Evaluation of Downburst Impact in the Electric Reliability of Transmission Line Spans Through Numerical Analysis

This work investigates the effects of downburst loading on multi-span transmission line conductor systems through two complementary computational approaches. The first is a semianalytical method based on the formulation developed by Aboshosha and El Damatty, which solves nonlinear equilibrium equations at each conductor-insulator connection point using

Newton-Raphson iteration. This technique explicitly considers conductor geometric nonlinearity while treating insulator chains as rigid pendulums, achieving computational times significantly lower than conventional finite element analyses—approximately 185 times faster according to validation studies. The second approach employs a decoupled numerical framework combining Computational

Fluid Dynamics (CFD) and Finite Element Analysis (FEA). A two-dimensional axisymmetric

CFD model simulates the transient downburst wind field using a cooling source methodology, which provides a physically realistic representation of the thermodynamic processes governing downburst formation. The resulting velocity and pressure distributions are then mapped onto a three-dimensional structural model that accounts for large displacements, geometric nonlinearities, and interaction across adjacent spans.

Comparative analyses are performed for a representative 9-span transmission line section with 400 m spans, subjected to downburst loading at various distances from the line corridor. Results demonstrate good agreement between methodologies for intermediate distances (750–1500 m), while discrepancies at extreme positions reveal the applicability limits of the semi-analytical method and are explained through the underlying wind field physics. The investigation identifies simultaneous longitudinal forces across all conductor phases that exceed conventional design assumptions, and demonstrates that phase-to-phase clearance violations can occur at wind intensities below structural failure thresholds — compromising electrical reliability independently of structural integrity. These findings offer valuable insights for transmission line design practices and contribute to improved understanding of conductor behavior under extreme localized wind events.