The measurement of Power Quality (PQ), typically performed at Low Voltage (LV), is increasingly gaining importance also at Medium Voltage (MV) due to the growing presence of switching power converters (both loads and generators) directly connected to MV networks. In this scenario, the use of Voltage Transformers (VT) is inevitable to reduce the voltage to levels suitable for PQ instruments’ input ranges. However, the current lack of an international standard for VT used in PQ measurements leaves manufacturers and users in a situation of complete uncertainty, as different products may have performance specifications tested and declared in completely different ways.

This work aims to define an integrated approach for assessing the accuracy of VT used in PQ measurements, focusing on harmonics and interharmonics. The study provides experimental results from tests conducted on an MV inductive VT following the proposed procedure. Consequently, it is demonstrated that the accuracy of VT in measuring a specific phenomenon should be evaluated with complex waveforms that include the simultaneous presence of different PQ phenomena.