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medium voltage instantaneous trip

D

dave

Jan 1, 1970
0
I have a typical 12470v dual service line up. Both feeders can never be
paralled. The mains and feeders are protected with ABB 51y very inverse
relays. The feeders supply mutliple transformers in sizes from 500 to
2500 kva. Maximum load on any line is about 200amps. Short circuit
current is about 9000 amps at the mains and about 8000 amps at the
furthest point. For some reason they've been running with the
instantaneous trip set rather low on both the mains and feeders. I
would never use the instantaneous on the mains because there's no way to
coordinate it with the feeders. The instantaneous on the feeders seems
difficult to set because the short circuit current isnt' that much lower
at the furthest point in the system.

Basically whenever anything trips, they locate the fault, fix it, and
turn everything back on. I'd prefer to get rid of the instantaneous on
the mains and possilby set it on the feeders.

Any suggestions?
Thanks
Dave
 
S

SQLit

Jan 1, 1970
0
dave said:
I have a typical 12470v dual service line up. Both feeders can never be
paralled. The mains and feeders are protected with ABB 51y very inverse
relays. The feeders supply mutliple transformers in sizes from 500 to
2500 kva. Maximum load on any line is about 200amps. Short circuit
current is about 9000 amps at the mains and about 8000 amps at the
furthest point. For some reason they've been running with the
instantaneous trip set rather low on both the mains and feeders. I
would never use the instantaneous on the mains because there's no way to
coordinate it with the feeders. The instantaneous on the feeders seems
difficult to set because the short circuit current isnt' that much lower
at the furthest point in the system.

Basically whenever anything trips, they locate the fault, fix it, and
turn everything back on. I'd prefer to get rid of the instantaneous on
the mains and possilby set it on the feeders.

Any suggestions?
Thanks
Dave

A coordinated system is what you want difficult is standard. Call an
engineering company and have a coordination study done. CH- SqD-Seimans-GE
all have people that do this for a living.
I am not nuts enough to just start changing settings on medium voltage
equipment.
You might even get a hold of the power company they might help you find some
one in your area. It is to their benefit for you to have a controlled
system.
 
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