A New 69-Kv Air Blast Circuit Breaker

A new air-blast circuit breaker rated at 69 kv, 2,000 amperes, 3,500 megavolt-amperes (mva) has been developed for outdoor service on the lines of a large metropolitan utility. Designed as individual rollout circuit breaker poles in dust-tight, phase-isolated, outdoor metal enclosures with current transformers on the roof entrance bushings, the circuit breaker has its isolators enclosed within the air blast columns for more reliable operation under icing conditions for future application of the circuit breaker as outdoor porcelain-clad units. Recovery voltage control resistors are used to insure satisfactory performance of the circuit breaker at any circuit recovery rate which may arise on any system in this country.