Pantograph-rigid catenary (PC) systems are used for transferring electric energy to locomotives via a sliding contact between the contact wire and the pantograph slide. Contact surface ablation caused by frequent offline arcs significantly affects the service life of the PC system. While previous studies mainly focus on PC arcs at static separation distances, this paper discusses the ablation characteristics of the contact wire caused by transient arcing during a single complete dynamic separation process of the PC system. First, the multi-physics theory of PC arcs is introduced, and a corresponding magnetohydrodynamic model is established to accurately simulate the arc occurrence, development, and extinction. Next, by accounting for heat loss due to material evaporation, an ablation model for transient arcing effects on the contact wire is developed, and the model is verified using experimental data from a metro line. Finally, by introducing different dynamic separation behaviors, the ablation characteristics of the contact wire under various factors are revealed. The results indicate that the ablation of the contact wire due to transient arcing is directly proportional to the current and inversely proportional to the crosswind velocity. Furthermore, the ablation is more severe during the re-contact process of the PC system than during its separation process.