Unsynchronized Parameter-Free Fault Location for Two or Three Terminal Double-Circuit Transmission Lines Sharing the Same Tower via Unscented Kalman Filter

This paper proposes a novel phasor domain fault location method for two or three terminal double-circuit transmission lines sharing the same tower without requiring line parameters. First, the models of the two and three terminal double-circuit lines with faults are derived. The line models fully consider the mutual coupling between the two line circuits, distributed line parameters, asymmetry of line structures, and extensive fault types. Through the modeling procedure, the fault location, line parameters, unsynchronized phase angle, fault resistance and other internal states of the line are introduced as unknown variables, resulting in a highly nonlinear problem. Afterwards, the line model is solved via the state estimation algorithm. Compared to the existing least square type algorithms such as Gauss-Newton and Levenberg Marquardt methods, the proposed Unscented Kalman Filter based algorithm greatly improves the convergence region. Compared to the existing parameter-free fault location method on double-circuit transmission lines, the proposed method more accurately presents the physical laws of the line and is compatible with common or split bus configurations. The proposed method is verified via numerous simulation experiments, proving that it can accurately locate faults for different fault resistances, locations and types. The method is also validated via field data experiments.