THE THEORY AND MEASUREMENT OF PARTIAL DISCHARGE TRANSIENTS

A theoretical approach to partial discharge transients is presented. This approach is based on the relationship between the charge induced on the measurement electrode by those created in the inter-electrode volume during partial discharge activity. The starting point of the analysis is the formulation of the measured-transient/induced-charge relationship. Thereafter the general relationship between the induced and the inducing charge is derived. This latter relationship is discussed with respect to both the D --> field and the P --> field. The D-field --> approach is the more relevant from a practical point of view, but the P-field --> approach provides a greater insight into the molecular physics of the phenomenon. An exposition of the currents related to these transient phenomena is then undertaken. The theory of void partial discharge transients based on the D-field --> approach is thereafter reviewed and extended. This theory has allowed the influence of all relevant void parameters to be quantitatively assessed. A general derivation of the measured transients associated with the time dependence of the induced charge is presented, and the application to multiple electrode systems of practical interest is illustrated. A discussion of the salient features and practical aspects of the theory concludes the work.