Capacitive coupling sensor application for monitoring and diagnosis of high voltage circuit breakers

Summary

Circuit breakers are protective electromechanical devices designed to conduct, reestablish and interrupt electrical currents at its point of installation. Generally, they are triggered to isolate a circuit's section in case of overloads or fault currents due to short circuits. Circuit breakers' malfunctioning might cause the interruption of power supply, destruction of the electric system's equipment and endanger lives. Therefore, a systematic inspection is a determining factor to assure a good operating state of the breakers, thus enabling the basic demands of the electrical system to be achieved. In recent years, a lot of techniques have been developed to evaluate the operative state of circuit breakers. Most of them are known to be more reliable and efficient than the techniques being currently used. However, the electric companies are still very reluctant to accept these new methodologies, being one of the most probable cause the fact that they require the periodic withdrawal of operation of the circuit breakers, greatly increasing the cost of maintenance/inspection activities. Therefore, in order to avoid such problems, the development of online monitoring techniques has been receiving a greater emphasis. In this paper, a new online monitoring and diagnosis system for circuit breaker is presented, which consists of a capacitive coupling sensor and a data analysis software. The breaker diagnosis is based on the signals induced in the sensor during opening operations. Aiming to analyze the measured signals and correlate them with the breaker operational condition, the mean and standard deviation of a couple characteristic parameters were used as input parameters for the developed software. Signal analysis in the frequency domain were performed using the Spectral Sub-band Centroid Energy Vectors (SSCEV) algorithm. The tests were performed with nine contact samples, with different degradation levels. For each sample, thirty measurements were made. The analysis of the results indicates that the energy and duration of the signals detected by this type of sensor are correlated with the degradation level of the arcing contacts.

Additional informations

Keywords

Circuit breaker, capacitive coupling sensor, monitoring, diagnostic, SSCEV