Automated calibration methods for a high-voltage Park divider

Two new methods of calibrating the 1/10 voltage ratio of a 100-kV Park divider, which has been provided with a set of tenths ratio taps is described. The proposed methods make PC-controlled measurements based on (1) Wheatstone bridge circuits configurable entirely with the resistive sections of the tapped divider, and (2) a digital conductance comparator, respectively. The 1/10 ratio measurements made by these quite different methods were found to be consistent to 3 ppm of the ratio. The conductance comparison method, with an assessed standard uncertainty of 2 ppm, determined precisely the effect of self-heating on the measured ratio, minute-by-minute after the rated input was applied. Subdividing the established 1/10 ratio to 1/100 and 1/10⁵ of input, however, is based on more conventional methods. These subdivided ratios have been given a standard uncertainty not exceeding 6 ppm in the absence of corona discharge