Method For Treating Cable Moisture

In the municipal 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. The cable insulation resistance is reduced by moisture or water, which is several important aspects of cable line operation accidents.

1. Causes of moisture or water ingress of polyethylene insulated cables.

Moisture or moisture enters the cable insulation during laying, installation and operation of XLPE insulated power cable, mainly in the following situations.

(1) The sealing of cable end cap is not tight 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) During cable test or operation, the cable insulation breaks down and destroys the cable sheath.

(4) The cable accessories (especially the intermediate joints during direct buried laying) are not tightly sealed. Once moisture or moisture enters the cable insulation from the cable end or cable outer sheath, it may penetrate longitudinally from the gap of the outer copper wire shielding of the insulation or from the gap of the conductor, endangering the whole cable system. The damp cable will produce "water tree" under the action of high electric field Phenomenon, so that the insulation performance of cross-linked polyethylene decreases, and * * * eventually leads to cable insulation breakdown. Therefore, cables affected with moisture must be treated with moisture removal. So far, there is no standard operation method for the dehumidification treatment of damp cables, and there is no unified identification standard for the results of dehumidification treatment. The following describes a cable moisture removal method and steps..

2、 The principle of dehumidification is to use compressed gas medium at one end of the cable (generally, four dry examples are used to analyze. When finding a cable grounding fault in 2004, our company used a megger to test that the resistance of phase B is zero, which is judged as a one-way grounding fault. The total length of the cable is 450m. Because it is a low resistance fault, the low-voltage pulse measurement method mentioned above can be used to directly calculate the distance between the fault point and the test end. After selecting the cable parameters, use the tester to find the generator There is a kind of cable head breakdown. It only took 30min from testing to finding the fault, which saved the rush repair time and reduced the loss.