Regional backup protection method for setting and simplifying distance III section protection

The invention discloses a regional backup protection method for setting and simplifying distance III section protection. The method is characterized by comprising the following steps: 1) calculating an impedance setting value Zset and a time setting value tset of distance III section protection of a protected line, and setting parameters; 2) acquiring impedance element information of distance protection of a current substation and an adjacent substation; 3) when a fault occurs in a set distance III section protection range of an outlet line of the current substation, starting a distance III section impedance element, and then starting regional backup protection of the current substation; 4) obtaining an action time step numerical value tN of the regional backup protection; 5) if a delay criterion of the regional backup protection is met, correcting the action time step numerical value tN; 6) if an acceleration criterion of the regional backup protection is met, correcting the action time step numerical value