Fault protection on shipboard A-C power-distribution systems

G. H. Welch (Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa.): This paper covers a very interesting discussion of the shipboard power-distribution system requirements and the problems involved. During the last several years, considerable development work has been done to improve the reliability of these floating power plants, particularly those on naval vessels. On one class of vessels new circuit-breaker developments were incorporated which provided a complete selectivity system. Two main switchboards were involved, each fed by a single a-c generator, and the boards were interconnected by a bus-tie cable having a circuit breaker at each end. Feeder breakers were connected to each switchboard bus. Tests demonstrated that a fault on a feeder circuit would trip only the feeder breaker and not trip the local generator, tie, or remote-generator breakers. Faults on the tie circuit tripped only the breaker at each end of the tie cable. Bus faults tripped only the local generator breaker and tie circuit. This tripping selectivity was accomplished by mechanical time-delay mechanisms integral to the breakers. Other developments are now in progress which will extend these improvements in the future.