CORONA FROM FLOATING ELECTRODES

It is not unusual to have insulated conducting objects located close t o the conductors of a Lightning Protection System. However, the separa tion of these objects from the Lightning Protection System could vary from a few millimetres to some centimetres. When the system is exposed to thunderstorm electric fields, discharge could be initiated between the Lightning Protection System and the floating conductive body. We have performed the study reported in this paper to gain knowledge conc erning this discharge process. The critical field for the initiation o f corona currents from a floating electrode, when a negative DC voltag e is applied to the main gap electrodes, is detected by the discharge of the floating electrode to the earth electrode. The electric field i ntensity at the high curvature (sharp) points on the floating electrod e surface was calculated numerically to determine this critical electr ic field. The discharge repetition frequency was studied as a function of the applied background electric field and a well-defined relations hip was observed between these two parameters. The corona currents wer e calculated and good agreement was found between calculated and measu red values.