NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
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NOYAFA Electronic specializing in testing instruments and cable testers for 16 years
Author: Noyafa–CCTV Tester
Cross-linked cable outer sheath fault tester is mainly used for the withstand voltage test of the cross-linked cable outer sheath. Pre-positioning of cable outer sheath faults The cross-linked cable outer sheath fault tester is mainly used for the withstand voltage test of the cross-linked cable outer sheath. Earth leakage faults in the HV cable outer sheath faults are pre-located. The output voltage of the cable outer sheath tester is 10KV and below, which fully meets the requirements of the cable outer sheath withstand voltage test of the Chinese national standard GB50150-2006, including the cable outer sheath handover test and preventive test suitable for the crossover system and the cable outer sheath. Fault location of the sheath. Quickly and accurately find 10kv-500kv single-core and three-core high-voltage and ultra-high-voltage cable outer sheath grounding faults and leakage currents and other hidden dangers, and at the same time can carry out 5kv-10kv,1 It is a special instrument necessary for the maintenance of cable equipment of 10kv-500kv single-core and three-core high-voltage and ultra-high-voltage cable operation units, ultra-high-voltage cable engineering companies, and power transmission and transformation engineering companies.
With the full development of urban network reconstruction, many power supply bureaus, construction parties, and even design units encountered 110kV XLPE cables for the first time. 1min). At present, the outer sheath is mostly made of HDPE sheath material, which has passed the DC 25kV/5min withstand voltage test in the factory, and the leakage current is as low as tens of tens ofμA. Therefore, most of the defects after laying are caused by external force damage during laying, including soil filling and cover.
Defects after operation are usually caused by termite bites; water ingress to the grounding box; deterioration of the original defect points; moisture permeation of the fork part of the grounding wire to reduce the insulation resistance, etc. Sometimes because the cable is buried too deep or the surrounding conditions are complicated, The positioning is very difficult, and some defects cannot be solved after many years, leaving hidden dangers to the operation. Power cables of 110kV and above are single-core cables. The sheath of single-core cables is an important part of the cable. The quality of its insulation directly affects the service life of the cable and the safe and reliable operation of the power grid. The reasons are as follows 3 Points: a. The damage of the sheath leads to multi-point grounding of the metal shielding layer of the cable. The metal shielding layer will generate a circulating current, which will cause loss and heating, which will lead to local overheating of the insulation and accelerate insulation aging, which will seriously affect the life of the main insulation. b. The damage of the sheath insulation leads to moisture intrusion, and the probability of water tree aging of the main insulation increases, which has a serious impact on the life of the cable.
c. The main insulation produces electric field concentration where the metal sheath is corroded, which is prone to partial discharge and electrical tree generation, posing a threat to the short-term operation safety of the cable. With the increase in the amount of XLPE cables and the increase in voltage level year by year, the environment of some cable laying sites is extremely harsh. In addition, the large-scale infrastructure excavation causes the cables to be damaged. The actual cable insulation sheath damage is very common and must be attached great importance. The insulation state of the cable and the outer sheath should be monitored in time, and the damaged parts of the sheath should be located and repaired to facilitate the safe operation of the urban underground power grid.
The non-metallic outer sheath of 110kV and above high-voltage cables has insulation requirements. The IEC standard requires that the outer sheath of 110kV cables can withstand 10kV for one minute during the completion test. If the outer sheath of the high-voltage cable is damaged, it will cause multi-point grounding of the metal sheath during operation, which will cause circulation loss and affect the safe operation of the cable. Therefore, it is necessary to detect and troubleshoot the outer sheath of the cable. The cable outer sheath fault tester can perform the following tests: pre-location of sheath faults on medium and high voltage shielded cables, pre-location of line ground faults on low-voltage cables with plastic insulation, and precise location of cable faults by measuring step voltage.
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