Explanation of the causes of Power Cable Heating

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 handled in time, the consequences can be imagined. 

Such as the PVC cable, considering the core temperature of 70 degrees as the upper limit, the surface temperature will be 5-10 degrees lower. 

Therefore, it is basically safe for the cable surface temperature to be below 60 degrees. From the perspective of power supply maintenance, of course, the lower the temperature, the better. 

Next, let's take a look at what are the reasons for the heating of power cables during operation.

The following factors lead to abnormal heating of the cable:

Cable Own Factors

1. The cable is not produced in accordance with the standard cross-section specified in the national standards, resulting in the cable's own resistance exceeding the standard.

2. The copper used in the cable contains too many impurities and does not meet the purity standard of electrical copper, resulting in the cable's own resistance exceeding the standard.

3. The thickness of the cable insulation layer is not up to standard or the amount of rubber contained in the insulation material is not up to standard, resulting in the insulation resistance of the inter-phase cable not being up to standard.

4. The cable selection does not match the load current, which exceeds the load capacity of the cable in normal operation for a long time.
   

Laying Environmental Factors

1. During construction, the terminal size is small or the terminal and cable are not crimped tightly, resulting in excessive resistance at the cable ends.
2. The cable is laid too closely, resulting in the heat emitted during normal operation of the cable not being dissipated in time.
3. The cable is laid in a slot box or a closed bridge, which is not conducive to heat dissipation.
4. Cables are laid around heat sources, e.g., near heat pipes, and are not insulated.
5. Common cables are used for high-frequency loads, resulting in overheating of the cables.
6. Harmonic content in the grid is excessive and does not match the cable design, resulting in overloads.

Solution for Cable Heating

The Cable Itself Causes Heat

1. Strictly in accordance with the parameters set by the national standards require suppliers to provide test reports, including indicators such as cross-sectional area, copper content, insulation layer thickness, and insulation material adhesive content.
2. Strict design selection, in accordance with national standards, the cable selection principle is: the cable load capacity should be greater than the rated current rectification value of the circuit breaker at this level. In the project, the use of load calculation current as the basis for selecting the cable load capacity is wrong.
3. Before the installation of the cable, the insulation resistance of the cable is tested in strict accordance with the operating procedure.

Laying Environmental Factors Lead to Heat

1. Wiring terminals meet the requirements of the standard cross-section, crimping construction standards, and specifications, in line with the construction process requirements.
2. Cable laying to avoid disorderly, stacking too dense, and other irregularities, fixed in accordance with the requirements of the specifications, try to avoid multi-layer stacking, should be laid in a single layer, up to two layers.
3. For cables laid in slot boxes or enclosed bridges, set ventilation holes appropriately, or take necessary ventilation measures.
4. When the cable is laid adjacent to the heat source, conform to the spacing distance required by the specification, or take measures such as a heat insulation plate.
5. High-frequency loads should use high-frequency special cables.
6. The harmonic management measures of the power grid are not only limited to the centralized management of substations but also increase the in-situ compensation appropriately according to the site conditions.

After the phenomenon of power wire heating, if the cause is not found in time to troubleshoot, the wire will continue to run continuously energized insulation thermal breakdown phenomenon, resulting in a phase-to-phase short circuit tripping of the wire, which may cause a serious fire.
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