1, insulation aging deterioration 
　　power cable insulation should be accompanied by electrical effects caused by thermal, chemical and mechanical action, so that the insulating medium physical and chemical changes occur, the medium insulation levels. Wet insulation. Middle connector or terminal head up and down due to structural seal or install wet insulation caused by poor quality; manufacture of lead cable connector package leaving blisters or cracks and other defects, but also make the cable from moisture. 
　　2, cable overheating 
　　caused by overheating of the cables for many reasons. Internal cable insulation is caused by localized heating of free internal air gap, so that the insulation charring. External cables are installed in built-up areas, cable tunnels, etc. The cable wear in dry tube cables and cable and pipeline close, due to overloading or improper cooling cables, accelerated damage the insulation. 
　　3, the mechanical damage 
　　caused by external force, mainly refers to a cable damage. This is mainly due to vehicle vibration and mechanical action, the cable deformation. Cable deformation causes bending over, or cause damage to the inner insulating air gap insulated internally generated. 
　　4, the corrosion protection layer 
　　electrolysis or chemical action because the cable lead package corrosion, due to the different nature and extent of corrosion of lead wrapped in red, yellow, orange, and yellow sponge pores or similar compounds. 
　　5, over-voltage caused by the breakdown 
　　atmospheric over-voltage and over-voltage cable insulation inside the stress exceeds the allowable value and cause breakdown. Moreover, the actual fault analysis showed that many outdoor terminal head failure is caused due to atmospheric over-voltage. 
　　6, the middle joints, terminations head design and production process problems 
　　stripping semiconductors, damaged insulation or insulated inner surface of particles, dust and other impurities; cable head bad seal moisture inside the insulation, causing wet insulation; cable connector process is not standard , seal is not standardized, resulting in the ground; production environment humidity is too large, causing the production site (cable head) insulation integrity damp; cable grounding errors, leading to the formation of ground loop or break. 
　　Maintenance measures 
　　for several types of power cables above faults, can be combined with the actual development of countermeasures. 
　　The intermediate connector and the terminal head of the production process, the cable network head attachment can enhance the test, on the basis of the related regulations, strict control; stripped jacket, insulation shield careful operation the semiconductor layer, the insulating surface polishing and cleaning thoroughly, prevent foreign particles left in the insulation; installation environment humidity less than 70%. 
　　Installation of the cable makes a series of clearly stipulates: armored layer and the copper shield must be grounded separately, and its cross-section of not less than 25 mm2; single cable receiving end must be a grounding point, three-core cable must be grounded at both ends, while done on tin-plated cable lugs. 
　　To prevent cable damage due to external forces, you can force parts do wear protective tube and secure the middle joint external be guarded on both sides plus a fixed joint protection; during the construction process to ensure that lines the nose is not deformed by external forces twist, if you must do twist handle, measures should be taken to make the surface smooth; cable near a construction team construction, eye-catching signage to increase, if necessary, sent to remind construction workers. 
　　Cut joints: the cut before the first check whether there is stagnant water and connectors moisture, if it exists, can not be cut with a torch connector, because the tidal heating burner drive from both sides of the cable connector inside, preferably with a hammer and chop knife to open the casing; if there is no moisture and water, you can use a blowtorch to open the hot lead sheath, in addition to the lead sheath dirt, scrape rust, wipe off solder residue, away from the cable connections to prepare for reuse. 
　　Remove moisture: Available baking method. It is baked with a blowtorch or charcoal, get rid of moisture. This method can only be used for a small moisture circumstances. When the paper damp air heavy insulated wire, can be poured wax method, using hot wax to remove moisture. From 60% ash and 40% medium-sized Vaseline heated to 130-140 degrees after mixing brewed and poured wax is controlled at 120-130 degrees, pouring wax from both sides of the cable connector cable lead sheath cables cut at 10-15cm lead sheath began to gradually shift to the incision poured until after the incision December condense material to the joint central casting, until no bubbles and impregnated core wire voice so far.