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.

I. Introduction

The decarbonisation of energy systems has been a political decision taken in the recent years by all most industrialized countries in the world. European Commission's energy and climate policy, such as the SET-Plan, foresees that the context of the future scenarios for electric power networks will be that of ensuring a stable and secure power supply as Renewable Energy Sources (RES) penetration increases up to 100%.