Components of power transmission lines

Components of power transmission lines

Power transmission lines are transmission lines in which masts and beams are used to maintain cables. Usually, in these lines, air takes over the role of cable insulation. This is a low-cost and common transmission method that is responsible for keeping the cables. These lines are made of wood, steel, aluminum, concrete and sometimes plastic, which are reinforced. Usually, the cables used in airlines are made of aluminum, which is reinforced by a strip of steel inside. Copper cables are used in medium and low voltage transmission lines and in the connection to consumers.

Types of power transmission lines

Airline transmission lines

Ground transmission lines

Components of power transmission lines

Usually, the power transmission tower consists of the following parts.


Conductors are the most important component of the transmission network, through which the flow path is established. The conductors are made of aluminum, copper and steel, each of which is used in its place.


Overhead distribution lines are placed on foundations. These foundations are made of concrete, wood or metal and must be able to withstand two vertical forces that include the weight of the wire and the ice layer around the wire and the horizontal force that includes the wire ingot, pressure and wind.

Basic types





They isolate the conductor from the body of the console and the bases. There are different types of insulators in terms of size, material and shape, which are used depending on their location. Insulators should have two properties of high electrical resistance and high mechanical endurance.

Types of insulators


a plate



Consoles and crossarms

These parts are used to place the insulators on them and connect to the handles.

Types of cross logos



a flag

The top of the transfer tower

The upper part of the holding tower is called the top of the transmission tower. Earth is attached to the tip of this peak.

Transmission tower support arm

This arm maintains the power transmission conductor. The size of the holding arm depends on the amount of transmission voltage, configuration and the smallest angle formed for dividing the stress.

Transfer tower chest

The part between the body of the tower and the peak is called the chest of the transmission tower.

Transmission tower body

The body of the transmission tower is the part that extends from the lower part of the support arm to the top of the ground. This section plays a very important role to create the required distance between the conductor of the transmission lines and the ground.

Conductor group

It is responsible for restraining power transmission cables.


It is done by considering the weight of the mast and the cooperation of civil engineers.

Inspection of fittings of power transmission lines

The steps of moving electric power are called electric energy transfer. This process includes the transfer of electric energy from the producer to the distribution stations and it means that the delivery of electric energy to the consumer is in the space of electric energy distribution. The role of power transmission fittings is specified in this division. These fittings and connections play an important role in the transmission network and must have mechanical and electrical characteristics and special movement properties during operation. These components create a connection between the conductor wire and the protective wire with the tower through insulation or directly.

The characteristic of fittings is their high mechanical resistance; Because they must be connected to the wire that is made of aluminum layers and have many shapes. The design of this equipment is very important; Because they are affected by constant mechanical force and on the other hand, they bear different forces due to atmospheric conditions. For this reason, the wires that are in charge of transferring the current are directly and indirectly connected with the equipment. Some of these connections must be able to withstand short-circuit currents and prevent parts from melting.
After these equipments are connected with the insulators and a complete chain is created in the form of stretching and hanging in different directions, at this time they are energized. As a result, they need to be made in such a way that they can move in all directions.

Fittings of power transmission lines

They are divided into two categories, which are:

Radial fittings

These fittings in the radial network of broadcast lines do not connect to any other source after being separated from the broadcast post. They are usually used in rural networks or remote places.

Linked power transmission line fittings

These link networks are usually used in cities. The distribution paths of this network include two or more connections to other paths, where the consumer power has several paths to connect to the source.

These link networks are usually used in cities. The distribution paths of this network include two or more connections to other paths, where the consumer power has several paths to connect to the source.

The effect of fittings on the performance of transmission lines

The wires that carry the current are directly or indirectly connected to the equipment and fittings. Some of these connections must be able to withstand short circuit currents and prevent melting of parts. Also, the shape and form of these parts must be preserved so that a phenomenon called corona does not occur when voltage is applied. For this reason, designers and manufacturers should pay great attention in choosing the part and its ingredients and consider the following points.

Appropriate technical specifications

Based on their type and application, these parts should have characteristics such as suitable mechanical resistance, resistance to corrosion, required electrical conductivity, proper shape and no obvious and unnecessary protrusions. Things like easy production, easy installation, the possibility of moving and the finished price should be considered in the selection of fittings.

Types of connections

When we divide the fittings, the category in which the mechanical behavior should be considered can be divided into 2 groups.

Ready-to-install fittings

This category of fittings is used immediately at the place of consumption. If the mechanical properties of these fittings are specified in the factory, its properties will not change at the place of use, and the behavior of this piece in the place where it is used is not much different from its behavior in the laboratory environment.

Semi-finished fittings

In this group, due to the fact that part of the manufacturing process is carried out at the place of consumption, the mechanical behavior of the part changes due to the existence of operational differences at the time of installation.
The first group includes almost all insulating chain connections, and the second group includes connections that must be pressed or twisted in order to achieve optimal conditions. The connections of the second group are generally useful for conductors, and the final process that is performed on them at the place of use definitely affects their mechanical behavior. Both groups follow almost similar production methods; But the sensitivity of the second group is higher, which should be carefully monitored in its production and installation.

General methods of production

Different methods are used for the production of fittings, and here we mention some of these methods.


In this method, sheet or bar ingots are cut. This work can also be cut cold or guillotine or saw or hot with air.


In this method, the parts are prepared by melting the raw material and pouring it into the mold, which is done in different ways. The most common ones are sand casting and pressure casting.

Hot pressing or forging

This method is used for small parts; In this way, the ingot of metal or alloy is heated up to a certain temperature in the furnace and then poured into the mold and formed under the pressure of the heavy impact of the press. After cooling, the payment will be made on it.

Payment with sand and shot

Polishing should be done on the parts made by casting or hot pressing due to the unevenness of the outer surface. This action is done by spraying small sand and pellets and especially with high pressure on it, which results in a smooth and smooth surface.

Heat treatment

Different ways that are used for production can affect the mechanical behavior of parts, which can be changed by heat treatment. This heat treatment consists of heating and cooling the metal cutting in a space where heat and time are under control. This space can be air, water or different oils.

work payment

The operation used to complete the final shape of the part and remove its excess parts is called polishing, which is usually done with machine tools, lathes, grinders and other methods.

cold press

It is similar to a hot press; But the metal is cold pressed. In this method, only small parts can be produced.


In order to connect two pieces of the same metal to each other, welding is done with several methods, the most common of which is welding under the powder, which is specific to heavy metals, and welding with neutral metals, which is used for light metals. Usually, welded joints are not a suitable method to use in power transmission lines and should be avoided as much as possible. If you have to use this method, it is better to use the hot welding method.