Causes of Cable Heating and Considerations When Selecting Cables

When the power cable passes a certain load current, it always exceeds or exceeds the maximum continuous working temperature allowed by the cable (the cross-linked polyethylene insulated cable allows 90 °C). 

The cable will heat for a long time. 

If the fault is not found, the cable will continue to be energized continuously. 

After the operation, the insulation thermal breakdown will occur, causing the cable to cross-phase short-circuit tripping, which may cause a fire. 

The heating of the cable during operation may be caused by the following reasons:

1. The cable conductor resistance does not meet the requirements, causing the cable to generate heat during operation.

2. The cable selection type is improper, causing the conductor cross-section of the cable to be used to be too small, and an overload phenomenon occurs during operation. 

After a long time of use, the heat generation and heat dissipation of the cable is unbalanced to cause heat generation.

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

4. The joint manufacturing technology is not good, the crimping is not tight, and the contact resistance at the joint is too large, which may cause the cable to generate heat.

5. The cable phase insulation performance is not good, resulting in less insulation resistance, and heat generation during operation.

6. The partial sheath of the armored cable is damaged. 

After the water enters, the insulation performance will be slowly destructive, resulting in a gradual decrease in the insulation resistance, which will also cause heating in the cable operation.

In order to ensure the safe operation of the cable, the following factors should be considered when selecting the power cable for cable design.

1. The rated voltage of the cable should be greater than or equal to the rated voltage of the power supply system at the installation point.

2. The continuous allowable current of the cable should be equal to or greater than the maximum continuous current of the power supply load.

3. The core section must meet the stability requirements of the short circuit of the power supply system.

4. Check whether the voltage drop meets the requirements according to the cable length.

5. The minimum short-circuits current at the end of the line should enable the protection device to operate reliably.

6. High breakdown strength.

7. Low dielectric loss.

8. Quite high insulation resistance.

9. Excellent discharge resistance.

10. Has a certain degree of softness and mechanical strength.

11. The insulation performance is stable for a long time.