Analysis of the Thermal Expansion Effect on Measurement Precision of Rogowski Coils

Rogowski coils are increasingly used to measure AC current or transient current in power industry. Thermal expansion can change the cross-sectional area of the coils when the ambient temperature varies. In order to evaluate the thermal expansion effect on Rogowski coils, two factors are proposed, which can be described as the ratio error of induced voltage per unit rise in temperature of the coils winding and the coils former respectively. Each of them has been verified as a function of the thermal expansion coefficient of the employed material. Mathematical models are theoretically developed for calculating the ratio voltage error caused by thermal expansion effect. The primary experimental results show that the ratio voltage error tendency with temperature is the same as the error tendency from theoretical analysis; the summation of two kinds of ratio errors predicted by the novel factors is included within errors from measurement. It is instructive in designing the high precision Rogowski coils