1500kVA transformer failure

Status
Not open for further replies.
T

Tango9415

Member
Location
Oklahoma
Occupation
Electrical Engineer
On site there was a 14400/7200V to 480/277V wye/wye three phase 1500 kVA transformer. Upon commissioning of the transformer it only had a load from a 100 kVA dry type delta step down transformer, the dry type was on the A and B phase of the 1500 kVA. The total load on the A and B phase was 120A, C phase had very little amperage at this point. The transformer's C phase burned up three days into being heated up, no knew load was added to do so. Neither the bayonet fuse or secondary side fuse at the disconnect were blown. The utility is saying an imbalance of load caused the burnt up phase. Thoughts?
 
A 1500 KVA xfmr at 480 V should be good for > 1800 Amps. 120 A is not even 10%. It may have been miswired, or just failed. Sometimes things fail. Might have been damaged in shipment. Did anyone do any tests on it before putting it into service?
 
petersonra said:
A 1500 KVA xfmr at 480 V should be good for > 1800 Amps. 120 A is not even 10%. It may have been miswired, or just failed. Sometimes things fail. Might have been damaged in shipment. Did anyone do any tests on it before putting it into service?
Click to expand...
Have not received any preliminary test, utility took the transformer and haven’t got much feed back from them.
 
Tango9415 said:
Yes, neutral

No neutral on the primary
Click to expand...
A transformer that size wye/wye has the primary grounded internally, unless the H0 is brought out.
Sure it was a wye/wye?
14,400/7200 sounds like Delta.
12470/7200 should be wye/wye
 
David Castor said:
A phase to phase load as you describe should not be a problem and should not have caused the failure. Have they meggered the windings and taken an oil sample?
Click to expand...
I also wondered whether the transformer was commissioned properly! They should have the commissioning docs, tests done as well as the results!
 
Status
Not open for further replies.
Top