As China's industrial level is getting higher and higher, it can be said that wires and cables are everywhere. In recent years, the construction and development of cables into the ground has also been very rapid. However, with the increasing number of cable lines and the growth of operation years, cable faults have gradually increased, and the faults of cable body, cable accessories and cable auxiliary equipment during cable operation have also increased significantly, Let's take a look at the causes of these faults.

With the increase and accumulation of cable service time, the most likely problem of the cable is insulation aging. The reason for this situation may be that the cable did not select a suitable model during laying at that time, resulting in the cable working under overvoltage for a long time or close to heat source around the cable line, resulting in premature aging due to long-term heating of part of the cable or the whole cable line. The working environment of the cable is also a factor affecting the service life of the cable insulation layer. If it is used in a bad environment with chemical reaction, or multiple cables run side by side, but one or several of them are in poor contact, it will also cause overload operation of other parallel cables, resulting in failure. When the cable accessories are made, the cable connecting pipe is not crimped firmly, Overheating caused by the increase of contact resistance is the cause of insulation failure, which must be reasonably avoided.

Accessories are also very prone to problems, and this proportion is also very high. The reason is that the cable intermediate joint and terminal head are usually completed by the installation personnel on site at the laying site. If you pay little attention to the installation, it is easy to make mistakes. Problems with accessories will affect composite interface discharge and aging of accessory materials. The problem of accessories is often due to poor manufacturing process and poor product quality. During the manufacturing process, there are defects such as bubbles, moisture and impurities in the accessories, resulting in partial discharge and insulation breakdown. Not only high-quality accessories should be selected, but also should not be neglected in the installation process.

The problem of outer sheath is also common. In medium and high voltage power grids, the outer sheath of wires and cables is the first line of defense to protect cables. Its integrity is directly related to the safety of internal structure and the service life of cables. The reasons for the problems of the outer protective layer are: there are hard objects and sharp corners directly contacting the outer protective layer above and below the directly buried cable, especially in the road section with vehicle traffic, the sharp corners of hard objects may pierce the outer protective layer for a long time, resulting in damage to the internal structure. In addition, the cable load changes, the thermal expansion and contraction of the cable itself and the uneven distribution of electric field at the damaged parts, resulting in damage to the insulating layer; During pipe laying, the outer protective layer may be damaged if the steps or inner wall at the pipe connection are not smooth; The outer sheath is damaged due to mechanical construction or pipe jacking around the cable path.

In the process of cable laying, the damaged and cracked parts of the outer sheath will not be found in time if they are in the row pipe; After running for a period of time, cracking occurs, the insulation of the outer sheath decreases, the metal sheath is grounded at multiple points, and the circulating current increases, resulting in thermal aging and breakdown of the insulation. Termite erosion is also one of the reasons for the appearance of the outer protective layer. Once a termite erosion part is found, there are often multiple erosion parts on the cable line, which should be paid enough attention. Termites are in danger of decay, which is relatively rare in the north.