A novel current transformer saturation detecting method based on parameter identification

A novel current transformer(CT)saturation detecting method based on parameter identification is proposed. By analyzing the fault component network of external faults, it is derived that the voltage and current at the relay location satisfy an equivalent L-R model. When the CT is not saturated, the parameters identified by least square method reflect the real parameters of the system and have barely variation. However, once the CT is saturated, the parameters identified by side current will have great fluctuation. Thus, by calculating the dispersions of parameters fluctuation, CT saturation can be detected. The performance of this proposed method is applicable to the DC component and harmonics, is not affected by operation mode of system and fault inception angle, so the criterion is easy to set. The algorithm of the criterion based on time-domain shows a fast response time and is selective. Moreover, this method is able to detect all types of CT saturations. The more severe the saturation is, the more sensitive the criterion is. It can be used to improve the performance of differential protection. EMTP simulation results verify the effectiveness of the proposed method.