Comparison of voltage transformer measuring systems at 110 kV and 10 kV

A comparison of measurements of voltage transformer (VT) voltage ratio and phase displacement was performed between the National Center for High Voltage Measurement (NCHVM), China and the National Measurement Institute (NMI), Australia, with two voltage transformers provided by the NCHVM being used as the travelling standards. Voltage ratios of the 10 kV/100 V transformer measured by the two institutes differed by less than 5 μV/V and the phase displacement by less than 6 μrad, while voltage ratios of the (110/√3 kV)/100 V transformer differed by less than 16 μV/V and 13 μrad. These results confirmed that measurement results of the two institutes agreed within detailed measurement uncertainties evaluation. The comparison further enhances the confidence in both methods, which are widely used for calibration of voltage transformers in the electricity industry.