A High-Resolution Hybrid Digital Wattmeter for Measurements at High Voltage

A development of a high-voltage high-resolution digital sampling wattmeter system for on-site/in-situ calibrations of metering systems for high-voltage power/energy measurements is described in the paper. The current input uses an optically isolated hybrid two-stage current transformer with electronic circuitry that performs A/D conversion. Data is transmitted to a ground station through a fiber optic link. Another laser-driven fiber optic link transmits power to the electronic circuitry of the remote module at high voltage. The voltage input uses a current- comparator-based high voltage divider to provide low voltage replica that is converted into a digital form by A/D conversion. The uncertainty of the power measurement (2sigma) is estimated to be less than 200 muW/VA.