Estimating the Location of Sheath-to-Ground Faults Occurring at Any Distance Away From Joints in Cross-Bonded Cables in Online Condition

Locating sheath-to-ground faults in cross-bonded power cables is challenging, particularly when faults occur away from joint locations. Most existing techniques are limited to joint-based fault assumptions and require measurements from multiple links and grounding boxes, which restricts their practical applicability. This paper proposes an online method for estimating the location of sheath to ground faults at arbitrary positions along cross-bonded cables using only sheath earthing currents measured at grounding boxes. A comprehensive circuit model incorporating the mutual coupling between conductors and sheaths of all phases, including cross-bonding effects, is developed. Based on this model, an analytical expression for SGF location estimation is derived. The proposed method is validated through laboratory experiments, circuit simulations, and field measurements on a 220 kV transmission cable system, demonstrating accurate fault location without the need for link-box current measurements.