Power cable through a certain load current, will certainly heat, with the load current increases, the cable surface temperature is higher, if not timely treatment, the consequences can be imagined. such as: PVC (PVC) cable, is based on the core temperature of 70 degrees for the upper limit, the surface temperature will be low 5~10度.
So the cable surface temperature below 60 degrees is basically safe, from power maintenance considerations, of course, the lower the better.
The reason why the cable is hot in operation is as follows:
1, cable conductor resistance does not meet the requirements, resulting in the operation of cable heating phenomenon.
2, improper selection of cable, resulting in the use of the conductor section of the cable is too small, the operation of overload phenomenon, long time to use, the cable heating and heat imbalance caused by fever.
3, cable installation is too dense, ventilation cooling effect is not good, or cable near other heat source too close, affecting the normal cooling of the cable, but also may cause the cable in the operation of heating phenomenon.
4, joint manufacturing technology is not good, the pressure is not tight, resulting in joint contact resistance too large, will also cause heating phenomenon cable.
5, cable phase insulation performance is not good, resulting in small insulation resistance, running will also produce fever phenomenon.
6, armored cable local sheath damage, water after the insulation performance caused by slow damage, resulting in the insulation resistance gradually reduced, will also cause heating in the cable operation. When the cable produces heating phenomenon, if not find out the reason in time to troubleshoot, cable continue to power running will produce insulation thermal breakdown phenomenon. Causes the cable to have the phase short circuit trip phenomenon, the serious possibility causes the fire.