A New Canadian Compressed Air Circuit Breaker [includes discussion]

This paper covers the development of a 5,000,000-kva compressed air circuit breaker rated 115,000 and 138,000 volts with 1,200-ampere continuous current-carrying capacity. The breaker is of the conventional dead-tank outdoor construction with one tank per phase. It has two condenser-type bushings extending through the top of each tank for connecting to the customer´s bus structure and for mounting of current transformers and potential devices. Preliminary dielectric tests were made with a variety of electrode shapes over a wide pressure range in a grounded-steel pressure vessel. Verification tests were made with 88 kv and 66 kv to ground across two interrupters in series and with 44 kv and 22 kv to ground across a single interrupter. Additional testing was done to establish the thermal capacity and line-dropping ability of the breaker, and to check the voltage distribution across the series interrupters.