What types of insulators are commonly used in overhead power lines
Insulators used in overhead transmission lines have similarities and differences with those commonly used in distribution lines. The insulators used on distribution lines mainly include pin-type insulators, column-type porcelain insulators, suspension insulators, butterfly-type insulators (also known as tea-table porcelain bottles), rod-type porcelain insulators, pull-line porcelain insulators, ceramic cross-arm insulators, and discharge clamps. Porcelain insulators, etc. There are two types of low-pressure porcelain bottles for low-voltage circuits: needle type and butterfly type. Today I will mainly share insulators for distribution lines and introduce insulators for overhead transmission lines.
1. Pin insulator
Needle insulators are mainly used on straight rods and corner rods with small angles to support wires. They are divided into high voltage and low voltage.
The main models are:
(a) Long pole pin insulator
(b) Short pole pin insulator
2. Butterfly insulator
Also called Chatai. It is composed of a hollow ceramic piece, which is combined with two pull plates and a through bolt. It is usually used on the corners, sections, branches, terminals of the power distribution line and the poles that need to withstand tension.
There are two types of high voltage and low voltage. The high voltage is used at 10kV and the low voltage is used at 400V and below.
3. Suspension insulator
Suspension porcelain insulators are mainly used for overhead power distribution lines. Generally, low-voltage lines use one piece of suspension insulators to suspend the wires, and 10kV lines use two pieces of insulator strings to suspend the wires. Suspension insulators can be divided into slot type and ball type according to the connection method of its cap and foot. The ball type is mostly used in use, because the connection of the ball type is more convenient than the groove type.
(a) Groove type
(b) Ball type
In the picture: 1- cast steel cap; 2- cement admixture; 3- porcelain part; 4- pin connecting rod; H- porcelain bottle height; D- porcelain bottle width
4. Rod insulator and porcelain cross arm
The shape of the rod insulator is a whole, the dirt on the insulator is easily washed away by rain, and flashover is not easy to occur. It has the advantages of saving steel, light weight and short length. The manufacturing process is more complicated, the cost is higher, and it is easy to break during operation.
5. Pull-line porcelain insulator
Tension porcelain insulators, also known as pull-wire round porcelain, are generally used for the terminals, corners, and tension rods of overhead distribution lines to pass through the wires to insulate the lower and upper wires. The insulators are as follows, and sometimes suspension insulators are used instead of cable insulators.
6. Discharge clamp insulator
The discharge clamp circuit insulator includes an insulator body, the upper end of the insulator body is fixed with an upper mounting seat, the lower end of the insulator body is fixed with a lower mounting seat, the top of the upper mounting seat is provided with a metal wire clamp, and the metal wire clamp is provided with Insulated wires, the upper part of the lower mounting seat is provided with an insulating sheath, the bottom of the lower mounting seat is fixed with an arc-strike fitting, and the arc-strike fitting and the insulated wire are intersected, and the upper mounting seat is covered with a protective cover, and the metal wire clamp is located in the protective cover , The protective cover is provided with an arc opening at the position of the arc ignition end of the arc ignition cover; the insulation layer is properly stripped at the fixed point of the insulation wire, and a metal clamp is installed to withstand the power frequency continuous current to avoid burns to the wire. The ignition arc discharge gap is set so that the continuous current of the power frequency will not burn the insulators, thereby greatly reducing the lightning strike and disconnection accidents. In addition, an insulating protective cover is installed to improve the reliability of power supply and prevent the insulated core from entering water.