Correspondence between phase resolved partial discharge patterns and corona discharge modes

Corona discharge under super low frequency (30–300 Hz) voltage is common in high-voltage transmission lines and equipment. The phase resolved partial discharge (PRPD) pattern is the most commonly used tool for power equipment condition-monitoring in the electrical engineering field. The present study centers on the correspondence between PRPD patterns and corona discharge modes under a wide range of applied voltage. Electric and optical emission characteristic measurement methods are applied to obtain PRPD patterns and phase resolved discharge images. The transition of corona discharge types and space charge behavior under different applied voltage are investigated. The electric field generated by negative needle electrode is shown to erase residual positive ions, which leads to an abundance of positive streamer bursts when applied voltage is low. Once the negative glow corona emerges under higher applied voltage, dense positive ions in the cathode sheath suppress the positive streamer bursts. The existence of residual positive ions is crucial for the transition from positive streamer discharge to glow corona discharge. A comprehensive understanding of PRPD patterns may help electrical engineers to assess the threat of partial discharge of the power equipment correctly.