An Adaptive Distance Relay Based on Transient Error Estimation of CVT

Simple delay solutions are usually used to prevent transient overreach caused by the transient error of a capacitor voltage transformer (CVT), which is very harmful to the safety and stability of operation of the power system. A proposed real-time CVT transient error estimation approach based on the chosen fundamental wave algorithm and the rated CVT parameters consists of two stages. The first stage obtains the error coefficient. The second stage estimates the measured error of the voltage amplitude according to the secondary side voltage. A novel adaptive distance relay approach is proposed, which can adjust operating thresholds according to the error. The approach hardly affects the performance for lines of normal length and operates rapidly for short lines with close-in faults, which is verified by the simulation studies. The overall performance is improved greatly in comparison with the general approach for distance relays