Characterization of Three-Phase Calibrator for Traceable Measurement of Voltage Unbalance

The approach to establishing the metrological traceability of the results of measuring the zero sequence ratio in the conditions of unbalance of the three-phase power supply network is proposed. The standardized definition of this parameter of power quality for the simplification of cumbersome mathematical expressions of processing the obtained results is considered. In characterizing the three-phase calibrator of the voltage and current, the measurement uncertainty in reproducing the voltage unbalance was evaluated, which allows using this instrument for calibrating the power quality analyzers. To reproduce the accurate value of the zero sequence ratio, the three-phase calibrator was characterized by a precision alternating voltage meter (digital multimeter). The procedure for calibrating the measure of power quality parameters for the reproducible zero sequence ratio is briefly described, the measurement results at typical points are presented. The research results also include the derived analytical expressions that allowed evaluating the uncertainty of measuring the characteristics of the voltage unbalance using the universal software.