ACSR Cable is the bridge between power supply equipment and electrical equipment, which plays the role of transmitting electric energy. It is widely used, so faults often occur. The following briefly analyzes the causes of common problems of YJV high-voltage cable. According to the causes of faults, they are roughly divided into the following categories: Manufacturer’s manufacturing reasons, construction quality reasons, design reasons of design unit and external force damage.
1、 Reasons for construction quality there are many cases of high-voltage cable system failure caused by construction quality. The main reasons are as follows:
1. The site conditions are poor, the environment and process requirements of cables and joints are very high when they are manufactured in the factory, and the temperature, humidity and dust on the construction site are not easy to control.
2. During cable construction, small slip marks will inevitably be left on the insulation surface, and semi-conductive particles and sand particles on abrasive cloth may also be embedded in the insulation. In addition, moisture will be absorbed in the insulation due to insulation exposure in the air during joint construction, which will leave hidden dangers for long-term safe operation.
3. The installation did not strictly follow the process construction or the process regulations did not consider the possible problems.
4. DC withstand voltage test is adopted for completion acceptance, resulting in the formation of reverse electric field in the joint, resulting in insulation damage.
5. Due to poor sealing treatment. The intermediate joint must adopt the sealing structure of metal copper shell plus PE or PVC insulation and anti-corrosion coating, and the lead seal is dense during on-site construction, so as to effectively ensure the sealing and waterproof performance of the joint.
2、 The manufacturer’s manufacturing reasons are divided into cable body reasons, AAAC Cable joint reasons and cable grounding system reasons according to different parts.
1. Reasons for cable joint manufacturing high voltage cable joints used to be wrapped, molded, molded and other types, which requires a large amount of work to be made on site. Moreover, due to the limitations of on-site conditions and manufacturing process, there will inevitably be air gaps and impurities between insulating tape layers, so problems are easy to occur. The commonly used types in China are assembled type and prefabricated type. The cable joint is divided into cable terminal joint and cable intermediate joint. No matter what type of joint, the cable joint failure generally occurs at the fracture of cable insulation shield, because this is the part where the electrical stress is concentrated. The reasons for the cable joint failure due to manufacturing reasons include manufacturing defects of stress cone body, insulation filler problems, oil leakage of sealing ring and so on.
2. Cable grounding system cable grounding system includes cable grounding box, cable grounding protection box (with sheath protector), cable cross interconnection box, sheath protector, etc. The common problems are mainly due to the poor sealing of the box and the water inflow, resulting in multi-point grounding and excessive induced current of the metal sheath. In addition, unreasonable parameter selection or poor quality of sheath protector and unstable zinc oxide crystal are also easy to cause sheath protector damage.
3. The reasons for the manufacture of the cable body generally include insulation eccentricity, uneven insulation shield thickness, impurities in the insulation, protrusions in the internal and external shields, uneven crosslinking degree, cable moisture, poor sealing of the cable metal sheath, etc. some conditions are more serious, and faults may occur in the completion test or shortly after putting into operation, Most of them exist in the form of defects in the cable system, causing serious hidden dangers to the long-term safe operation of the ABC Cable.
