Improvements for current measurements with rogowski coil and development of calibration system for non-conventional sensors

Rogowski coils (RCs) known as non-conventional current sensors are widely used for measuring the magnitude of AC currents and well suited for high voltage applications. Nevertheless, the weak points of RC are the adverse effects produced by external varying magnetic fields and the sensitivity to the primary conductor positions. In order to reduce these effects, the magnetic shielding is applied to the RCs. Currently, in literature, magnetic circuit solutions for magnetic shielding effectiveness which is the critical parameter of magnetic shield assume a rectangular shell structure of shielding under vertical external magnetic fields, leading to inaccuracies in parametric analysis. Therefore, in the first part of the dissertation, improved magnetic circuit models are proposed by taking the hollow cylindrical and the toroidal structures of the shielding into consideration to investigate magnetic shielding effectiveness in RCs. The proposed models are verified by simulation studies based on the finite element method for a wide range of design parameters. It is shown that magnetic shielding effectiveness of magnetic circuit models for the hollow cylindrical and the hollow toroidal structures have no more than a 27 percent error when the shielding thicknesses and the shielding distances from non-magnetic former are varied from 5 mm to 30 mm. Moreover, the models are validated for the changes in air gaps, permeability of shielding materials, and the major radius of the non-magnetic former. In the second part of the dissertation, a magnetically shielded RC has been designed and implemented. And then, for the calibration of the RC with traditional measurement bridges, unique measuring systems are developed by adapting RC's output level to traditional levels with transducers. In addition, the novel measurement setup is developed for calibrating the analogue non-conventional input of commercially available measuring bridge with the uncertainty of 10 µA/A and 10 μrad. The magnetically shielded RC is tested and its immunity to the primary conductor position, and pick-up from nearby current conductors is found to be less than 10 µA/A.