The basic testing methods of vacuum circuit breakers: The traditional method is the power frequency withstand voltage method, and the new method is the ion charge sampling and excitation discharge principle, which is a qualitative and quantitative testing method.
When the vacuum circuit breaker is in the closed state, a certain voltage is applied between the moving and stationary contacts to detect the magnitude of leakage current or observe the magnitude of leakage current. The discharge phenomenon in the switch is used to infer the quality of the vacuum. The advantage of this method is that it is simple, but the disadvantage is that it can only qualitatively detect the vacuum degree, and because the applied voltage is not high, that is, the experimental results of the withstand voltage method are basically the same, it is therefore impossible to reasonably judge the degree of developable leakage (that is, the degree of leakage compared to the previous time) for the same vacuum switch. This method can only roughly judge the switch whose vacuum degree has seriously decreased, which is a qualitative test.
The principle of ion charge sampling, qualitative and quantitative detection: excitation discharge. Select a special test instrument for measurement and add one or several high voltage pulses between them, and the pulse width is several tens to several hundred milliseconds, and synchronous pulse current passes through the magnetic field coil to generate the same pulse magnetic field as the high voltage, and the vacuum degree can be measured. According to the national regulations, the vacuum degree is qualified at 0.066 Pa, approaching or below 0.6 is unqualified and needs to be updated. When the vacuum degree is greatly reduced, the trial period should be shortened, and it should be decided whether to upgrade according to the development status.
Principle of ion charge sampling: In the study of electromagnetic discharge, it was found that when the external excitation power supply, the geometric size of the vacuum arc-extinguishing chamber and the material used are true, the vacuum degree in the gap of the vacuum switch has a very accurate value corresponding to the amount of ion charge, and is related to the probability of the peak value of ion current. The use of ion charge sampling technology greatly improves the accuracy of vacuum measurement of arc-extinguishing chamber.
The vacuum tester has high precision in physical principles, effectively suppresses the interference of the pulse power supply during testing, and makes the test stable and reliable. This is a qualitative and quantitative test, using special vacuum testers for measurement. At present, due to the development of science and technology, various complete measuring instruments for vacuum circuit breakers have been manufactured, and quantitative on-site measurements can be completed without disassembly. Using quantitative measurement methods, it is not only possible to measure whether the vacuum degree of the vacuum arc-extinguishing chamber is within the normal range, but more importantly, for some vacuum arc-extinguishing chambers with faster leakage rates, after comparing the measurement results of the entire vacuum chamber, the actual service life can be roughly estimated in years. This is actually to prevent accidents. For example, the vacuum tester is suitable for measuring the vacuum degree of various high voltage circuit breakers, and can quantitatively measure the vacuum degree in the arc-extinguishing chamber of various types of vacuum circuit breakers.