Corona effect discharge activities radiate energy in the form of light. This is mainly ultra-violet light which is invisible to the human eye. A small protion of the energy is however just visible at night and appears as "bluish flames" at sharp edges on high voltage equipment. During the day, the energy radiated by the sun in the UV spectrum, is orders of magnitude larger than that released from corona discharges. The corona discharge energy is thus almost completely absorbed by the solar energy. Consequently, to observe corona during the day is impossible with the naked eye.
The corona cameras had overcome this. It has been developed a day light corona observation and recording system, which uses three unique technologies. The first one uses an UV optimised detector with the appropriate filters, the second one controls the aperture of the lens, and the last one enhances the pictures obtained.
What is corona?
St Elmo's fire was probably the first recorded form of corona. During stormy weather at sea, flame like reddish or bluish lights appeared occasionally on the tops of ship masts. Sailors associated it with a form of protection and named it after their patron saint, St Elmo.
During the course of electrostatic investigations in the 17th century, the same light-like phenomenon was first observed in the laboratory. It was also traditionally referred to as corona. The term corona is now commonly used to describe this external electric gas discharge phenomenon.
- Generation of light
- Audible noise
- Vibration due to electric wind
- A deterioration of materials due to ion bombardment
- Deterioro de los materiales como consecuencia de un bombardeo de iones
- Generation of ozone, oxides of nitrogen, and in the presence of moisture, nitric acid
- Dissipation of energy
Corona may typically occur:
- Around line conductors
- On spacers and dampers
- Damaged insulators - ceramic or non ceramic
- Polluted insulators
- At the live ends of insulator assemblies and bushings
- At any point of your electrical equipment, where the electrical field strength exceeds 3kV/m
Another category of electrical discharge on high-voltage equipment, is gap discharge. This can be described as follows:
- Descarga de chispa ocurriendo entre dos superficies metálicas cualesquiera unidas eléctricamente
- Spark discharge, occurring between any two metal surfaces bound together electrically
- Micro-spark discharge, occurring in a miniature air gap formed between a conducting and insulating surface