When the power cable passes through a certain load current, the maximum allowable continuous working temperature of the cable is always higher or higher (the maximum allowable temperature of cross-linked polyethylene insulated cable is 90 ℃), and the cable will be heated for a long time. If the fault is not found out in time, the insulation thermal breakdown phenomenon will occur after the cable continues to operate continuously, resulting in phase to phase short-circuit tripping of the cable, and serious fire may be caused. Heating of cables during operation may be caused by the following reasons:

　　1. The DC resistance of the cable conductor does not meet the requirements, resulting in heating of the cable during operation.

　　2. Improper selection of cable type causes the conductor section of the cable to be used to be too small, resulting in overload during operation. After long-term use, the heating and heat dissipation of the cable are unbalanced, resulting in heating.

　　3. When cables are installed, the arrangement is too dense, the ventilation and heat dissipation effect is not good, or the cables are too close to other heat sources, which affects the normal heat dissipation of cables, and may also cause heating of cables during operation.

　　4. Poor joint manufacturing technology and tight crimping will cause excessive contact resistance at the joint and cause heating of the cable.

　　5. Poor inter phase insulation performance of cables leads to low insulation resistance and heat generation during operation

　　6. The local sheath of the installed cable is damaged, which will slowly damage the insulation performance after the water enters, causing the insulation resistance to gradually decrease, and also causing the heating phenomenon during the cable operation.