Method for online measurement of optical current transformer onsite errors

This paper describes a method for the online measurement of an optical current transformer (OCT) onsite errors comparing with a conventional electromagnetic current transformer (CT) as the reference transformer. The OCT under measurement is connected in series with the reference electromagnetic CT in the same line bay. The secondary output signals of the OCT and the electromagnetic CT are simultaneously collected and processed using a digital signal processing technique. The tests developed on a prototype clearly indicate that the method is very suitable for measuring errors of the OCT onsite without an interruption in the service. The onsite error characteristics of the OCT are analyzed, as well as the stability and repeatability. (paper)