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Commercial LMS are widely used by High Voltage (HV) transformer and reactor manufacturers. Typical state-of-the-art accuracies in industrial loss measurements are in the range of 1-3 % for power factors down to 0.01, corresponding to an LMS uncertainty of 100–300 µW/VA. Driven by the Ecodesign Directive, utility companies are now calling for 3-5 % accuracies down to a power factor of 0.001, particularly for shunt reactors, requiring LMS uncertainties of 30-50 µW/VA.

In the ELPOW project, a reference setup for reactor loss measurement was produced with a voltage range of 500 V, as well as reference setups for calibration of transformer LMS up to 100 kV but with an uncertainty of only 50 µW/VA. As required by the power transformer community, this project is realising the extension of this reactor measurement setup to the multi-kV range whilst still maintaining high accuracy. Furthermore present primary reference setups at National Metrology Institutes (NMIs) are being improved by a factor of 2– 5 in uncertainty to better than 20 W/VA.

An important extension of the state of the art is a study of detrimental factors that occur on-site in the industrial environment where these systems are used, such as interference and non-sinusoidal input signals. This will ensure that the required challenging uncertainties can be achieved by industrial end-users. Given the complexity of loss measurements, the uncertainty evaluation of these measurements is also complex. Therefore the project is developing good practice guides to provide end-users with the necessary guidance in this uncertainty evaluation, extending the present guidance of the IEC 60076-19 standard.