Guidelines for Condition Monitoring of Vacuum Circuit Breakers at Distribution Voltages

Since the 1960’s Electricity Supply Companies around the world, including Australia, have purchased and installed Vacuum Circuit Breakers (VCB) for use in their medium voltage networks. The VCB design is such that it utilises a Vacuum Interrupter (VI) to limit arcing during operation of the circuit breaker. The design has proven to be relatively inexpensive as they are intended to be maintenance free for at least 20 years and has also maintained an excellent service record with relatively few significant failures or records of deterioration. However, with an industry wide focus on cost reduction, there is a strong likelihood that the VCB’s currently in-service will be called upon to provide ever increasing service lives which will be significantly longer than the expected 20 year lifespan. Partial Discharge Testing is a non-destructive condition monitoring testing method widely used for various tests in the High Voltage industry. The research documents the development of recommended guidelines for condition monitoring vacuum circuit breakers and considers the development of a field testing method, utilising Partial Discharge Testing techniques, that successfully allows for the condition assessment of the VCB’s vacuum interrupter and associated vacuum level. The development of a Standard Work Practice document for use throughout Ergon Energy, who supported the project, as well as other Electrical Supply entities, was also considered for the project. By enabling a safe, practical way of determining the condition of the vacuum interrupter, the industry may potentially save substantial costs in maintenance, replacement and future procurement