Wednesday, December 23, 2015

Medium and High Voltage Circuit Breaker Testing

medium voltage circuit breakers

Circuit breakers are automatic switches that interrupt the flow of current in the event of an overload or a short circuit. Whereas a fuse interrupts current flow just once, a circuit breaker is designed to be reset and used again. Circuit breakers can be reset manually or automatically. Available in a wide range of sizes, from household use all the way up to high voltage breakers which are used in power transmission for cities and municipalities. This post focuses on medium-voltage and high-voltage breakers.

Medium-voltage breakers are generally rated between 1 to 72 kV, use current sensing protective relays with current transformers for operation, and use air, oil, SF6, or vacuum as the arc extinguishing medium.

High-voltage circuit breakers are, generally speaking, anything above 72.5 kV. High-voltage circuit breakers are mostly operated via solenoids and protective relays with current transformers.

The video below (courtesy of OMICRON) provides an excellent description of the design, operation, and testing of medium and high voltage circuit breakers.