Study On On-line Monitoring Vacuum For Vacuum Circuit Breaker

With the advantages of simple construction, high reliability, long life, outstanding breaking capacity and great ability to withstand high voltage, vacuum circuit breaker is widely used in low and medium voltage field of power system. Vacuum circuit breaker is a switch equipment in which vacuum is used as insulation interrupter. To ensure safe and stable operation of vacuum circuit breaker, the vacuum degree of interrupter must be less than10-2Pa. Due to various field reasons, the vacuum degree may reduce gradually after installation or operation. Once the pressure intensity of the interrupter exceed the threshold value, the breaking capacity of vacuum circuit breaker will be directly affected or even lost, which causes large hidden danger. Consequently, vacuum degree test of vacuum circuit breaker is the urgent need in practical application.This paper firstly introduces the structure of vacuum circuit breaker and arc quenching principle. Then sevral common vacuum degree test methods, advantages and disadvantages of both online and offline test methods are illustrated. The measuring principle of vacuum degree test system, in which sensors based on coupling capacitance and electric bridge are designed to achieve the measurement, is described in chapter3. To improve operation efficiency of test equipment, the hardware acquisition terminal provides trigger signals for application software of upper PC analysis system. After passive acceptance of the trigger signals, the PC analysis system actively calls the data like shiled potential and so on. The test results are given by compared and analysed. The design scheme of hardware construction is described in detail in chapter4where sensor circuit, signal filtering modulation, analog to digital conversion and data communication circuit are highlighted with the corresponding simulation waveforms and experimental results.