Incipient Fault Location Algorithm for Underground Cables

Cable failure process is gradual and is characterized by a series of single-phase sub-cycle incipient faults with high arc voltage. They often go undetected and eventually result in a permanent fault. The objective of this paper is to develop a robust yet practical incipient fault location algorithm taking into account the fault arc voltage. The algorithm is implemented in the time-domain and utilizes power quality monitor data to estimate the distance to the fault in terms of the line impedance. It can be applied to locate both sub-cycle as well as permanent faults. The proposed algorithm is evaluated and proved out using field data collected from utility distribution circuits. The average absolute error in locating incipient faults for three underground cable failures analyzed in this paper was found to be 7.37%, 4.69% and 3.58%, respectively.