fuse

[sahelrahman]

Hi,

I am trying to select a S&C vista device. Downstream of this device is a fused transformer rated at 2500kVA, 34500kV/480V. The transformer fuse is rated at 8A. The current on the primary side of the transformer is only 5A. Can I select a vista fuse rated at 100A? Is it too high?

 

[sahelrahman]

sorry I gave wrong information. The current on the primary side of the transformer is approximately 42Amps

 

[Kiribanda]

sahelrahman,
I donot know why you are referring to S&C "VISTA" for 34.5 kV side fuse.As far as I know, VISTA is a model name of switchgear made by S&C.
If your application is outdoor,then you should have Model:SM-4,50E Amp (standard) fuse made by S&C.Verify non-fusing due to mag inrush with proper selectivity. 100 A fuse looks too high.If indoor select a current limiting model.

 

[rbulsara]

S&C has very good technical bulletins for transformer fuse protection. Check them out from their website. You can also refer to IEEE 242 or Buff book for Protection and Coordination.

Rafiq Bulsara

http://www.srengineersct.com

 

[rbulsara]

Plus if this is where NEC or CEC applies, refer to NEC 450.

Rafiq Bulsara

http://www.srengineersct.com

 

[dpc]

If I understand the question correctly, the overcurrent protection on the Vista tap would typically be set slower than the fuse on an individual transformer. However, if this transformer is the only load on this Vista tap, you may wish to set the overcurrent pickup to a lower setting. It does need to be able to withstand the transformer inrush on energization without operating.

David Castor

http://www.cvoes.com