Corona discharge

Ionization of air around a high-voltage conductor Long-exposure photograph of corona discharge on an insulator string of a 500 kV overhead power line. Corona discharges represent a significant power loss for electric utilities. The corona discharge around a high-voltage coil Corona discharge from a spoon attached to the high-voltage terminal of a Tesla coil Large corona discharges (white) around conductors energized by a 1.05-million-volt transformer in a U.S. NIST laboratory in 1941 A corona discharge is an electrical discharge caused by the ionization of a fluid such as air surrounding a conductor carrying a high voltage. The discharge appears in cases where the voltage exceeds a critical value, but an electric arc cannot form. Instead, the discharge appears as a colored glow around an object. The corona discharge represents a local region where the air (or other fluid) has undergone electrical breakdown and become conductive, allowing charge to continuously leak off the conductor into the air. A corona discharge occurs at locations where the strength of the electric field (potential gradient) around a conductor exceeds the dielectric strength of the air. It is often seen as a bl