A phasor estimation algorithm during CT saturation

This paper proposes a phasor estimation algorithm based on the least square curve fitting technique for the distorted secondary current due to CT saturation. In this paper, the mathematical form of the secondary current during CT saturation is represented as the scaled primary current with the magnetizing current. The information of the scaled primary current is estimated from the data of saturated section. Therefore the proposed method can estimate the phasor of a fundamental frequency component during the saturated period, and accordingly can decrease the unnecessary time delay of the protection relays. The performance of the algorithm is validated under various fault and CT conditions using a C400 CT model. A series performance evaluations show that the proposed phasor estimation algorithm can estimate the phasor of the fundamental frequency component with high accuracy, regardless of fault conditions and CT characteristics.