Optical Measurement of Partial Discharge Propagation Phenomena including Leader Transition in SF₆ Gas

Abstract

This paper described optical phenomena of propagating partial discharges (PDs) including leader transition from streamer discharge in SF₆ gas under positive and negative standard lightning impulse voltage. The optical measurement was performed using by special optical instruments like a framing camera composing of three ICCD cameras with optical filters to obtain spatial- or time-resolved spectroscopic images, a streak camera for a streak image or streak spectrum with a spectroscope, and a phot-multiplier tube (PMT) for light emission intensity, together with PD current and applied voltage waveform measurement by controlling the gate timing of the framing and streak cameras. As a result, typical optical properties to understand the leader transition based on stem or precursor mechanism were clarified, and optical features to identify the streamer and the leader discharge as well as the precursor that has not yet led to leader transition were found. These new findings could contribute to better understanding of PD mechanism as well as improvement of PD diagnostics of gas-insulated switchgear.