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# KA Rating of a Panel

05/04/2010 12:16 AM

Hi All,

Is it mandatory that, if a panel is rated for 50kA(say ACDB panel shall be 50kA), the breakers which we are using (both Incomer & outgoings) shall be of 50kA. or other wise can we use incomer & Bus bar rated to 50KA, and all other outgoings can be less kA(<50kA) rated.

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Commentator

Join Date: Oct 2009
Location: Dubai,UAE
Posts: 62
#1

### Re: KA Rating of a Panel

05/04/2010 12:27 AM

If your required short circuit current level is 50KA,then in your ACDB the upstream(incomer) and the busbar system should be 50KA.....downstreams (Outgoings) need not to be 50KA,caculate the outgoing loads individually and find out the short circuit current level for each outgoing,accordingly you choose KA ratings for your outgoing breakers.....

Ask me if you need more clarification

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Commentator

Join Date: Aug 2009
Posts: 91
#2

### Re: KA Rating of a Panel

05/04/2010 6:15 AM

The SC rating of outgoing < SC rating of incomer .For busbar rating SC rating and rated amps it should satisfy the normal conditions as well as design calculations .

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Guru

Join Date: Jun 2007
Location: chennai,India
Posts: 586
#3

### Re: KA Rating of a Panel

05/06/2010 11:40 PM

I have different view on sc level of outgoing switch gear on a switch board/Panel.

The interupting rating of outgoing switch gear should also be selected as that of incoming switchgear.

Supposing the short circuit occurs on the busbar the sc current may be 45 kA in which case the incoming switch gear should be capable of interrupting the fault current, there we will be choosing 50 kA switch gear.

In the case the outgoing supposing the short circuit occurs at the outgoing terminal of the switch gear ,the short circuit current will be same as that of 45 kA or little less.In this instant the outgoing switchgear should interrupt the fault current of 45 kA or little less.

Therefore ,in my opinion the outgoing and incoming of the switch board should have the switch gear of same interrupting capacity

Any views on this is welcome.

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Ramesh,Freelance Electrical/automation Consultant
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#4

### Re: KA Rating of a Panel

05/08/2010 3:39 AM

Hi vinod, I am confused.

Because what I know is that If your incoming breaker sc is 50 KA and you have 5 outgoing breakers with different loads,then you have to chose outgoing breaker's sc KA ratings according to your individual loads and that will be less than the incoming breaker sc rating.

Purpose is that when sc occurs in busbar side then Incomer should trip and If occurs on any outgoing side then the individual outgoing breaker should trip without disturbing other outgoing breakers...........

correct me if i am wrong

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#5

### Re: KA Rating of a Panel

05/09/2010 3:31 AM

Dear

Yes Incomer will take care of it

outgoing will be take care of their individual circuits

no complex things

cheers

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