A transformer loss measurement (TLM) system calibration setup consists of three main components, a voltage divider (VD), current transformer and a power meter. The phase errors of the individual components of the reference setup for TLM system calibration should not be more than 10 µrad to achieve an overall system uncertainty of better than 20 µW/VA. We have verified the uncertainty level of the developed VD both from the component level and as a whole. Different practical conditions relevant for on-site measurements are considered, e.g. measurement cable lengths, cable types and grounding. The results shows that uncertainties of less than 10 µV/V in ratio error and 10 µrad in phase displacement are achievable.

This research is performed within the "TrafoLoss" EU joint research project, which has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. Additional funding is received from the Dutch Ministry of Economic Affairs and Climate. Author's accepted version of a paper presented at the 2020 Conference on Precision Electromagnetic Measurements (CPEM 2020), Colorado/USA. August 24-28, 2020