Utility pole

Utility poles are essential structures used to support overhead public utilities.

These columns hold electrical power lines, fiber optic cables, and coaxial cables. They also support equipment like transformers, street lights, and cellular antennas. Using poles is an inexpensive way to route wires. This method keeps lines insulated from the ground. It also keeps them away from people and vehicles.

Electricity moves through two main types of lines on these poles. Subtransmission lines carry high-voltage power between regional and local substations. These lines typically carry 46 kV, 69 kV, or 115 kV. Distribution lines, also called feeders, carry power from substations to customers. They usually carry voltages between 4.6 and 33 kV. To make this power safe for homes, a pole-mounted transformer steps the voltage down. This lower voltage then travels through a service drop to the customer's premises.

Utility poles are organized into specific vertical zones for safety. The top section is called the supply space. This area is reserved for electric power distribution lines. Below the power lines, there is a communication worker safety zone. This gap allows technicians to maneuver safely without touching live wires. The lower section is the communications space. This area holds telephone lines, fiber optic cables, and cable TV wires.

History shows how poles evolved from early telegraphy. In 1843, telegraph pioneer William Fothergill Cooke used poles along the Great Western Railway. In America, Samuel Morse also used poles for telegraph systems in the mid-19th century. Morse originally attempted to bury a line between Baltimore and Washington, D.C. However, that underground system proved faulty. He moved the lines above ground to improve reliability.

Materials for poles vary based on location and durability needs. Most poles are made of wood treated with preservatives. This prevents rot, fungi, and insect damage. In the United States, Southern yellow pine is the most common species. Other trees like Douglas fir and western red cedar are also used. Some poles are made of aluminum, steel, or concrete. In South Australia, they use a unique Stobie pole. This design uses two steel joists held apart by a concrete slab.

Maintaining these structures requires careful engineering and safety standards. In the United States, the National Electrical Safety Code sets construction standards. This code is published by the Institute of Electrical and Electronics Engineers. Wood poles have a lifespan of about 25 to 50 years. This depends on the local climate and soil conditions. Woodpeckers can also cause significant damage to wooden poles. To prevent fires, some poles are grounded with copper wire. This provides a path for leakage currents to reach the ground safely.

Modern technology is changing how we use utility poles. Many residential neighborhoods now use underground distribution lines instead. This is often done because poles can be considered unsightly. Underground lines also reduce power outages during heavy snow, ice, or hurricanes. Some poles even feature solar panels to power auxiliary equipment. This is useful when connecting to a main power line is too expensive.