A Method for Medium Voltage Underground Cables Incipient Fault Detection and Location using Sudden Change of Sheath Current

The medium voltage underground cable incipient fault has the characteristics of small fault current with short duration, which is difficult to identify effectively. The detection and location of incipient faults of medium voltage cables can timely find the local defects of cables, and timely replace the cables that may have permanent faults, so as to avoid the impact of permanent faults on the power grid. However, the sheath current of underground cable is very large when incipient fault occur, because the sheath current is almost zero under normal operating conditions. This paper uses this feature to identify the incipient fault of medium voltage three core cable in the case of small resistance grounding system through the sudden change of the sheath current, and realizes the fault section location of the incipient fault through the peak value of the sheath current. Compared with the traditional methods, the method proposed in this paper has the advantages of no additional cable parameters or conditions, less interference from other disturbances and noise, simple measurement, and no additional measurement equipment. The feasibility of the method is verified by simulation. The cable length and system parameters have little effect on the proposed method.