A Scheme for Detection and Assessment of Current Transformer Saturation

Current transformer (CT) saturation may result in the distortion of CT secondary current, which will give rise to improper operation of relay protection devices in power system. In this paper, a novel scheme is proposed to detect CT saturation and assess the level of saturation. After analyzing the probability distribution of current sampling data, it is found that the calculated skewness using data within given data window is positive when saturation occurs. However, under unsaturation condition, the calculated skewness using relevant data is negative. Utilizing this difference, a criterion function is defined to detect CT saturation, and a coefficient is determined to assess the level of saturation. Simulation results show the effectiveness of the proposed scheme, and tests using the on-site recorded current signal revel that there is an obvious advantage to implement the proposed scheme in a real system.