What does the power frequency withstand voltage test detect?

Breakdown test is one of the main methods to test the overvoltage resistance of electrical appliances, electrical equipment, electrical devices, electrical circuits and electrical safety appliances. Frequency division withstand voltage test and DC withstand voltage test. The test voltage of power frequency withstand voltage test is more than 1 multiple of the rated voltage of the tested equipment and not less than 1 000 V. Its pressurization time is1minute for the equipment with porcelain and liquid as the main insulation, 5 minutes for the equipment with organic solid as the main insulation, 3 minutes for the voltage transformer and1minute for the oil-immersed power cable. The DC withstand voltage test can draw the leakage current-voltage characteristic curve through the leakage current value under different test voltages. Electrical equipment can find local defects, humidity and aging of insulation through withstand voltage test. Advantages and disadvantages of DC and AC withstand voltage test: DC withstand voltage test: it can effectively find the overall defects of insulation such as moisture and dirt, and can find the local defects of insulation through the relationship curve between current and leakage current. Because DC voltage is divided by insulation resistance, end insulation defects can be found more effectively than AC. At the same time, DC withstand voltage is less destructive to insulation because insulation will not produce dielectric loss under DC voltage. In addition, because DC withstand voltage only needs to provide a small leakage current, the required test equipment has a small capacity and is easy to carry. Ac withstand voltage test: the voltage of the tested equipment is 2.5 times or more. From the thermal breakdown angle of dielectric loss, local free defects and insulation aging weaknesses can be found effectively. Because the voltage is mainly divided by the capacitor under AC voltage, the insulation defects of the equipment can be effectively exposed. However, AC withstand voltage is more destructive to insulation than DC, and because the test current is capacitive current, large-capacity test equipment is needed. To sum up, DC withstand voltage test and power frequency AC withstand voltage test can effectively find insulation defects, but they have their own characteristics, so the two methods cannot replace each other. If necessary, they should be carried out simultaneously and complement each other.