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Analysis of common wiring problems and faults in the use of power cables.
Common line Failures
Short-circuit fault: There are two-phase short-circuit and three-phase short-circuit, more for the manufacturing process left behind the hidden trouble.
Grounding fault: Cable a core or several core to the ground breakdown, insulation resistance lower than 10kω said low resistance grounding, higher than the 10kω called low resistance grounding. Mainly due to cable corrosion, lead crack, insulation dry, joint process and materials.
Disconnection fault: Cable a core or a number of cores are all broken or not completely broken. The cable is affected by mechanical damage, topographic changes or short circuit, which can cause disconnection.
Mixed fault: Above two kinds of faults.
Reason and countermeasure of power cable line fault
External damage: In the cable storage, transport, laying and operation of the process may be damaged by external forces, especially the direct buried cable has been running in other projects in the ground construction is vulnerable to damage. Such accidents tend to account for 50% of cable accidents. In order to avoid such accidents, in addition to strengthening the cable custody, transport, laying and other aspects of the work quality, more important is the strict implementation of the system of passive Earth.
Corrosion protection: The electrochemical corrosion of underground stray currents or the chemical corrosion of neutral soils make the protective layer ineffective and lose the protective effect on insulation. The solution is to install the discharge equipment in the dense area of the stray current, when the local soil on the cable line contains chemicals that damage the cable lead pack, the cable should be installed in the pipe, and the neutral soil should be used as the liner and cover of the cable, and the cable should be coated with asphalt.
Overvoltage, over load operation: improper selection of cable voltage, sudden high pressure in operation or long-term overload, may cause the cable insulation strength damaged, the cable breakdown. This needs to be strengthened patrol inspection, improve operating conditions to resolve in a timely manner.
Outdoor terminal head in water immersion: due to poor construction, insulating rubber is not filled, to the end of the water immersion, the final explosion occurred. Therefore, strict implementation of construction technology procedures, serious acceptance, strengthen inspection and timely maintenance. Terminal Head oil leakage, damage the seal structure, so that the end of the cable impregnation Agent drain dry, increase thermal resistance, insulation accelerated aging, easy to absorb moisture, resulting in thermal breakdown. found that the end of the oil leakage should be strengthened patrol, serious when the power failure to redo.