Study of Condition Monitoring by Operating Sound Diagnosis for Circuit Breaker in Substation

It is necessary to identify the abnormal portion and take countermeasures when an operation failure occurs on a circuit breaker in a substation. However, after an operation failure many circuit breakers often operate normally when retried, and as a result, it has been difficult to identify the abnormal portion. The authors have focused attention on the sound generated from the operating mechanism of a circuit breaker, and investigated an operating sound diagnosis technique to identify the difference between normal and abnormal operations using some sample devices of 6.6 kV vacuum circuit breakers. As a result, it was found that the Fast Fourier Transform (FFT) color mapping technique and Partial Over All (P.O.A.) time-trend technique are effective methods for analyzing the operating sound of a circuit breaker. The FFT color mapping technique is an analytic method that visually evaluates the strength of sound pressure in time series for each frequency, and it makes it possible to grasp the qualitative difference in the operating sound of a circuit breaker. The P.O.A. time-trend technique is an analytic method that numerically evaluates the value of generated sound pressure from the 13 kHz to 15 kHz band as a time trend, and makes it possible to grasp the quantitative difference in the operating sound of the circuit breaker. By using these two methods, it has been possible to identify some operating sounds having different abnormal portions. As a result of the above investigation, it has been confirmed that operating sound diagnosis of the circuit breaker is an effective condition monitoring technique for detecting abnormality, since the operating sound is generated in chronological order related to the operation process of the circuit breaker. Then, the operating sound of an actual 500 kV circuit breaker with hydraulic driving gear was analyzed by using the methods. As a result, it was found that both close and open operations can be described by an FFT color map.