Algorithms and field experiences for estimating transmission line parameters based on fault record data

The impedance parameters of overhead transmission lines are fundamental input data for various power system studies. The data are traditionally calculated based on the structure information of a line. This study proposes a method for estimating the parameters using fault records captured by digital relays. The fault records are the unsynchronised voltage and current waveforms recorded at both ends of a line. One of the main contributions of this work is the use of the wave propagation speed equation to simplify the problem and to improve the estimation accuracy. As a result, both the positive and zero sequence parameters can be estimated using simple algorithms in a decoupled solution process. Simulation results show that the proposed approach has good accuracy. Finally, the method was applied to estimate the impedance data of several actual transmission lines based on the fault record data provided by a utility company.