Multiphysical Field Simulation and Experimental Verification of Initial Stage of Tree-Contact Arc Grounding Fault in Distribution Networks

Due to tree growth and wind-induced disturbances, tree-contact arc grounding faults (TAGFs) occur frequently in distribution networks. In the initial stage of the fault, the fault signal is weak and can frequently be undetected by protective devices. Therefore, a multiphysics simulation model coupling arc plasma behavior with distribution system response is developed based on magnetohydrodynamic (MHD) theory. The influences of tree species, moisture content, and branch swing velocity on arc temperature, morphology, and fault current amplitude are analyzed. A time-domain energy balance analysis is conducted to reveal the mechanisms underlying current zero-crossing behavior. Experimental results validate the model's ability to accurately reproduce key TAGF features, including high fault impedance, arc temperature fluctuations, and neutral-point voltage oscillations. The findings provide a physically interpretable foundation for early detection and suppression of TAGFs in ungrounded distribution systems.