What is an electric pole?
An electric pole is a vital structure that holds overhead power lines and provides support for various related equipment. Whether it’s a power pole, transmission pole, or hydro pole, these sturdy structures carry higher voltage power through sub-transmission lines to substations, where it is then reduced to lower voltage power for customers. The distribution lines ensure that electricity reaches homes and businesses efficiently. These poles also hold streetlights and transformers, making them essential for urban and rural infrastructure.
Different materials are used to build utility poles, including wood, concrete, metal, and fiberglass composites. Some specialized types, like the Stobie pole found in South Australia, use steel joists and a slab of concrete for durability. Electrical wires and cables are routed along these poles, keeping them insulated and off the ground to protect people and vehicles. An inexpensive alternative to underground wiring, these poles ensure safe and efficient electricity distribution while supporting telegraph poles and telecommunication systems in various applications.
Type of electric pole
Wood Poles
A traditional wood pole offers great flexibility for attaching hardware and cable apparatus. Holes can be drilled to meet exact requirements, allowing fasteners, lags, and screws to be applied easily. These structures provide strong support for OSP and other outside plant apparatus.
Non-Wood Poles
Concrete, steel, and fiber-reinforced composite (FRC) poles are strong structures used for power lines. Their intrinsic characteristics affect the design and manufacture of attachment hardware. These materials allow hardware to be securely mounted for long-lasting performance.
Concrete Poles
Concrete poles are ideal for coastal zones and marine environments because of their strong corrosion resistance against seawater and salt fog. Their heavy weight makes them stable in high winds, especially in coastal areas and marsh regions. These poles come in various designs, such as round poles, tapered structures, and hybrid models that mix steel with solid concrete.
Since drilling into installed concrete poles is not feasible, attachment hardware must be secured differently. Many opt for banded hardware or have the cable plant fixed during pole manufacture. Some pre-stressed concrete poles, including spun-cast and statically cast types, provide extra durability in extreme conditions.
Industry standards like ASTM C935, ASTM C1089, ASCE-111, and ACI-318 set the requirements for design and safety. These industry documents ensure that each pole meets strict regulations for strength and stability. Proper guidelines help reduce operational difficulties and maintain long-term performance.
Steel Poles
Steel poles are used for taller structures in high-voltage applications, offering higher strength and enhanced clearances. Tubular steel poles are made from 11-gauge galvanized steel, while 7-gauge materials and 5-gauge materials are used for tall tower-type structures. These poles are built to handle longer span requirements while maintaining a rigid design.
Drilling bolt holes on steel poles is not recommended, though attachment points can be built into the pole during manufacture. Instead, a feasible option is to use attachment ledges or secure hardware with steps and other general attachment points. Welding in the field may be an alternate approach, but operational hazards and practical hazards make it undesirable and sometimes uneconomical.
To ensure a good quality pole, industry standards like TIA/EIA-222, TIA/EIA-222-G, and TIA/EIA-RS-222 define structural standards for steel poles. These industry specifications establish an equivalent requirement for durability and safety. Following the structural standard for antenna-supporting structures and antennas ensures that each pole meets reliability expectations in power distribution.
Parts of an Electric Pole
- Electric poles play a crucial role in power transmission by supporting essential components that ensure safety and efficiency. Below is a detailed breakdown of the key parts of an electric pole:
- Primary wires carry high-voltage electricity from substations to distribution transformers. These wires are typically insulated to minimize power loss and protect against environmental factors. They are placed at the top of the pole to prevent interference with other components.
- Insulators are vital for preventing the flow of electricity from the wires to the pole structure. They are made of porcelain or fiberglass. They ensure that the electricity travels through the wires. They also protect the pole and nearby structures.
- Crossarms are horizontal supports fastened to the poles. They hold multiple wires at a safe distance from one another, preventing short circuits and ensuring structural stability. Crossarms are often made of wood, steel, or fiberglass and include protective features like UV resistance for durability.
- Lightning arrestors protect the pole and its components from lightning strikes. By diverting excess electrical currents safely to the ground, they prevent damage to the system and reduce the risk of outages.
- Electric poles have transformers. They reduce the high voltage of primary power lines to a lower, safe level for homes and businesses. They are critical for delivering power efficiently and safely to end users.
Other Components
Other essential parts include:
Ground wires for earthing.
Neutral wires for returning current.
Pole fixtures, like braces and brackets, are for support.
Together, these parts guarantee the pole’s strength and safety.
Uses of electric poles
Electric poles play a crucial role in delivering electricity through electric power lines to homes and businesses. They support both distribution lines and sub-transmission lines, ensuring power reaches local substations before it is delivered to customers. Transformers help reduce the primary voltage to a lower secondary voltage, making it safe for use at the premises. The service drop connects the final stretch of power to buildings efficiently.
Power Distribution and Transmission
For long-distance power transfer, subtransmission lines carry higher voltage power from regional substations to local substations. These lines typically operate at 46 kV, 69 kV, or 115 kV, extending up to 100 km. When power needs to travel even further, transmission lines over 230 kV are used, often supported by metal pylons and transmission towers rather than electric poles. Some systems use H-shaped towers with three poles for extra stability over long distances.
In urban areas, using joint-use poles is a practical way to save space while supporting both power lines and telecommunication cables. To maximize efficiency, a subtransmission line may be mounted above a distribution line, a setup known as underbuild. In areas where dedicated poles are not feasible, these shared structures help maintain a reliable power grid while keeping infrastructure costs low.
Structure of electric poles
A standard utility pole in the United States is typically 35 ft tall and is buried about 6 ft deep for stability. In urban areas, these poles are spaced around 125 ft apart, while in rural areas, they can be 300 ft apart. The distances between poles vary depending on the terrain and clearance regulations to ensure safe installation. Some poles reach 120 ft in height to meet specific standards for power and communication lines.
Most joint-use poles are owned by a utility company, which leases space for cables used by other services. Safety guidelines are set by the National Electrical Safety Code, created by the Institute of Electrical and Electronics Engineers (IEEE), while the National Electrical Code is regulated by the National Fire Protection Association. Regular maintenance and construction of poles and equipment ensure they remain safe and functional. Some poles, especially in critical areas, extend up to 40 meters or 100 meters for better coverage.
Types of pole materials
Many utility poles are made from wood, specifically Southern yellow pine, Douglas fir, and Pacific silver fir because they grow as long, straight trees. To protect them, they undergo wood preservation processes using preservative chemicals like creosote, pentachlorophenol, and borates. These treatments help prevent rot, fungi, and insects, extending their lifespan to 25 to 50 years. However, woodpecker damage and decay over time require remedial preservative treatments and regular inspections.
Alternative materials such as steel, aluminum, fiberglass, and concrete are used where durability is needed. In Australia, the Stobie pole, a patented utility pole, consists of steel posts with a slab of concrete in between for strength. Environmental concerns have led to the use of copper naphthenate instead of harmful chemicals. Various standards like ANSI, ASTM, and test criteria in the United States (U.S.) regulate wood preservative materials to ensure safety in different climates and soil conditions.
Power Distribution Wires and Equipment
Electric power distribution lines use three-phase systems to deliver electricity efficiently across cities and towns. These systems rely on three wires, each carrying power through a conductor connected to a transformer’s primary source. In North America, homes receive split-phase power at 240/120 V, while in Europe, electricity is delivered at 34,500 V through a Greek letter Δ (delta) system. To regulate high voltages, pole-mounted step-down distribution transformers lower the current to a lower secondary voltage for safe use.
For added protection, poles include insulators and overhead ground wires (OGW) to create a low-resistance path to ground. A surge arrester or lightning arrester is installed to divert dangerous spikes caused by lightning or flashovers. If an overload occurs, fuse cutouts will ensure safety by allowing the fuse-melt process to disconnect the affected line. These devices provide a visual indication of a problem, helping linemen quickly identify and resolve issues.
To prevent accidents, communication cables are placed below electrical wiring in the supply space, ensuring separation. In China, joint-use utility poles allow multiple services like communication wiring and distribution lines to share the same infrastructure. In storm-prone areas, aerial bundled conductors are used instead of uninsulated conductors to reduce damage from fallen trees and wind. These measures help prevent wildfires and improve electrical safety.
Additionally, poles are often grounded using heavy bare copper or steel wire, which is connected to a metal rod at the bottom. If a storm or equipment failure occurs, the hot stick tool allows linemen to perform disconnect operations safely. In some cases, spur lines are installed to provide power to side streets, residential buildings, and light commercial areas. With careful planning, electrical power distribution lines ensure consistent electricity delivery while protecting infrastructure from hazards.
Conclusion
Steel poles are a strong and reliable choice for high-voltage work. They offer more strength, better clearances, and can support taller structures. Their strong design lets them handle longer spans. This makes them great for tall tower structures. Drilling bolt holes on-site is not a good idea. Instead, look for other ways to attach parts.
Instead of welding on-site, which can be dangerous and costly, attachment points can be added to the pole during production. Attachment hardware, attachment ledges, and other general attachment points ensure secure mounting. Meeting industry standards like TIA/EIA-222, TIA/EIA-222-G, and TIA/EIA-RS-222 ensures that the steel poles meet structural requirements. This leads to high-quality poles for power distribution.
