Electrical engineers first worked out the importance of insulation protection when they installed insulating material onto telegraph poles. When the telegraph network was first being established in the nineteenth century, wires were simply mounted directly onto wooden telegraph poles. In dry weather, this worked fine but signal disruption became very poor in wetter conditions.
Since those days, the role of insulation has moved onto other systems, notably the power distribution network. Without proper insulation, electrical power would be conveyed into the pylons that carry transmission lines which would be dangerous and lead to shorts in the system. For this reason, the lines are separated from the pylons by insulated lugs, clamps or by porcelain, glass or polymeric insulators.
These days, insulation is just as important as it has ever been for providing safe and reliable electrical distribution over a network. What are the main insulation technologies in use today and what do the leading manufacturers of insulation products make to ensure that such technology works well in the field?
These products are widely used in overhead electrical wiring systems and are a direct descendant of the sort of insulation mechanisms that were first used to isolate telegraph wires. They are used to support radio antennae as well as overhead power cables. Basically, a strain insulator is placed between two lengths of cable to electrically isolate them from one another while a physical connection is still maintained. Obviously, therefore they are manufactured from materials which don’t conduct electricity. This means that high lines can be connected to physical infrastructure such as pylons without causing an unwanted electrical connection.
Also, often installed on pylons as well as poles, pin insulators form a single layer three-dimensional shape that is usually made out of porcelain or glass. This is then placed on a pin to connect it to the supporting structure. Since the pin insulator has a rim at the top of it, a wire can be connected to it with ease without it touching the pole it sits on.
Pin insulators are used widely in North America for both power distribution and to run telephone wires. A drawback of this sort of system is that a pin insulating system is only capable of handling one cable per pin. Those made from glass are less common nowadays and many older ones have become collector’s items. In some countries, they have largely been superseded by station post insulators which can handle multiple cables if needed.
Usually made from certain plastics or porcelain, bushings offer insulating properties by controlling the shape and strength of any electrical field that is associated with the cables they hold. As such, they tend to be used in high voltage power distribution networks. They help to lessen the electrical stresses from the electromagnetic fields that are inevitably generated in power system distribution networks. Resins and paper bushings were made in the past but plastic ones now tend to be the most up-to-date bushings on the market.