Transformer Differential Ground Relay
Transformer Differential Ground Relay
(OP)
Can anyone point me to the calculations need to set a transformer 87G differential ground relay? I have a customer with a nuisance trip and we believe it is set too low. I'm looking for a good explaination of the calculation. It's a delta-wye substation transformer 69kv-13.8kv, 18MVA.






RE: Transformer Differential Ground Relay
What is a type of relay:
1. Low impedance or high impedance?
2. What is a CT's?
3. Are you check CT performance?
4. Are you check stability. polirity?
5. What is a setting?
And last: What is relay, type, mnf?
Maybe was external ground fault?
To your Q, actualy...no calculation, set is low as possible.
Best Regards.
Slava
RE: Transformer Differential Ground Relay
RE: Transformer Differential Ground Relay
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If we learn from our mistakes I'm getting a great education!
RE: Transformer Differential Ground Relay
87G is, or at least was common terminology in the US for what we call ground differential.
RE: Transformer Differential Ground Relay
RE: Transformer Differential Ground Relay
I stop understand those symbols.
for me 87G is generator differntial
and 87N is ground differential, but 64N/G is REF too.
Now we start learn IEC61850 symbols PDIS, PTOC, etc.
Good Luck to us.
Best Regards.
Slava
RE: Transformer Differential Ground Relay
I haven't seen the actual ANSI spec: does it assign letters to specific functions, or is that left to the discretion of the protection engineer? G and N seem to get confused far too often in relation to earth fault relaying. I agree with Slava that G signifies a generator function, but I am bound to say that with my background.
What is a 'ground differential' fucntion - a core balance or residually connected relay? We continue to be separated by a common language.
Good luck... and may the Force be with us!
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If we learn from our mistakes I'm getting a great education!
RE: Transformer Differential Ground Relay
Confusion reigns with the letter designations. Sometimes G is Generator and other times it means Ground. I recommend using a legend on the one line diagram.
RE: Transformer Differential Ground Relay
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If we learn from our mistakes I'm getting a great education!