An Edge-Intelligent, Clip-on Rogowski Current Sensor With Wide Dynamic Range

Rogowski coil current sensors are popular solutions for current sensing having several advantages over current transformers (CTs), including size, bandwidth and dynamic range. These sensors have been used by electric utilities for gaining visibility into the electric grid directly helping in grid operations. This paper presents an overview of the design principles and test results for a PCB-based Rogowski coil that can be retrofitted around any existing conductor, resulting in a sensor that can be rapidly installed in the field. Due to the absence of any magnetic components in the coil, Rogowski coils cannot saturate and thus have a very high dynamic range, only limited by the accompanying signal conditioning or data converter circuits. In order to prevent saturation of the signal conditioning stage at higher current levels, a method to auto-tune the sensor has been presented, resulting in a dynamic range that is orders of magnitude higher than state of the art. The method, called dynamic range correction (DRC), uses edge intelligence to detect fault current scenarios and adjust the analog circuit to prevent saturation or distortion, while capturing the fault current waveforms. This feature enables post-event diagnostics for electric utilities at a very low cost.