The disadvantage of high voltage cable buried in the ground(2)

On the other hand, it is also the innate "hard" of the underground cable itself. In terms of heat dissipation of the wires, the overhead lines have an advantage in heat dissipation, and the cables buried in the ground are difficult to dissipate due to space and air circulation problems, which largely limits the level of power that the underground cables can carry.
Ultra-high voltage transmission can not find an effective insulating material to make the outer insulation layer of the wire. Therefore, the ultra-high voltage electric wires are bare and cannot be buried underground. There will be some distributed capacitance around the UHV wire. The current can leak through these capacitors. One is to increase the consumption, and the other is to prevent the proximity of other objects.
Air is an insulator, but the earth is a conductor. In the air, the wire rack can be directly placed on the pole, but in the underground, a layer of insulating shell should be added to the wire, otherwise the power in the wire does not go far, and the leakage leaks little.
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. In general, the cost of underground cables of the same voltage level will be several times or even tens of times higher than that of the high-voltage lines in the air.
The ultra-high voltage cable is buried in the ground. It has both safety and economic problems. If it fails, the engineering of inspecting and repairing the cable is very large, and it cannot withstand the toss. Therefore, the current ultra-high voltage cable should be hung in the high In the air.
The insulation layer and protective layer of the underground cable conductor are manufactured very strictly, and the human body normally contacts the outer skin of the cable without any danger. Cable laying is also very particular. Cables are mostly buried in dedicated cable trenches, cable ducts 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 buried the cable. deep.
Moreover, every few tens of meters on the ground where the cable is buried, there will be a cable working well or cable marking pile as a sign to remind people to pay attention to safety. Therefore, underground cables generally do not pose a danger to residents.