Tests on Westinghouse Oil Circuit Breakers at Baltimore

This paper deals with short-circuit tests made recently at Baltimore on dead tank oil circuit breakers of Westinghouse manufacture. Tests were made against the combined capacities of the Consolidated Gas, Electric Light & Power Company and the Pennsylvania Water & Power Company systems, and currents as high as 24,000 amperes at 13,200 volts were interrupted repeatedly. Tests on breakers of different sizes are described, the rupturing capacity ratings of the breakers referred to, ranging from 10,000 amperes at 15,000 volts up to 40,000 amperes at 15,000 volts. Improvements of design and construction have greatly increased the ability of this type and make of breaker to handle heavy short-circuit currents and severe duty cycles. The demonstration connected with the opening of heavy short circuits, including oil throwing and gas ejection, has been controlled and the fire hazard greatly reduced. A positiec means for preventing oil throw, while at the same time relieving gas pressures in breaker tanks, has been developed. Data are given regarding tripping speed, length of are duration, and condition of the oil and circuit-breaker structure after the tests.