Siemens SIPROTEC Manual page 223

Figure 2-107 shows the logic diagram. The tripping time depends on the level of the zero-sequence voltage U
For meshed earthed systems the zero-sequence voltage increases towards the earth fault location. The
inverse characteristic results in the shortest command time for the relay closest to the fault. The other relays
then reset.
Figure 2-107 Directional zero-sequence voltage time protection with non-directional backup stage
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
2.8 Earth Fault Protection in Earthed Systems (optional)
Functions
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