To What Extent Can the Current Amplitude Linearity of Rogowski Coils Be Verified?

Calibrations of Rogowski coils at power frequencies are often performed at currents of only tens of amperes even though the coils are used at currents larger by two to three orders of magnitude, or even more. The assumption of an ideal linearity versus current amplitude is true for ideal coils. This paper addresses the question on practical significance as to what extent the current amplitude linearity of real Rogowski coils can be verified at power frequencies. For this task, several different types of Rogowski coils were evaluated using a digital sampling system, with the best calibration uncertainties (k = 2) of 50 μA/A for magnitude and 50 μrad for phase and the estimated linearity better by a factor of two or more.