Using ferrite to improve directional sensing for pulse travelling in MV power cables with two inductive sensors

Inductive sensors are widely used for detection of high frequency signal, e.g. from partial discharge (PD) activity. A single inductive sensor, installed in a ring main unit (RMU) in a medium-voltage (MV) system, is not able to judge the direction of the signal origin. A method to determine its origin with two inductive sensors, proposed in earlier literature, employs a second sensor in the same RMU to determine signal propagation direction. This method can be extended for a recorded pattern, including reflections coming from both directions. This paper discusses a method to discriminate structures in a complete recorded pattern, originating from different sides. The method is tested on a 420m laboratory scale test set-up with two RMUs upon injected pulses. The main difficulty to extract the injected pulse from the recorded pattern, due to resonances caused by the RMU-components, could be relaxed by the use of ferrite material.