A corona ring, also known as a corona discharge ring or simply a corona device, is a specialized component used in high-voltage systems to mitigate the effects of corona discharge. Corona discharge occurs when an electric field around a conductor becomes strong enough to ionize the surrounding air, resulting in the formation of a faint, bluish glow or halo of light around the conductor. This phenomenon is undesirable in high-voltage systems as it can lead to several negative consequences, such as energy loss, audible noise, radio interference, and even localized damage to the insulation material.
The working principle of a corona ring involves controlling the electric field distribution around the high-voltage conductor, usually a transmission line or an insulator, in such a way that the electric field strength at the surface of the conductor remains below the threshold required for air ionization. Here's how it works:
Electric Field Distribution Control: The corona ring is typically made of a conductive material and is placed concentrically around the main high-voltage conductor. It's designed to have a larger radius than the conductor itself. The presence of the corona ring alters the electric field distribution by modifying the shape of the field lines and reducing the local electric field strength near the surface of the main conductor.
Equalization of Electric Field: By ensuring that the electric field near the surface of the main conductor is lower and more uniform, the corona ring helps prevent the buildup of high electric field strengths that would otherwise lead to air ionization and corona discharge.
Avoiding Ionization: As the electric field around the conductor is controlled and moderated by the corona ring, the voltage gradient along the surface of the conductor is reduced, making it less likely for the air to undergo ionization and form corona discharges.
Minimizing Energy Loss and Emission: Corona discharge is associated with energy loss due to the ionization of air molecules and subsequent recombination. By using a corona ring to suppress corona, energy loss is minimized, leading to a more efficient transmission of electrical power. Additionally, the elimination of corona helps reduce the emission of radio interference and audible noise, which is crucial in maintaining reliable high-voltage systems.
In summary, the corona ring functions by altering the electric field distribution around a high-voltage conductor to prevent the buildup of high electric field strengths that could lead to corona discharge. This aids in minimizing energy loss, reducing radio interference and noise, and preserving the integrity of the insulation materials in high-voltage systems.