The ultra-low frequency high-voltage generator is mainly used for insulation withstand tests of high-voltage power equipment. Due to its features such as fast voltage rise, high voltage level, and light weight, it is highly favored by a large number of power test personnel. So, what is the method and steps for conducting ultra-low frequency withstand tests on cables using the ultra-low frequency high-voltage generator? .
1. Disconnect all electrical equipment connected to the test sample from the test sample’s cables. All electrical equipment connected to the test equipment and cables must be completely disconnected. The grounding of the test equipment and test cables should be reliably connected using bare copper wires to the grounding system, and the environmental conditions of the test at that time should be recorded for future reference.
2. Before conducting the test, a 10,000V megohmmeter must be used to measure the insulation resistance of each phase of the test equipment and the cables. The tested cables should be preliminarily evaluated, and the test results should be recorded. If the initial test is successful, the withstand voltage test can be carried out.
3. Test voltage peak: Umax = 3Uo, where Uo is the rated operating voltage between the cable conductor and the ground or the metal shielding.
For example: For a cable with a rated voltage of 10KV, the single-phase rated voltage Uo:
Uo=10/√3kV
So the peak value of the test voltage is:
Umax = 3Uo = 17.32 kV
4. Test duration: The peak voltage during the test should be three times the rated line voltage of the test cable. If the voltage is set too low, it will not be possible to effectively detect the defects of the cable and equipment. To ensure the accuracy and reliability of the test, it is generally required that the test duration be no less than 60 minutes.
5. The test can be conducted in phases. When the capacitance value of the test sample cable is within the load capacity range of the test equipment, the three-phase conductors of the test sample cable can be connected in parallel and the withstand voltage test can be carried out simultaneously.
6. Connect the test equipment to the test sample cable using the specially provided flexible connecting cable. Turn on the power supply, set the test frequency, time, voltage, and the overcurrent protection value and overvoltage protection value on the high-voltage side, and then start the voltage rise test. During the voltage rise process, closely monitor the voltage indication of the high-voltage circuit, check if the cable has flashover or abnormal sounds, and start recording the time and reading the test voltage value after reaching the test voltage.
7. Once the test time is up, the ultra-low frequency high-voltage generator automatically shuts down. If during the test, no flashover or destructive discharge occurs in the test cable or equipment, it can be concluded that the withstand voltage test of the cable has been passed.
8. During the voltage boosting and withstand voltage processes, if abnormal waveform distortion is observed in the output, the current increases abnormally, the voltage fluctuates, the test specimen cable emits an unpleasant smell, produces smoke or abnormal sounds or flickers, etc., the voltage boosting should be immediately stopped. After stopping the machine, the cause should be investigated. If these phenomena are caused by the weak insulation of the test specimen cable, the withstand voltage test is considered不合格. If it is determined that the test specimen cable is due to reasons such as air humidity or surface dirtiness， the test specimen cable should be cleaned and dried before conducting the test.
9. During the test process, if the ultra-low frequency high-voltage generator triggers overcurrent protection due to insulation defects of the test sample cable, after identifying the cause, a full-time connection withstand voltage test should be conducted again. It is not allowed to only perform the “make-up time” test.
Post time: Jun-05-2026