Dynamic response of overhead transmission lines to ice shedding

Abstract

The main objective of this research was to study dynamic effects of ice shedding on overhead transmission lines using a reliable numerical model.Overhead transmission lines are subjected to various static and dynamic loads. Ice shedding from the conductors is one of the dynamic loads occurring in cold regions. This phenomenon happens when glaze ice formed on the cables suddenly falls under certain temperature and wind conditions. In extreme instances, clashing and breakage of insulator and conductors are potential consequences of these dynamic forces. Maximum vertical cable jumps and drops in unloaded and loaded spans, and axial cable stresses are particular concerns.The main assumptions and limitations of the proposed numerical model are discussed in detail, with appropriate stiffness, mass, damping, and ice-shedding load modelling. A nonlinear finite-element model using a commercial software (ADINA) was used to carry out simulations of 21 different ice-shedding scenarios varying the number of successive spans involved, the amount of ice accreted on the cables, different elevations of the central support, partial and sub-span ice shedding and the configuration and sequence of the shedding in adjacent spans. The analysis of the results focuses on the peak cable tensions generated, the insulator string swings and the maximum transient in-span cable displacements. Some of the results are compared with the design procedures used at Hydro-Quebec, which is based on static analysis