Investigation of Arc Trajectory Characteristics of Composite Insulators Based on Multifield Coupling Analysis

This paper proposes an arc propagation model based on electric and thermal field coupling to investigate the arc propagation mechanism around composite insulators. The charge simulation method reduces the computational complexity of the electric field calculation and simulates the leakage current density and charge motion during the arc propagation. The finite difference time domain method describes the continuous variation in the thermal field generated by the leakage current density and the arc close to the insulator. Different types of heat transfer are analyzed to evaluate the arc injection and dissipation energies. The stochastic arc trajectory property is modeled by the Markov process based on electric and thermal field coupling instead of the conventional deterministic flashover model. The modified model simulates three typical arc trajectories from ignition to extinction to analyze the mutual effects of arc trajectory and arc energy. The results show that the arc trajectories that travel away from the insulator and along the leakage distance are more likely to be extinguished during propagation than the arc trajectory bridging most sheds. The consecutively rising leakage current and relatively low energy dissipation during the arc propagation process are two dominant factors that cause flashover. The model explains the mechanism of the phenomena in which the probability of arc jumping between sheds increases when the insulator surface pollution level becomes severe, which leads to a decrease in the average flashover voltage.