Insulator is a special insulation control object, which can play an important role in overhead transmission lines. In the early years, insulators were mostly used in telephone poles, and gradually developed into high-voltage connection towers. Many disc-shaped insulators are suspended at one end to increase the creepage distance. They are usually made of glass or ceramics, so they are called insulators.
Insulators will not fail due to various electromechanical stresses caused by changes in environment and power load conditions, otherwise insulators will not play a significant role and will damage the use and operation life of the whole line.
Types and functions of insulators
1, pin insulator
Used for 35KV and below lines, mainly used for straight towers or small-angle corner towers, and also used for fixing jumpers of tension towers. Advantages: simple manufacture and low price; Disadvantages: it is not used for transmission lines, and is widely used for lines below 35kv, because it bears little conductor tension, low lightning resistance and is easy to flashover. Natural pollutants on the insulator surface are easily washed away by rain, while industrial pollutants are attached to the insulator surface and are not easily washed away by rain. When the air humidity is high, it can conduct electricity and the leakage current is greatly increased.
2. Columnar insulator
Widely used in distribution lines. Anti-pollution flashover ability is stronger than that of pin insulator. Flashover: refers to the discharge phenomenon of high-voltage electrical appliances (such as high-voltage insulators) on the insulation surface, which is called surface flashover.
3. Porcelain cross-arm insulator
Generally used in 10kv distribution line straight pole, which can play the dual role of insulator and cross arm.
4. Suspended insulator
Used for high-voltage and ultra-high-voltage transmission lines, used for hanging or tensioning wires and insulating them from towers. Suspension insulators have high mechanical strength and electrical strength, and can be used for various voltage levels and strength requirements through different series groups, so they are widely used at present. There are two types of disc-shaped suspension insulators: ordinary type and antifouling type. Ordinary type is suitable for general industrial areas. Compared with the common insulator, the antifouling insulator has a longer creepage distance and a shape convenient for wind and rain cleaning. When used in polluted areas, it can reduce the size of the tower and has great economic value.
5. Rod insulator
It is easy to be broken due to vibration and other reasons during operation. Generally, it can only be used on some load-bearing poles with less stress, and it is not easy to cross the line in important areas such as roads, railways, waterways or downtown areas.
6. Butterfly insulator
Butterfly insulator, named after its shape, is often used as a linear or tensile insulator in low-voltage distribution lines, and can also be used in conjunction with suspended insulators for tension towers, terminal pipes or branch towers of 10KV distribution lines.
7. Pollution-resistant insulator
It is mainly to increase or expand the umbrella skirt or umbrella rib of the insulator to increase the creepage distance of the insulator and improve the electrical strength of the insulator in a polluted state. At the same time, the structural shape of the umbrella skirt is changed to reduce the natural pollution on the surface, thus improving the anti-pollution flashover performance of insulators. The creepage ratio of pollution-resistant insulators is generally 20% ~ 30% higher than that of ordinary insulators, or even more. The double-layer umbrella-shaped pollution-resistant insulator is used in pollution flashover-prone areas of China power grid, which has strong self-cleaning ability and is convenient for manual cleaning.
8. Type A insulator and Type B insulator
The dry flashover distance of type A insulator is not more than 3 times (pouring resin) or 2 times (other materials); The breakdown distance of type B insulator is less than 1/3 (casting resin) or 1/2 (other materials) of dry flashover distance. The dry flashover distance of insulator refers to the shortest distance through air along the outer surface of insulator; Breakdown distance refers to the shortest distance that an insulating material passes through an insulator.
How to maintain and manage insulators
In wet weather, polluted insulators are prone to flashover discharge, so they must be cleaned to restore the original insulation level. General areas should be cleaned once a year, and polluted areas should be cleaned twice a year (once before fog season).
1, power outage cleaning
Power outage cleaning means that workers climb the pole and wipe it with a rag after power outage. If it is not clean, you can wipe it with a wet cloth or scrub it with detergent. If it is not clean, replace the insulator or replace it with a synthetic insulator.
2. Cleaning without power failure
Generally, an insulating rod with a brush is used or tied with cotton yarn to wipe the insulator on the running line. The electrical performance and effective length of the insulating rod used, and the distance between the person and the live part should comply with the provisions of the corresponding voltage level, and the operation must be supervised by a special person.
3, charged water flushing
Large water flushing and small water flushing are two methods. The effective length of washing water, joystick and the distance between people and live parts must meet the requirements of industry regulations.
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