Practical application of diagnostic method of circuit breaker by measuring three current waveforms

This paper describes a practical application of diagnostic technique that captures abnormalities of motor-spring driven-type circuit breaker (CB) by measuring three currents and evaluating the shape of their waveforms. The proposed diagnostic technique has been applied to 117 units of 22 kV vacuum circuit breakers (VCB) in Singapore. This application has detected 15 abnormal VCB units and 33 other units with symptoms of abnormality. The development and practical application of the new diagnostic technique has prevented VCB operation failures and improved the power supply reliability of 22 kV distribution system.