Designing and tuning an air-cored current transformer for partial discharges pulses measurements

A Rogowski coil can be done self-integrating becoming an air-cored current transformer. The constrains and the design of such a device has been published in previous works. The current transformer can be tuned to measure partial discharges without the need of an external integrator. The aim of this paper is to define a geometry adapted to measure signals in the frequency band where partial discharges have energy. All the electrical parameters such as the inductance, mutual inductance, resistance and capacitance of the coil are written in function of the geometry. Changing the length of the coil, the internal and external diameters and the number of turns will give different bandwidths and sensitivities; amongst them, the most appropriate to our usage is chosen. The coil has been effectively made and the study is complemented with the calculation of electrical parameters by a computerized finite element method and the measurement of the transfer function with a gain-phase analyzer.