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Instrument Transformers for Power Quality Measurements: a Review of Literature and Standards

Measurements of Power Quality (PQ) are gaining more importance due to increasing presence of switching power converters that deform the waveform of the distributed voltage further and further away from a sine wave. Especially at medium and high voltage levels, PQ measurements are carried out by means of Instrument Transformers (ITs). A recently started European metrology project, EMPIR 19NRM05 IT4PQ, aims at establishing the methods and procedures for assessing the accuracy of ITs used for PQ measurements. This paper, that is written in the framework of the IT4PQ project, presents a thorough review of the current state-of-the-art of literature and international standards about ITs and PQ. The main results from several papers and the main information from IT and PQ related international standards are summarized.