Overhead lines are generally divided into two types, low voltage bare conductors and high voltage bare conductors. There are generally four low-voltage overhead lines, three high pressure lines, and six high-voltage lines. Low-voltage cables are generally insulated. Such as Triplex Service Drop Cable Aluminum Conductor.High-voltage lines are bare wires, usually bare copper conductors, AAAC, ACSR, AAC ect.
The overhead lines are generally bare (no insulation outside). The overhead lines of 10kV and above are all three (representing A, B, C three-phase), and if it is six, it is usually double return. 380V overhead lines are generally four, representing A, B, C three-phase plus an N line (or zero line).
The overhead line is a wire placed in the air through a tower and a concrete pole. It is generally a bare wire. Overhead lines are cheap, but occupy a large channel area, which is currently the main line type. Overhead lines consist of conductors, lightning conductors, poles, towers, insulators and fittings. Conductors: Transmit electrical energy. Lightning conductors: Introduce lightning currents into the earth to protect power lines from lightning strikes. Towers: Support wires and lightning conductors Insulators: Maintain insulation between conductors and towers Gold fittings: support, connection, protection of wires and lightning conductors, connection and protection of insulators.
Generally, overhead lines are used for high-voltage cables. Because high-voltage lines are very high away from the ground, in order to reduce costs, therefore, bare wires are used. If they are underground or close to buildings, they must be insulated. The electric voltage flowing in the high-voltage line is high, the current is large, and it is easy to generate heat, burn insulation, and even breakdown the insulation.
Under high pressure, some materials that are originally insulated, such as rubber, plastic, dry wood, etc., will also become conductors and will not be able to withstand insulation. If insulation is still on the high voltage line, it will cost more money and waste money and things.
There is no insulation on the surface of the high-voltage wires. Hanging it on a tall iron tower may cause leakage due to contact with the tower. In order to prevent this phenomenon, high-voltage electric wires are always suspended under a long string of well-insulated porcelain, insulating the high-voltage lines from the tower.
High-voltage overhead lines are generally a group of three, that is, we often say that the three-phase line.