Why Can't High-Voltage Cables Be Buried In The Ground?

Ultra-high voltage transmission refers to the use of 500 kV-1000 kV voltage levels to transmit electrical energy. If the 220kV transmission index is taken as 100%, the relative investment per kilometer of UHV transmission, the relative cost of 100 kilometers per kilowatt-hour transmission, and the consumption of metal materials will be greatly reduced. In this way, the utilization rate of the line corridor has been significantly improved.

In daily life, we can often see overhead UHV power transmission projects. However, now there is a question, have you ever thought about it: Why can't high-voltage wires be buried underground like urban underground cables?

 

 

 

The current underground cables generally have lower voltage levels. The transmission of high-voltage lines is often overhead, which is mainly due to cost and technical factors.

First, the structure of underground cables is more complicated than that of overhead lines. The second is that underground cables have high technical requirements and difficult manufacturing and construction. The third is that the cables are buried in the ground, which makes it difficult to find faults and difficult to maintain. In terms of cost, the cost of underground cables of the same voltage level is generally 3 to 5 times higher than that of overhead lines.

Especially our common high-voltage lines are often used for long-distance power transmission. If underground cables are used, especially long-distance transmissions often have to traverse complex terrain, the cost and technical requirements will rise linearly.

On the other hand, it is also the congenital "defect" of the underground cable itself. Overhead lines have good heat dissipation conditions in the air, but the air around the underground cables does not flow and it is difficult to dissipate heat. Therefore, the level of power that can be transmitted by underground cables is largely limited.

 

Last but not least, there is currently no effective UHV insulation material as an insulation layer for wires. Therefore, UHV wires are exposed and cannot be buried in the ground. There are distributed capacitors around the wires, and current can leak through these capacitors, which increases consumption on the one hand. On the other hand, if any animal approaches, there is also a risk of electric shock. Air is an insulator, and the earth is a conductor. In the air, you only need to put the wires directly there, while in the underground, you need to add several layers of insulating shells outside the wires, otherwise the electricity in the wires will not go far and the leakage will be very small.

 

The insulation and protective layers of underground cable conductors are strictly manufactured. Normal contact with the cable sheath will not cause danger to the human body. The laying of cables is also very particular. Most cables are buried in special cable trenches, cable troughs or cable tunnels. They are well isolated and protected. The depth is generally less than half a meter. The higher the voltage level, the more cables are buried. deep.

 

Moreover, on the ground where cables are buried, there is a cable working well or cable marker pile as a sign every tens of meters to remind people to pay attention to safety. Therefore, underground cables generally do not pose a danger to residents.

Email: zms@kvcable.com