Precision UHVDC dividers for traceable calibration up to 1200 kV

High voltage testing and metering beyond voltage levels covered by presently available metrology infrastructures are needed to secure availability and quality of supply. Calibration has been available up 1000 kV and there is a need to extend the calibration capabilities for testing and with voltage instrument transformers for sub-station metering up to 1200 kV. This paper presents the results of calibration of two precision modular UHVDC dividers, providing traceability to 1200 kV with an unprecedented measurement uncertainty. The scale factors and measurements of the two dividers were calibrated with LV resistance measurement, using a HV step-up procedure, and in two comparisons. The agreement of LV scale factors traceable to RISE and PTB is within 2 µV/V, and the combined expanded uncertainty for a measurement system is better than 15 µV/V at 1200 kV giving new CMC claims of 20 µV/V at 1200 kV.