Incipient fault monitoring of medium voltage UD-EPR power cable using Rogowski coil

The cable dielectric break down or the cable splices flaw usually result in high arc voltages and cable incipient faults. These types of faults are repetitious and can lead to permanent cable fault if they are not rapidly removed. Since the incipient faults occur in a very short period of time (often less than a cycle), they cannot be detected by means of the protective relays. During an incipient fault a high frequency current pulse is produced. This paper uses Rogowski coil sensor to capture these fast current transients and to detect the fault. The captured signals can be used in SCADA system for monitoring and controlling of the feeder conditions. Besides, the Rogowski coils can be exactly calibrated for metering applications as well. The designed Rogowski coil is very simple and cheap. It is air-cored and there is no concern with the core saturation which may occur in CTs when measuring high-frequency currents caused by the incipient faults. Performance of the proposed technique is tested and validated in the laboratory using the Underground-Duct Ethylene-Propylene Rubber Insulation (UD-EPR) cable. A fault event is imposed to the cable and the results are recorded. The experimental results show that the proposed fault monitoring technique can effectively detect the incipient faults.