In the urban power grid reconstruction project, cables, especially polyethylene insulated power cables, have been widely used. However, due to the particularity of the cable, there are special requirements for the installation, operation and maintenance of the cable. Cable dampness or water ingress reduces the insulation resistance of the cable, which is an important aspect of the cable line running accident.
1. Causes the polyethylene insulated cable to get wet or ingress. XLPE insulated power cables cause moisture or moisture to enter the cable insulation during installation, installation and operation, mainly in the following cases. (1) The sealing of the cable end cap is not strict or the cable end cap is damaged by external force during cable transportation and laying. (2) The cable sheath is damaged by external force during cable transportation or laying. (3) Cable insulation breakdown damages the cable sheath during cable testing or operation. (4) The cable accessories (especially the intermediate joints during direct burial) are not tightly sealed. Once moisture or moisture enters the cable insulation from the cable end or the cable sheath, it is possible to penetrate longitudinally from the gap of the insulated outer copper wire or from the gap of the conductor, jeopardizing the entire cable system. The cable after the damp will produce a "water branch" phenomenon under the action of a high electric field, so that the insulation performance of the XLPE is degraded, eventually leading to cable insulation breakdown. Therefore, the cable after the damp must be dehumidified. So far, there is no standard operation method for the dehumidification treatment of damp cables, and there is no uniform appraisal standard for the results of dehumidification treatment. The following describes a method and steps for cable dehumidification. .
2. The principle of dehumidification treatment uses compressed gas medium at one end of the cable (usually analyzed by the case of dry 4 cases. In 2004, when we found a cable ground fault, we tested the phase B resistance with a shaker to zero, and judged to be unidirectional ground. The cable has a total length of 450m. Because it is a low-resistance fault, the low-pressure pulse mentioned above is used. The middle measurement method can directly calculate the distance from the fault point to the test end. After selecting the cable parameters, use the tester to find a question. Cable head breakdown. It took only 30 minutes from testing to finding the fault, saving the repair time and reducing the loss.