Design of 3D Rogowski Coil Using Distributed Model for High Current Steep Front Pulsed Signal Measurement and Finite Element Method-Based Investigation with Experimental Validation
Rogowski coil (RC) is a current transducer that can be used in electric power applications to measure transient. To ensure highly accurate measurements, it is imperative to study and analyze all factors influencing the construction of coils. The accuracy for current measurement using RC is subjected to its physical, geometrical, and electrical properties. The core of RC is normally made of magnetic material, but in order to avoid magnetic saturation, nonmagnetic material is used for the core. The position of primary conductor has great influence on the flux distribution around the coil. There are many researchers critically investigated and analyzed acute parameters influencing mutual inductance based on position between the RC and primary conductor. For some cases (non-self-integrative systems) it is necessary to integrate the output voltage of the coil so that a voltage proportional to the measured current can be obtained. One of the problems associated with RC is difficulty in performing accurate modelling because of the complex and diverse structure of the coils and at high frequencies, difficulty in resisting interference with RCs. So, this proposal concern about the distributed model approach based on finite element simulation. Effective design of measurement systems using RC primarily needs electrical equivalent circuits modeling including additional components such as damping, integration, display and calibration. Hence, this proposal extensively deliberates the modeling of the 3-D structure of the RC in Ansys Maxwell. A similar circuit model is developed by using MATLAB Simulink and the development of an RC hardware prototype in the laboratory. For theoretically finding the electrical parameters (self-resistance, self-inductance, mutual inductance, inter turn capacitance, capacitance associated with the return wire) of the coil, a distributed model is to be considered. The RCs are distinguished by their bandwidth and amplitude capabilities, which span from low frequency (tens of Hz) to ultra-high frequency (hundreds of GHz). Frequency content in signals can be assessed directly for sinusoidal waves or through Fourier transform analysis for non-sinusoidal signals. So, the frequency response of RC needs to be analyzed using Fourier transform to find the operating bandwidth of the proposed model. Testing of RC performance is conducted through by applying steep front pulsed current signal as an input to primary conductor. This proposal extensively explores the impact of terminal resistance on the RC's output characteristics, highlighting its critical role in determining the coil's sensitivity and accuracy in measuring pulsed current signals. Also, consistency in coil sensitivity is to be observed across different methods such as simulation, finite element method and experimental method. The proposed PC model helps to detect partial discharge currents, lightning currents and handle high-speed spikes.