High-Voltage Circuit-Breaker Insulation Fault Diagnosis in Synthetic Test Based on Noninvasive Switching Electric-Field Pulses Measurement

In the synthetic test of high-voltage circuit breakers, insulation failures occur very often when the breaker operates frequently. It is very important to diagnose the early insulation fault of the breaker in the synthetic test. However, the installed voltage and current sensors of the synthetic test circuit are designed to measure the low-frequency components, such as the power frequency voltage and current. It is difficult to detect the high-frequency partial discharge caused by the breaker's insulation fault. The partial discharge can generate a radiated electromagnetic pulse. Even the weak partial discharge, which causes a small change in the voltage and current, can generate a large electromagnetic pulse, because of the large rate of change of the voltage and current. So the breaker's insulation status can be assessed by the E-field (electric field) pulses measurement. First, a portable measurement system is developed to measure the transient E-field produced by the breaker's switching operation. The wide frequency response band and large measurement range of this system guarantee the accuracy of the pulse measurement. Then, the test results show that the working process of the synthetic test circuit can be reflected by its corresponding transient E-field pulses. By analyzing the waveform characteristics of the E-field pulses of the synthetic test, the partial discharge caused by the breaker insulation fault can be distinguished.