A stable and accurate current-comparator-based quadrature-current reference for power frequencies

A current-comparator technique for obtaining a pure quadrature-current reference for power frequencies is described. The current in a solid dielectric capacitor of relatively high capacitance value or in an electronic inductor is compared, using the current comparator, to the current in a “lossless” gas-dielectric capacitor of relatively low capacitance value. The difference current derived from the output of the detection winding is added, through a feedback circuit, to the current in the solid dielectric capacitor or the electronic inductor resulting in a stable and pure quadrature current. The instability and loss angle of the quadrature current are not more than ±5 ppm and ±5 μrad, respectively. This quadrature current source is used to provide a reference current in an active/reactive power comparator bridge for calibration of active/reactive power meters.