Measurement Methods and Procedures for Assessing Accuracy of Instrument Transformers for Power Quality Measurements

Instrument transformers (ITs) are vital components of power quality (PQ) measurement systems in electrical transmission and distribution grids. Whereas measurement methods and accuracy are well defined for PQ measurement instruments, accurate knowledge about IT performance in presence of grid disturbances is missing. Main research themes of a project recently funded within the EMPIR program are described in the paper. The project focuses on the set-up of a metrological framework to enable the traceable measurement of PQ parameters when ITs are included in the measurement chains. Attention is focused on the development of reference measurement systems and the definition of IT test procedures, as well as on the quantification of the performance of ITs under realistic disturbance conditions. Moreover, an extensive characterization of voltage and current ITs will provide the basis for the identification of different sets of limits for the IT accuracy performance in PQ application and the definition of PQ accuracy classes.