Transformer Engineering, 2nd Edition

Appendix D: Stress and Capacitance Formulae

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 + ρ_L and −ρ_L (charges per unit length) placed at x = +m and x = −m respectively as shown in Figure D.1. Now, due to single line charge ρ_L, the electric field intensity at a distance r is given by

$E=\frac{{\rho }_L}{2\pi \epsilon r}$

(D.1)

where ε is permittivity of medium. ...