When the wires and cables are energized, the metal core will generate heat. As the power-on time increases, the surface temperature of the wires and cables will become higher and higher. If not handled in time, the consequences can be imagined. The PVC wires and cables we commonly use have polyvinyl chloride sheaths. The upper limit of the wire core temperature is 70 degrees, and the surface temperature will be 5 to 10 degrees lower. Therefore, the cable surface temperature is basically safe when it is below 60 degrees. From the perspective of power supply maintenance, of course, the lower the temperature, the better.
It is normal for wires and cables to heat up, but there are some situations that can cause wires and cables to overheat. Today we will talk about the reasons why wires and cables overheat during use.
1. The wires and cables are not crimped tightly at the joints, resulting in excessive resistance at the joints, which may cause the wires and cables to overheat when powered on for a long time.
2. Insufficient considerations were taken when designing, planning and installing wires and cables, and wires and cables that did not match the cable conductor resistance were selected. When the energizing current is greater than the large negative current, overheating will occur.
3. Improper cable selection causes the conductor cross-section of the cable used to be too small, causing overload during transportation. After long-term use, the cable's heating and heat dissipation are unbalanced, causing overheating.
4. Due to the unprofessional installation personnel, 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 overheat during operation.
5. The insulation performance between cable phases is not good, resulting in low insulation resistance and overheating during transportation.
6. The partial sheath of the armored cable is damaged. Water intrusion will slowly damage the insulation performance, causing the insulation resistance to gradually decrease, and also cause overheating during cable operation.
7. Many inferior wires and cables on the market have poor insulation, resulting in low insulation resistance and overheating after long-term operation.
8. Improper selection of wire and cable models. For example, fire-resistant wires and cables should be selected in high temperature or flammable environments.
