A
utility pole, alternately referred to as a
telephone pole,
power pole,
telegraph pole or
telegraph post (all names commonly misused colloquially, as these names refer to their specific equipment), is a (usually wooden)
pole used to support overhead
wire,
cable,
fiber optic cable, and related equipment such as
transformers and
street lights. A single pole is often used to support both
electric power distribution lines and
telecommunications cables, as well as their associated equipment. Wire and cable are routed overhead as a relatively inexpensive way to keep them
insulated from the ground and each other, and out of contact with pedestrians or vehicles. Utility poles were first used in the mid-1800s with
telegraph systems.
Utility poles are commonly used to carry two types of electric power lines[1] distribution lines (or "feeders") and subtransmission lines. Distribution lines carry power from local substations to customers. They generally carry voltages from 4.6 to 33 kilovolts (kV) for distances up to thirty miles, and include transformers to step the voltage down from the primary voltage of the lines to the lower secondary voltage used by the customer. A service drop carries this lower voltage to the customer's premises. Subtransmission lines carry higher voltage power from regional substations to local substations. They usually carry 46 kV, 69 kV, or 115 kV for distances up to 60 miles. Voltages of 230kV can be placed on two- or three-pole towers. Transmission lines carrying voltages of above 230kV are usually not supported by poles, but by metal pylons (known as transmission towers in the United States).
For economic or practical reasons, such as to save space in urban areas, a distribution line is often carried on the same poles as a subtransmission line but mounted under the higher voltage lines; a practice called "underbuild". Telecommunication cables are usually supported by the same poles that support the power lines; poles arranged in this fashion are known as joint poles. However, they may also have their own dedicated poles.
Different length poles, up to 120&_160;ft (37&_160;m) or more, are used to satisfy clearance requirements, but the standard utility pole in the US is about 40&_160;ft (12&_160;m) long and is buried about 6&_160;ft (2&_160;m) in the ground, for a height above ground of about 34&_160;ft (10&_160;m).[2] They are spaced about 125&_160;ft (38&_160;m) apart. Joint use poles are usually owned by one utility, which leases space on it for other cables. In the USA the National Electrical Safety Code, published by the Institute of Electrical and Electronics Engineers (IEEE), sets the standards for construction and maintenance of utility poles and their equipment.
