Bus transfer tests on station auxiliary system

TWO METHODS are used to transfer powerhouse auxiliary busses supplying station auxiliary motors from one source to another; namely, “closed transition” and “open transition.” For maximum safety with closed transition the feeder circuit breakers should be capable of interrupting a feeder fault when the two sources are tied together. For open transition the feeder circuit breakers have interrupting capacity to handle the short-circuit kilovolt-amperes from only one source at a time. There is an optimum time interval at which reclosure should be made on open transition to give the least disturbance and provide maximum safety to the station equipment. To determine this time interval, transfer tests were made on the auxiliary power system of the Phillips Power Plant, Duquesne Light Company, Pittsburgh, Pa.