How to Do Ultra-Low Frequency Withstand Voltage Test for Power Cables? HZDP Operation Process and Voltage Calculation Method

The voltage withstand test of cables cannot be directly stepped up after connecting the wires. Whether the preliminary confirmation is done solidly is directly related to the test results and equipment safety. Taking the HZDP ultra-low frequency high-voltage generator as an example, the following approach can be followed on site.

Firstly, disconnect other electrical equipment connected to the test cable and confirm that the cable is completely isolated. Measure the insulation parameters of each phase with a megohmmeter, and only enter the ultra-low frequency withstand voltage stage after the insulation resistance is qualified. When wiring, the controller, booster, tested cable shielding layer, and grounding wire should be in a reliable and unified grounding system.

The test voltage can be determined based on the rated phase voltage Uo of the cable. The commonly used calculation relationship given in the manual is Umax=3Uo. For example, for cables with a rated line voltage of 10kV and a rated phase voltage of 6kV, the peak test voltage can be set to 18kV. The handover test time is 60 minutes, and the preventive test time is 15 minutes. Specific projects must also be carried out in accordance with current regulations and contract requirements.

After inputting the capacitance of the test sample, estimate the capacitive current based on I=2 π fCU, and then set the overcurrent protection value according to the reliability factor. The parameter interface sets the frequency, test time, set voltage, voltage limit, and current limit. After clicking start, the equipment will perform self check, boost, equal amplitude output, shutdown, and automatic discharge.

During the process of boosting and withstanding voltage, it is necessary to continuously observe the voltage, current, waveform, and cable status. If there is unstable voltage, severe waveform distortion, odor, smoke, abnormal sound or flashover, the machine should be stopped immediately. After the experiment is completed, it is necessary to fully discharge with a discharge rod and confirm that there is no residual charge before disconnecting the wire.