One mill´s experience using MAC testing to evaluate vacuum interrupter integrity in 15KV vacuum circuit breakers

For most of the first 100 years of existence of electrical power distribution systems, circuit breakers used either air- or oil-media interrupters. In the 1970´s, the application of vacuum interrupter (VI) circuit breakers changed that but also left a void for how to predict remaining service life of the necessarily sealed VI. This paper reports the results of use of alternate testing technology employing a magnetron device to apply a magnetic field, external to the VI, to enable estimation of vacuum integrity. Results are reported from one mill outage, encompassing approximately 50 VI´s, which were also subjected to the mill´s regular regimen of PM testing for vacuum circuit breakers. The data collected is presented along with suggestions for integration of the MAC testing technology into existing circuit breaker PM efforts.