Single-end Transient Current Protection Algorithm for UHV AC Double-circuit Transmission Lines

The current of the UHV AC double-circuit transmission line has complex waveform characteristics and change rules, including the fundamental current in normal operation, fault current in short circuit, transient overcurrent, and so on. Distinguishing different types of current and accurately judging whether it is a fault current is the key to the accuracy of transient current protection. Therefore, the single-end transient current protection algorithm of the UHV AC double-circuit transmission line is designed. The objective model and constraint conditions of single-ended transient current protection for UHV AC double-loop transmission lines are constructed, and the optimization method of single-ended transient current protection is solved based on the gray Wolf algorithm. The experimental results show that the current per unit value changes abnormally after the 2 s fault occurs, and the shape of the current waveform changes obviously after the application of the research method, indicating that the transient current protection plays a role. In the application of this paper, the current fluctuates only at the beginning of the test but quickly recovers to a stable state and maintains the state all the time.