GSU Ground Fault CT Size
GSU Ground Fault CT Size
(OP)
Brothers,
I have been asked by an equipment supplier to size a CT for ground fault protection on the primary side of a 1500KW 480-34.5KV land fill gas generator. The available fault current at the transformer primary is 2000A. I assume that they will want to detect much smaller magnitude currents. I am stumped. Any guidance would be appreciated. System one line is attached
JD
I have been asked by an equipment supplier to size a CT for ground fault protection on the primary side of a 1500KW 480-34.5KV land fill gas generator. The available fault current at the transformer primary is 2000A. I assume that they will want to detect much smaller magnitude currents. I am stumped. Any guidance would be appreciated. System one line is attached
JD






RE: GSU Ground Fault CT Size
Your ground fault is more smaller then 2000A. it's high impedance grounfing. 480/(1.73x55.4)=5A
in your drw CT 5/5A. Why? Isn't good solution
what is a current input of relay 1A or 5A or 0.2A?
I recommend use CT 75-100/1A and connect to very sensetive current input.
Regards.
Slava
RE: GSU Ground Fault CT Size
If ground fault is limited to say 5A, why use a core CT with primary current so high (75-100A)?
RE: GSU Ground Fault CT Size
Why not just measure voltage across the impedance?
RE: GSU Ground Fault CT Size
RE: GSU Ground Fault CT Size
Cranky108, you are right, of course more better voltage principle!!!!
HVmariner.
Your Q is very logical Q.
It's CT performance issue.
5/5A Ct is more accuracy in range from 1A up to 5A.
if you have setting lower, for example 0.5A ( BTW it will be lower setting) 75-100/1A more accuracy.
I sent once graph of CT performance, will try fornd and will attached.
Regards.
Slava
RE: GSU Ground Fault CT Size
Please attached
thread238-212599: Earth fault protection
Regards.
Slava
RE: GSU Ground Fault CT Size
I appreciate your input but my question is about the ct on the primary transformer ground not the ct on the neutral grounding resistor.
Thanks again,
JD
RE: GSU Ground Fault CT Size
With CT on the main trafo ground, you don't have any problem. you can use 2000/5A, for example 5% .
Regards.
Slava
RE: GSU Ground Fault CT Size