Development and use of a medium voltage RC divider for on-site calibration

The development and the characterization of a resistive-capacitive divider, intended for indoor calibrations and measurements at medium voltage level, are described. A numerical tool is developed and largely used in the design phase to optimize the divider performances with respect to frequency behavior and insulation strength. The divider, with a coupled matching stage, is laboratory characterized both at low and high voltage, taking into account the expected operating conditions. The estimated measurement uncertainty associated with its on-site use as a reference is within 550 ppm for the ratio error and 310 μrad for the phase displacement. Results of the first tests performed in MV/LV substations confirm that it can be effectively used in the calibration of medium voltage measurement transformers.