Firstly, Corona Effect or Discharge are the same things. Electrical discharge caused by the ionization of the fluid (air) surrounding a conductor which is already charged electrically is known as the corona discharge or effect. this is the continuous waste of the energy.

This is a spontaneous process and occurs naturally in High voltage (H.V.) power lines unless special care is taken to limit the electric field strength. The Corona effect can cause a “hissing sound” around the conductor because it ionizes the surrounding air. This sound is no much loud.

What is Corona Effect?

Generally in High voltage transmission (>30 kV) lines (AC or DC), electrical discharge occurs due to ionization of the fluid. It shows a region around the conductor where the charge leaks continuously to ionize the air. This is called the corona effect or discharge. Also there are other effects related to transmission line too.

As Corona effect ionizes the surrounding air. Resulting in the bluish color aura around throughout the conductor. This color can be seen in natural light by naked eyes. And much more visible at night or dark atmosphere. As you observe there is a bluish covering around the conductor. But it gets weaker as you travel from the center of the conductor radially. Beyond this color there is no corona interference to the objects.

Factors affecting corona

These are the general factors affecting the corona effect or discharge.

• Spacing between the conductors
• Condition of the conductors.
• Atmospheric conditions.

Effects of the corona discharge

Such an effect is not bearable as it produces several losses in the system. In the air, corona generates gases such as ozone (O3) and nitric oxide (NO), nitrogen dioxide (NO2), and thus nitric acid (HNO3) if water vapor is present. As these gases are corrosive they may cause corrosion in nearby equipment.

• Electrical Shock affects if any bird or mosquito travels in the aura of corona around the transmission/power line.
• Radio interference.
• Of course, there will be power loss.
• A charge may travel to Electrical towers.
• Finally, Production of the OZONE gas around the conductor.

Methods to reduce Corona discharge or Effect

Corona loss or discharge or Effect may be reduced by using the following steps.

• Conductor – An increase in conductor diameter may reduce this effect drastically.
• Spacing – Increase Spacing between the conductors or phases.
• Bundling – Use bundle conductor. Because gives more diameter expansion.
• Corona ring or Guard ring – As you know a sharp edge gives more electrical discharge as compared to broader ones. In transmission lines, there are also some sharp points where the corona is severe. Like edges of the conductor, turning points, and sharp points. Here we use a Guard ring. A Guard ring is a circular conductor placed at sharp points to reduce charge leakage to the air.