Objective: With the continuous development of ultrahigh-voltage (UHV) power transmission projects, transmission corridors often traverse mountainous regions that are prone to seasonal icing and deicing. Ice shedding on transmission lines, especially nonuniform ice shedding, can cause severe tension imbalances, large vertical jumps of ground wires, and transient dynamic forces acting on suspension insulator-hardware string systems. These effects pose significant threats to structural integrity, including geometric interference, insulator deflection, and potential mechanical failure. Moreover, conventional static-based design approaches often underestimate these dynamic events, as they neglect transient load amplification and complex system interactions.However, the mechanical modeling of suspension systems under such abrupt loading conditions remains underdeveloped, especially in the context of unbalanced tension resulting from nonuniform ice shedding. Methods: To address this issue, this study develops a detailed finite element model of a two-span UHV transmission line segment using the OpenSeesPy platform. This model simulates a coupled system comprising ground wires, suspension insulators, and hardware components, introducing time-dependent ice-shedding loads to reproduce realistic deicing scenarios. The modeling framework accounts for nonlinear cable behavior, interactions among components, and geometric nonlinearity due to large displacements to capture the full dynamic response. Full-span instantaneous ice shedding on the large-span side, recognized as the most critical and unfavorable scenario due to severe transient excitations, is specifically analyzed. To ensure the accuracy of the results, the model was validated against comparable experimental benchmarks prior to extensive parametric simulations. Results: Through dynamic simulations, this study evaluated the responses of the suspension string system under various initial wire tensions, ice thicknesses, and structural damping ratios. Parametric sensitivity analysis revealed that increasing the initial tension increased the axial stiffness, reduced insulator swing and unbalanced horizontal force, but magnified the vertical jump amplitude of the ground wires. Thicker ice significantly amplified the dynamic responses, including larger insulator deflections and increased unbalanced forces. Although greater damping effectively reduced jump heights, it had a limited influence on the maximum deflection angle and tension imbalance of the insulator during the initial impact phase. In addition, two failure criteria based on experimental benchmarks were established: a maximum allowable unbalanced horizontal force (5.98 kN) and a critical insulator deflection angle (10.58°), beyond which geometric interference occurred between components. The simulation results showed that for certain combinations of low initial tension and high ice thickness, these thresholds were exceeded, indicating high failure risk. Response surfaces were constructed to visualize how different parameter combinations approached or surpassed these limits, providing intuitive references for assessing safety margins. Conclusions: This study highlights that current design standards may underestimate the dynamic effects of ice shedding on suspension systems. The findings emphasize the necessity of integrating mechanical interference checks and parametric robustness assessments into the design process for suspension insulator assemblies in UHV systems. The modeling framework and sensitivity results guide for configuring damping, wire tension, and hardware design to mitigate dynamic risks during extreme weather conditions. Overall, this study provides a comprehensive mechanical analysis and failure risk evaluation of UHV transmission line suspension systems under ice-shedding events, offers validated simulation tools, insights into governing parameters, and practical recommendations to improve the resilience of power transmission infrastructure in cold-climate regions.