Directional relay based on traveling-wave comparison using intrinsic mode function for EHV transmission lines

This paper presents a high-speed directional relay for EHV transmission line. The basic principle of the directional relay is based on comparing high-frequency component energy of directional traveling waves of each bus outgoing line. The relay comparison scheme is designed with intrinsic mode function (IMF) from empirical mode decomposition. The IMF is used to extract transient features from fault-generated traveling-wave signals propagating along transmission lines during a post-fault period. And the arithmetic differential of the IMF first layer can represent the time instant corresponding to the initial traveling-wave arriving at the directional relay. An actual 500-kV extra high voltage (EHV) transmission system has been simulated by PSCAD/EMTDC to evaluate the scheme. The analysis and simulation results show that the scheme is capable of providing correct responses under various fault conditions, and confirm the validity of this proposed scheme as a fast and secure protection scheme.