Electrical insulator is a very important component in the electric power systems such as sub-stations and distribution & transmission lines. In-depth study and practical knowledge on this subject is necessary for the electrical professionals in the electrical power field. In the early days, insulators were made of ceramic and glass materials.
But in 1963, polymeric insulators were developed and its improvements in design and manufacturing in the recent years have made them attractive to utilities. It is consist of a fiberglass core rod covered by weathersheds of skirts of polymer such as silicone rubber, polytetrafluoroethylene, EPDM (ethylene propylene diene monomer) and equipped with metal end fittings. It is also called composite insulators, which means made of at least two insulating parts – a core and housing equipped with end fittings.
Polymeric insulators have many advantages over the ceramic and glass insulators such as good performance in contaminated environment, light weight, easy handling, maintenance free, and considerably low cost etc. Because of these properties it is gaining popularity worldwide and replacing the conventional ceramic and glass insulators.
Components of Polymeric Insulators
Core (FRP ROD) –
The core is the internal insulating part of a composite insulator. It is intended to carry the mechanical load. It consists mainly of glass fibers positioned in a resin matrix so as to achieve maximum tensile strength.
Weathersheds & Housing (SILICONE RUBBER)–
The housing is external to the core and protects it from the weather. It may be equipped with weather sheds. Some designs of composite insulators employ a sheath made of insulating material between the weathersheds and the core. This sheath is part of the housing. Weathersheds are insulating parts, projecting from the housing or sheath, intended to increase the leakage distance and to provide an interrupted path for water drainage.
End Fitting –
End fitting transmit the mechanical load to the core. They are usually made out of metal.