Influence of Intense Vertical Component Electric Field With the Direction Away From Insulation Surface on Streamer Discharge

The surface discharge along the valve-side bushing can directly result in a single-pole or even bipolar shutdown of the UHVDC project, leading to a significant power grid operation accident. The ac-dc combined voltage and intense vertical component electric field exert a significant influence on the design of the external insulation of the valve-side bushing. This article presents measurements of the stable propagation fields, velocities, and luminous intensity of the streamer discharge in a three-electrode device subjected to combined ac-dc voltage and an intense vertical component electric field directed away from the insulation surface. The propagation of the streamer discharge is inhibited by the intense vertical component electric field directed away from the insulation surface, thereby enhancing the stable propagation field and reducing the propagation velocity. The length of the embedded electrode specifically influences the magnitude of the vertical component electric field along the dielectric surface, thereby significantly impacting the progression of streamer discharge. The influence mechanism of the electric field distribution and ionization effect is investigated to explore the characteristics of streamer discharge under intense vertical component electric fields directed away from the insulation surface. The sliding flashover discharge mechanism along the valve-side bushing belonging to the UHVDC converter transformer is elucidated and explicated from the streamer discharge perspective.