Open Delta Connection of PTs

The Open Delta Connection is used to connect PTs. The connection uses two transformers one on each phase. The output current, though, is only 57.5 percent of a normal three phase connection. The capacity is consequently reduced to 86.6% of a normal three phase configuration.

The Open Delta connection can be used where one transformer of a three phase PT assembly has failed.

The open delta connection is cheaper that a conventional delta connected PT. Another advantage of the open delta connection is that it can be used service one transformer in a connection while the system runs on the other two.