Total Electric Field due to an Isolated Electron Avalanche

The corona on high voltage overhead lines apart from other aspects, are known to be a source of electromagnetic noise. The basic mechanism behind corona discharge is an electron avalanche. The rapid spatial and temporal rate of charge separation in the avalanche results in dynamic electromagnetic field spanning a wide frequency spectrum ranging up to GHz. The literature relating basic avalanche process to the resulting electromagnetic field is rather limited and available ones deal only with far field component of an isolated avalanche. However, the near field components of the corona dominate in dictating the induced currents in the supporting conductor. These induced currents propagate along the lines and hence can be a strong source of electromagnetic noise. Therefore, a complete knowledge on the corona produced electromagnetic field i.e. the near and far field components are essential for evaluating the resulting electromagnetic noise. The present work is aimed to take a step forward and for this starting form Townsend's model for avalanche and retarded potentials, an expression for the total field due to an isolated electron avalanche is deduced. Validation is provided with a recent work, which deals only with the radiated field, as well as, by using the electric field integral equation for the total field. This work therefore, can be considered as a first step towards evaluation of electromagnetic fields due to different manifestations of corona