What is tension?

Tension is the force applied to the conductor to keep it between the two towers. The force needed to break the conductor is called ultimate tensile strength.

What is the sag of the conductor and its effect on the line design?

The largest vertical distance between the lowest point of the conductor installed between two towers and the ground. The lower the sag of the conductor, the lower the height of the supporting tower.

What is span?

The horizontal distance between two towers is called Span. As the span length increases, the sag of the conductor also increases.

What is a section?

 A section of the line that is limited by two towers, between which there are a number of hanging towers.

What is the maximum tensile strength (Rated Strength) of the conductor?

The maximum force implemented on the wire before breaking is called maximum tensile strength. In line design, tension is considered between 18 and 25% of the maximum tensile strength for normal conditions.

What is the coefficient of linear expansion of conductor and what does it depend on?

The increase in the conductor length is proportional to the increase in its temperature. This coefficient depends on the material of the wire.

What is elasticity?

The ratio of the change in tension to the change in the length of the conductor is called elasticity. The lower the elasticity of the conductor, the lower the length of the conductor will be due to the force applied to it, and the sag of the conductor will be less. The elasticity depends on the conductor material.

What is the hot and cold curve?

The arrangement conditions of the conductors in hot seasons are called hot curves and in cold seasons are called cold curves.

What is a typical curve in line design?

The minimum permitted distance of the conductor from the ground is called a normal curve.

What is the application of power transmission tower and what are its types?

The supporting construction for transmission lines is called a tower and it comes in various forms.

Which factors affect the DC resistance of an overhead conductor?

The electrical resistance of the conductor depends on the cross-section, length, and operating temperature of the conductor. The larger the cross-section of the conductor and the lower the length and operating temperature of the conductor, the lower the resistance.

What is the effect of bundel in power transmission lines?

A group of conductors in each phase is called a bundle, each phase can be 2, 3 or 4 bundles. By bundling the conductors, the geometric mean radius is increased and it causes the reduction of line inductance, reduction of skin effect, reduction of voltage gradient, reduction of corona losses, and increase of line capacitance.

What is skin effect in conductor?

The skin effect causes non-uniformity of the current density in the cross section of the conductor. The higher the frequency of the current, the tendency of the current to pass through the outer layer of the conductor will be more causing the increase of the resistance of the conductor.

What is the difference between AC electrical resistance and DC electrical resistance of a conductor?

In conductors, the skin effect occurs due to the flow of AC current, causing the AC resistance of the wire to be higher than the DC resistance of the wire.

What are the effective factors in reducing energy losses in energy transmission lines?

The presence of electrical resistance in the wire causes all the energy provided by the energy supplier not to reach the receiver and some of the energy is lost as heat. Energy losses can be reduced by increasing the number of circuits, bundling transmission lines and using conductors with lower resistance (higher cross section).

How does the corona phenomenon occur and what is its effect?

When the magnetic field around the conductor exceeds the intensity of the effective field (21.2 kV/cm2), the air around the conductor begins to ionize and produces ozone gas, this phenomenon will be accompanied by a violet halo and energy losses called Corona.

What are the effective factors in the occurrence of Corona?

Atmospheric conditions,  surface, and geometrical conditions of the conductor affect the Corona phenomenon (increasing the radius of the conductor will decrease the voltage gradient. Decreasing air density will increase the voltage gradient of the conductor).

What is the effect of wind on conductor?

Wind decreases the temperature of the wire and increases the permissible current carrying capacity, on the other hand, the horizontal wind will cause a horizontal force applied to the conductor. This will cause the sag of the wire to increase.

What is the effect of temperature on the conductor?

 As the ambient temperature increases, the conductor temperature will increase, causing an increase in the electrical resistance of the conductor and a decrease in the permissible current carrying capacity. On the other hand, the increase in temperature will increase the length of the conductor and increase the sag of the conductor.

What is the galvanic phenomenon?

Chemical reactions that cause corrosion between two dissimilar metals are called galvanic reactions. This phenomenon is common in ACSR conductors having galvanized steel cores in humid weather conditions or polluted industrial areas. To prevent this phenomenon, nowadays ACSR conductors with aluminium-clad steel cores (ACSR/AW), all aluminum conductors (AAC), all aluminum alloy conductors (AAAC), or aluminium conductor composite core conductors (ACCC) are used.

What is galloping?

Galloping is the term used to describe the high-amplitude and low-frequency oscillations of power lines, which can be caused by wind, the formation of ice on the wires, or sudden changes in the conductor's weight. Galloping plays an important role in determining the spacing between power lines and the loading of towers.

What is the effect of conductor parameter on conductor sag?

 The ratio of the tension applied to the conductor to the weight of the conductor under certain weather conditions is called the conductor parameter. The larger the conductor parameter, the less the sag of the conductor will be.

Why the conductors are stranded?

In order for the conductors to have proper flexibility in stranding, packaging and installation, they are stranded.

What is the use of overhead shield wire?

Shield wire is used to prevent lightning from affecting the phase conductors and is installed above the phase conductors and parallel to these conductors at the highest point of the tower.

What are the effective factors affecting the maximum allowable current capacity of the conductor?

Electrical resistance, wind, surface conditions of conductor, conductor temperature, and ambient temperature.

What are the standard voltages of Iran's electricity lines?

Transmission lines: 230 kV and 400 kV

Sub-distribution lines: 63 kV and 132 kV

Distribution lines: 20 V and 400 V.