By hvhipot 
HV Hipot Electric Co., Ltd. specializes in producing series resonance (also known as cable withstand voltage test device). Next, we will share with you the main methods of power cable withstand voltage test?
Cable withstand voltage test is a method of detecting faults in the presence of cables. During the testing process, it is susceptible to various factors that may cause malfunctions, short circuits, and other issues. Below are several main methods for cable withstand voltage testing.
1、 Ultra low frequency withstand voltage test
The ultra-low frequency (0.1Hz) withstand voltage test method first appeared in 1980, mainly used as a non-destructive testing method to observe whether there are insulation defects in cable operation. This method has been extensively studied and confirmed. Laboratory testing and on-site testing. The low-frequency withstand voltage test has a good application effect in the withstand voltage test of low-voltage power cables. This method utilizes the principle of converting 50Hz AC power into DC voltage through rectification and filtering, and then converting the DC voltage into 1kHz AC voltage through an inverter circuit, followed by amplitude modulation processing at 0.1Hz. Sine oscillator, amplitude modulated, 1kHz. Convert the amplitude waves of AC voltage into beam waves with a variation of 0.1Hz. It is mainly based on the high voltage formed between the high voltage transformer and the voltage doubling circuit. Its main feature is a sine wave, and it is mediated by a varistor, so that the output of the AC high voltage load is a 0.1Hz high voltage sine wave waveform.
The advantages of ultra-low frequency withstand voltage test mainly include: 1. No damage; 2. High precision; 3. Small size, easy to carry. But this method has a lower output voltage level and is mainly used for voltage withstand testing of medium and low voltage cables. Its main feature is a sine wave, which is mediated by a varistor, resulting in a 0.1Hz high-voltage sine waveform output from the AC high-voltage load. But this method has a lower output voltage level and is mainly used for voltage withstand testing of medium and low voltage cables.
2、 Modulation frequency series resonance test
This method mainly utilizes the inductance of the reactor and the capacitance of the tested cable to generate resonance in a 50Hz power frequency environment, and generates high voltage during this process. The advantages of modulating power frequency series resonance test are: 1. The output current waveform is basically a sine wave; The specificity of 2 is high. Only when the series resonant circuit meets the conditions for resonance, will a high voltage be formed and tested on the tested cable once. If there is a problem, it will cause circuit abnormalities, equivalent to cable short circuits. The high pressure will also experience a uniform decrease. Moreover, since the reactor can limit the short-circuit current and the protection device is not affected, there is no need to install a resistance protection device. The disadvantages of this testing method are complex operation, low system quality factor, low degree of automation, high noise, which limits its practical application.
3、 Variable frequency series resonance test
The principle of frequency conversion series resonance test is similar to the principle of frequency modulation series resonance test mentioned above. Differently, the frequency conversion series resonance test achieves the resonance of the test circuit by adjusting the output voltage frequency in the frequency conversion power supply; In the power frequency series resonance test, the resonance of the test circuit is achieved by adjusting the inductance generated by the reactor at 50Hz power frequency. The advantage of frequency conversion series resonance test is that when the required power capacity for the test is lower than the power capacity of the tested cable, the test can be carried out at a power much lower than the required power, which can effectively improve the efficiency of on-site testing and overcome the disadvantages of modulation frequency withstand voltage testing devices, making it more widely used in real life. In addition, the operating frequency of the variable frequency series resonance test is only 30-300Hz, which can improve the problem of low frequency withstand voltage test with low loss and non-compliance with standards. Actual losses. Therefore, the results obtained from the frequency conversion series resonance withstand voltage test are accurate, comprehensive, and reliable. The working frequency of the frequency conversion series resonance test is only 30-300Hz, which can improve the problem of low frequency and low loss in the ultra-low frequency withstand voltage test, which does not match the actual loss.