The device has a built-in overvoltage protection function. When the output test voltage exceeds the set value by 10%, the control unit cuts off the high-voltage output within 20 milliseconds. This threshold can be adjusted according to the insulation margin of the test specimen to avoid prolonged overvoltage damage to the specimen. During design and selection, it is necessary to confirm that the protection action time matches the withstand capability of the specimen.
Under 0.1Hz very low frequency testing, the capacitive current per kilometer of cable is far lower than that at power frequency. Taking a 35kV rated voltage, 240mm² cross-sectional area XLPE cable as an example, the equivalent capacitance per kilometer is about 0.17μF. The load capacity of the device must cover the capacitance value corresponding to the total length of the cable under test. During selection, the total cable capacitance must be calculated to ensure it does not exceed the rated load upper limit of the device.
The equipment should be used in an environment with a temperature of -10°C to 40°C and a relative humidity not greater than 85%. For long-term storage, it should be kept dry and ventilated, and powered on for inspection every three months to prevent moisture in capacitor components from causing insulation degradation.
Before each test, confirm that the high-voltage output cable is not damaged and that the grounding terminal is reliably connected. Regularly clean dust accumulated in the heat dissipation air duct and check the response of the control panel buttons. If the equipment is out of service for a long time, a no-load voltage rise verification should be performed before it is put into use again.
The connecting line between the high-voltage output end and the test specimen should be as short as possible to reduce corona loss. The cross-sectional area of the grounding wire should not be less than 4mm², and the grounding resistance should be less than 4Ω. Safety fences must be set up in the test area and warning signs hung.
