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/p3 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.

Capacitive leakage and adjacent interference are the main influence sources of the measuring error in the traditional series step-up method. To solve the two problems, a new algorithm was proposed in this study based on a three-ports network. Considering the two influences, it has been proved that response of this three-ports network still has characteristics of linear superposition with this new algorithm. In this threeport network, the auxiliary series voltage transformers use a two-stage structure that can further decrease measurement uncertainty. The measurement uncertainty of this proposed method at 500/√3 kV is 6.8 ppm for ratio error and 7 μrad for phase displacement ( k = 2). This new method has also been verified by comparing its results with measurement results of the PTB in Germany over the same 110/√3 kV standard voltage transformer. According to test results, the error between the two methods was less than 2.7 ppm for ratio error and 2.9 μrad for phase displacement.

The equivalent circuit of traditional capacitive voltage transformers often faces the problem of complex data calculation and difficulty in grasping the internal nonlinear characteristics of transformers when constructing broadband models, resulting in poor power accuracy and stability. Therefore, with the help of electromagnetic transient physical models, the admittance sub model and nonlinear model are established by considering the frequency and saturation characteristics of the transformer. Based on the characteristics of capacitive voltage transformers, the model is processed in parallel to obtain a broadband coupling transformer model. The results showed that the error between the simulated current peak amplitude and voltage results of the model and the measured values was less than 2% and 1%, respectively. In the fault results, the harmonic error of the load voltage of the improved transformer was relatively small, far less than the error result of 2.73% of the traditional transformer. The proposed transformer model can better characterize its characteristics and has good transient response ability, providing reference tools and value for the operation and state detection of power systems.