Hi Rafiq,
This is the formula used for cables: I^2 x t = constant
I2 = I1 x sqrt(t1/t2)
if I1=31.5kA, t1=3s, t2=1s, then I2=54kA
I am more inclined to agree with ppedUK that this cannot be applied to CBs. I just wish to get 2nd opinions on this issue. If you have technical references on...
Thanks for your reply ppedUK. The system is actually HV. A large CCGT plant will connect to an HV substation that will increase the fault level to around 50kA. Two connection options are available at nearby 132kV SS and 230kV SS. Both were found to exceed kA rating of existing CBs if the new...
Hi,
Normally MV & HV circuit breakers have 3 and 1 sec fault duration rating. If a CB has a 31.5kA rating for 3sec, is it correct to consider that it can withstand 31.5kA x 1.732 for 1 sec as derived from the formula used for cables (I2t = constant)? Will this formula apply to circuit breakers...
