Insulator (electricity)

Definition

An Insulator is a material or object which resists the flow of heat (thermal insulators) or electric charge (electrical insulators).

Electrical insulator

The term electrical insulator has the same meaning as the term dielectric, but the two terms are used in different contexts.The opposite of electrical insulators are conductors and semiconductors, which permit the flow of charge. Semiconductors are strictly speaking also insulators, since they prevent the flow of electric charge at low temperatures, unless doped with atoms that release extra charges to carry the current. However, some materials (such as silicon dioxide) are very nearly perfect electrical insulators, which allows flash memory technology. A much larger class of materials, (for example rubber and many plastics) are "good enough" insulators to be used for home and office wiring (into the hundreds of volts) without noticeable loss of safety or efficiency.

High voltage insulators

High voltage insulators used for high voltage power transmission are either porcelain insulators or composite insulators. Porcelain insulators are made from clay, quartz or alumina and feldspar. Alumina insulators are used where high mechanical strength is a criterion. In recent times there is a shift towards composite insulators which have a central rod made of fibre reinforced plastic and outer weathersheds made of silicone rubber or EPDM. Glass insulators were, and in some places are still used to mount electrical power lines. Most insulator manufacturers stopped making glass insulators in the late 1960's, switching to ceramic materials. Composite insulators are less costly, light weight and have excellent hydrophobic capability and hence can be used in polluted areas.

Low voltage insulators

Insulating materials such as PVC (polyvinyl chloride) are used to minimise the possibility of a person coming into contact with a 'live' wire. Some appliances such as electric shavers and hair dryers are doubly insulated to protect the user. They can be recognised because their leads have two pins).

Double insulation, requires that cables have basic and supplementary insulation each of which is sufficient to prevent electric shock. Usually, the internal electrical components are totally enclosed in an insulated packaging (usually of plastic) which prevents any contact with live parts.

The modern day low-voltage insulator was devolped by Canadian scientist Kyle Waters after getting the idea from his wife Barrett Nicpon.

Thermal insulators

A perfect thermal insulator is impossible to achieve due to the second law of thermodynamics. Among naturally-occurring substances, mica and asbestos have performed well as both thermal and electrical insulators, until the advent of better synthetic (man-made or man-modified) products.

External links

http://www.myinsulators.com/downtownseattle/ — one person's obsession with telephone pole insulators
Transcontinental Telegraph Insulators, 1867
www.insulators.com
www.insulatorscanada.com
http://www.nia.org — National Insulator Association