Cold Fusion
Senior Member
- Location
- way north
Thanks for the conversation on the Y primary transformers. That helped.
I've got another one I'm curious about some of the design issues - and a code issue as well.
This one is a transformer feeding a long (2000') feet feeder.
Feeder transformer output is 4160V, 3ph, Delta, ungrounded and no ground detection. Feeder transformer has MV fusing in the 4160V output. Terminal end transformer is 4160D primary. Link is 300kva.
Code issue first:
I can't find any code requirement to ground the 4160 link. I can't find any code requirement to have ground detection on the 4160 link.
Am I missing anything?
Design issue:
I'm thinking the 4160 link should either be grounded or should have ground detection. Right now, any line to ground fault is undetectable. Maybe that is okay, but it seems odd.
The few MV links I have been around were 4160V grounded Wye on the feeder end and Delta primary on the terminal end. This seems reasonable.
So how to deal with the ungrounded 4160D?
One source (should be knowledgable) told me that a zero sequence relay using a CT, set around 10%FLA, to alarm or trip, is is sufficient. I don't see that as alerting for a phase to ground fault. Any one line to ground fault is undetectable.
How would one connect ground detectors to a 4160D?
Three 4800:120 transformers, Wye connected and grounded. Put the ground detections on the 120?
What is normal for this type of installation?
I'm interested in your thoughts.
cf
I've got another one I'm curious about some of the design issues - and a code issue as well.
This one is a transformer feeding a long (2000') feet feeder.
Feeder transformer output is 4160V, 3ph, Delta, ungrounded and no ground detection. Feeder transformer has MV fusing in the 4160V output. Terminal end transformer is 4160D primary. Link is 300kva.
Code issue first:
I can't find any code requirement to ground the 4160 link. I can't find any code requirement to have ground detection on the 4160 link.
Am I missing anything?
Design issue:
I'm thinking the 4160 link should either be grounded or should have ground detection. Right now, any line to ground fault is undetectable. Maybe that is okay, but it seems odd.
The few MV links I have been around were 4160V grounded Wye on the feeder end and Delta primary on the terminal end. This seems reasonable.
So how to deal with the ungrounded 4160D?
One source (should be knowledgable) told me that a zero sequence relay using a CT, set around 10%FLA, to alarm or trip, is is sufficient. I don't see that as alerting for a phase to ground fault. Any one line to ground fault is undetectable.
How would one connect ground detectors to a 4160D?
Three 4800:120 transformers, Wye connected and grounded. Put the ground detections on the 120?
What is normal for this type of installation?
I'm interested in your thoughts.
cf