Multiple-Grid Breakers for High-Voltage Service

There are occasional demands for high-voltage circuit breakers to interrupt in five cycles or less, and to meet this demand, a ``De-ion grid´´ interrupter has been developed which may be used in multiple unit groups for apparatus rated 138 to 230 kv. Records of field tests up to 2,250,000 kva at 220,000 volts are given, showing interrupting times averaging 2.6 cycles (50-cycle frequency). Cathode-ray oscillograms indicate a comparatively small amount of transient overvoltage, less than would be expected from the usual magnetic oscillograph records. With the fast breaker operation, the apparent system voltage dip was small, and freedom from system disturbance and loss of synchronous equipment is noteworthy.