Based on similarity principles, this study proposes a reduced-scale modeling and testing method to investigate the dynamic responses of twin-bundle conductor lines after ice-shedding. The processes of ice-accretion and subsequent shedding on sub-conductors of bundled conductors were successfully simulated. A reduced-scale experimental platform was established to measure the in-plane, out-of-plane, and torsional motions of conductors after ice-shedding, as well as the time histories of conductor tension and the longitudinal, vertical, and horizontal components of reaction forces at the suspension points. Reduced-scale tests were conducted on a representative twin-bundle conductor line under three conditions: partial ice-shedding and unzipping ice-shedding from a single sub-conductor, and asynchronous ice-shedding between two sub-conductors. The variations in jumping height, lateral swing amplitude, torsion angle, and conductor tension, along with the reaction forces at suspension points over time, were recorded and analyzed.

Variation in ice thickness with altitude results in a non-uniform icing distribution on conductors. This study defines non-uniform icing and ice-shedding conditions and employs an additional element method to numerically simulate the dynamic response of tower-line systems after ice-shedding from conductors with non-uniform icing. Finite element models of typical isolated and multi-span tower-line coupling systems for 500 kV quad-bundle transmission lines are established, and their dynamic responses are analyzed. The variation patterns of characteristic parameters, including load impact factors, maximum reaction forces at connection points, longitudinal unbalanced tension, and de-icing jump height, with respect to line span, elevation difference ratio, and icing thickness are examined under varying structural, icing, and ice-shedding parameters. The strength of towers under extreme conditions is also analyzed. The obtained results provide critical guidance for the design of transmission tower heads in ice-prone regions.

The mechanical behavior of transmission towers and the maximum jump height of conductors following ice-shedding are critical factors in tower head design. In ultra-heavy ice zones, ice thickness on ultra-high voltage direct current (UHV DC) line can reach 60 mm to 80 mm, exceeding the maximum values specified in current transmission line design codes. This study establishes finite element models of UHV DC tower-line systems in ultra-heavy ice zones and numerically simulates their dynamic responses under ice-shedding conditions for varying span lengths. The analysis evaluates tower stresses, longitudinal unbalanced tensions, and maximum conductor jump heights to assess both structural performance and electrical isolation clearances. Results indicate that longitudinal unbalanced tensions surpass estimates from current design codes, and maximum conductor jump heights exceed predictions from existing empirical formulas. To enhance design accuracy, the study proposes revised values for longitudinal unbalanced tensions and modifications to the conductor jump height formula.