Overhead cable generally low and high pressure two, low-voltage overhead lines are generally four, was a zigzag arrangement, the high pressure is three, was the product-shaped arrangement, the tower must be high-voltage line, the general is a total of two six. Low-voltage lines are generally used with a leather line, and now rarely used, replaced by cables, high-voltage lines are bare lines, the core for the wire, the appearance of aluminum, commonly known as ACSR. Overhead cable also called cable, not called overhead line.
Overhead lines, literally understood is the frame in the air of the wire. The cable on the pole can not be an overhead line, it is only overhead laying of the cable. Overhead Cable General overhead lines are bare wires (no insulation outside). 10kV and above the overhead lines are three (on behalf of A, B, C three-phase), if it is 6, then the general double back. 380V overhead lines are generally four, on behalf of A, B, C three-phase plus an N line (or zero line)
Overhead lines are through the tower, the cement tower tower in the air of the wire, usually bare wire. Overhead line low cost, but occupied area is large, for the current main line type. Overhead lines from the wire, lightning lines, towers, insulators and fittings and other components of the wire: transmission of lightning lines: the lightning current into the earth to protect the power line from the lightning tower: support wire and lightning protection insulators: the wire and the tower between the insulation Fittings: Supports, connects, protects wires and lightning lines, connects and protects insulators.
Are generally high-voltage lines using overhead cables, high-voltage lines due to the ground is very high, in order to reduce costs, therefore, and the choice of bare wire, Overhead Cable if it is in the ground or from the building is very close to the case, must choose insulation cable. High voltage lines in the high voltage, the current is very large, easy to heat, will burn the insulation, and even breakdown insulation. Under high pressure, Overhead Cable some of the original insulation materials, such as rubber, plastic, dry wood, etc. will become a conductor, can not afford insulation.
If still high-pressure line package insulation, it is necessary to spend more money, wasted money and things. High-voltage wire surface does not contain insulation, put it hanging in the high tower, Overhead Cable it may be due to contact with the tower and leakage. In order to prevent this phenomenon, high-voltage wire is always hanging in a long string of good insulation under the porcelain, so that high-voltage lines and insulation tower. High-voltage overhead lines are generally a group of three, that is, we often say that the three-phase line. Low-voltage overhead line directly used is insulated single-core cable, not bare wire, because more than a zero line, so it is four.
Overhead cable is not the ordinary oil-paper insulated cable or cross-linked insulated cable directly on the overhead tower, but with a similar cross-linked cable manufacturing process to create a dedicated cable.
The general overhead cables are single-core, according to their different structure can be divided into hard aluminum structure, hard pull copper structure, Overhead Cable aluminum alloy wire structure, steel core or aluminum alloy core support structure and self-supporting three-core structure (Core can be hard aluminum or hard copper) and so on