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