Applications of multi-resolution morphological analysis in ultra high speed protection of transmission line

A new but effective technique, multi-resolution morphological analysis (MMA) is introduced to protection relay in this paper. An approach to ultra-high-speed (UHS) direction protection of power transmission line is developed based on MMA. In the proposed scheme, a multi-resolution morphological opening-closing (MMOC) filter is used to suppress interference noise mingled with transient travelling wave. After that, a 1-level multi-resolution morphological gradient (MMG) transform is designed to identify the polarities of current and voltage waves, the fault direction is recognized accordingly. The feasibility and efficiency of the proposed UHS directional protection algorithm are verified by a typical 500 kV transmission line model set up by PSCAD/EMTDC. According to the simulation results, the proposed MMOC filter can effectively remove intense noise from the transient waves, including random noise as well as pulse function-type noise, and polarities of the travelling waves can be exactly identified by the MMG transform even under the worst-case scenarios such as close in faults or fault inception angle at zero crossing.