Influence of ground wire protection angle on upward leader from 110–1000 kV AC lines

The problem of upward leader inception from transmission lines in lightning shielding failure is still not well understood, essentially because the upward leader emerging from transmission lines is difficult to be captured under natural circumstances. Previous studies have mainly focused on reduced-scale experiments or single-phase test lines. In this context, a real-size experimental system aimed at studying upward leader characteristics on both phase conductor and ground wire is designed, where an ac voltage and an impulse voltage are respectively applied on the phase conductor and the plate-rod electrode simultaneously. Various experiments targeting 110 kV, 220 kV, 500 kV and 1000 kV ac transmission lines based on long air gap discharge between the plate-rod electrode and phase conductor or ground line, were carried out to study the influence of change of ground wire protection angle on phase conductor regarding upward leader characteristics.