A novel sheath fault location method for high voltage power cable

It is important for power cable, especially high voltage single core cable, to have a healthy sheath. Once the cable sheath is faulty, it would accelerate the aging process of cable insulation, and result in failure of the conventional on-line condition monitoring system due to inaccurate insulation measurement. Traditional fault location methods for main insulation of power cable such as the radar method are no longer valid for sheath insulation fault. The bridge method and voltage comparison method are applicable for sheath fault location, but their accuracies are subject to influences of the contact resistance and resistance of test leads. A novel fault location method for power cable sheath fault is presented in this paper. The resistance of outer metal layer of the fault cable between the terminal and the fault position is measured, and then compared to the known unit resistance to calculate distance to fault. Therefore, it is free from the influence of contact resistance and intrinsic resistance of test leads. Case studies show that the proposed method is effective to determine the position of sheath faults of high voltage power cable on-site.