The different stages of PRPD pattern for negative point to plane corona driven by a DC voltage containing a ripple

This paper presents the different patterns, which can be observed by means of a phase resolved partial discharge analysis, when a negative dc voltage is applied to a point to plane arrangement in air. The required phase relation is obtained due to the ripple being present on the dc voltage generated by a half-wave rectification. Phase resolved partial discharge patterns are given from corona onset to glow inception. Discharge pulses appearing at the test object are used to support physical explanations of the pattern occurrence. It is shown that five clearly identifiable patterns accompany the evolution of corona discharges when a dc voltage with a ripple is used. The uniqueness of the different patterns and the accompanied reduction in test effort for dc partial discharges is emphasized.