Fault levels and breaking capacity

S

Thread Starter

Self

I would like to know if a 4 pole, 630 Amp MCCB, rated with a 50kA breaking capacity @415 VAC needs to be replaced if it is connected as a 350 kVA DG feeder CB to a 415 VAC, 3 ph 4 W, 3000 Amp (80kA for 1 sec) bus. If yes, why, and if no why not? Please give your answers with clear cut reasons. As further info, please note that the 3000 Amp bus is also fed thro a 6.6 / 0.415 kV, 2 MVA transformer with a 6.8% impedance that can be isolated through a 4000 amp 4 pole ACB, with a breaking capacity of 80 kA.

Could you also give me the procedure to calculate the fault current that will be seen by the bus in this query?
 
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