Reviews of Electrical Insulator

Published: 24th November 2011
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An insulator, also called a dielectric, is a material that resists the flow of electric charge. In insulating materials valence electrons are tightly bonded to their atoms. These materials are used in electrical equipment as insulators or insulation. Their function is to support or separate electrical conductors without allowing current through themselves. The term also refers to insulating supports that attach electric power transmission wires to utility poles or pylons. Electrical insulation is the absence of electrical conduction. Electronic band theory (a branch of physics) says that a charge will flow if states are available into which electrons can be excited. This allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator.
Materials that lack electron conduction are insulators if they lack other mobile charges as well. For example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. Electrolytes and plasmas contain ions and will act as conductors whether or not electron flow is involved. Insulators are commonly used as a flexible coating on electric wire and cable. Since air is an insulator, in principle no other substance is needed to keep power where it should be. High-voltage power lines commonly use just air, since a solid (e.g., plastic) coating is impractical. However, wires which touch each other will produce cross connections, short circuits, and fire hazards. In coaxial cable the center conductor must be supported exactly in the middle of the hollow shield in order to prevent EM wave reflections.
Suspended wires for electric power transmission are bare, except where they enter buildings, 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.
The most important insulation material is air. A variety of solid, liquid, and gaseous insulators are also used in electrical apparatus. In smaller transformers, generators, and electric motors, insulation on the wire coils consists of up to four thin layers of polymer varnish film. Film insulated magnet wire permits a manufacturer to obtain the maximum number of turns within the available space. Windings that use thicker conductors are often wrapped with supplemental fiberglass insulating tape. Windings may also be impregnated with insulating varnishes to prevent electrical corona and reduce magnetically induced wire vibration. Large power transformer windings are still mostly insulated with paper, wood, varnish, and mineral oil; although these materials have been used for more than 100 years, they still provide a good balance of economy and adequate performance. Bus bars and circuit breakers in switchgear may be insulated with glass-reinforced plastic insulation, treated to have low flame spread and to prevent tracking of current across the material.
Electrical insulators, or dielectrics, are materials that can withstand the flow of electrical current. In other words, they are non conducting materials. They are the opposite of electrical conductors which allow electricity to flow through a material. Electrical insulators help coat, protect or support electrical conductors so that the electrical current flows through the conductor. Insulators are protective materials that help prevent electrical shock or sparks.

Electrical insulators are made up of substances with electrons, or energy particles that are compressed together by chemical process. It is almost impossible to get electrical voltage to pass through these materials. Some insulators are considered to have higher thresholds for electrical voltage than others do, and are aptly called high voltage insulators.

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