A high voltage divider having an uncertainty of 5 p.p.m. at 100 kV

A high-voltage DC divider has been designed and constructed for use as a standard at 100 kV. A self-shielding arrangement controls leakages due to corona currents. A modular version having three 50-kV sections, which can be used singly or in any combination, is also available and used in the calibration process. The design can be extended and versions have been made elsewhere for use at voltages up to 1 MV. The divider ratio is first established at a low voltage. Influences which may change the ratio at the working voltage are identified and limits to their effects are estimated. A high-resolution isolated current measuring instrument has been developed which makes it possible to compare the currents entering and leaving the divider resistor chain at the high and low potential ends. This provides a resolution better than 1 p.p.m. on a current of 100 μA. In use, the divider ratio is known to an uncertainty of 5 p.p.m. (1σ)