Study of the impact of longitudinal variations in ambient conditions on transmission line voltage stability margin

Electric power transmission lines span through wide geographical areas, experiencing different ambient conditions. Varying weather conditions along the length of the line introduce changing conductor temperatures and hence non-uniform distribution of line electrical parameters along its length. This non-uniform distribution of electrical parameters is expected to impact line power handling capabilities. In order to investigate the impact of longitudinal variations in weather conditions on line voltage stability margins, a line model segmentation approach is used in this work. This line modeling approach, which accounts for non-uniformities in line parameters, divides the line model into multiple lumped parameter segments based on the degree of change in weather conditions. The multi-segment line model and a simple weighted average approach, in which a single segment with parameters calculated at the weighted average conductor temperature along the line is employed, are used in this paper to study the impact on line voltage stability margin. Simulation results are compared with the static line rating approach, in which a set of predefined weather conditions is used for line modeling. Noticeable differences were found in line voltage stability margins when longitudinal changes in ambient conditions were taken into account.