What is the reason for high voltage lines having a larger diameter than low voltage lines?

Analysis of reasons why the diameter of high voltage line is larger than that of low voltage line

The diameter of the high-voltage line is larger than that of the low-voltage line, mainly due to the following reasons:

Energy conservation and power matching

According to the law of conservation of energy, the transformer keeps the power constant while converting the voltage. Even at different voltage levels, the total power of input and output is the same 1. Since the higher the voltage, the smaller the current (according to the formula P = V * I, when the power is unchanged, the voltage is inversely proportional to the current), the current of the high-voltage line is smaller, and the diameter of the line can be naturally reduced. In contrast, low-voltage lines have a larger diameter because they need to transmit a larger current to meet the same power requirements.

Line loss consideration

The diameter of a line affects not only the ability to transmit current, but also the line loss. A wire with a larger wire diameter has a lower resistance, which reduces energy loss during transmission 2. Because the transmission distance of high-voltage transmission lines is long, the line loss is relatively small, so the line diameter can be appropriately reduced. Low voltage line due to the short distance, the line loss is relatively large, need a thicker line diameter to reduce energy loss.

Voltage classes and safety requirements

The voltage level of high-voltage lines is higher, usually used for long-distance transmission, and the insulation requirements for the wires are also higher. In order to ensure the safe operation of the line and prevent the influence of the electric field on the outside world, although the diameter of the high-voltage line is small, its insulation materials and structure may be more complex.

Mechanical strength and durability

Although the high voltage line current is small, considering the long-term operation and possible extreme weather conditions, such as wind and ice heavy, the line diameter of the high voltage line also needs to be sufficient mechanical strength to withstand these loads.6

In summary, the main reason why the diameter of the high-voltage line is larger than that of the low-voltage line is the current difference caused by the principle of conservation of energy, line loss control, safety and mechanical strength requirements. These factors together determine the different choice of line diameter in the design of high-voltage and low-voltage lines.