1. Measure insulation resistance

It should be carried out on each phase separately, the other two-phase conductors, the metal shield or metal sheath and armor layer at both ends of the cable are connected. For this test, just note that the cable is a capacitive device, and you should pay attention to the insulation resistance and absorption ratio of the capacitive device. For example: full discharge before and after the test, fire first and then overlap, disconnect first and then power off and shake the meter.

2. DC withstand voltage and leakage current test

Oil-paper insulated cables are only used for DC withstand voltage, not AC withstand voltage. Because the increase in AC may cause thermal breakdown; in the hot state, the electric field is not uniformly distributed, and the cable is easily damaged. Note: The cable core wire is connected to the negative polarity: after the cable is damp, the water is positively charged. If the core is connected to the negative polarity, the water Will concentrate on the core wire, increase the moisture in the insulation, increase the leakage current, and easily find defects. If the core wire has a positive polarity, the moisture will penetrate into the lead package, the moisture in the insulation will decrease, and the leakage current will decrease, making it difficult to find defects in the DC high voltage generator.

3. Rubber and plastic cable test

Rubber-plastic cables refer to polyvinyl chloride, cross-linked polyethylene, and ethylene-propylene rubber insulated cables. It is characterized by large capacity, high voltage level, light structure and easy bending. It has gradually replaced oil-paper insulated cables. The difference between the XLPE cable and the familiar oil-impregnated paper turnkey cable is that the main insulation between the phases is XLPE plastic, and there are two layers of semiconducting glue coating. The outer surface of the core wire is coated with a semiconducting glue to overcome corona and free discharge, so that there is a good transition between the core wire and the insulating layer. On the outer surface of the interphase insulation, the second layer of semiconductor body is coated in the copper tape shielding layer glue. The copper tape shielding layer is just a layer of thin copper tape with a thickness of 0 to 1 mm, which forms the shielding layer between phases.