Abstract
A reference setup for system calibration of industrial transformer loss measurement (TLM) systems consists of three main components, a voltage divider, a current transformer, and a power meter, and their phase displacements should each not be more than 10 $\mathrm {\mu }$ rad to achieve an overall system uncertainty of better than 20 $\mathrm {\mu }\text{W}$ /VA. We have extensively verified the uncertainty level of the current-comparator-based capacitive voltage divider (CVD) used in the TLM reference setup of the Van Swinden Laboratorium (VSL), both from the component level and the system as a whole. Different practical conditions relevant for on-site measurements are considered, e.g., measurement cable lengths, cable types, and grounding. The verification measurement results show an agreement of better than $(6 \pm 6) \times 10^{-6}$ in ratio error and $(4 \pm 6)~\mathrm {\mu }$ rad in phase displacement between the CVD component and system calibrations up to 100 kV. Requirements for achieving this agreement are adequate grounding of the CVD and the use of triax cable between the high-voltage (HV) capacitor and the CVD low-voltage electronics in case large distances have to be covered on-site. The $(4 \pm 6)~\mathrm {\mu }$ rad agreement in phase displacement is well within the required 10 $\mathrm {\mu }$ rad limit for voltage measurements as part of on-site TLM system calibrations with 20 $\mathrm {\mu }\text{W}$ /VA overall uncertainty at low power factors.
Highlights
P OWER transformer losses account for a significant part of the total network losses
In order to find out what agreement can be achieved in the capacitive voltage divider (CVD) verification, first, an LV experiment was performed on the 2-kV range of the 200-kV CVD with high-quality (GR) reference capacitors
Verification, an experiment was performed on the 2-kV range of the 200-kV CVD, following the schematic shown in Fig. 2, using high-quality 100- and 1000-pF capacitors (GR, model 1404) for CHV and CH V and CLV and CL V, respectively
Summary
P OWER transformer losses account for a significant part of the total network losses. Commercial transformer loss measurement (TLM) systems are used by power transformer manufacturers to verify the loss specification of their products during the final factory acceptance tests. These TLM systems need to be calibrated with a much more accurate reference system to guarantee sufficient TLM accuracy and reliable TLM test results. Date of publication February 11, 2021; date of current version February 24, 2021. The Associate Editor coordinating the review process was Dr Branislav Djokic. (Corresponding author: Gert Rietveld.)
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