To enhance the reliability of protection for hybrid multi-terminal DC transmission systems under complex converter station topologies and non-uniform boundary conditions

it introduces and constructs a longitudinal protection method based on the direction discrimination characteristics of traveling wave mutation quantity.Firstly

it constructs a refined model of three-terminal hybrid DC transmission on the PSCAD/EMTDC platform to deeply analyze the propagation characteristics of the fault traveling wave mutation quantity.Secondly

it innovatively integrates ICEEMDAN(improved complete ensemble empirical mode decomposition with adaptive noise)and Spearman correlation coefficients

constructing a joint analysis model for traveling wave signals.Finally

it accurately extracts the modal components of the transient traveling wave through ICEEMDAN

and quantifies the correlation differences of the fault components by using the Spearman correlation coefficient to form the fault area discrimination criterion.This protection scheme does not rely on the characteristics of boundary components and effectively suppresses the influence of capacitive current through modal component correlation analysis.The simulation results show that this protection method not only meets the requirements of high reliability and rapid action

but also has good robustness against noise interference.