2. Use a megohmmeter to test the insulation resistance of each phase of the test cable. Only when it is qualified can the ultra-low frequency withstand voltage test device be used for low-frequency withstand voltage testing.



3. Peak test voltage: Umax = 3Uo, where Uo is the rated value of the cable phase voltage. For example: for a cable with a rated voltage of 10kV, the single-phase rated voltage Uo = 10÷3kV square root = 5.774kV, so the peak test voltage is Umax = 3Uo = 17.32kV.

4. Test time: set according to the power test requirements.



5. Phase separation test. When the capacitance of the test cable is within the load capacity of the test equipment, the test cable can be connected in parallel with the three-phase cores and tested simultaneously.



6. Connect the test equipment and the test cable with the accompanying special soft connection cable. Turn off the power, set the test frequency, time and voltage on the high-voltage side, overcurrent protection value and overvoltage protection value, and then start to strengthen the test. During the boosting process, the high-voltage circuit should be closely monitored, and the test cable should be monitored for abnormal sounds. When the test voltage rises, record the test time and read the test voltage value.



7. After the test time is up, the ultra-low frequency high voltage generator will automatically stop. If no destructive discharge occurs during the test, it is considered to have passed the pressure test.



8. During the boosting and withstand voltage process, if abnormal output waveform, abnormal current, unstable voltage, peculiar smell, smoke, abnormal sound or flame on the test cable are found, the booster should be stopped immediately, and the cause should be found out after the machine stops. If these phenomena are caused by the weak insulation layer of the test cable, it is considered that the withstand voltage test is unqualified. If it is determined that the test cable is caused by air humidity or surface dirt, the test cable should be cleaned and dried before the test.



9. During the test, if the instrument overcurrent protection is caused by insulation defects of the non-test cable, the full-time withstand voltage test should be performed again after finding out the cause.