ( Icw)

§ MAKING Making Capacity (Icm)


§ Circuit Breaker - IEC 60947-2

Making capacity of a circuit breaker is the maximum current which thebreaker can conduct at the instant of closing. The making capacity isconsidered to the peak value of the first cycle when there is animaginary short circuit between the phases.


A mechanical switching device capable of breaking, making and carrying currentsunder normal circuit conditions but only making and carrying, for a specifiedtime, currents under specified abnormal circuit conditions such as those of short-circuit.

§ BREAKING Breaking Capacity

§ WITHSTAND Short time withstand

§ MAKING Capacity


§ Switch Disconnector - IEC 60947-3

Switch disconnector, Load switch ;Load Breaker Switch



A device fulfills the isolating function stipulated under IEC 60947-1 whenin the“Open” position the isolation at a defined withstand voltage isassured between the open contacts of the main circuit of the switchgear.

§ Disconnector - IEC 60947-3

According to IEC 60947-3, an isolator must only be able tomake and break a circuit, if either a current of negligible size isswitched on or off, or if during switching no noticeable voltagedifference between the terminals of each pole occurs.


SwitchChangeover Switch

ATS by OTMSwitch fuse


– Air circuit breaker (ACB): a circuit breaker having a supporting housing ofmoulding insulating material and a metallic frame, forming an integral partof the circuit breaker (Emax2)


Electronic trip Unit

IEC 60947 - ACB is Cat B Circuit breaker withWithstand short circuit current Capacity Icw



Moulded case circuit breaker (MCCB): a circuit breaker having a supporting housing ofmoulding insulating material, forming an integral part of the circuit breaker (Isomax,Tmax)

IEC Standard definitions§ Circuit breaker type

Thermo magnetic trip

Electronic trip Unit


Thermo magnetic Trip



MCCB Electronic trip Unit


Miniature Circuit Breaker

IEC 60947 defines 5 trippingcharacteristics for MCB: B, C, D, K, Z


Miniature Circuit Breaker


A circuit breaker with a break-time short enough to preventthe short-circuit current from reaching its peak value

Current limiting circuit breaker

§ Current limiting circuit breaker (IEC 60947-2 def. 2.3)

A current-limiting circuitbreaker is able to reduce thestress, both thermal anddynamic, because is has beendesigned to start the openingoperation before the short-circuitcurrent has reached its firstpeak, and to quickly extinguishthe arc between the contacts.


Value of the limited peakof the short circuit currentaccording to the value ofthe symmetrical shortcircuit current Irms


§ Peak limitation curves


16,8kA

50kA

54kA

Peak

Irms

105kA

10kA 100kA

10kA

100kA

S6L800 In800

T2L 160 In160

§ Example



Time

Current

Energy limitation


§ Energy limitation


Value of the let-throughenergy according to thevalue of the symmetricalshort circuit current Irms


n I2t curves


Protection against short-circuit (IEC 60364)To protect a cable against short-circuit, the specific let-through energy ofthe protective device must be lower or equal to the withstanding energy ofthe cable:

where– I2 t is the specific let-through energy ofthe protective device which can be read onthe curves supplied by the manufacturer;– S is the cable cross section [mm2]; in thecase of conductors in parallel it is the crosssection of the single conductor;– k is a factor that depends on the cableinsulating and conducting material.

0.1kA 1kA 10kA 100kA

1E-2MA²s

0.1MA²s

1MA²s

10MA²s

100MA²s

1E3MA²s

Specific let through energy curve LLL


§ Energy limitation


In = 1600 A

Iu = 1600 AUe = 415 V

Icu= 50 KAIcs = 50 KAIcs = 50 KA (1s)

Choice criteria


§ Rated values (Iu, Ue)

n Limit values (Icu, Ics, Icw, Icm)

n Insulation values (Ui, Uimp)

Choice criteria



the rated uninterrupted current of an equipment is a value ofcurrent, stated by the manufacturer, that the equipment can carryin uninterrupted duty (at 40 °C)

IEC 60947-1 def. 4.3.2.4

Rated value Iu

§ Rated uninterrupted current Iu


Rated value Iu

§ The rated uninterrupted current Iu is different from the ratedcurrent In, which is the rated current of the thermomagnetic orelectronic trip unit and is lower or equal to Iu.A new conceptfor setting thecurrent In: therating plug



T4 320 - Fixed

T4 320 - Plug-in / Withdrawable

Rated value Iu

§ Rated uninterrupted current IuSome factors may reduce the Iu of a circuit breaker


Rated value Iu

§ Rated uninterrupted current IuSome factors may reduce the Iu of a circuit breakerCircuit breakers do not undergo any alterations in their performances up to analtitude of 2000m. Above this, as the altitude increases, the atmospheric propertiesare altered in terms of composition, dielectric resistance, cooling capacity andpressure; therefore the rated uninterrupted current decreases.


the rated operational voltage of an equipment is a value of voltagewhich, combined with a rated operational current, determines theapplication of the equipment and to which the relevant tests andthe utilization categories are referred.

IEC 60947-1 def. 4.3.1.1

Rated value Ue

§ Rated operational voltage Ue



§ Limit values (Icu, Ics, Icw, Icm)

§ Insulation values (Ui, Uimp)

Choice criteria



Breaking capacity for which the prescribed conditionsaccording to a specified test sequence do not include thecapability of the circuit breaker to carry its rated currentcontinuously

- test sequence: O - 3 min - CO- dielectric withstand at 2 x Ue- verification of overload release at 2.5 x I1

Limit value Icu

Icu = RATED ULTIMATE SHORTCIRCUIT BREAKING CAPACITY

IEC 60947-2def. 4.3.5.2.1


Breaking capacity for which the prescribed conditionsaccording to a specified test sequence include the capabilityof the circuit breaker to carry its rated current continuously

- test sequence: O - 3 min - CO - 3 min – CO- dielectric withstand at 2 x Ue- verification of temperature rise at Iu- verification of overload release at 1.45 x I1

Ics = RATED SERVICE SHORTCIRCUIT BREAKING CAPACITY

IEC 60947-2def. 4.3.5.2.2

Limit value Ics


Breaking capacity is always referred to the operational voltage; thebreaking capacity decreases when the voltage increases.

Rated value Ue

§ Rated operational voltage Ue


Limit values Icu and Ics

The service breaking capacity Ics can be expressed as

a value of breaking current, in kA;

Standard ratios between Ics and Icu

§ Relation between Ics and Icu This relation is always true!!!

Ics ≤ Icu

a percentage of Icu, rounded upto the lowest whole number,in accordance with the table (forexample Ics = 25% Icu).


Main circuit breakers or circuit breakers for whicha long out-of-service period can not be accepted

(for example naval installation)

CB selectionbased on

Ics

Icu

Normal / terminal circuitsand / or economic applications

Limit values Icu and Ics

§ Icu and Ics: selection criteria


Limit value Icw

Icw = RATED SHORT-TIMEWITHSTAND CURRENT

IEC 60947-2def. 4.3.5.4

Example of use of category B circuit breakersin electrical plant

Trafo 630kVAUcc%=4%

400V

ACB E1B12

MCCB T4

22.7kA

MCCB T3

The upstream circuitbreaker can withstandthe fault current up to 1sec, thus guaranteeingan excellent selectivitywith downstreamapparatus


Circuit breakers specifically intended for selectivity in shortcircuit conditions in relation to other protection devices inseries, that is with an intentional delay (adjustable) applicablein short circuit conditions.

These circuit breakers have a specified rated short-timewithstand current Icw.

IEC 60947-2Table 4

CATEGORY BCIRCUIT BREAKER

Limit value Icw


Circuit-breakers “not specifically” intended for selectivity undershort circuit conditions with respect to other protection devicesin series on the load side, that is without intentional short-timedelay provided for selectivity under short-circuit conditions.

These circuit-breakers have not a specified rated short-timewithstand current value Icw.

Limit value Icw

IEC 60947-2Table 4

CATEGORY ACIRCUIT BREAKER


It is the value of short-time withstand current assigned to thecircuit-breaker by the manufacturer under specified testconditions. This value is referred to a specified time (usually 1s or 3s).

It must be stated when the circuit-breaker is classified incategory B and its value must be greater than:

§ the highest value between 12 Iu and 5 kA for CBs with Iu £ 2500A

§ 30 kA for CBs with Iu > 2500A

Circuit breakers without Icw value are classified in category A

Limit value Icw

IEC 60947-2Table 3

Icw = RATED SHORT-TIMEWITHSTAND CURRENT


IEC 60947-2def. 4.3.5.1

Icm = RATED SHORT-CIRCUITMAKING CAPACITY

Making capacity for which the prescribed conditions accordingto a specified test sequence include the capability of the circuitbreaker to make the peak current corresponding to that ratedcapacity at the appropriate applied voltage.

Limit value Icm

It is always necessary to verify that:

Icm ³ Ipeak


Limit value Icm

The peak of the short-circuit current Ip is the maximum possibleinstantaneous value of the prospective short-circuit current; itmay be calculated by the following formula (IEC 60909-0):

§ Short circuit current: how to calculate the peak?

I”k is the short-circuit current (rms value)at the initial instant of the shortcircuit

The peak is a function of the power factor!!!


Distance from thepower source

Perspectivecurrent IKLLL 10 - 100 kA

10 - 50 kA

6 - 20 kA0,5 – 4,5 kA

§ The Standard hypothesis

Limit value Icm


Limit value Icm

Icm ≥ n x Icu

For a.c. the rated short-circuit makingcapacity of a circuit-breaker shall be notless than its rated ultimate short-circuitbreaking capacity, multiplied by the factorn of the table.

IEC 60947-2Table 2


§ SACE product features

If the cosj of the plant is higher than the standard prescribedvalue, it is not necessary to take into account the rated short-circuit making capacity of the circuit-breakers (Icm)

If the cosj of the plant is lower than the standardprescribed value, usually near to the transformer and/orgenerator, it is necessary to verify Icm ³ Ipeak

Limit value Icm


Example Icm - Ip

If the cosjk of the plant is equal to 0.16 (lower than the standard prescribed value)the evaluated Ip=175kA.

e.g. Short circuit current of the plant is Icc = 75kA ;the used circuit breaker has an Icu = 75 kA;according to the table 2, cosjk=0.2 and n=2,2 so Icm = n x Icu = 165 kA

Since Ip > Icm the CB selected is not correct. I will use a CB with a greatervalue of Icu in order to have an Icm value suitable to the peak current of the plant





Choice criteria



IEC 60947-1def. 4.3.1.2

Ui = RATED INSULATIONVOLTAGE

The rated insulation voltage of an equipment is the valueof voltage to which dielectric tests and creepagedistances are referred

It shall be always verified that:

Ue < Ui

Limit value Ui


IEC 60947-1def. 4.3.1.3

Uimp = RATED IMPULSEWITHSTAND VOLTAGE

The peak value of an impulse voltage of prescribed form andpolarity (1,2/50ms) which the equipment is capable of withstandingwithout failure under specified conditions of test and to whichthe values of the clearances are referred.

It shall be always verified that:

Uimp > transient overvoltage inthe plant

Limit value Uimp



International Standard References

IEC 60898

Applicable to circuit-breakers for protection of wiring installationin buildings and similar applications, and designed for use byuninstructed persons, and for not being maintained.

Part 1: Circuit-breakers for a.c. operationPart 2: Circuit-breakers for a.c. and d.c. operation (additional requirements)

Miniature Circuit Breakers MCB


§ Rated values (In, Ue)

§ Limit values (Icn, Ics)


Choice criteria


§ Rated uninterrupted current (In):§the rated uninterrupted current of an equipment is a value ofcurrent, stated by the manufacturer, which the equipmentcan carry in uninterrupted duty, at a specified referenceambient air temperature (30 °C).

§The rated current doesn’t exceed the 125A.

IEC 60898-1 def. 5.2.2

Rated value In


§ Rated operational voltage (Ue):The rated operational voltage of a circuit-breaker is the valueof voltage, assigned by the manufacturer, to which itsperformances (particularly the short-circuit performance) arereferred.

The rated operational voltage doesn’t exceed the 440Vac220Vdc.

IEC 60898-1 def. 5.2.1.1

Rated value Ue



§ Limit values (Icn, Ics)§ Limit values (Icn, Ics)

Choice criteria


The rated short-circuit capacity is the value of the ultimateshort-circuit breaking capacity for which the prescribedconditions, according to a specified test sequence, do notinclude the capability of the circuit-breaker to carry 0,85 timesits non-tripping current for the conventional time.

The rated short circuit capacity doesn’t exceed the25kA in ac and 10kA in dc

test sequence: O - 3 min - CO- leakage current at 1.1 Ue (< 2 mA)- dielectric strength test at 900 V- verification of overload release at 2.8 x In

IEC 60898-1def. 5.2.4

Icn = RATED SHORT CIRCUITCAPACITY

Limit value Icn


The service short-circuit capacity of a circuit-breaker is thevalue of the breaking capacity for which the prescribedconditions according to a specified test sequence include thecapability of the circuit-breaker to carry 0,85 times its non-tripping current for the conventional time.

IEC 60898-1def. 3.5.5.2

Ics = RATED SERVICE SHORTCIRCUIT CAPACITY

Limit value Ics


§ Service Short Circuit capacity (Ics):

- test seq. : O - 3 min - O - 3 min – CO (for one or two poles cb)O - 3 min - CO - 3 min – CO (for three or four poles cb)

- leakage current at 1.1 Ue (< 2 mA)- dielectric strength test- verification of no tripping at 0,85 x InA circuit-breaker with a rated short-circuit capacity (Icn) has a corresponding service short-circuitcapacity (Ics) as from this table:

The circuit breaker withIcn < 6000A Ics is equal to 1xIcn6000A < Icn < 10000A Ics is equal to 0,75xIcn Minimum value of Ics is 6000A.Icn > 10000A Ics is equal to 0,5xIcn Minimum value of Ics is 7500A.

Limit value Ics


Tripping Curves

The main difference between the overload protection curve of the CBs responding toIEC 60947 or IEC 60898 are referred to the conventional non tripping current.The prescibed conditions are given in this table:

Overload characteristics


Tripping Curves

The CBs according to IEC 60947 usually have the instantaneous threshold at 5 or 10 timesthe rated current with a tolerance of + 20%.

The CBs according to IEC 60898-1 (ac applications) have different instantaneousthreshold referred to the type B , C , D as indicated in the table below:

Magnetic characteristics


Tripping Curves


Comparison (summary)

IEC 60947-2 IEC 60898-1

People Instructed UninstructedMaintenance Possible Not possible

Rated Voltage(Ue)

< 1000 Vac

< 1500 Vdc

< 440 Vac

< 220 VdcAmbient

Temperature 40° C 30° C

Rated CurrentNo limits

(Iu < 6300 A)In = 125 A

Short circuitbreaking current No limits for Icu

Icn = 25 kA (ac)

Icn = 10 kA (dc)

© ABB Group, BU Breakers and SwitchesOctober 14, 2015 | Slide 63

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Standard Guidelines 60947 vs 60898 2015