Design Of Internal Pressure Estimation System Of Vacuum Circuit Breaker Based On High Frequency Impulse Current Method

Vacuum circuit breaker which is with simple structure, high withstand voltage intensity, outstanding breaking capacity and high operation reliability, etc. is widely used in many fields of power system. Vacuum interrupter is the most important part of vacuum circuit breaker where the arc extinguishes. In order to ensure the operation reliability, the vacuum degree in the vacuum interrupter should be kept above 10^-2 Pa. But for reasons, the vacuum degree in the vacuum interrupter which is operated for a period of time will come down. Once overriding the threshold value of the vacuum degree, vacuum circuit breaker will lose its breaking capacity, even its electric insulated capacity after one or two order above the threshold value, and that will take much harm to power system risking in danger. Thereby, it's quite necessary to detect or recheck the vacuum degree of vacuum interrupter after longtime service.There are many methods of detecting the vacuum degree, different methods fit in different occasions. However, each method has its own disadvantages.In this paper, a method for detecting vacuum degree in vacuum interrupter based on measuring the maximum amplitude of high frequency (HF for short) impulse current is introduced, furthermore, the procedure of designing and implementing the whole experiment kits and experiment results are also presented. To use this method, a high frequency-high voltage source is needed between the two contactors of vacuum circuit breaker to initiate and establish the pre-breakdown current. The relationship between the maximum amplitude of HF impulse current superimposed in the emission current after compensating capacitive current of pre-breakdown current and vacuum degree under testing is directly and uniquely corresponding. Thus, vacuum degree in vacuum interrupter can be calculated from a graph called maximum amplitude-vacuum degree calibration curve through measuring the maximum amplitude of HF impulse current if needed. This method only needs a few operations, has little accuracy error and wide measurement range, can offer a quantitative result and a safety margin, so it promotes an effective way to detect vacuum degree in field.First of all, vacuum circuit breaker and several methods of detecting vacuum degree in common use including their disadvantages are introduced in the paper. Then the fundamental of detecting vacuum degree in vacuum interrupter based on measuring the maximum amplitude of HF impulse current and total scheme for the whole experiment are put forward.Later, the detail of how to design and complete entire experiment kits is offered in the third chapter, including inversion source, trigger signal generator, HF impulse current measurement circuit with their corresponding fundamental or designing program respectively. As for the fourth chapter, the testing results of the experiment kits are listed in detail, including the driving signal waves, the inversion circuit output waves and HF impulse current measurement circuit simulation waves. In the last, it comes to the conclusion of the whole experiment kits based on the testing results above.