Instrument transformers are vital components of the equipment for measuring Power Quality (PQ) in electricity transmission and distribution networks.

While measurement methods and the accuracy of supply quality measurement instruments are well defined, there is a lack of in-depth knowledge of the behavior of instrument transformers in the presence of disturbances.

The article describes the main research themes of a project recently funded under the EMPIR programme. The project is focused on defining the metrological context to allow traceable measurements of Power Quality parameters when instrument transformers are included in the measurement chains. Attention is focused on the development of reference measurement systems and the definition of test procedures for instrument transformers, and on the quantification of the behavior of instrument transformers in the face of realistic Power Quality events.

Furthermore, an extensive characterization of voltage and current transformers will provide the basis for the identification of different accuracy classes for the behavior of instrument transformers in Power Quality measurements.