Fault Analysis and Precontrol Measures for Power Cable ( I )
The construction of power cable to the ground is the direction of the development of the city’s modernization. With the increasing number of cables and the increase of operation years, cable failures are also increasing. Cable failures, such as cable body, cable accessories and cable accessories, are also increasing. According to the maintenance practice of maintenance personnel for many years, the fault location of the cable is mainly concentrated in the insulation, accessories and outer protective layer.
1. Insulation aging. The main causes of insulation aging are:
(1) the cable selection is improper, which causes the cable to work under overvoltage for a long time.
(2) the cable line is near the heat source, so that the cable part or the whole cable line is hot for a long time and aging too early.
(3) the cable work is prematurely aged in an environment with a bad chemical reaction with the insulation.
(4) when multiple cables are run side by side, one or more of them are in bad contact, resulting in the operation of other cables with parallel cables.
(5) when the cable accessories are made, the connection pipe of the cable is not tightly connected, causing the increase of the contact resistance to cause overheating.
2. Appendix issues:
(1) the cable intermediate joint and terminal head are usually completed by the installation site at the site of the installation. The fault of the cable accessories is the main part of the cable fault, and its macro performance is the composite discharge and the aging of the accessories. Cable fault is often because the production process is not fine, personnel careless thinking, in the production process, so that the internal accessories appear bubbles, moisture, impurities and other defects, leading to partial discharge caused by insulation breakdown.
(2) the cable expands with heat and contracts with cold due to the change of load and environmental factors during the operation. The breathing effect is formed between the insulation layer of the cable and the cable, and the moisture and moisture in the atmosphere are brought into the attachment, which causes the fault of the internal short circuit of the cable accessories. The quality of the cold shrink accessories is not high, the shrinkage force is reduced, or there are defects in the need for reliable sealing parts, which will lead to external water intrusion and eventually lead to cable failure.
(3) when the cable head is made, the environment humidity and humidity are too large. There is no reliable dehumidification and tide control measures. The cable insulation is local damp, and the insulation performance decreases. It develops into a penetrating channel in operation and leads to the cable breakdown accident.