Problems to be paid attention to in DC withstand voltage test

by:AAA     2020-04-02
1. Test the cable before the test, and fully discharge to the ground; Disconnect the equipment connected to both ends of the cable and do not attach other equipment to the test; Wipe the insulation surface of the cable heads at both ends to reduce the error caused by surface leakage current. If necessary, add insulation baffles to the cable heads. 2. The test site should take safety measures such as safety fence, especially hang a warning sign at the other end of the cable and send a special person to guard it to prevent outsiders from approaching, and check whether the grounding wire and discharge rod are connected properly. 3. When pressurizing, the voltage should be gradually increased slowly in sections to prevent the charging current from being too large and at 0. 25, 0. 5, 0. 75, 1. Read the leakage current value after staying at 0 times the test voltage for 1 minute; Finally, the withstand voltage test shall be carried out at the specified time under the test voltage, and the leakage current value after withstand voltage shall be read before the end of the withstand voltage test. 4. According to the different types of cables, microammeters have different wiring modes. Generally, microammeters are connected to the high-voltage side, and high-voltage leads and microammeters are shielded. For the power cable with copper wire shielding layer and insulated to the ground, the microammeter can also be connected in series to the ground circuit of the tested cable, and a discharge switch can be connected at both ends of the microammeter, and the switch can be pulled open during measurement, after measurement, close the switch before discharge to avoid the impact of discharge current and damage the microammeter. 5. The test voltage shall be measured directly on the high voltage side. Because when half-wave rectification or voltage doubling rectification is adopted, such as the method of converting the measured voltage on the low voltage side to the voltage on the high voltage side, due to the influence of voltage waveform, ratio error and stray current, it may cause large error in the amplitude of high-voltage test voltage, so the test voltage should be directly measured on the high-voltage side. 6. After each withstand voltage test is completed, the pressure should be reduced first and the power supply should be cut off. Then discharge the tested cable to the ground several times with a current limiting resistor of about 80 kHz per kilovolt, and then directly discharge to the ground again. The discharge time should be not less than 5 minutes to ensure full discharge.
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