1. Before the test, the cable should be checked and fully discharged to the ground;
Disconnect the connected equipment at both ends of the cable and do not attach other equipment during the test;
Clean the insulation surface of both ends of cable ends to reduce errors caused by surface leakage current. If necessary, add insulation baffle to the cable ends.
2. Safety measures should be taken in the test site, such as installing a fence, etc. In particular, a warning sign should be hung at the other end of the cable and a special person should be assigned to guard against outsiders, to check whether the ground wire and discharge rod are properly connected.
3. When pressurizing, the voltage should be gradually raised gradually in stages to prevent the charging current from being too large, and the leakage current value should be read after staying at 0.25, 0.5, 0.75 and 1.0 times of the test voltage for one minute respectively;
Finally, the withstand voltage test is carried out at a specified time under the test voltage, and the leakage current value after the withstand voltage is read before the end of the withstand voltage test.
4. According to the different types of cables, microammeter has different wiring, generally adopt the microammeter connected in the high-voltage side, high-voltage lead and microammeter plus shielding.
For power cables with copper wire mesh shielding layer and ground insulation, the microammeter can also be connected in series in the ground circuit of the tested cable, a discharge switch is connected in parallel at both ends of the microammeter, the switch will be pulled open during measurement, and the switch will be closed before discharging after measurement to avoid damage to the microammeter caused by discharge current shock.
5. The test voltage should be measured directly on the high voltage side.
When half-wave rectification or voltage doubling rectification is used, if the voltage is measured on the low-voltage side to convert to the high-voltage side, the voltage amplitude of the high-voltage test voltage may have a large error due to the influence of voltage waveform, ratio error and stray current, so the test voltage should be measured directly on the high-voltage side.
6. Step down and cut off the power supply after each voltage withstand test.
Then, the test cable is discharged to the ground several times with a current-limiting resistance of about 80 kilobyts per kilovolt, and then directly to the ground. The discharge time should be no less than 5 minutes to ensure full discharge.