Insulators Picture Insulators are used to connect the wires to towers or poles. They are called insulators because they "insulate" the energized wire from the grounded pole or tower. Insulators are usually made of porcelain, a ceramic material which does not conduct electricity. They are placed or hung from the cross-arms which extend outward from the towers and poles and support the wires.

Stacked Insulators PictureIndustry electrical codes dictate the minimum distance a circuit may be to the cross-arm or tower. The higher the voltage, the larger the distance required. Rather than purchase a larger insulator, it is common practice to use small insulators stacked together on a special mounting.

In fact, once you know how a certain utility builds their lines, it is easy to estimate the voltage of a transmission line when driving past by judging the length of the insulator.