Current Transformer Saturation On Distance Protection

With the increase of the electric power system capacity as well as the short lines, high currents will possibly occur in the transmission line when a fault happens at the end of the line. The iron core of the current transformer (CT) will become saturated easily because of the large current, or when the secondary load of the CT doesn't match the 10% error curve. The secondary current will be distorted when the CT undergoes saturation, which will bring some influence on the distance relay inevitably. Furthermore more and more people pay attention to this problem. Through a large number of digital simulations by ATP, this paper analyzes the impact of the CT's saturation of the distance protection in detail. Then a new scheme anti CT's saturation for distance protection has been put forward. At last, some compensation methords have also been introduced, and a compensation algorithm of ANN (Artifical Neural Network) based on MATLAB has been discussed as an emphasis.