Simulation Research On The Effect Of Corona Space Charge On The Lightning Shielding Performance Of HVDC Transmission Lines

Lightning shielding failure is the main reason causing lightning flashover of EHV and UHV DC transmission lines. Large amount of space charge generated by corona discharge of bundle conductors and ground wires under the effect of DC operation voltage and thundercloud background electric field seriously affect the subsequent discharges, such as streamer discharge and leader discharge. As the existing electro-geometric model(EGM) and leader progression model(LPM) both ignore the influence of space charge, it's a must to carry out research on shielding performance of transmission lines taking space charge into consideration in order to optimize the lightning shielding design. This paper focuses on EHV and UHV DC transmission lines, and researches the establishment of lightning shielding performance assessment model considering the effect of space charge in deep.Based on the mechanism of corona discharge and numerical simulation methods of fluid dynamics, coupled with solving Poisson's equation and particle transport equations, a time-domain simulation model aimed at calculating the distribution of corona space charge of DC transmission lines under lightning conditions was proposed. The validity of the model was verified by both measurement results and references simulation results.Using this simulation model, the temporal and spatial distribution of DC transmission lines under both the effect of DC operation voltage and thundercloud background electric field were analyzed and the dynamical corona inception process of bundle conductors and ground wires was revealed. The influence of height from base to the first arm, thundercloud background electric field and wind speed on the distribution of corona space charge were studied.A leader progression model which considers the impact of corona space charge was developed. Based on this model, numerical simulations of lightning shielding performance for typical DC transmission lines were conducted, the differences of upward leader discharge behaviors were compared while considering the space charge or not, the mechanism of space charge on the lightning shielding performance was revealed, the lightning shielding performances of different tower height and protection angle were acquired and finally the better lightning protection measures for EHV and UHV transmission lines were proposed.