On power lines, how come down leads are often extended off the pole using fiberglass posts?

Answer 1

The device you're describing is known a strain insulator. they are generally made from fiberglass, but were originally made from apitong wood. The strain insulator is used to prevent the guy wire from being energized due to a damaged, cracked, or contaminated insulator.

The wires supported by those insulators are typically energized at voltages between 4,000 and 34,000 volts.

Your question specifically describes the fiberglass insulator at the pole. There is sometimes another insulator in the middle of the guy wire. This one is generally porcelain and is known as a johnny-ball. The johnny-ball is installed below the electric wires and above the phone or cable TV wires. This is done to prevent an energized guy wire from affecting the other utilities or en-dangering the public.

Contrary to what some people believe, it is NOT installed to prevent a charge on the wire. If there were no johnny-ball, there would be a continuous steel wire down to a steel anchor embedded in the ground. This connection grounds the guy wire, preventing any charge from building up.

Answer 2

The device you're describing is known a strain insulator. they are generally made from fiberglass, but were originally made from apitong wood. The strain insulator is used to prevent the guy wire from being energized due to a damaged, cracked, or contaminated insulator. The wires supported by those insulators are typically energized at voltages between 4,000 and 34,000 volts.

Answer 3

These are called insulators. They insulate the pole from the current and heat produced by the lines.