Transmission Line Length Estimation based on Electrical Parameters

Abstract

Some grid data sets contain only electrical parameters, but not the individual transmission line lengths. The failure rates of transmission lines are often estimated based on aggregated statistics given in failure rate per unit length of transmission line. These failure rates are key input parameters to power system reliability assessments. When length data are not available, such data need to be estimated to carry out reliability assessments. A simple and practical method is proposed for estimating transmission line lengths from the electrical parameters inductance and capacitance (which normally are available in grid data sets). The validity of the method is corroborated by testing it on a grid data set of the Danish transmission system that contains length information. The average error was 3.7 % for calculating the length of overhead lines and 27.3 % for estimating the length of all transmission lines (overhead, cable and combinations of these). The value of the method is illustrated by applying it in a case study on the reliability assessment of a part of the Norwegian transmission system, where length information was not available.