An Algorithm for Locating Faults in Three-Terminal Multisection Nonhomogeneous Transmission Lines Using Synchrophasor Measurements

This paper presents a fault location algorithm for three-terminal multisection nonhomogeneous transmission lines using synchronized phasor measurements (synchrophasors) obtained from GPS based PMUs or digital relays with embedded PMUs or off-line data synchronization algorithms. The algorithm is extended from a two-terminal fault location technique to an algorithm for three-terminal multisection nonhomogeneous lines which combine overhead lines with underground power cables. An exclusively three-terminal faulty branch indicator/fault locator for nonhomogeneous lines is proposed, which can not only distinguish an external/internal fault but is able to locate a fault on an overhead line or an underground cable as well. The algorithm provides an exact solution for fault location estimation and excludes computational costs since neither fault type selections nor iterative operations are required. An extensive series of simulations and field evaluations have been conducted to show the effectiveness of the method. The proposed algorithm has already been implemented in Taiwan 161 kV transmission system. So far the technique yields excellent accuracy and robustness compared to existing fault location functions of digital relays in Taiwan.