In recent years, thermal power plant in cable and cable installation updates when most of the cross-linked polyethylene cable (XLPE cable), this is because it is not affected by the high drop limit, copper core bear high temperature, the transmission capacity is relatively large, low dielectric loss, installation, operation and maintenance of the advantages such as simple and convenient, but in use, the XLPE insulating material retained within the stress should be paid more attention.
The thermal power plant for power cables are generally below 1000V, due to the low voltage, the installation of cable. Follow the old habits of construction, ignoring the XLPE material in the production of internal stress remains the fact that when installing accessories need to XLPE insulated cable cut off when the stress time will disappear naturally. The main insulation shrinkback. Thermal power plant repair in case of an accident, because time is tight, can not eliminate all stress to install cable joints, such measures are not taken or in the construction process is not in place, installed after the operation, continue to shrink in the operation of the main insulation of XLPE, the formation of the air gap, which is the fatal defect of cable joint. Once the formation of the air gap, the gap will definitely lead to partial discharge, leading to joint breakdown, shorten the life of cable joint, affect the safety in production. So what measures can be taken to overcome and eliminate the hidden dangers? Here to talk about the installation of cable joints from the process should pay attention to the problem. In the connecting wire, the side insulation end cut cone (i.e., reaction force, the inner shield wire cone) stay longer than normal about 10mm, crimping or welding, remove the connecting pipe surface of burr and flash, gasoline wet cloth will be connected to the tube surface of metal dust wipe, then first with a semi conductive rubber self-adhesive tape (or semi conductive tape) fill the pit connecting pipe (ring filled indentation) and half folded around, wrapped around the way filled gap between the connecting pipe and the core in the semi conductive shielding layer, must be carefully wrapped, no gap left hand pressure evenly, play uniform electric field. Then on the connecting tube half folded around 2 layers of semi conductive tape and extend to the reaction force of cone 10mm on insulator (connecting pipe on both sides), so the wrapping treatment, even if the retraction of the main insulation of XLPE, generally below 10mm, the shielding effect still exists. In increasing around the insulation, self insulating tape package layer 6, and stretched to its width at half folded around half way, the bag after the strip has a certain stress inward tightening, while winding by hand according to the winding to press to discharge the air gap.
After adopting the above measures, the joint breakdown caused by the main insulation of the XLPE can be prevented effectively.
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