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DC Short Circuit Current Capacity of Circuit Breaker

DC Short Circuit Current Capacity of Circuit Breaker

DC Short Circuit Current Capacity of Circuit Breaker

(OP)
Hi,

I have the question regarding to the MV short-circuit rating of circuit breaker.

According to IEC standard, the following short-circuit rating of circuit breaker will be used in comparison with the calculated short-circuit current to verify whether such CB have sufficient short-circuit capacity or not;

CB Rating;
Symmetrical Breaking Capacity, Ib sym.
Asymmetrical Breaking Capacity, Ib asym.
Making Capacity, Ip
DC Short-circuit capacity, Idc

Calculated Short-Circuit Current;
Symmetrical Breaking short-circuit current, Ib sym.
Asymmetrical Breaking short-circuit current, Ib asym.
Peak short-circuit current, Ip
DC Short-circuit current, Idc

My question lies on the last one, the Idc. Someone said that only the followings are considered in verification of the adequacy of CB breaking capacity ;
Ib sym.
Ib asym
Ip

The Idc is not required by standard to be used in direct comparison between the calculated short-circuit current and DC short-circuit breaking capacity because Idc effect is already included in Ib asym. So comparison is made only the above 3 parameter to justify CB short-circuit capacity.

However someone said that the Idc is also must be used in comparison, so there are 4 parameters to be compared;
Ib sym
Ib asym
Ip
Idc

Can anyone advise me which one is correct ? due to I have one project which I use ETAP to calculate short circuit current and the result shows that all 3 parameters are within CB  capacity except Idc which the calculated Idc is higher than the CB Idc rating. So can I conclude that this CB have enough short-circuit capacity ?

Thank you,

Schwatzernov
 

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