How Much Radius Should Be in The Transmission Line?

Indeed, the radius is a line segment from the center to the perimeter. In short, the radius is the diameter of a circle. However, we see the overhead transmission line or underground transmission line. But do we know, how much radius should be in the transmission line? Indeed, transmission line radius depends on the voltage, current, conductor materials, and others. However, if the overhead transmission line voltage or high tension power lines voltage becomes 11KV to 66KV then the radius should be 0.5 to 1 cm. But this radius may vary depending on a few factors.   

How Much Radius Should Be in The Transmission Line?

Radius length both are crucial things, if we would like to measure something. For specific voltage and length, overhead and underground transmission must have a radius. Though radius depends on some crucial factors, such as

  • Line voltage. Note that a higher transmission voltage line has a higher radius to prevent the corona effect.
  • Line current. Those power lines carry more current they must have a higher radius to dissipate heat.
  • Spacing between the conductors.
  • Materials of the conductors.

However, I have given here, how much radius should be in the transmission line for a specific line voltage in KV. Remember this radius can be changed depending on the transmission line length, voltage, current, distance, and materials.

  • If the line voltage becomes less than 60 kV then the radius should be 0.5 to 1 cm.
  • For a medium line voltage (60 kV to 138 kV), the transmission conductor radius should be 1 to 2 cm.
  • For a high transmission line voltage or high tension line voltage (138 kV to 765 kV), the radius should be 2 to 5 cm.
  • If the line voltage becomes above 765 kV (Extra high voltage), then the radius should be 5 cm or more.

The transmission line is used to transfer electric energy from the generating power station to several distribution units. It transfers the voltage and current from one station to another. The electrical transmission lines are made by conductors of uniform cross-section. Air is the dielectric medium between conductors.

What Is GMR in Terms of the Radius of a Transmission Line?

GMR or Geometric Mean Radius and GMD in transmission line or Geometric Mean Diameter are two significant parameters in the design of transmission line conductors. GMR represents the average radius of a conductor considering its irregular shape. GMD represents the average diameter of the conductor. These parameters are used to calculate the electrical reactance, resistance, and inductance of the conductor, which are vital for determining the electrical performance of the transmission line.

GMR and GMD are measured based on the diameter of the conductor at diverse points along its length. The GMD is measured as the square root of the product of its two diameters at two perpendicular points. The GMR is calculated as the square root of the ratio of the conductor’s cross-sectional area to its circumference, and

In general, transmission line conductors with bigger GMR and GMD values have lower electrical resistance & better current carrying capacity. Which makes them appropriate for high voltage power lines or high tension electricity carriers. Instead, smaller GMR and GMD values are required for overhead ground wire applications, as they lessen the wind load & ice load on the conductor

138 KV Transmission Line Safe Distance 

The safe distance to stay from power lines is a subject of ongoing research. While there are no rules and guidelines, authorities suggest maintaining a distance of at least 300-500 feet or approximately 91-152 meters from high-voltage power lines as a safety measure.

For safety causes, the distance between the ground and transmission is much more. The electrical tower or pole is used to support the conductors of the transmission line. Towers are made of steel to give high strength to the conductor. High voltage direct current is used in the transmission line for transmitting high voltage over long distances.

We should always maintain a distance of at least 10 feet from overhead transmission lines and more than 10 feet if the voltage to ground is over 50 kilovolts. The higher the voltage, the greater the distance that is required between the lines and the workers.

What Are the Parameters of the Transmission Line?

The transmission line performance depends on the parameters of the line. The transmission line has mostly four parameters, inductance, capacitance resistance, and shunt conductance. These parameters are consistently distributed along the line. Therefore, it is also called the distributed parameter of the transmission line.

The inductance and resistance form series impedance while the capacitance and conductance form the shunt admittance. Several critical parameters of the transmission line are explained below in detail


The existence of resistance is because every electric conductor offers some opposition to the flow of electric current through it. The resistance is the main reason for the power losses in the transmission line.

Generally, the presence of resistance in the transmission line is because every electric conductor offers some opposition to the flow of electric current through it. 

Line Inductance 

Inductance opposes a change in the electric current flowing through it. The electric current creates a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the electric current, & follows any changes in the magnitude of the current. 

Internal inductance represents the smallest component because of the magnetic field distribution inside the conductor. The external inductance is owing to the total current within the conductor, as it involves the magnetic field distribution outside the conductor.

Line Capacitance

The capacitance of a transmission line gives rise to the leading current between the conductors. It depends on the length of the conductor. The capacitance of the line is proportional to the length of the transmission line. 

Capacitance is small in short transmission lines while in long transmission; it is the most significant parameter. It affects the voltage regulation, efficiency, power factor, and stability of the system.

Shunt Conductance 

 Shunt conductance is the flow of leakage current among conductors or between a conductor & earth at the insulators of the transmission line. This flow of leakage current depends on the state of the air between transmission lines. Usually, the value of shunt conductance is very small and could be neglected.

It is distributed uniformly along the whole length of the line. The symbol Y represents it, & it is measured in Siemens.

So the transmission line parameters (inductance resistance, and capacitance) affect the performance of the transmission line. Therefore, it is essential to consider all the parameters while designing & determining the performance of a transmission line.

What Is the Difference Between Radius and Length?

The radius of a circle is a line segment that connects the center to the boundary of a circle. The length of the radius remains identical from the center to any point on the circumference of the circle. The radius is half the length of the diameter.


  • In geometry, the radius refers to the distance from a circle’s center, defined by the letter r.
  • For a circle, the radius is half of the diameter.
  • For a sphere, the radius is the distance from the center to the outer surface.


  • Length refers to the measurement of an object from one end to the other.
  • It can be applied to various geometric shapes, such as lines, segments, curves, etc.
  • Length does not specify a particular geometric figure and can refer to one-dimensional measurements in a broader sense.

Is The Distance Equal to The Radius of the Given Circle?

The distance across a circle throughout the center is called the diameter. The distance from the center of a circle to any point on the boundary is named the radius. The radius is half of the diameter. The line segment that joins two points on the circle is a chord.

Extremely Low Frequency (ELF) Radiation

Travel of electrical current through a conductor causes ELF radiation. Extremely low frequency or ELF radiation can cause cancer. This was first investigated by IARC in 2002. Thereafter, it was authenticated by WHO in 2007. Extremely low frequency (ELF) radiation, is related to an increase in childhood leukemia by 200%. 

About Extremely Low-Frequency EMF

Extremely low-frequency electromagnetic fields (EMF) are unseen waves that travel through space & exert force on charged particles.

Extremely low-frequency EMF consists of electric fields & magnetic fields in the frequency range of 1 Hertz to 3 kilohertz) of the electromagnetic spectrum.

An electric field is formed when you plug a wire from an electrical product, like a lamp, into an outlet. While you turn the lamp on, the flow of current, identified as alternating current forms a magnetic field. The electric and magnetic field radiates out like a wave and is identified as electromagnetic fields or EMF.

The electricity that is distributed to our homes and other buildings is AC with a frequency of 60 Hz. This is considered extremely low-frequency EMF.

Sources of Extremely Low-Frequency EMF

Electrical products generate shallow frequency or EMF when they are plugged into a wall outlet & are turned on. Common sources of extremely low-frequency EMF are:

  • household wiring
  • electrical appliances & household electrical products
  • power lines, transformer boxes &electrical substations
  • Power lines & your home

Power lines that distribute electricity around your home discharge extremely low-frequency EMF. These fields are strongest at their source. This means you are exposed to stronger extremely low EMFs while you are close to a source for example:

  • right beside a transformer box
  • directly under a high voltage power line

As you move away, your level of exposure quickly decreases. When you are inside your home, the electric fields from transformer boxes & high voltage transmission lines

are weaker than the fields from household electrical appliances.

Recommended Human Exposure Limits

The prospective health effects of extremely low-frequency EMF are studied extensively. While some people are concerned that long-term exposure to extremely low-frequency EMF might cause cancer, the scientific proof does not support such claims.

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has issued rules for limiting exposure to extremely low-frequency EMF. These rules and guidelines help confirm that exposures to extremely low-frequency EMF do not generate electric currents that are stronger than the ones made naturally in your body. The electric signals used by your brain & nervous system make it possible for you to move, think, and feel.

Extremely low-frequency EMF exposures in homes, schools, and offices are far below the limits suggested in the ICNIRP guidelines. You do not need to take precautions to protect yourself from these types of exposures.

Exposure to extremely low-frequency EMF is not similar to electrical shock. Electrical shock can occur when an electrical product is used incorrectly. 

Is It Safe to Live Near Power Lines?

ELF radiation from power lines is dangerous to the body. It is known to cause headaches, dizziness, fatigue & insomnia. This leads to listlessness, irritability, hypertension, decline in energy levels, obesity, etc. Thus, even while there is no scientific proof, ELF radiation is a health hazard. Therefore, it is not safe to live near power lines. But, there is regulation for safety from these power lines.

Most of the safety regulations about power lines are included in the area of land on both sides of the HT power line. This is named “Right of Way”. Right of way is an allowance of land around the power lines wherever no human habitation should be allowed. In most cases, it is the land 20-23 meters on both sides of the HT power transmission line. Power distribution rules command that this land is left alone. This is to accommodate any accident that can cause a current-carrying power cable to fall on the ground and risk electrocuting.

The right of way does not account for the concentration of ELF radiation in the area around the current-carrying conductors.

  • ELF hazard values are connected to living near high voltage power lines.
  • First, we provide the related definitions connected to this model.
  • The threshold of human exposure value is taken at 2.5mG. This is delivered by the Environment Protection Agency (EPA, USA).

Safe ELF value is shown in Green and is taken as a zone where ELF is lower than 1mG. This is as per building biology standards.

Between the threshold value & the safe value – we have the tolerance zone. Several sensitive people like children and older adults will have a problem spending longer exposures in this zone.

A hazard zone is an area where the ELF is not appropriate for sustained exposure and human living. This is marked in Red

Do Electrical Sources Cause Any Health Effects?

Exposure to ELF EMF at high levels could affect the operation of the nervous system. Yet, exposure to high levels of ELF EMF is not usually found in the daily environment from electrical sources. While such exposures are very rare, there are international guidelines on limits of exposure that are intended to prevent established damaging effects.

There is a lot of research on whether exposure to ELF-EMF from electrical sources below the exposure limits reasons for any health effects. Most of the research specifies that ELF-EMF exposure usually encountered in the environment, including in the locality of power lines, does not pose a risk to human health. 

Yet, some epidemiological (population) studies have reported a possible association between long exposures to ELF magnetic fields at levels below the exposure limits but higher than what is typically encountered and increased rates of childhood leukemia. 

Based largely on this limited proof the International Agency for Research on Cancer has classified ELF magnetic fields as possibly carcinogenic to humans.

There are difficulties with the approaches in epidemiological studies that weaken the conclusion from these results. It is not known how magnetic fields could cause childhood leukemia. Generally, other research including studies on cells and animals has not confirmed these results. On balance, the proof related to childhood leukemia is not strong; yet people should be aware of the issue to make informed decisions.

Is It Dangerous to Live Near Power Lines?

There are numerous risks related to living near distribution power lines. The biggest are increased risks of fire & electrocution, as well as radiation exposure from the EMF radiation of the power lines, which can cause health problems. Moreover, it can be harder to sell a home situated near power lines. 

Increased Electrocution Hazard

Electrocution will always be a hazard when you are dealing with any conduit for electricity. A live cut wire could always lead to shocking results. Even if it does not shock you, it might lead to severe property damage.

 Increased Fire Hazard

One of the leading disadvantages of living next to power lines is the higher risk of fire. Even if you maintain your yard & home well, electrical fires could still be a severe risk. This is especially true in an area with power lines. It just takes a dropped branch, a live wire, and some old leaves to ignite your lawn into a ball of flames. 

Luckily, most municipalities made a point to have safety features installed to decrease the chance of a fire or breakage. Yet, if you notice a break, stay in your home and call 911.

Increased Radiation Exposure

So, this is something that several people don’t think about when they consider power lines. Yet, it is a risk to consider. Power lines that are in use give off electromagnetic radiation just because they are conducting electricity.

In maximum cases, the radiation exposure is negligible. It is not like you have a pot of uranium at the edge of your house. Yet, this can add up to an increased cancer risk over time. That is what around 20 percent of all studies on this subject have found. 

Around half of all studies reveal no negative side effects from the low-grade radiation from power lines. The studies on this differ, but it is a risk you should know. How risky it is, however, is up for debate.

Buzzing Noise

While this is not a main risk for most people, we have all heard the low hum and buzz that high-voltage power lines can make. A similar can be said about larger power stations with multiple hubs, too. 

For maximum of us, the buzzing noise can be an irritating addition to daily background noise. Yet, for a small handful of people, that constant hum could be a source of migraines or a worsening factor for migraines that can already be there.

How Close Can I Live or Work Near Power Lines or Other Electrical Sources?

There is no established proof that exposure to magnetic fields from electrical power plants, substations, power lines, transformers, or other electrical sources, irrespective of the proximity, causes any health effects. In view of the epidemiological studies, the possibility remains that long exposure to higher-than-typical magnetic fields may upsurge the risk of leukemia in kids.

For homes near high voltage (HV) power lines, the magnetic field exposure will vary as per the amount of current carried by the power line & the distance of the home from the power line. Usually, homes that are more than 50 m from a high voltage power line are not anticipated to have higher than usual magnetic fields. For electrical substations and electrical transformers, the magnetic fields at distances of 5-10m away are usually indistinguishable from typical background levels in the home. 

It is important to note that living further away from high voltage power lines will not essentially decrease magnetic field exposures in the home or decrease any possible risks related to magnetic fields from electricity.

Power Lines Safety Rules and Precautions

Some provisions must be followed to avoid electrical hazards & risks:

  • Towers carrying live conductors must not be climbed as it could cause electric shock if the tower is energized.
  • Animals must never be tied to a transmission tower or pole as it can risk their life.
  • Any item made up of metal or conducting material must not be thrown on overhead lines.
  • During rain, towers or poles must not be touched by any individual since the tower body becomes energized because of the conductivity of water.
  • During storms or strong winds, we should keep a safe distance from powerlines as live conductors might accidentally fall over a person.
  • If an individual sees any spark on overhead live conductors, his first duty should be to inform the related authorities to avoid accidents.
  • Any construction work must not be carried out under or near HV power lines.

Besides the precautions, there are also several safety rules for the linemen who work on HV transmission lines. These areas following:

  • Linemen must be acquainted with all the safety rules & regulations.
  • A lineman who will do any operation must be trained well. Without any experience or training, he must not try to take any risk as it can put his life in danger.
  • A lineman must be equipped with all required PPEs before starting an operation.
  • Before the start of work, it must be made sure that the tower on which the lineman is going to work is totally de-energized.
  • If a lineman is not acquainted with any tool, then he should never try to use it as it can be dangerous.
  • A lineman must be in continuous communication with other team members when doing an operation.
  • A lineman must not be in a rush as it can cause an accident to him or other team members.


Electricity is a great blessing for us as it has advanced & automated our lives to an infinite extent. But along with these advantages, electricity is also very dangerous at the same time. It generates several hazards and health issues therefore endangering our lives. If we correctly follow the safety rules, standards, & precautions, then we can decrease and even remove the risks and hazards caused by electricity. Finally, it is up to us whether we make our lives comfortable or full of risks.

Leave a Comment