Partial discharges induced by small floating potential metallic elements

Abstract

Partial discharge (PD) measurements are commonly employed in non-destructive testing of dielectrics and systems. Often voids, interface adhesion problems, or electrode surface irregularities can be detected. Another type of defect is the small metallic element which is not connected to an electrode but can also cause partial discharge. The partial discharges from such elements at floating potential are associated with the local field intensifications which they cause. The geometry of a metallic element, its orientation with respect to the applied fields, and the net charge accumulated by the element have been found to influence both the inception and steady-state partial discharges. A model for PD behavior based on charge transport to and from the element is developed to describe the voltage and time dependence. The results are compared to time-synchronized pulse height-analyzed measurements.