Effect of Frequency on the Linearity of Double-Layer and Single-Layer Rogowski Coils

Abstract

The Rogowski coils are usually used to measure high frequency currents due to their air core. The higher the turn number, the higher the mutual inductance between Rogowski coil and the primary conductor. Performance of Rogowski coil with a high turn number is very difficult to figure out by simulation software. This paper presents an improved lumped parameter model of Rogowski coils. According to the model, the influence of parasitic turn-turn capacitance, turns self-inductance, turn-turn inductance, turn-shielding capacitance, turns resistor, sample resistor and others on the linearity of Rogowski coil with a high turns number at several different frequency ranges are explored. The model is applicable to both double and single layer coils. Three high-turn-number coils of double and single layer are studied and compared in this paper. The improved lumped parameter model is verified by experiments. Five main influence factors on the linearity of the Rogowski coil at a certain frequency range are studied both theoretically and experimentally. The five influence factors include sampling resistors, turns density, shielding layer, positions of the primary conductor, and turns nonuniformity. The numerical and experimental results analyze the influence of the factors on the linearity of the output voltage of the coils at different frequencies quantitatively and qualitatively. The principle of the improved model can be used for multi-layer coils. The model can be a useful guidance in designing coils with suitable structure for special applications at different frequencies.