1. Common line faults

① Short circuit fault: There are two-phase short circuits and three-phase short circuits, which are mostly caused by hidden dangers left during the manufacturing process.

② Grounding fault: When one or several cores of a cable break through to ground, and the insulation resistance is below 10k Ω, it is called low resistance grounding, and above 10k Ω, it is called low resistance grounding. Mainly caused by cable corrosion, lead skin cracks, insulation drying, joint technology and materials, etc.

③ Linear fault: One or more cores of the cable are completely broken or not broken. Cable breakage can occur due to mechanical damage, terrain changes, or short circuits.

④ Mixed fault: Two or more types of faults mentioned above.

2. Causes and Countermeasures of Power Cable Line Faults

① External force damage: Cables may be damaged by external forces during storage, transportation, laying, and operation, especially for buried cables that have already been in operation and are prone to damage during ground construction in other projects. This type of accident often accounts for 50% of cable accidents. To avoid such accidents, in addition to strengthening the quality of work in cable storage, transportation, and laying, it is more important to strictly implement the excavation system.

② Corrosion of protective layer: The electrochemical corrosion of underground stray currents or chemical corrosion of non neutral soil causes the protective layer to fail and lose its protective effect on insulation. The solution is to install drainage devices in areas with high stray current density; When the local soil on the cable line contains chemical substances that damage the cable lead sheath, the cable should be installed in a pipe, and neutral soil should be used as a cable liner and cover. Asphalt should also be applied to the cable.

③ Overvoltage and overload operation: Improper selection of cable voltage, sudden high-voltage surge during operation, or long-term overload can all damage the insulation strength of the cable and cause it to breakdown. This needs to be resolved in a timely manner by strengthening inspections and improving operating conditions.

④ Outdoor terminal head immersed in water: Due to poor construction, the insulation glue was not fully filled, resulting in the terminal head being immersed in water and eventually causing an explosion. Therefore, it is necessary to strictly follow the construction process regulations and carefully inspect; Strengthen inspection and timely maintenance. The terminal head leaked oil, damaged the sealing structure, caused the impregnating agent at the cable end to dry up, increased thermal resistance, accelerated insulation aging, and easily absorbed moisture, resulting in thermal breakdown. When oil leakage is found at the terminal head, inspection should be strengthened, and in severe cases, power should be cut off and redone.