ABSTRACT
A dielectric material that resists the flow of electric charge is called an insulator. In an electrical machine, the electrical insulation ensures that current flows only along the conductors and not between individual conductors or between the conductor and the ground. Insulating materials are used in electrical equipment not only for separation of current-carrying parts from each other and from the environment, but also for support of electrical conductors. In electrical systems insulators are commonly used as a flexible coating on electric wire and cable to avoid wires from touching each other and be touched, and therefore preventing electrocution and fire hazards. The chapter discusses the aging issues of some insulating materials used in power distribution and transmission. In electric power transmission, suspended wires are bare except where they enter buildings, and they are insulated by the surrounding air. Insulators are required at points where they are supported by utility poles or pylons.
