The traditional power frequency pressure resistance devices are often large in size and heavy in weight, and are not convenient for on-site transportation. They are not convenient for any combination and have poor flexibility. In practice, the AC withstand voltage tests of various large-scale power transformers, power cables, turbines and turbine generators and other capacitive devices must be conducted in strict accordance with the test procedures. The traditional power frequency withstand voltage device can no longer meet the requirements of the current test procedures. At present, a generally better method is to perform a withstand voltage test using a series resonant method. Here, please go to the Shanghai Baixie Electrical professional engaged in more than 10 years of senior power engineers combined with their many years of practical operating experience and professional knowledge of electricity, to explain in detail.
Application of variable frequency series resonant voltage test in power system
1. The required power supply capacity is greatly reduced. The series resonant power supply uses the resonant reactor and the capacitor of the test product to generate high voltage and high current. In the whole system, the power supply only needs to provide part of the active power consumption of the system, so the test required power is only 1 of the test capacity. /Q.
2. The weight and size of the equipment are greatly reduced. In the series resonant power supply, not only the cumbersome high-power voltage regulation device and the common high-power power frequency test transformer are omitted, but also the resonant excitation power supply needs only 1/Q of the test capacity, which greatly reduces the weight and volume of the system, and is generally normal. 1/10-1/30 of the test device.
3, to improve the output voltage waveform. The resonant power supply is a resonant filter circuit, which can improve the waveform distortion of the output voltage and obtain a good sinusoidal waveform, effectively preventing the false breakdown of harmonic peaks on the test sample.
4, to prevent large short-circuit current burn point of failure. In the series resonance state, when the insulating weak point of the test piece is broken down, the circuit immediately detunes and the loop current rapidly drops to 1/Q of the normal test current. When the parallel resonant or test transformer method is used for the withstand voltage test, the breakdown current immediately rises several tens of times. Compared with the two, the short-circuit current is different from the breakdown current by several hundred times. Therefore, the series resonance can effectively find the weak points of insulation, and there is no major short circuit current burn point of trouble.
5. No recovery overvoltage will occur. When the sample breaks down, due to the loss of resonance conditions, the high voltage immediately disappears, the arc extinguishes instantly, and the re-establishment process of the recovery voltage is very long. It is easy to disconnect the power supply before the flash voltage is reached again. This voltage recovery The process is a kind of intermittent oscillation process of energy accumulation. The process is long and there will not be any recovery overvoltage.
