Spark conditioning procedures for vacuum interrupters in circuit breakers

The breakdown voltage between the open contacts of vacuum circuit breakers (VCBs) immediately after manufacturing is low and subject to high scatter. To attain a sufficiently high breakdown voltage, these unknown and undefined surface conditions must be improved by conditioning. Several usual conditioning procedures applied to a large number of 12-kV circuit breakers of a standard design are compared. A large number of conditioning experiments have been made and statistically evaluated. Additional studies have been performed in a vacuum test chamber in which the contacts could be interchanged easily. The aim was to find the most important conditioning parameters and to explain the underlying physical processes. The studies show that the conditioning procedure can be optimized. >