Triple Point Surface Discharge Photography in Atmospheric Gases Using Intensified High-Speed Camera System

Abstract

In this article, investigations of surface discharges using an ultraviolet (UV) intensified high-speed camera system are presented, accompanied by high-frequency response and resolution current recordings. A needle-plane electrode configuration is employed for the generation of a strongly nonuniform electric field on the surface of disk-shaped insulator samples made of polytetrafluoroethylene (PTFE) or epoxy resin. The electrode arrangement is further insulated by a gaseous medium of either technical air (21% O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /79% N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), nitrogen (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ), or carbon dioxide (CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). An alternating (ac) voltage waveform at power frequency (50 Hz) is maintained at levels sufficiently below the flashover voltage corresponding to each presented case. Detailed descriptions of the technical specifications of the utilized equipment are provided for both optical and electrical measurements in the experimental setup. The obtained results demonstrate the discharge propagation during the ac-cycle and its dependence on the insulator type and gaseous insulating medium. Individual surface discharges are captured in the microsecond range to describe the discharge morphology based on the generated current pulse and instantaneous applied voltage level. Back-discharges on the insulating disk are also discussed, and relevant image capture is presented.