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The cable is the bridge between the power supply equipment and the electric equipment, and plays the role of transmitting electricity.
Widely used, so the fault also occurs frequently, the following brief analysis of the causes of YJV high-voltage cable common problems, according to the reasons for the breakdown is roughly divided into the following categories: manufacturers cause, construction quality reasons, Design unit design reasons, external damage four categories.
First, manufacturers manufacturing reasons
Manufacturers manufacturing reasons according to the occurrence of different parts, but also divided into cable body reasons, cable connector reasons, cable grounding system for three categories.
1, cable body manufacturing reasons Generally in the cable production process is prone to the problems of insulation bias, insulation shielding thickness is uneven, there are impurities in the insulation, internal and external shielding has raised, uneven crosslinking degree, cable damp, cable metal sheath sealing bad, and some of the more serious may be in the completion of the test or after the operation of the failure,
Most of the cable system in the form of defects, the long-term safe operation of cable caused serious problems.
2, cable connector manufacturing reasons High-voltage cable connectors used around the package type, mold casting, mold type, and other types, the need for on-site production of the workload, and due to on-site conditions and the reasons for the production process, insulation zone between the inevitable air gap and impurities, so easy to occur problems.
The commonly used types in China are assembled and prefabricated.
Cable connectors are divided into cable terminal connectors and cable middle connectors, no matter what the joint form, cable joint fault generally appears in the cable insulation shielding fracture area, because this is the location of electrical stress concentration, due to the cause of the cable connector failure caused by the stress cone body manufacturing defects, insulation filler problem, sealing ring oil leakage and so on.
3. Cable grounding system Cable grounding system includes cable grounding box, cable grounding protection box (with protective layer protector), Cable crossover interconnect box, protective layer protector and so on. Generally, the problem is mainly because the casing seal is not good enough to lead to a lot of grounding, causing the metal protective layer induced by too large.
In addition, the parameter of protective layer protector is unreasonable or the quality is not good. Zinc oxide crystals are unstable and can easily cause damage to protective layer protectors.
Second, the Construction quality reason
Because the construction quality causes the High-voltage cable system Breakdown Many cases, the main reason has the following several aspects:
1, the site conditions are relatively poor, cables and joints in the factory manufacturing environment and process requirements are very high, and the construction site temperature, humidity, dust is not good control.
2, cable construction in the insulation surface will inevitably leave a small slip marks, semi conductive particles and emery cloth on the sand may also be embedded in the insulation, the other joint construction process due to insulation exposure in the air, insulation will also be inhaled moisture, these are long-term safe operation left hidden dangers.
3, installation is not strictly in accordance with the process of construction or technical provisions do not take into account the possible problems.
4, the completion of the acceptance of the use of DC voltage test results in the joint formation of the reverse electric field resulting in insulation damage. 5, due to improper sealing treatment caused.
The middle joint must adopt the metal copper shell plus PE or PVC insulation anti-corrosion layer sealing structure, in the field construction to ensure the tightness of the seal, so as to effectively guarantee the sealing waterproof performance of the joint.
Iii. Design Reasons The cable squeeze caused by the heating expansion of the cable leads to breakdown. When the cross-linked cable is in high load, the core temperature rises, the cable expands, the cable in the tunnel bends the top in the bracket façade, the long-term large load operation cable peristalsis strength is very big, causes the bracket to break the cable outer sheath, the metal sheath, squeezes the cable insulation layer to cause the cable breakdown.