In this appendix, formulae are derived for the electric stress and capacitance of two commonly occurring electrode configurations in transformers, viz. a configuration of two round electrodes and a round electrode-plane configuration.
D.1 Stress Calculations
The distribution of the electric field intensity and potential field between two parallel cylindrical electrodes can be determined by considering equivalent line charges. Consider two line charges + ρL and −ρL (charges per unit length) placed at x = +m and x = −m respectively as shown in Figure D.1. Now, due to single line charge ρL, the electric field intensity at a distance r is given by
where ε is permittivity of medium. ...