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Figure 2-25
Logic diagram of the undervoltage protection for phase voltages
Phase-phase undervoltage
Basically, the phase-phase undervoltage protection operates like the phase-earth protection except that it
detects phase-to-phase voltages. Accordingly, both phases are indicated during pickup of an undervoltage
stage if one of the stage thresholds Uph-ph< or Uph-ph<< was undershot. Beyond this, Figure 2-25 applies
in principle.
It is sufficient for the current criterion that current flow is detected in one of the involved phases.
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009
2.5 Under and over-voltage protection (optional)
Functions
103
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