In the daily operation of power system, often due to the quality of power cables, improper construction and unreasonable operation and maintenance and many other factors, affecting the normal operation of the cable, the following power cables in the course of the common line problems and failures analysis.
Common line failure
Short-circuit fault: There are two short-circuit and three-phase short circuit, mostly caused by the hidden dangers in the manufacturing process.
Grounding fault: A certain number of core or core of the cable to ground breakdown, insulation resistance below 10kΩ said low resistance ground, higher than 10kΩ called low resistance ground. Mainly due to cable corrosion, lead cracks, insulation dry, joint technology and materials caused.
Broken linear fault: a cable core or a few broken or not completely broken. Cable by the mechanical damage, terrain changes or the occurrence of short circuit, can cause disconnection.
Mixed fault: the above two kinds of faults.
Reasons of power cable fault and countermeasures
External Damage: External damage may occur during the storage, transportation, laying and operation of the cable. In particular, the buried cable that has been operated may be easily damaged in the ground construction of other projects. Such accidents often account for 50% of cable accidents. In order to avoid such accidents, it is more important to strictly enforce the system of earth-shaking, in addition to strengthening the quality of work in all aspects of cable storage, transportation and laying.
Protective Layer Corrosion: Electrochemical corrosion of stray currents underground or chemical attack on non-neutral soil invalidates the protective layer and loses its protective effect on insulation. The solution is to install drainage equipment in a stray current-dense area. When the local soil on the cable contains chemicals that damage the cable lead package, the cable should be installed in a tube and cabled with a neutral soil And cover, but also coated with asphalt on the cable.
Over-voltage, over-load operation: improper selection of the cable voltage, sudden high-pressure operation in the fleeing or long-term overload, may damage the dielectric strength of the cable, the cable breakdown. This needs to be strengthened inspection tour, improve operating conditions to solve.
Outdoor terminal immersion: due to poor construction, insulation plastic is not filled, resulting in terminal immersion, the final explosion. Therefore, we must strictly implement the construction process rules, serious acceptance; strengthen inspection and timely maintenance. Terminal head oil spills, destroyed the sealing structure, so that the end of the cable loss of impregnating agent, thermal resistance increased insulation accelerated aging, easy to absorb moisture, causing thermal breakdown. It should be strengthened inspection tour terminal leakage of oil, severe blackout should be redone.
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