On-Line Evaluation of Voltage Transformer Accuracy

The accuracy of voltage and current transformer (VT and CT) is a key factor in electric power metering. Ratio error and phase displacement calibration of VT and CT is traditionally carried out off-line. As a result of the expansion of the power grid and the increasing metering quality requirements from customer side, the off-line metering of VT and CT becomes more and more difficult. In this paper, a VT accuracy on-line evaluation system is developed, which can evaluate the accuracy of VT under on-line operating status. The principle and adopted key techniques in the development of the VT accuracy on-line evaluation system is introduced. Some on-site test results are also presented and analyzed as application demonstration.