An optically isolated hybrid two-stage current transformer for measurements at high voltage

The development of a high-voltage (HV) current measurement system for on-site/in-situ calibrations in power systems is described in the paper. The system is based on an optically isolated hybrid two-stage current transformer with electronic circuitry that performs A/D conversion. It uses a fiber optic link for data transmission to a ground station and a laser-driven fiber optic link for supplying power to the electronic circuitry of the remote module at HV. The uncertainty of the current-ratio measurement is estimated to be less than 100middot10^-6 both in-phase and quadrature