Low power voltage transformer accuracy class effects on the residual voltage measurement

The paper addresses one of the new and most important issues arising when Low Power Voltage Transformers (LPVT) are used in power network substations for evaluating, among others, also the residual voltage. Conversely to open-triangle inductive instrument transformers, the use of phase voltage transformers for measuring the residual voltage gets challenging due to the very high accuracy required for the three LPVTs. In the paper, an analytical study will be presented along with simulation results in order to show the relationship between the accuracy class and the uncertainty affecting the residual voltage value