When using very low frequency (VLF) hipot tester to test cables, the following aspects should be noted:
Before test
The engineers must be trained and pass the assessment before they can operate the equipment. It is strictly prohibited to change the equipment parameters.
The VLF tester must be reliably grounded; the grounding terminal should be securely connected to the object being tested during the test, and it is strictly prohibited to open the circuit; It is necessary to ensure that the high-voltage output is 0 and in the reset state when connecting test object.
When calibrating the tester and adjusting the high voltage without loading, the leakage current indicator shows an initial current, which is normal and does not affect the test accuracy.
Use the insulation resistance tester to test first, and discount the cables with other electrical equipment. If the cable length is short (less than 300 meters) and the test specimen capacitance is less than 0.05 μF, the test voltage increase cannot be achieved. In this case, please connect a high-voltage capacitor in parallel.
During test
The test can be conducted in every phase. 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. Test voltage peak: Umax = 3Uo, where Uo is the rated operating voltage between the cable conductor and ground or between the metal shield.
Turn on the power supply, set the test frequency, time, and voltage, and then start the voltage rise test. During the voltage rise process, closely monitor the high-voltage circuit and listen for any abnormal sounds from the test specimen cable. When the test voltage is reached, start recording the test time and reading the test voltage value.
The power generator must be more than 8KW. The generator output frequency should be stable. Use a frequency converter power supply or a digital frequency generator.
After test
When the test time is up, the instrument will automatically shut down. After powering on and starting the voltage rise process, if you need to interrupt it, do not turn off the power switch. Instead, make sure to use the stop button and the discharge rod to fully discharge the test sample before turning off the power.If the power indicator light does not light up or the screen shows no display when the device is turned on, it might be that the fuse has burned out. Simply replace it with a new fuse.