Power Transformers
Power Transformers
(OP)
We have two 6KV XFR that feed two individual 380V MCCs with an ATS that closes the Tie brkr between them whenever one of the XFR feeders fail. Last night one of the XFR feeders tripped on over current and we found the XFR that tripped is pulling five times (300amps) on the primary side then the other XFR, while the Tie brkr is open. When we open the XFR feeder and close the tie putting all the load on the other XFR, the amperage on that XFR goes from 65 amps up to 160 amps. which indicates normal load. We can close the brkr on the XFR that tripped without any problem, but as soon as we close the secondary side brkr it will go into this high current condition on the primary, are we looking at a possible secondary winding fault problem, that only the primary side protection is picking up?. Any help will be appreciated at this time, as we are in the process of further investigation at the present time.






RE: Power Transformers
I presume that when you close the transformer secondary of the second transformer, the tie breaker is open.
Rafiq Bulsara
http://www.srengineersct.com
RE: Power Transformers
Rafiq Bulsara
http://www.srengineersct.com
RE: Power Transformers
RE: Power Transformers
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Power Transformers
Rafiq Bulsara
http://www.srengineersct.com
RE: Power Transformers
RE: Power Transformers
I encountered that type of incident once, not too long ago. There, in fact, one the CTs was connected backwards, but on low loads it was not evident.
Rafiq Bulsara
http://www.srengineersct.com
RE: Power Transformers
The CT ratio is identical on both XFR's and both have been on line since the beginning with a comparable load, which is why this has thrown us for a cruve since it just appeared a couple nights ago. The other XFR is carring the load for both MCC's without any problems @ +/- 150 amp primay load
Any way to verify a bad XFR (the damaged insulation) ???? as we are in a remote location, thanks for the help
RE: Power Transformers
RE: Power Transformers
Although checking the transformer itself should be easy, as you are able to isolate it without affecting the load.
Rafiq Bulsara
http://www.srengineersct.com
RE: Power Transformers
Bill
--------------------
"Why not the best?"
Jimmy Carter