Comparison of Four Different ppm-Level Methods for Traceability of HVDC Measuring Systems

A typical way to trace back measuring equipment for HVDC is carried out by means of the step-up method. A 10 V standard voltage source is calibrated against the Josephson standard with a typical measurement uncertainty of less than 1 µV/V. Using this source, a voltage divider is calibrated at 10 V. Thereafter, another voltage divider is calibrated at a higher voltage (e.g., 1000 V). In this way, HVDC dividers can be calibrated up to the megavolt range by gradually increasing the voltage level with the price of deteriorating the measurement uncertainty. The worldwide lowest expanded measuring uncertainties using this method are below 5 µV/V at high voltages up to several hundreds of kilovolts. This paper presents three new methods for ppm-level traceability of HVDC measuring systems. These three methods are described and compared to each other and to the well-known step up method regarding the advantages and disadvantages.