Abstract :
The paper first deals with the data and formulae necessary for evaluating the self and mutual surge-impedance values of a 3-conductor overhead system equipped with a single earth wire. It then indicates how these impedances may be used for obtaining, by an original method, the theoretical attenuation and distortion, below corona, of standard unidirectional surges. Good agreement is shown to exist between theory and experiment. Above corona, loss factors for the short surges employed are deduced from experimental results, and formulae are given to enable the corresponding factors for any single-circuit line conductor to be found. Formulae for determining the visual critical corona voltages of one, two or all three conductors of a system are also given, in terms of the relevant surge-impedance values. Finally, several values for a typical line are included.
