Numerical Modeling of Streamer Propagation in a Nonuniform Electric Field to Assess the Lightning Impulse Flashover Voltage of Polymeric Insulators

Assessing the dielectric withstand strength of every equipment in a power system is crucial for insulation coordination. The flashover voltage (FOV) of polymeric insulators due to a lightning impulse (LI) is computed by modeling the air discharge using air plasma chemistry and the movement of the charged species using the charge transport model. The formation of corona streamers and breakdown (BD) streamers from the anode and cathode under the influence of a nonuniform electric field is analyzed. Charge concentrations are formed due to the accumulation of ions of opposite polarity, and the propagation of BD streamers due to the influence of these space charges (SCs) is illustrated. The final air BD is observed to be a combination of cathode- and anode-directed streamers. The velocity of the streamers decreases as they propagate through the low-field region, and the velocity of the anode-directed streamers is found to be less than that of the cathode-directed streamers. The computed FOVs are in agreement with the experimentally determined FOVs.