Reference system for current sensor calibrations at power frequency and for wideband frequencies
This paper describes the reference system for current sensor calibrations at power frequency and for wideband frequencies. The reference system is lately used for researches at PTB in the frame of two European projects: “IT4PQ - Measurement methods and test procedures for assessing the accuracy of instrument transformers for power quality measurements” and “WindEFCY - Traceable mechanical and electrical power measurement for efficiency determination of wind turbines”. The relevant standards of IEC61000 were used for the power quality related tests. The proposed calibration system was validated for current sensor calibrations with the expanded uncertainties (k = 2) below 20 μA/A and 10 µrad at 50 Hz up to 5 kA and 0.01 % and 0.04 crad for the frequencies up to 9 kHz. Additionally, a centring unit for the Rogowski coil improved the measurement uncertainty 10-fold.