Composite insulators презентация

The insulators or dielectric, is a material that resists the flow of electric current.
An insulating material has atoms with tightly bonded valence electron
Material like glass, paper, Teflon are very good electric insulators.
INTRODUCTION

A composite insulator in one made of at least two insulating parts, namely a core and a housing equipped with metal fittings. Composite insulators, for example, can consist either of individual sheds mounted on the core, with or without an intermediate sheath, or alternatively, of a housing directly moulded or cast in one or several pieces on to the core. This kind of insulator can be used on transmission and distribution lines, and also the electric railways.
WHAT ARE COMPOSITE INSULATORS?

The first electrical systems to make use of insulators were telegraph lines; direct attachment of wires to wooden poles was found to give very poor results, especially during damp weather. The first glass insulators used in large quantities had an unthreaded pinhole. These pieces of glass were positioned on a tapered wooden pin, vertically extending upwards from the pole's crossarm (commonly only two insulators to a pole and maybe one on top of the pole itself). Natural contraction and expansion of the wires tied to these "threadless insulators" resulted in insulators unseating from their pins, requiring manual reseating. Amongst the first to produce ceramic insulators were companies in the United Kingdom, with Stiff and Doulton using stoneware from the mid 1840s, Joseph Bourne (later renamed Denby) producing them from around 1860 and Bullers from 1868. Utility patent number 48,906 was granted to Louis A. Cauvet on July 25, 1865 for a process to produce insulators with a threaded pinhole. To this day, pin-type insulators still have threaded pinholes. The invention of suspension-type insulators made high-voltage power transmission possible. Pin-type insulators were unsatisfactory over about 60,000 volts. A large variety of telephone, telegraph and power insulators have been made.
HISTORY

TYPES OF COMPOSITE INSULATORS
Composite Suspension Long Rod Insulators
Used on overhead suspension or tension power transmission lines, and suitable for the middle and above contamination areas, particularly in the heavy contamination areas. There are several ways of connecting of fitting:ball & socket, clevis & tongue, Y- clevis. Generally, the voltage level is from 10 KV to 1000KV.
15kv, 25kv, 35kv ANSI deadend insulator, 66KV, 110KV, 220KV, 400KV,500KV silicone rubber insulator and etc is normally used.

Silicone Rubber Composite Pin/Line Post Insulator:
It is suitable for the rebuild of city lines. The voltage levels typically from 6 to 36 KV. 11kv and 33kv pin composite insulators are normal types. Its top and bottom installed are the same as the corresponding size of porcelain insulator, so they can be interchangeable use.
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Composite/Silicone Rubber Post Insulator:
The composite station post insulators mainly apply to transformer substation and switches and other apparatus. The voltage can be upto 220KV and now most of the small apparatus has chosen polymer post insulator to instead of porcelain ones since they have more advantages.

Composite Cross Arm Insulators
It has an effective use of a narrow corridor pressure transmission and applicable to rebuild of city power net. It can also reduce the tower height, saving manpower, material and financial resources. It has a superior performance than porcelain insulator.

Electrified Railway Composite Insulators
Composite insulator for railway traction lines is used in tunnels of electrified railway under severe conditions. They can effectively prevent pollution flashover outage and free from cleaning and maintenance work. It will hold on not only tension, but also bending. With a very small size, they can hardly be substituted by porcelain or glass insulators in case if small tunnel space

Composite Stay Insulators
It is a new type to instead of porcelain buy strain insulators and have better tensile strength, low weight and good looking, the normal type develop now is 97KN. Normally used in Africa. only the end fitting and fiber glass core and covered with something special to have better performance.

Outdoor Switch Post Composite Insulators
This type insulator is suitable for outdoor used in AC switchgear and switch disconnectors with voltage up to 25 kV and 38.5KV.
Main advatages are low weight, outstanding dielectric strength and extreme mechanical endurance

Light weight (25-30% less than ceramic insulator)
Silicone rubber sheds provides perfect hydrophobic performance, Good resistance to aging, tracking and erosion.
Stable behavior at extreme climate conditions.
Long term surface hydrophobicity.
Suitability for polluted environment, salty atmospheres etc.
Resistance to breakage and vandalism, Practically unbreakable.
Superior anti-tracking properties.
High mechnical strength.
Ease of installation (easier handling with lighter equipment and labor at the job site)
Resistance to Seismic Shock
BENEFITS

The paper discusses selected advantages of composite insulators and structures for lines with compact requirements.
Beside the recognized properties of Silicone Rubber insulators in polluted areas, the mechanical performance
offers with the safe failure mode a feature that improves the line reliability significantly and permits suitable arrangements for areas with limited right of ways. In respect to the principle performance, the shown examples for transmission level are applicable to distribution level as well. The substitution of steel as reinforcing material by carbon fibres is shown on the example of an 110kV pole for a line upgrade from 52 kV.
CONCLUSION