The power frequency withstand voltage test, also known as the alternating current withstand voltage test, is a type of insulation withstand voltage test in the power system. The power frequency withstand voltage test device consists of a test transformer and an intelligent control console. It is widely used in power and research institutions to conduct various high-voltage insulation withstand voltage tests on electrical motors, cables, transformers, switches, electrical appliances, etc. It is also applicable for conducting power frequency withstand voltage tests and DC leakage tests on various high-voltage electrical equipment, electrical components, and insulating materials. It is an indispensable instrument in various high-voltage insulation withstand voltage tests.
The limiting resistor R1 in the power frequency withstand voltage test should be selected according to the rated capacity of the test transformer. For example, when the rated output current on the high-voltage side is between 100-300 MA, it can be selected as 0.5-1 Ω/V (test voltage); when the rated output current on the high-voltage side is above 1 A, it can be selected as 1 Ω/V (test voltage). Water resistors are commonly used as the limiting resistors, and the length of the tube can be considered as 150 KV/m. The tube and its thickness should have sufficient heat capacity (the method of preparing water resistive liquid: add an appropriate amount of copper sulfate to distilled water to prepare various resistive values).
The spherical gap and protection resistor: When the voltage exceeds the set value of the spherical gap (generally set at 110%-120% of the test voltage), the spherical gap discharges, providing protection for the tested item. The protection resistor of the spherical gap can be selected as 1 Ω/V (test voltage).
In the power frequency withstand voltage test, the measured voltage on the low-voltage side (instrument voltage) is not very accurate. The reason is that the test transformer has leakage reactance. The leakage reactance of the test transformer must have a voltage drop. To accurately measure the voltage applied to the tested item, a RCF resistive-capacitive divider is often connected on the high-voltage side to measure the voltage.
Main features of the power frequency withstand voltage test device:
Professional withstand voltage test control system, which can be equipped with various test transformers, including AC/DC dual-purpose, tap-changing or cascading
Fully enclosed integrated structure, suitable for harsh environments such as high cold and high altitude
Fully automatic and intelligent microcomputer measurement and control, ensuring high precision and high reliability of various performance
Comprehensive monitoring function, capable of simultaneously monitoring the voltage and current of the tested item, as well as the input and output current of the transformer
Complete protection, multiple protections for high and low voltage voltage and current
Zero position safety interlock, and external door control or infrared detector interlock
Safety precautions for on-site operation of the power frequency withstand voltage test device:
(1) The test personnel should make a division of labor, clearly define the communication methods among each other. And there should be a dedicated person to monitor the safety on site and observe the state of the tested item.
(2) The tested item should be cleaned and dried to avoid damaging the tested item and introducing errors during the test.
(3) For large-scale tests, generally, an empty rise test should be conducted first. That is, without connecting the tested item, raise the voltage to the test voltage, calibrate various meters, and adjust the gap.
(4) When using the power frequency withstand voltage test device, the rising speed should not be too fast, and sudden voltage application should be avoided. For example, sudden closing of the regulating switch when it is not at zero position, or sudden cutting off of the power supply. Generally, the switch should be turned off when it drops to zero position.
(5) When the voltage rises to the test voltage, start timing. After 1 minute, quickly reduce to 1/3 of the test voltage. Then, the power can be turned off.
(6) Before and after the withstand voltage test, measure the insulation resistance of the tested item to check the insulation condition.
(7) During the voltage rising or withstand voltage test process, if any abnormal situation is found, immediately reduce the voltage, cut off the power supply, stop the test, and investigate the cause: ① The pointer of the voltage meter swings greatly; ② Insulation is burned or smoking; ③ There is abnormal sound inside the tested item.
Post time: Aug-25-2026