Impulse voltage characteristics of circuit breakers

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 levels 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 basic impulse level may be present and will require special consideration to insure insulation co-ordination.