Interrupting Rating for Medium Voltage Fuses

[hydropowerengr]

I have an application where I am tapping off isolated phase bus(13.8 kV) at the generator terminals with 15 kV cable to provide power to a step down power transformer(645 KVA 13,800/400 V). At this tap location, we have calculated a fault current of 83.7 kA symmetrical. I have been unable to find a medium voltage fuse that can handle this fault duty (highest found is 60 kA). Any help would be appreciated.

 

[dpc]

Your best hope is a current-limiting fuse such as a GE EJ-1. I'm away from my reference material but you should be able to check interrupting rating on-line.

Check with GE and S&C.

 

[cuky2000]

I have a few questions:

a) What happen to the generator if you have phase-to-phase fault in the cable?

b) How far can the cable be tapped from the IPB to comply with the tapping rules of the NEC?

c) Is the primary protection on the high side of the GSU capable to protect the small new transformer?

d) Since 700 kVA transformers at 13.8kV/400 V is relatively easy to find as out of the self item, it is acceptable to take the risk of replace it if a fault happens?

 

[dpc]

I agree with Cuky2000 that this may not be a great idea in terms of tapping a generator bus duct - it compromises a lot of your generator protection schemes.

But aside from that, I'd check with S&C and ask about their "Fusitor". I have seen these used for VT fuses with up to 80 kA of fault current, but they may not have a large enough size for your power transformer.

 

[Borti]

Try G&W Electric

http://www.gwelec.com/product_current/hclimite.cfm

 

[alehman]

I would also be concerned with the magnetic effects of modifying the bus shielding to allow the cables to exit.

 

[ScottyUK]

Some of Siba's HV fuses are rated to 85kA. Maybe an option for S/C protection or backing up a smaller fuse? Page 19 of the link shows some.

http://www.sibafuses.com/pdf/hhd.pdf

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