Structural performance and full-scale test of V-string tangent tower with wing-shaped cross-arm

Abstract

The conventional triangular cross-arm configuration for V-string insulators in transmission systems, while it is necessary to satisfy stringent electrical clearance requirements, results in excessively large tower heads. This geometric necessity elevates wind loads on both conductors and tower structures, consequently increasing risks of wind-induced insulator string dropouts that degrade overall system reliability. To address these limitations, this study proposes an innovative wing-shaped cross-arm design. Using a 500 kV double-circuit V-string tangent tower as a case study, two structurally distinct tower head configurations (triangular vs wing-shaped cross-arms) were engineered with identical electrical clearances to enable a comparative structural performance analysis. Key design parameters, including cross-arm layer spacing, cross-arm height, line spacing, string length, tower weight, and foundation forces, were systematically compared. The results demonstrated that the wing-shaped cross-arm scheme achieved significant reductions in all the aforementioned design parameters compared to the conventional triangular design. Subsequently, a full-scale test was conducted on a 500 kV double-circuit V-string tangent tower featuring a wing-shaped cross-arm. Seven critical load cases, including those caused by broken wires, installation loads, and strong winds, were evaluated. The study further analyzed the discrepancies between the experimental results and the FEM analysis of the tower’s displacement and member internal forces, along with the underlying causes of these differences. Despite these differences, the experimental results demonstrated that the overall displacement and internal force behavior was well-captured by the FEM model. This indicates that the computational model for the wing-shaped cross-arm, utilizing bar elements, provides a reasonably accurate representation of the structural response under the actual loading cases. Notably, a tower with a wing-shaped cross-arm demonstrated outstanding structural performance, offering significant economic benefits.