Selection of VCB as per short circuit current

S

Thread Starter

Shaheed

Sir,

Do we need to replace the VCB of a machine with higher short circuit rating if more machines add parallel at same bus bar.

Below 4 machines required to run parallel at one bus bar and I have to select VCB for each machine. Question is that KA rating of each VCB would be selected equal to total KA 23.62 of all machines or would be selected according to individual fault current KA of each machine.

1. 16000 KW Turbo gen Fault current KA: Fault MVA/1.732*KV=8.33KA

2. 16MW Turbo generator fault current level is 8.33 KA.

3. Diesel generator fault current level is: 0.89KA.

4. Grid transformer fault level is: 14.4KA.
Total fault level: 8.33+0.89+14.4= 23.62KA.

Is VCB KA rating for above mentioned 16MW would be 8.3KA or it would be selected as 23.62KA?

Best Regards,
Shaheed
 
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