Research On The Test Method Of Vacuum About High-voltage Circuit Breaker

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 fieldsof power system. In order to ensure the operation reliability, the vacuum degree in the vacuumcircuit breaker should be kept under 10^-2 Pa. But for all kinds of reasons, the vacuum degreein the vacuum circuit breaker which is operated for a period of time will come down. Onceoverriding the threshold value of the vacuum degree, vacuum circuit breaker will lost itscapacity of breaking current, and this will take serious harm to power system risking in danger.Therefore, it's quite necessary to detect or recheck the vacuum degree of vacuum circuitbreaker.First, the relative background knowledge about vacuum circuit breaker is introduced inthe paper. Then several familiar methods on measuring the vacuum degree of high-voltagebreaker are recommended. In the third chapter, the fundamental of HF method and the schemeof detection system are expounded. HF method means a high frequency-high voltage source isapplied between the two contactors of vacuum circuit breaker to initiate and establish thepre-breakdown current. The relationship between the maximum amplitude of HF impulsecurrent superimposed in the emission current after compensating capacitive current ofpre-breakdown current and vacuum degree under testing is directly and uniquelycorresponding. Thus, vacuum degree in vacuum circuit breaker can be calculated from agraph called maximum amplitude-vacuum degree calibration curve through measuring themaximum amplitude of HF impulse current if needed. This chapter mainly introduces thedesign of amplification circuit, filter circuit, peak current measurement circuit, A/Dconversion circuit and display circuit. In chapter 4, the fundamental of coupling capacitancemethod and the scheme of detection system are particularized. Coupling capacitance methodis according to the rationale of charge distribution and voltage-dividing capacitor. Forcoupling capacitance method, it needs to measure the effective value of the feeler search.Then, according to the function between the voltage of capacitance sensor output and theinternal pressure of vacuum circuit breakers, the vacuum degree can be got. is designed,including: amplification circuit, filter circuit, peak value detection circuit, A/D circuit anddisplay circuit. Then the relative waveform is given. In chapter 4, coupling capacitancemethod is introduced in detail, corresponding hardware circuit scheme included, especially insensor circuit, filter circuit and data traffic circuit. And the relevant waveforms are got.At last, through comparing with these two methods, summarize their own advantages and disadvantages. For HF method, it must detect periodically and the peak current is not themonodrome function of the vacuum. It needs the RMS of HF current as auxiliary parameter.For coupling capacitance method, the relative position between coupling capacitance andshielding cover is an important factor to the veracity of measure. Also the distribution ofspace electromagnetic field is another key factor.