As can be seen from Table 6, when a positive earth fault (f1 ) occurs on
the DC line, the respective K2 values are less than 0.6 for each earth
resistance case; when a negative earth fault (f2 ) occurs on the DC
line, the respective K2 values are greater than 1.5 for each earth
resistance case; when a double pole crossover fault (f3 ) and a double
pole crossover earth fault (f4 ) occur, the respective K2 values are
greater than 0.6 and less than 1.5, which are in accordance with the
fault pole identification criterion. Therefore, according to the fault
pole identification criteria, the identification of the fault poles can
be achieved.
6.4 Protection action results
Combining the analysis in Section 3.1 with the simulation results in
Section 6.1-6.3, the final protection actions are shown in Table 7.
Table 7 Protection action results during fault simulation