There are relatively many factors that should be considered when selecting the cross-sectional area of wires and cables, and the selection should be based on actual needs.

Transmission capacity

The first thing to consider is the power transmission capacity. The larger the power transmission capacity, the larger the conductor cross-section needs to be. The capacity most directly depends on the conductor cross-section of the wire and cable, which is the most important factor.

Transmission distance

When the power transmission distance is long, the line loss and voltage drop of the line must be considered. If the voltage drop is small, the conductor cross-section must be larger.

Wires and cables themselves and their structures

1. The raw materials of conductors, such as square copper, aluminum, and aluminum alloys, are essentially the resistance of the conductor. The cross-section of copper conductors is smaller than that of aluminum and aluminum alloy conductors with the same transmission capacity. This is why most long-distance overhead lines use AAAC conductors, AAC conductors or ACSR conductors for power transmission.

2. The heat resistance of the cable insulation material, that is, the long-term working temperature of the insulation, such as: PE and PVC are 70 degrees Celsius, XLPE and EPR are 90 degrees Celsius. For the same power transmission capacity, the conductor cross-section that can withstand excessive temperature can be relatively smaller.

3. Cable structure: The multi-core structure of cables will cause certain differences in the flow rates between cables. For the same transmission capacity, the selection of conductor cross-sections will also be different. In addition, some armored cables have metal sheaths and armor layers on the outer layer, which will also directly affect the selection of conductor cross-section.

Cable laying method

The laying method and condition of the cable have a great impact on the current carrying capacity of the cable, and must be paid great attention to, otherwise it will affect the safe power supply and the life of the cable. There are two main factors that affect the current carrying capacity of cable laying conditions:
1. Induced current increases the loss of the cable and increases the heat generation of the cable;

2. The laying conditions will affect the heat dissipation of the cable. Cables dissipate heat quickly, which will increase the carrying capacity, so the conductor cross-section can be appropriately selected. On the contrary, cables are not easy to dissipate heat, which increases the working temperature of the cable and will reduce The current carrying capacity of wires and cables, then the conductor cross-section should be larger.

Environmental factors

Environmental factors have the greatest impact on the current carrying capacity of cables, and have a greater impact than the wires and cables themselves and their laying conditions. The most obvious ones are ambient temperature and air circulation. If the ambient temperature is high and the air circulation is poor, the cable carrying capacity will decrease, and the conductor cross-section must become larger; on the contrary, if the ambient temperature is low and the air flow is good, the cable carrying capacity will be high, and the conductor cross-section can be selected to be appropriately small.

 

In short, there are relatively many factors that should be considered in the selection of wires and cable cross-sections. The selection of cables and their conductor cross-sections should be based on actual needs and comprehensive consideration of various factors to achieve scientific and rational use of wires and cables.