Transmission & Distribution: Insulators

Glass electrical insulator, ca. 1880

Glass electrical insulator, ca. 1880
Item 74833   info
Maine Historical Society

Most of Maine’s electrical grid is wired on utility poles; only urban areas such as Portland and the cities of Auburn-Lewiston have significant underground systems.

What is on the poles? The three wires at the top are distribution wires—they carry electrical power from the local substation to the customers.

These wires, which operate at 12,470 volts, are mounted on porcelain insulators to prevent the current from "leaking," which would waste it or create a hazard.

The insulators and distribution wires are mounted on a wooden crossarm. Insulators are used in other parts of the system as well.

Insulators are made of a variety of materials and come in an array of special shapes, each intended to provide a particular function.

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