Evaluation of phase-to-phase clearances of transmission line conductors under turbulent wind
Parent, Louis-Philippe; Langlois, Sébastien; Sad Saoud, Kahina
Abstract: "Wind loads govern the design of a large number of overhead transmission lines worldwide. The spatial and temporal variation of wind speed and the buffeting response of cables may induce swings not fully synchronized between two parallel cables, thus raising serious concerns regarding phase-to-phase clearances. Accurate assessment of the minimum mid-span clearances to be considered in the design of transmission lines is essential to avoid repetitive flashover episodes and hence ensure the reliability of the electrical system. In practice, a wide range of empirical formulae is proposed to evaluate the critical phase-to-phase clearance distances for various transmission line configurations. For instance, the European standard CENELEC EN-50341  provides a simple equation for the minimum horizontal spacing in the case of standard line heights not exceeding 60 m . However, such formulae do not consider all the geometric and wind parameters affecting the phase-to-phase clearances, which is of key importance for efficient and economic design. This paper seeks at studying the most influential parameters affecting the phase-to-phase clearances in extreme wind events. A time-history numerical model is specifically developed using the finite element open software Code_Aster, where the behavior of both the conductors and insulator strings is represented using one-dimensional elements accounting for large displacements. The applied turbulent wind signals are also generated numerically, as functions of time and space coordinates. A two-span transmission line section including two phase conductors is considered herein to carry out a parametric study for various geometric and wind conditions. The results reveal that an empirical formula, considering only the conductor sag and insulator length, often yields misleading results [...]."
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