PROTECTION OF CLOSED TERTIARY WINDING

[appunni]

SIR,
HOW THE PROTECTION OF A CLOSED TERTIARY WINDING OF A TRANSFORMER CAN BE IMPLEMENTED? WILL CONVENTIONAL TWO WINDING DIFFERENTIAL RELAY WILL PROTECT? THANKS..

 

[peterb]

Differential protection of the transformer will be provided by a standard two-winding relay. In addition, a single set of CTs can be provided on one leg of the closed tertiary to supply a backup overcurrent relay.

 

[kcsubeng]

Another option to backup protection of the transformer would be to use an overcurrent or distance relay. Also, you might possibly be able to use the neutral CT for ground protection, but you'll have to investigate this very carefully. The neutral current more often than not will reverse for faults on the high side of the transformer - which plays havoc with your overcurrent coordination.