A special purpose ac voltage divider system having voltage ratios of 600 V, 480 V, 360 V, and 240 V to 120 V has been developed to extend the voltage range of primary electric power calibrations from 120 volts to 600 volts at power frequencies of 50 and 60 Hz. The system consists of a special two-stage resistive divider compensated with an active circuit, thereby reducing the error contributions to below 1 /spl mu/V/V. The developmental goal to realize ac voltage scaling within 5 /spl mu/V/V uncertainty in a device verifiable with dc resistance ratio measurements has been attained.