Surge impedance modeling of high power transmission towers and electrical grounding

Abstract

Several transmission line sections, composed of towers with 120 up to 350 meter high, are proposed to overcome natural barriers and technical issues in a few countries in Asia and also in the link from the Northern Brazil to the Interconnected National System (SIN). The geometrical characteristics and environment which these towers are immerse have a direct influence in the electrical performance of these systems, taken into account that these characteristics are intrinsically related to the electrical parameters of this stretches, in steady state as well as in transient state. In a first approach, the principal electrical variations are evaluated between the tall line sections and a conventional line configuration, with approximated 40 meters height. The electrical parameters and propagation characteristics of the two line sections will be compared and properly analyzed. In a second stage, the conventional tower models applied for analysis of fast and impulsive transients (atmospheric impulses), will be evaluated for simulation of electromagnetic transients on tall line sections. An evaluation of the surge impedance and possible overvoltages is proposed as a function of the tower height and available modeling techniques. The same modeling techniques developed for power transmission towers can be applied for modeling of grounding grids and electrodes of tower and various electrical systems or even buildings. (AU)