Comparison of Reference Setups for Calibrating Power Transformer Loss Measurement Systems

Abstract

A unique comparison has been performed of two reference setups for the calibration of industrial power transformer loss measurement systems (TLMSs). The setups are developed by the Van Swinden Laboratorium (VSL), Delft, The Netherlands and Physikalisch-Technische Bundesanstalt (PTB), Brunswick, Germany, with the aim to calibrate industrial TLMS as a complete system, rather than just via its individual components, with an uncertainty better than 50 µW/VA, for voltages up to 100 kV, currents up to 2 kA, and power factors down to 0. The results of the comparison show excellent agreement of the PTB and VSL reference setups, both for the individual components as for the complete system. The phase agreement in the VSL and PTB component calibration results is better than (2 ± 5), (5 ± 12), and (10 ± 15) µrad for all calibration points in current ratio, voltage ratio, and power, respectively. In the full system comparison, the difference in the results of the VSL and PTB systems is less than 12 µW/VA for currents up to 1000 A and voltages up to 70 kV, with a −7 µW/VA difference averaged over all comparison measurements. This is well within the present 25 µW/VA measurement uncertainty of each of the VSL and PTB reference setups.

Reliable Power Transformer Efficiency Tests

“…In a recent comparison of the VSL and PTB LMS reference setups this accuracy was independently verified. The measured difference in the VSL and PTB results was less than 12 W/VA (0.12 % loss power at PF = 0.01) for currents up to 1000 A and voltages up to 70 kV [23]. This is well within the measurement accuracies of the VSL and PTB reference setups.…”

Verification of a Capacitive Voltage Divider With 6-μrad Uncertainty Up To 100 kV

“…Considering all uncertainty contributions, if the total uncertainty of the entire setup needs to reach 20 µW/VA (0.2 % in loss power at = 0.01), the phase uncertainty of the CVD should be better than 10 µrad. In an earlier verification of the VSL reference setup [17], the agreement between the VSL and Physikalisch-Technische Bundesanstalt (PTB) phase measurement results component was better than (2 ± 5) µrad, (5 ± 12) µrad, and (10 ± 15) µrad in current, voltage, and power respectively ( = 2). The aim of the present study is to bring the uncertainty of the phase verification of the voltage channel well below 10 µrad.…”