Mitigating dynamic insulation breakdown in iced overhead ground lines: A differentiated dielectric shielding method with sequential electro-mechanical coupling analysis

Abstract

In regions prone to severe icing, the nonlinear spatial galloping of overhead transmission lines can induce dynamic instability in conductor-to-ground wire clearances, leading to transient insulation breakdown. To address this dynamic dielectric failure mechanism, this paper proposes a novel differentiated insulation protection strategy that, for the first time, integrates explicit dynamic clearance analysis with electrostatic field computation to establish a spatial risk-zoning framework for overhead ground wires. Initially, a detailed explicit dynamic model of a 110 kV tower-line coupled system is constructed to elucidate the spatial risk evolution of ice-shedding induced transient responses; the resulting time-varying clearances are then subsequently fed into a dynamic gas–solid composite dielectric electric field model that is established to clarify the electric field distortion and ionization mechanism, where local field strength surges to 3.9 kV/mm (exceeding the air breakdown threshold) under critical micro-gap conditions. It is demonstrated that a 4–6 mm silicone rubber coating effectively suppresses the electric field to a safe margin through dielectric shielding by reconfiguring the interfacial capacitance distribution. Based on these findings, an adaptive gradient coating scheme is devised, assigning 6 mm full-arc, 5 mm semi-arc, and 4 mm partial coatings to high, medium, and low-risk sections, respectively, thereby optimizing both insulation resilience and material efficiency. Full-scale power frequency withstand voltage tests conclusively validate this mechanism, showing a substantial 47.26% increase in breakdown voltage under the extreme 1.9 m critical condition. This research provides a rigorous theoretical framework and an engineering paradigm rooted in sequential electro-mechanical coupling for proactive defense against transient electrical faults in power grids.