Voltage Ratio Traceability of 10 kV Low-Voltage Excited Two-Stage Voltage Transformer

To establish a series of ppm-level high-voltage ratio standards up to 110 kV, we propose and have designed low-voltage-excitation two-stage voltage transformers (LVE-TSVTs) for high voltage. Ratio traceability for a 10 kV/100 V LVE-TSVT is vital in this scheme. This paper focuses on the voltage ratio traceability of the 10 kV LVE-TSVT by measuring the errors of the reference voltage and the voltage coefficient separately. A 1 kV double-TSVT with a 1 kV/100 V TSVT and a 100 V/10 V TSVT in cascade was developed and calibrated, and then was used to calibrate the error of the 10-kV LVE-TSVT at 10% rated voltage. The voltage coefficient was measured by comparing with a high-voltage capacitive divider through a current comparator bridge. The measurement was implemented in the range of 10%–120% rated voltage. The calibration results showed that the ratio errors of the 10-kV LVE-TSVT were less than $0.95 \times 10^{-6}$ in magnitude and $-1.26\,\,\mu $ rad in phase displacement at the 10% rated voltage. The expanded uncertainties are about $1.8 \times 10^{-6}$ in ratio and $2.2~\mu $ rad in phase, respectively, with coverage factor $k = 2$ .