The cable is the bridge between the power supply equipment and the electrical equipment, and plays the role of transmitting electrical energy. Because of its wide range of applications, faults often occur. The following briefly analyzes the causes of the common problems of YJV high-voltage cables. Classification according to the causes of faults can be broadly classified into the following categories: manufacturer's manufacturing reasons, construction quality reasons, design unit design reasons, external forces Destroy four major categories. The cable is the bridge between the power supply equipment and the electrical equipment, and plays the role of transmitting electrical energy. Because of its wide range of applications, faults often occur. The following briefly analyzes the causes of the common problems of YJV high-voltage cables. Classification according to the causes of faults can be broadly classified into the following categories: manufacturer's manufacturing reasons, construction quality reasons, design unit design reasons, external forces Destroy four major categories. First, manufacturers create reasons According to the different parts, the manufacturer's manufacturing reasons are divided into three categories: cable body reason, cable joint reason, and cable grounding system reason. 1, cable body manufacturing reasons The common problems in the cable production process include insulation eccentricity, uneven insulation shield thickness, impurities in the insulation, protrusions inside and outside the shield, uneven cross-linking, moisture in the cable, poor sealing of the cable metal sheath, etc. Severe failures may occur during or shortly after the completion of the test, most of which are in the form of defects in the cable system, causing serious risks to the long-term safe operation of the cable. 2, cable connector manufacturing reasons High-voltage cable joints have previously been of the wrap-around type, die-cast type, molded type, etc., and require a large amount of work to be performed in the field, and due to the limitations of on-site conditions and manufacturing processes, there is inevitably an air gap between insulating tape layers. With impurities, it is prone to problems. The types commonly used in China are assembly and prefabrication. 3, cable grounding system The cable grounding system includes the cable grounding box, the cable grounding protection box (with protective layer protector), the cable cross-interconnect box, and the cover protector. The general problem that is easy to occur is mainly because the poor sealing of the box body leads to multi-point grounding, causing the metal sheath induction current to be too large. In addition, the selection of protective layer protector parameters is unreasonable or the quality of the zinc oxide crystal is unstable, and it is easy to cause damage to the protective layer protector. Second, the construction quality reasons There are many cases of high-voltage cable system failure due to construction quality. The main reasons are as follows: Cable breakdown caused by thermal expansion of the cable causes breakdown. When the cross-linking cable load is high, the temperature of the core is increased, the cable is thermally expanded, and the cable is turned on the bracket elevation at the turning point in the tunnel. The long-term heavy-duty operation of the cable has a large amount of peristaltic force, which causes the bracket facade to crush the outer jacket of the cable. , Metal sheathing, intrusion into the cable insulation leads to cable breakdown.
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The cable joints are divided into cable end connectors and cable intermediate joints. No matter what the joint type is, the cable joint failure usually occurs at the fracture of the cable insulation shield because it is the location where the electrical stress is concentrated and the cause of the cable joint failure due to manufacturing reasons is stress. Cone body manufacturing defects, insulation filler problems, oil leaking seals and other reasons.
1, the site conditions are relatively poor, cables and joints in the factory manufacturing environment and process requirements are high, and the construction site temperature, humidity, dust are not well controlled.
2. In the course of cable construction, it will inevitably leave tiny sliding marks on the insulating surface. The semi-conductive particles and the sand on the abrasive cloth may also be embedded in the insulation. In addition, during the construction process of the joint, the insulation is exposed to the air and the insulation is also inhaled. Moisture, these all leave hidden dangers for long-term safe operation.
3, the installation did not strictly in accordance with the process of construction or process regulations did not take into account the possible problems.
4. Acceptance and acceptance of a DC voltage withstand test results in the formation of a back-EMF in the joint resulting in insulation failure.
5, due to poor sealing caused. The middle joint must adopt the sealed structure of metal copper shell plus PE or PVC insulation coating to ensure the solidity of the seal during construction on site, which effectively ensures the sealing and waterproof performance of the joint.
Third, the design reason 