Short-Time Impulse Voltage Characteristics of Tank-Type Oil Circuit Breakers [includes discussion]

Insulation co-ordination is a major consideration in the cost and design of a complete electric power system and of all individual pieces of apparatus. Basic impulse insulation levels (BIL) have been standardized so that apparatus and protective equipment can be co-ordinated. These levels are measured by withstands on specified test waves. Depending upon the type of protective device and the physical arrangement of the station, short-time voltage surges having crests above the BIL may be present and will require special consideration to insure insulation co-ordination. To determine the short-time impulse voltage characteristic of tank-type oil circuit breakers, tests were made on a representative breaker. The conclusion is that the short-time impulse characteristic of the complete breaker is comparable to that of the bushing alone.