Real Time Compensation Algorithm for Air-Gapped Current Transformers Saturation Effects

A platform implemented with Digital Signal Controllers (DSCs) developed for real time studies of the dynamic behavior of the air-gapped current transformers (CTs) used in power grid protection and measurement systems is presented. The implemented algorithms simulate the fault current in an electric power system as well as the transient response of the current transformer. It is also presented a method of correcting the distortion of the current transformer secondary current which has a negligible value of remanent flux. For this, a tertiary winding must be available and accessible. Thus, the ratio and phase errors, as well as the distortions produced in secondary current due the core saturation in fault situations are properly corrected. Several cases were tested and the results indicate that the proposed method proved to be very effective in improving the performance of protection schemes based on the current measurement.