Insulators

110 kV ceramic insulator, showing sheds Reusing this image

"Suspended wires for electric power transmission are bare, except when connecting to houses, and are insulated by the surrounding air. Insulators are required at the points at which they are supported by utility poles or pylons. Insulators are also required where the wire enters buildings or electrical devices, such as transformers or circuit breakers, to insulate the wire from the case. These hollow insulators with a conductor inside them are called bushings. Material Insulators used for high-voltage power transmission are made from glass, porcelain, or composite polymer materials. Porcelain insulators are made from clay, quartz or alumina and feldspar, and are covered with a smooth glaze to shed water. Insulators made from porcelain rich in alumina are used where high mechanical strength is a criterion. Porcelain has a dielectric strength of about 4-10 kV/mm. Glass has a higher dielectric strength, but it attracts condensation

The Definitive Guide to Colorful Insulators

and the thick irregular shapes needed for insulators are difficult to cast without internal strains. Some insulator manufacturers stopped making glass insulators in the late 1960s, switching to ceramic materials. Recently, some electric utilities have begun converting to polymer composite materials for some types of insulators. These are typically composed of a central rod made of fibre reinforced plastic and an outer weathershed made of silicone rubber or EPDM. Composite insulators are less costly, lighter in weight, and have excellent hydrophobic capability. This combination makes them ideal for service in polluted areas. However, these materials do not yet have the long-term proven service life of glass and porcelain." This information found: Wikipedia Encylopedia

Insulators

Glass Insulators

Ceramic Insulators

Porcelain Insulators

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