Thank you for all the replies.
The event occured when a (B phase) jumper from an air-break switch failed and welded to the C phase conductor. All of the three phase transformers connected downstream of this switch were effectively fed from an A phase conductor and two C phase conductors...
I am looking for a good explaination to what theoretically happens to a three phase transformer (gnd wye-gnd wye connected) supplying three phase load when two of the source phases are the same? (Basically a three phase transformer is supplied by two A phases and a B phase?)
