NRC-PTB intercomparison of voltage transformer calibration systems for high voltage at 60 Hz, 50 Hz, and 16.66 Hz

An intercomparison of voltage transformer (VT) calibration systems was performed at the PTB high-voltage laboratory. A “portable” current-comparator-based VT calibration system of the NRC was compared with the PTB voltage-divider-based system, using a reference multiratio inductive VT as a transfer standard with voltage ratios of (110/2 kV)/(100/2 V) up to (400/√3 kV)/(100/√3 V) at frequencies of 16.66 Hz, 50 Hz, and 60 Hz. At frequencies of 50 Hz and 60 Hz with a resistive burden of 10 kΩ and test voltages of 20% up to 120% of rated voltage, the test results of the two different methods at all ratios were found to differ by no more than 15 parts in 10⁶ for the voltage ratio and 30 μrad for the phase displacement. For the ratio (110/2 kV)/(100/2 V) at 16.66 Hz, the results agreed within 15 parts in 10⁶ for the voltage ratio and 50 μrad for the phase displacement