Overhead lines mainly refer to overhead open lines, which are set up on the ground. It is a transmission line that uses insulators to fix the transmission wires on the poles and towers upright on the ground to transmit electric energy. The erection and maintenance are convenient and the cost is low, but it is easy to be affected by weather and environment (such as wind, lightning strike, pollution, snow and ice, etc.) and cause faults. Meanwhile, the whole power transmission corridor occupies a large area of land, which is easy to cause electromagnetic interference to the surrounding environment.
The main components of the overhead line are: conductor and lightning rod (overhead ground wire), tower, insulator, gold tools, tower foundation, cable and grounding device.
conductor
A wire is a component used to conduct current and transfer electrical energy. Generally, there is one aerial bare conductor for each phase. 220kV and above lines, due to their large transmission capacity, and in order to reduce corona loss and corona interference, adopt phase split conductors, that is, two or more conductors for each phase. The use of split wire can transport larger electric energy, and less power loss, has better anti-vibration performance. Wire in operation is often tested by various natural conditions, must have good conductive performance, high mechanical strength, light quality, low price, strong corrosion resistance and other characteristics. Because aluminum resources are more abundant than copper, and the price of aluminum and copper is much different, almost all steel core aluminum twisted wires are used. Each conductor shall have only one connection within each gear distance. In crossing roads, rivers, railways, important buildings, power lines and communication lines, conductors and lightning arresters shall not have any connection.
Lightning arrester
The lightning rod is generally made of steel core aluminum stranded wire, and is not insulated with the tower but directly erected on the top of the tower, and connected with the grounding device through the tower or grounding lead. The function of lightning arrester wire is to reduce the chance of lightning strike wire, improve the lightning resistance level, reduce the lightning trip times, and ensure the safe transmission of power lines.
Pole and tower
Tower is the general name of electric pole and tower. The purpose of the pole is to support the wire and the lightning arrester, so that the wire between the wire, the wire and the lightning arrester, the wire and the ground and the crossing between a certain safe distance.
insulator
Insulator is a kind of electrical insulation products, generally made of electrical ceramics, also known as porcelain bottle. There are also glass insulators made of tempered glass and synthetic insulators made of silicone rubber. Insulators are used to insulate wires and between wires and earth, to ensure reliable electrical insulation strength of wires, and to fix wires and withstand vertical and horizontal load of wires.
Gold tools
In overhead power lines, fittings are mainly used to support, fix and connect wires and insulators into strings, and also to protect wires and insulators. According to the main performance and use of the hardware, can be divided into the following categories:
1, line clip class. Wire clamp is used to hold the guide, ground wire of the gold
2. Connecting hardware. Coupling fittings are mainly used to assemble suspension insulators into strings, and connect and suspend insulator strings on the rod
On the cross arm of the tower.
3, the continuation of the gold category. Connector used for connecting various wire, lightning rod end.
4, protect the category of gold. Protective equipment is divided into mechanical and electrical two categories. Mechanical protection equipment is to prevent the guide and ground wire from breaking due to vibration, and electrical protection equipment is to prevent premature damage of insulators due to serious uneven voltage distribution. Mechanical types have anti-vibration hammer, pre-stranded wire protection bar, heavy hammer, etc.; Electrical gold with pressure balancing ring, shielding ring, etc.
Tower foundation
The underground devices of overhead power line tower are collectively referred to as the foundation. The foundation is used to stabilize the tower, so that the tower will not be pulled up, sinking or topple due to vertical load, horizontal load, accident breaking tension and external force.
Pull wire
The cable is used to balance the transverse load and wire tension acting on the tower, which can reduce the consumption of tower materials and reduce the cost of the line.
Earthing device
Overhead ground wire is above the wire, it will be connected to the earth through the ground wire or ground body of each base tower. When lightning strikes the ground wire, it can quickly spread the lightning flow to the earth. Therefore, the grounding device