Motor bus transfer system performance testing and the search for a new transfer success criterion

The petrochemical industry presently has no industry standards on the performance requirements for relays used to supervise critical process motor bus transfers. A device testing protocol is proposed, and the results of extensive performance testing of relays used to implement the Fast and In-Phase methods of motor bus synchronous transfer are analyzed. The existing industry criteria for determining the success of a completed transfer are used to evaluate these test results. The development of digital motor bus transfer systems with data recording capabilities provided a means of recording transfer data and provides key insight into what happens during actual transfers. Case studies of a number of live motor bus transfers are presented and analyzed to begin to determine if a new transfer metric can be derived, based on recorded transfer inrush current and power when transfer is completed.