When the power cable passes a certain load current, it will definitely heat up. As the load current increases, the surface temperature of the cable will be higher. If it is not dealt with in time, the consequences can be imagined. For example, for polyvinyl chloride (PVC) cables, the upper limit of the core temperature is 70 degrees, and the surface temperature will be 5 to 10 degrees lower. Therefore, the surface temperature of the cable is basically safe below 60 degrees. From the perspective of power supply maintenance, of course, the lower the temperature, the better.
The reasons for the heating of power cables during operation are as follows:
1. The cable conductor resistance does not meet the requirements, causing the cable to generate heat during operation.
2. Improper selection of cables will cause the conductor cross-section of the cables used to be too small, resulting in overload during operation. After long-term use, the heating and heat dissipation of the cables are unbalanced, resulting in heat generation.
3. The cables are arranged too densely during installation, 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 the cables, and may also cause the cables to generate heat during operation.
4. The joint manufacturing technology is not good, and the crimping is not tight, resulting in excessive contact resistance at the joint, which will also cause the cable to generate heat.
5. The insulation performance between the phases of the cable is not good, resulting in a small insulation resistance and heating during operation.
6. The partial sheath of the armored cable is damaged, which will slowly destroy the insulation performance after entering the water, causing the insulation resistance to gradually decrease, and will also cause heating during the operation of the cable.
After the power cable generates heat, if the cause is not found and the fault is eliminated in time, the insulation thermal breakdown will occur after the cable continues to run continuously. It will cause the short-circuit tripping phenomenon between the phases of the cable, which may cause a fire in serious cases.