Composite Insulator

8/13/2019 Composite Insulator

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The insulators or dielectric, is a material that resiststhe flow of electric current.

An insulating material has atoms with tightly bonded

valence electron Material like glass, paper, Teflon are very good electric

insulators.



A composite insulator in one made of at least twoinsulating parts, namely a core and a housingequipped with metal fittings. Composite insulators,for example, can consist either of individual shedsmounted on the core, with or without an intermediatesheath, or alternatively, of a housing directly mouldedor cast in one or several pieces on to the core. This kindof insulator can be used on transmission and

distribution lines, and also the electric railways.



The first electrical systems to make use of insulators were telegraph lines;direct attachment of wires to wooden poles was found to give very poorresults, especially during damp weather. The first glass insulators used inlarge 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 tothese "threadless insulators" resulted in insulators unseating from their pins,requiring manual reseating. Amongst the first to produce ceramic insulatorswere companies in the United Kingdom, with Stiff and Doulton usingstoneware from the mid 1840s, Joseph Bourne (later renamed Denby)

producing them from around 1860 and Bullers from 1868. Utility patentnumber 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-typeinsulators still have threaded pinholes. The invention of suspension-typeinsulators made high-voltage power transmission possible. Pin-typeinsulators were unsatisfactory over about 60,000 volts. A large variety oftelephone, telegraph and power insulators have been made.



Composite Suspension LongRod Insulators

Used on overhead suspension or tension power transmission lines, and suitablefor the middle and above contaminationareas, particularly in the heavycontamination areas. There are severalways of connecting of fitting:ball &socket, clevis & tongue, Y-

clevis. Generally, the voltage level isfrom 10 KV to 1000KV.

15kv, 25kv, 35kv ANSI deadendinsulator, 66KV, 110KV, 220KV,400KV,500KV silicone rubberinsulator and etc is normally used.



It is suitable for the rebuild

of city lines. The voltage

levels typically from 6 to 36

KV. 11kv and 33kv pin

composite insulators arenormal types. Its top and

bottom installed are the same

as the corresponding size of

porcelain insulator, so theycan be interchangeable use.

.



The composite station postinsulators mainly apply totransformer substation andswitches and other

apparatus. The voltage can be upto 220KV and nowmost of the smallapparatus has chosen

polymer post insulator toinstead of porcelain onessince they have moreadvantages.



Composite insulator forrailway traction lines is usedin tunnels of electrifiedrailway under severeconditions. They can

effectively prevent pollutionflashover outage and freefrom cleaning andmaintenance work. It willhold on not only tension, butalso bending. With a verysmall size, they can hardly besubstituted by porcelain orglass insulators in case ifsmall tunnel space



It is a new type to insteadof porcelain buystrain insulators and have

better tensile strength, low

weight and good looking,the normal type developnow is 97KN. Normallyused in Africa. only theend fitting and fiber glasscore and covered withsomething special to have

better performance.



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 andlabor at the job site)

Resistance to Seismic Shock



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 steelas reinforcing material by carbon fibres is shown on the

example of an 110kV pole for a line upgrade from 52 kV.

Composite Insulator

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