The disadvantage of high voltage cable buried in the ground(1)

Ultra-high voltage transmission refers to the transmission of electrical energy between voltages of 0.5 kV to 1 k kV.
If the 220 kV transmission index is 100%, the relative investment per kilometer of EHV transmission, the relative cost per 100 kWh of electricity transmission per kWh, and the consumption of metal materials are greatly reduced, and the utilization rate of the corridor is obvious. improve.
In daily life, we can often see overhead EHV transmission projects. Have you ever thought about such a question: Why can't the high-voltage wires be buried underground like urban underground cables?
Most of the cables buried in the ground are relatively low voltage grades. Most of the lines with high voltage levels are overhead, which is mainly due to cost and technology.
Underground cables are more complex than overhead lines, have high technical requirements, are difficult to manufacture and construct, and are buried in the ground. It is not easy to find faults, and it is difficult to repair and maintain. From a cost perspective, cables buried at the same voltage level are three to five times more expensive than being buried in the air.
In particular, our common high-voltage line is often used for long-distance transmission. If underground cables are used, especially for long-distance transmission, often through complex terrain, the cost and technical requirements will rise linearly.