A 230-Kv 3-Cycle Oil Circuit Breaker for Extra-Heavy Arc Rupturing Duty

As the ultimate generating capacity of Grand Coulee Dam is approached, designers of high voltage circuit-interrupting devices are challenged to produce circuit breakers capable of interrupting faults far in excess of the present maximum standard rating of 3,500,000 kva. An oil circuit breaker designed for extra-heavy are rupturing duty is described in this paper. Results of varification tests made in the laboratory are compared with those obtained on subsequent field tests at Grand Coulee Dam. The close correlation of circuit breaker performance in the field and laboratory confirms the accuracy of the laboratory method of testing. With successful correlation up to 7,500,000 kva and laboratory tests simulating still higher rupturing duty, there is now a sound basis for design of oil circuit breakers with a rated interrupting capacity up to 10,000,000 kva.