A Method for Medium Voltage Underground Cables Incipient Faults Diagnosis and Location Using Sheath Current

In order to solve the problem that the condition sensing and fault warning methods of medium voltage power cables need to be carried out by power outage or the cost of installation and operation and maintenance is high, this paper presents a new scheme to detect and locate the fault line segment after the incipient fault occurs based on the cable sheath grounding current. The dynamic simulation model of incipient fault of medium voltage cable is established, and the characteristics of disturbance waveform and cable sheath grounding current fault are analyzed. According to the direction and amplitude characteristics of the cable sheath grounding current when the incipient fault occurs, the section location of the incipient fault cable is realized. A new criterion combining the fixed threshold value with the whole area feeder is proposed, which will help to determine the incipient fault feeder segment.