In electricity, a corona discharge is an electrical discharge brought on by the ionization of a fluid surrounding a conductor, which occurs when the potential gradient exceeds a certain value, but conditions are insufficient to cause complete electrical breakdown or arcing.
Coronas can generate audible and radio-frequency noise, particularly near electric power transmission lines. They also represent a power loss, and their action on atmospheric particulates, along with associated ozone and NOx production, can also be disadvantageous to human health where power lines run through built-up areas. Therefore, power transmission equipment is designed to minimise the formation of corona discharge. Corona discharge is generally undesirable in:
- Electric power transmission, owing to loss of power in corona processes and noise
- Inside electrical components such as transformers, capacitors, electric motors and generators. Corona progressively damages the insulation inside these devices, leading to premature equipment failure.
- Situations where high voltages are in use, but ozone production is to be minimised
(fonte: http://en.wikipedia.org/wiki/Corona_discharge )