A New 69-Kv Oil Circuit Breaker for High Interrupting Duty [includes discussion]

This paper describes the development of a circuit breaker for the high interrupting duty required on many 69-kv metropolitan systems. Recognition of the peculiar problems of such systems resulted in the development of an oil circuit breaker for an interrupting duty of 3,500 megavolt amperes (mva). The results of complete laboratory tests give proof of mechanical and electrical performance with adequate margin. The breaker is mounted on a unit base enabling it to be shipped completely assembled with all adjustments made at the factory. The breaker has successfully interrupted currents equivalent to 5,000 mva, and these tests indicate that the breaker with a minimum of additional development work will be suitable for interrupting ratings of 5,000 mva when they are required. The standard interrupter recognizes some cable-switching applications at this voltage, interrupting up to 150 amperes of capacitance load without producing serious overvoltage. The standard interrupter may be modified for switching higher capacitance loads up to 240 amperes.