What is Corona Effect in Transmission Line?

Corona Effect in Transmission Line
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The corona effect in transmission lines is the phenomenon of ionization of the air around a conductor, leading to a luminous glow and hissing noise. It occurs when the electrostatic field across the conductors produces a potential gradient, resulting in corona discharge.

Understanding Corona Effect In Transmission Line

Corona Effect in Transmission Line: The corona effect in a transmission line is the phenomenon of ionization of the air surrounding the conductor, resulting in a luminous glow and hissing noise. Several factors affect the corona discharge, including conductor shape, air density, and various atmospheric factors.

What is Corona Effect in Transmission Line

Here’s what you need to know about the corona effect:

1. Characteristics:

  • Violet-colored glow around the conductor
  • Hissing or crackling sound
  • Production of ozone gas
  • Increase in conductor diameter (virtual)
  • Power loss
  • Interference with radio communication

2. Occurrence:

The corona effect occurs when the applied voltage exceeds the critical disruptive voltage (Vd) of the air surrounding the conductor. Vd depends on several factors, including:

  • Conductor surface: Rough surfaces have lower Vd than smooth surfaces.
  • Conductor diameter: Larger diameter conductors have higher Vd.
  • Spacing between conductors: Greater spacing increases Vd.
  • Air pressure: Higher pressure increases Vd.
  • Air temperature: Lower temperature decreases Vd.
  • Air density: Higher density increases Vd.

How Corona Discharge Effect Occur in Transmission Line?

Corona discharge occurs in transmission lines when the electric field strength around the conductor exceeds the dielectric strength of the surrounding air. This dielectric strength is the maximum electric field that air can withstand before it breaks down and becomes conductive.

Here’s a breakdown of the process:

1. High Electric Field:

  • When high voltage electricity flows through a transmission line, it creates a strong electric field around the conductor.
  • The electric field strength is highest at the surface of the conductor and decreases with distance away.

2. Air Molecules Ionize:

  • If the electric field strength exceeds the dielectric strength of air, it can break down air molecules into positive and negative ions.
  • This process is called ionization.
  • The free ions become charged particles that can move through the air, making it conductive.

3. Chain Reaction:

  • The free electrons created by ionization are accelerated by the electric field and collide with other air molecules, ionizing them in turn.
  • This creates a chain reaction, resulting in a sustained flow of current through the air, which is known as corona discharge.
What is Corona Effect in Transmission Line

Factors Affecting Corona Discharge:

  • Applied voltage: The higher the voltage, the stronger the electric field and the more likely corona discharge is to occur.
  • Conductor diameter: Larger diameter conductors have a higher surface area and a lower electric field strength, making them less susceptible to corona discharge.
  • Spacing between conductors: Increasing the spacing between conductors reduces the electric field strength and makes corona discharge less likely.
  • Air pressure and temperature: Higher air pressure and lower air temperature increase the dielectric strength of air and make it harder for corona discharge to occur.
  • Conductor surface roughness: Rougher surfaces have a higher electric field strength at the peaks and valleys, making them more susceptible to corona discharge.

Effects of Corona Discharge:

  • Power loss: The energy dissipated in the corona discharge represents a loss of power from the transmission line.
  • Electromagnetic interference: Corona discharge generates electromagnetic waves that can interfere with radio communication.
  • Ozon production: Corona discharge produces ozone, which can be harmful to human health and the environment.
  • Conductor damage: The ultraviolet radiation and chemical reactions associated with corona discharge can erode the conductor surface, reducing its cross-sectional area and increasing its resistance.
What is Corona Effect in Transmission Line

How to reduce corona effect in transmission line?

Mitigation Techniques:

  • Increase conductor diameter: This increases the surface area of the conductor and reduces the electric field strength at the conductor surface.
  • Increase spacing between conductors: This increases the distance that the electric field must travel to ionize the air.
  • Use bundled conductors: Bundled conductors consist of two or more conductors arranged in a circle around a central core. This reduces the electric field strength at the surface of each individual conductor.
  • Use smooth conductor surfaces: Smooth surfaces have a higher Vd than rough surfaces.
  • Control air pressure and temperature: Higher air pressure and temperature increase Vd.


In understanding the corona effect in transmission lines, one can see the significance of its impact on power systems. From its causes and consequences, to methods of mitigation, it is evident that the corona effect holds a substantial role in the functioning of transmission lines.

Here are some additional resources that you may find helpful:

As we continue to develop and innovate in the field of electrical engineering, a comprehensive grasp of the corona effect is essential for creating efficient and reliable power systems.

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