Home >>  blog

Overhead Power Line Accessories

Most of the electricity generated by power plants is transmitted and distributed overhead lines. The transmission and distribution of power through overhead lines uses conductors supported on towers or poles with appropriate spacing between them. This spacing is provided to avoid discharges between conductors by increasing insulation. Compared to underground transmission and distribution lines, overhead lines are much cheaper.

For transmitting electricity at higher voltages over long distances, overhead lines are the best choice. For the same power transmission, underground cables require more insulation costs and conductor sizes. Overhead costs are much lower and overhead lines are easy to maintain.

However, there are some disadvantages to using overhead lines, for example, they are subject to uncertain weather conditions that reduce overall efficiency, conductors can be damaged by high winds or fallen trees, causing external interference, faulty short circuits due to lightning or faults, etc. However, these drawbacks can be overcome by using appropriate safety factors. Let's look at the various components of overhead lines in a power system.

Components of overhead lines


Conductors play an important role in overhead transmission and distribution lines, which carry electricity from the generating station to the receiving end and then to the consumer. A major part of the total capital is invested in the conductors. Therefore, the choice of conductor material and the size of the conductor should be selected appropriately. Depending on the current to be carried and the span of the line, the composition of materials such as copper, aluminum or ACSR is selected.

Protective wire

Protective lines are provided above or below the transmission line when crossing communication lines and are firmly connected to earth.

Lightning arrester

It is a device used to provide protection against traveling waves or high voltage caused by lightning by discharging excessive voltage from the line to ground.


The insulator is set on a support (pole or tower) to support the conductor, thus providing the necessary insulation for the support with the conductor. This further prevents leakage currents from the conductor to earth through the support. Insulators also prevent short circuits between conductors and metalwork. The most commonly used insulating materials are porcelain, glass and Stealite. the various types of insulators are, the

Pin insulators

Suspension insulators

Strain insulators

Unbuckled insulators

Retention insulators.


The function of a line support is to support the conductor and keep the conductor at a proper level from the ground. Generally, poles or towers are chosen as supports. These are used depending on the operating voltage and the area of use. There are various types of electric poles or towers, such as.

Wooden electric poles

Steel poles

RCC poles and

Lattice steel towers.

Cross arms and clamps

These are provided on the pole structure to support insulators and conductors. These are composed of wood or steel angles.

Poles and brackets

Used to resist lateral forces on terminal or angular poles by securing brackets or cables to the pole.

Fuses and disconnect switches

These are used to isolate different parts of the transmission system.

Grounding lines

Grounding wires are run at the top of the tower to protect the line from lightning strikes.


For public safety, these are provided underneath the base overhead lines along the street.

Miscellaneous components

Phase plates, bird protection plates, hazard plates, barbed wire, shock absorbers, top dampers, beads for jumpers, etc. The phase plates provide information on the various phases used, barbed wire, which is wrapped around a 2.5 meter high pole to prevent unauthorized climbing. However, there are also hazard plates at a height of 2.5 meters above the ground.


Various types of conductor materials used for overhead lines


Copper is the most common material used to construct overhead line conductors. It conducts current easily and is readily available. There are three types of copper wire, hard drawn copper, medium hard drawn copper and soft drawn copper. Of these, hard-drawn copper is mostly used to construct conductors because of its low elasticity and high mechanical strength.

Copper has a high current density and therefore requires less cross-sectional area than the others. Other advantages include durability, higher scrap value and homogeneity. Because of its advantages, all small conductors and heavy power cables are composed of copper. However, due to its high capital cost, it is not the preferred choice for overhead transmission and distribution lines.


Aluminum is the most common material used in power systems for transmission and distribution lines. It is cheaper and lighter in weight than copper. Because of its light weight, the tower structures used do not need to be as strong as copper. It is mainly used to carry heavy currents.

In this application, a special configuration called ACSR conductor (aluminum conductor steel reinforcement) is used. In this configuration, small strands of aluminum are wrapped around a steel core. This not only increases the current carrying capacity, but also increases flexibility and mechanical strength.

The main disadvantages of aluminum are its poor electrical conductivity (60% of copper), low tensile strength (45% of copper), low melting point, and difficulty in making joints. Despite its disadvantages, aluminum is commonly used as a transmission and distribution conductor.

Galvanized steel

Galvanized steel is the cheapest of all materials and is therefore used in areas where economy is a major factor. However, it has some drawbacks such as low conductivity, high resistance and therefore it is used only for low power and short distance applications. It is also used in applications where longer spans are required.

Cadmium copper

Cadmium copper is used for applications that require long spans and small cross-sectional areas. Cadmium is used together with copper to increase the tensile strength. It is used for some specific applications due to its higher cost.

Copper-welded steel

Copper welded steel conductors are nothing more than steel wires with a copper coating. This configuration is used to get the advantages of copper and steel, i.e. higher conductivity, greater strength and lower cost. It is basically used for rural lines, overhead wires and overhead grounding wires. The main advantage of this conductor is that its conductivity can be increased to any percentage by providing the necessary thickness of copper coating.

Overhead Power Line Accessories

Which instrument is used in overhead lines?

The most common material used for overhead line insulators is porcelain. However, sometimes glass, talc and some other special composite materials can be used.

What are the transmission line accessories?

Transmission line hardware accessories

Insulator string fittings.

Conductor accessories.

Vibration and spacer dampers.

OPGW accessories.

Substation fittings and accessories.

Accessories for power distribution lines.

Accessories and fittings for railroad electrification.

What type of wire is used for overhead?

The short explanation is that aluminum is the all-around best material for overhead cables because of its unique characteristics. Aluminum wire's low density, low price and high electrical capacity make it ideal for long distance lines.

What is wire support?

Definition: A different type of structure (pole or tower) used to support overhead lines or wires, this type of structure is called a line support. Line supports play an important role in the transmission of electricity.

What are the main requirements for line supports?

The main requirements for line supports are

High mechanical strength to withstand conductor weight, wind loads, etc.

Lighter weight without loss of mechanical strength.

Cheaper cost.

Lower maintenance costs.

Longer life.

Good looks.

Easy to paint and install line conductors.

Why do line supports need high mechanical strength?

In general, line supports should have the following characteristics: High mechanical strength to withstand conductor weight, wind loads, etc. Light weight, no loss of mechanical strength. Low cost, low maintenance cost.

What is the role of line supports?

The line support plays an important role in power transmission. It maintains the proper spacing between conductors and keeps the conductors at the specified distance from their grounded parts. It also maintains the specified clearances from the ground. These clearances are determined by electrical and mechanical factors.

What are the different types of line distribution?

There are three basic types of distribution system designs: radial, loop, or network. As you might expect, you can use a combination of all three systems, and often do so.

What is the breaking strength of overhead line conductors?

Each overhead telecommunication line erected on a support containing power lines must consist of conductors with a breaking strength of not less than 270 kg.

Which overhead transmission line has the shortest life span?

Wooden pole: It is one of the cheapest types of line supports and is used for lines with short spans and low tension. It has a very low life span.

Concrete poles: Concrete poles gave greater strength and used in place of a wood pole. It has a longer life than that of a wood pole because of little degradation. Their maintenance cost is low. Concrete poles are very heavy and are liable to damage during loading, unloading, transportation and erection due to their brittle nature.

Steel poles: For low and medium voltage tubular steel poles are used. Longer spans are possible with steel poles. The poles need to be galvanised or painted periodically to prevent them from corrosion. Their maintenance expense is high.

Get in Touch

Related Information