Determining mechanical condition of high-voltage circuit breakers

BY JOZEF LEVI, Doble Engineering Company

Life expectancy of a newly installed high-voltage circuit breaker is approximately 40 years. Throughout its life, under normal circuit conditions, the circuit breaker will operate less than ten minutes. During abnormal circuit conditions, the breaker will operate less than one minute in its lifetime.

The primary goal of circuit breaker testing is to determine the condition of the circuit breaker. Breakers have moving parts, components that allow electrical contacts to separate (an ‘open’ or ‘trip’ operation) or to close. Whether those contacts are in a vacuum, in oil or in a gaseous medium, it makes sense to test the moving parts of the breaker—a ‘motion’ or ‘travel’ test.

If the motion of the contact system is in accordance with manufacturer specifications, then we can reasonably conclude that all mechanical parts, from the mechanism that provides the movement to the contacts themselves, are in good condition.