Overhead lines are hardly visible in the new urban area of the city, and both high-voltage and low-voltage cables are buried underground. There are also high-voltage lines covered with insulating layers, also called high-voltage cables. Compared with the ordinary cable, the cost of high-voltage cable is 10 times that of it. And the ordinary overhead lines will not be used unless necessary.
The Feature of Voltage Cable
High-voltage and low-voltage cables are generally bare conductors. In the old city of low-voltage overhead lines, there are many buildings, and also generally used wires or cables with insulating layers. Because of the high insulation requirements of the overhead transmission line on the insulation layer, the complex construction process, and the high cost. So it usually chooses the bare conductors, and the overhead line can prevent electric shock accidents because of the increased height.
Air itself is indeed a good insulator. The breakdown voltage is generally above 3kv/mm, which is equivalent to the effect of ordinary resin-based insulating plastics. It means that people are safe if the distance is more than 40mm. But actually, the separation distance is 5 meters as usual, and at least 2 meters or more. So there is no need to wrap any other insulators, as long as a certain space distance. So the air can play a great insulating role to protect personal safety.
The Dangerous of Exposed High-voltage Cables
Someone also said the high-voltage cables can wrap with a plastic insulator, such as resin. But on the one hand, the cost of the wires will be higher than before. On the other hand, the weight and the erection difficulty of the wires have been increased. Furthermore, the safety of the high-voltage line has not been improved in any way because the effect of insulating plastic is similar to that of the air.
The only danger of exposed high-voltage lines is that they fall on the ground or buildings after breaking, which will cause a great risk of electric shock. The power sector has high requirements on strength, erection technology, and daily inspection of electric wires. They are sufficient to prevent the danger of breakage and leakage. When some events of natural disasters happened, it needs to power outages timely. Doing that can prevent some possible danger of leakage. Whenever you find a high-voltage cable that is break and falls to the ground, keep away at least 20 meters. It is safe to keep a distance to prevent electric shock accidents. High voltage or low voltage cables, can use bare wires. They can reduce the construction cost.