Incipient fault location method for distribution networks with underground shielded cables: A system identification approach

Incipient faults in underground shielded cables can affect greatly distribution system reliability. These faults are usually a consequence of a gradual aging process on cable isolation material and over time become permanent faults. This paper presents an incipient fault location method for distribution networks with underground shielded cables. The fault location method is composed by a time domain system model and a parameter estimation approach. The model is derived by using phase component representation of voltage and current signals, considering 1-terminal measurements and realistic hypotheses. Inherent characteristics of underground distribution networks with shielded cables and incipient faults, as unbalanced operation, complete line model, and arcing phenomena are considered during the problem statement. The time-domain model is an overdetermined system of linear equations. Incipient fault location is estimated through a parameter estimation approach, based on a non-negative weighted least square estimator. Input data are preprocessed with smooth and curve-fitting approaches. Output data are postprocessing using a back substitution approach. Validation using real-life distribution network with underground shielded cables data is presented. Comparative test results with the state of art characterize the proposed approach precision and robustness. High accuracy, easy to implement methodology without hard-to-design parameters, and only local terminal measurements consideration highlight potential aspects for real-life applications.