Particle simulation of streamer discharges on surface of DC transmission line in presence of raindrops

The streamer discharge occurring on the surface of a conductor in rain is one of the critical problems associated with the design of high voltage direct current (HVDC) transmission lines. In this paper, the streamer discharges on the conductor surface in the presence of raindrops at atmospheric pressure are studied by use of two-dimensional particle-in-cell simulations with Monte Carlo collisions included. The influences of the drop angles, volumes, and spatial distributions of raindrops on the development of streamer discharges have been demonstrated. The formation of streamer discharges and the involved electric fields, plasma densities, propagation velocities, and discharge currents are presented. It is found that the discharge intensity decreases significantly with an increasing of the drop angle. The dividing point at the 95° angle is suggested. With an increase of the raindrop volume and the distance of raindrops, strong discharges with the advanced discharge time, faster propagation velocity, larger electric field, and higher plasma density are initiated. Moreover, the electron energy probability functions of different discharges have been studied, which are nonequilibrium and reveal kinetic behavior of the discharges. The simulation results, which are qualitatively in agreement with the previous experimental observations, bring new insight into the discharge dynamics and provide useful references for the protection of HVDC transmission lines in rainy days.