Fault positioning method for overhead line-high voltage cable mixing line

The present invention provides a fault positioning method for an overhead line-high voltage cable mixing line, comprising the steps of: (1) respectively measuring three-phase voltage and current phasors of M and N end points at two sides of the line, respectively calculating negative sequence voltages, negative sequence currents, positive sequence voltages and positive sequence currents of the two sides through a symmetrical component method; (2) judging a fault type according to the negative sequence voltages; (3) if the fault type is asymmetric fault, respectively calculating a negative sequence voltage amplitude of each point along the line through the three-phase voltage and current phasors of two-terminal electrical quantities M and N sides, and determining that the points with the equal negative sequence voltage amplitude are fault points; (4) if the fault type is three-phase symmetrical fault, performing fault positioning through a method for comparing positive sequence voltage amplitude variations, and determining that the points with the equal positive sequence voltage amplitude variation are fault points. The fault positioning method of the present invention aims at parameter characteristics of the overhead line-high voltage cable mixing line, does not require synchronous two-terminal electrical quantities, does not need to perform fault section judgment in advance, does not have a pseudo root identification problem, and can adopt various quick search algorithms in the process of fault position search.