When the power cable passes through a certain load current, it will heat up. With the increase of the load current, the cable surface temperature is higher. If it is not dealt with in time, the consequences can be imagined. For example: polyvinyl chloride (PVC) cable is the core temperature of 70 degrees for the upper limit to consider, the surface temperature will be 5~10 degrees lower. Therefore, the cable surface temperature below 60 degrees is basically safe, from the power maintenance considerations, of course, the lower the temperature, the better.
The cable is heating during operation, for the following reasons:
1, the cable conductor resistance does not meet the requirements, resulting in cable heating in operation.
2, improper cable selection, resulting in the use of cable conductor cross section is too small, overload in operation, after a long period of use, the cable heating and heat imbalance, resulting in fever.
3, cable installation is too dense arrangement, ventilation, heat dissipation is not good, or cable near other heat sources too close, affecting the normal heat dissipation of the cable, but also may cause cable heating in operation.
4, the joint manufacturing technology is not good, crimping is not tight, resulting in contact resistance at the junction is too large, but also lead to cable heating phenomenon.
5, cable and interphase insulation performance is not good, resulting in less insulation resistance, the operation will also have a fever.
6 、 the local sheath of armored cable is damaged, and the insulation performance is slowly damaged after water inflow, which leads to the gradual decrease of insulation resistance, and also leads to heating phenomenon in cable operation.
If the cable is heating up, if the reason is not found out in time, the cable will continue to operate continuously, and then the insulation thermal breakdown will occur. Causes the cable to occur the interphase short circuit trip phenomenon, serious possibly causes the fire.