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Problems needing attention in DC voltage withstand test
Mar 20, 2018

 1. Before the test, the cable is tested and fully discharged, the connecting equipment at both ends of the cable is disconnected, the test is not accompanied by other equipment, the insulation surface of both ends of the cable is wiped clean to reduce the error caused by the surface leakage current, and the insulation baffle should be added in the cable head when necessary


2. The test site should be safe, such as security fence, especially at the other end of the cable to hang a good warning card and send special guard to prevent outsiders near, check the grounding wire, discharge rods are connected.


3. When the pressure, should be phased gradually slowly rising voltage to prevent the charging current too large, and respectively at 0.25, 0.5, 0.75, 1 times times the test voltage to stay for 1 minutes after reading the leakage current value, and finally at the test voltage at the specified time for the pressure test, and before the end of the pressure test, read the leakage current value after the voltage withstand. 4. Depending on the type of cable, the micro-safety table has different wiring methods, generally take the micro-safety table connected to the high-pressure side, high voltage lead and micro-safety table plus shielding.


For power cables with copper wire mesh shielding and ground insulation, the micro-safety table can also be connected to the ground circuit of the tested cable, the two ends of the micro-meter parallel a discharge switch, the switch is opened when measuring, and the switch is closed before the discharge of the measurement, to avoid the damage of the micro-safety meter by the discharge current impact. 5. The test voltage should be directly measured at high pressure side.


Because of the use of half wave rectifier or double voltage rectifier, if the method of measuring voltage in the Low-voltage side is converted to the high-voltage side voltage, because of the influence of voltage waveform and ratio error and stray current, the voltage amplitude of the high-voltage test may be greatly error, so the test voltage should be measured directly on the high side. 6. Each pressure test is completed, should first buck, cut off the power. The tested cable is then discharged several times with a current limiting resistor of about 80,000 euro per kv, then discharges directly to the ground, and the discharge time should be not less than 5 minutes to ensure full discharge.


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