A Time-Frequency Algorithm for CT Saturation Detection in the Presence of Noise

Current transformer (CT) saturation may cause phase shift between unsaturated and saturated signal and thus results in distance relay overreach or underreach. In this letter, a time-frequency technique based on iterative Hilbert Huang transform is proposed for detection of current transformer saturation interval. The basic idea is to detect the saturation interval using an index based on second derivative of the instantaneous amplitude. The instantaneous amplitude is obtained using iterative Hilbert Huang spectral analysis. The method is independent of the presence of noise and also the computational burden on the digital relay is less by the proposed method. The method is validated using real-time current signal obtained using RTDS.