Cable ultra-low frequency withstand voltage test using operation method

The cable's ultra-low frequency withstand voltage test uses the operation method :

1. Disconnect all the electrical equipment connected to the sample from the test cable.

2. Use 10000V Megohmmeter to perform insulation resistance test on each phase of the cable of the test product, and record the test value.

3. Test voltage peak: Umax = 3U0, where U0 is the rated working voltage between the cable conductor to earth or metal shield. For example: Rated voltage is 10KV cable, single-phase rated voltage U0: U0 = 10KV÷√3

Therefore, the test voltage peak is: Umax = 3U0 = 3 × 10KV ÷√ 3 = √ 3 × 10KV = 17.32KV

4. Test time: 60 minutes.

5. The phase can be tested. When the capacitance of the sample cable is within the test equipment load capacity range, the three-phase cable core of the sample cable can be connected in parallel and the withstand voltage test can be performed at the same time.

6. Connect the test equipment and test cables to the method shown in Figure 17a/b using the supplied special flexible connecting cable. Close the power supply, set the test frequency, time and voltage, and the high-side over-current protection value and over-voltage protection value, and then start the boost test. The boosting process should closely monitor the high voltage loop and monitor the test product cable for abnormal noise. When the test voltage is reached, the test time is recorded and the test voltage value is read.

7. When the test time is up, it will stop automatically. If no destructive discharge occurs during the test, the pressure test is considered to pass.

8. In the process of boosting and withstanding voltage, if the output waveform is found to be abnormally distorted and the current is abnormally increased, the voltage is unstable, and the sample cable is odor, smoke or abnormal noise or flashing, etc., and the boosting should be stopped immediately. After stopping the machine, find out the reason. If these phenomena are caused by weak insulation of the cable of the test product, the pressure test is considered unacceptable. If it is determined that the sample cable is due to air humidity or surface contamination, etc., the cable of the sample should be cleaned and dried before testing.

9. During the test process, if there is a non-prototype cable insulation defect that causes the device to exhibit over-current protection, after checking the cause, a full-time connection withstand voltage test shall be performed again. The “replenishment time” test shall not be performed only.