A Full 3-D Model for Positive Long Air-Gap Discharge Simulation

Long air gap discharge is one of the fundamental issues in high voltage engineering. The simulation of long air gap discharge can provide essential data for designing ultra-high voltage transmission and serves as the foundation for lightning protection. This study introduces an enhanced numerical model for simulating long air gap discharge, accounting for time-varying leader charge density and streamer region with direct experimental extraction. The comprehensive three-dimensional (3-D) model integrates novel parameters, including the streamer region angle, direction, and stochastic leader development, surpassing mere empirical descriptions. Additionally, the updated methodology for determining the streamer region makes the model adaptable to symmetric and asymmetric geometric engineering structures. Simplifying assumptions render the model computationally lightweight in full 3-D demand. The model simulated the current, velocity, and leader path of long air gap discharge under various voltages, then compared with experimental results. By incorporating new physical quantities, the model exhibited improved accuracy and precisely predicted current and velocity. Furthermore, the model calculated the breakdown voltage of typical engineering gaps, yielding results closely aligned with experimental data, with an accuracy exceeding 90%.