Rogowski coils are increasingly designed for measurement of alternating current or transient current in electronic transformers .in power industry, and they are important parts that influence the accuracy of current measurement. Thermal expansion can change dimensions and mutual inductance of a Rogowski coil when the ambient temperature varies, which results in current measurement error of an electronic current transducer. A quantitative analysis of thermal expansion effect on Rogowski coil is important for the design of a high perfomnance electronic current transducer. Based on a definition of a novel factor, ratio error of induced voltage per unit rises in temperature, formulas for calculating the coils factors are derived, which are used for describing the typical Rogowski coils with rectangular cross section, circular cross section and the cross section in racetrack shape respectively. The analysis of the results shows that each of the factors has been described as a function of the thermal expansion coefficient of the employed material. The numerical value of the factor describing coil＇s former is equal to the numerical value of the thermal expansion coefficient of the former material; the numerical value of factor describing coil＇s winding is approximately the double of the thermal expansion coefficient of the winding wire material. By employing the factors above, a mathematical model is introduced for calculating the ratio voltage error caused by thermal expansion effect on the Rogowski coil. The proposed method and resultant data are instructive in design of the Rogowski coil with high measurement precision.
High Voltage Engineering