Transfer of bulk electric power required in the modern world can be realized only through EHV and UHV transmission lines. The scenario is dominated by overhead lines in which electromagnetic noise generated by corona is an important concern. Corona induced currents propagate along line conductors producing electromagnetic noise, which is essential to be quantified. In literature, large amount of work is based on experimental investigations which considers only limited frequency ranges and is not applicable to new line configurations. A set of semi-analytical methods have also been proposed, which employ the transmission line model for analysis. However, quasi-TEM mode of propagation inherently assumed by them has been questioned. Moreover, the corona current is modeled as shunt source without relating to the mechanism of induction due to corona. The present work aims to investigate the basic mechanism of current induction using an isolated avalanche developing under space charge modulated background field. The corresponding induced currents are quantified and the structure of the electric and magnetic fields is extracted. The basic issue with the long transmission line modelling is amply demonstrated. Even though single avalanche, being the basic process building corona is considered, general inferences can be drawn regarding corona on lines.
