Functions
2.8 Undervoltage and Overvoltage Protection 27/59 (Optional)
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
124
Figure 2-51 Logic diagram of the undervoltage protection for positive sequence voltage system
2.8.3 Setting Notes
General
The voltage protection can only operate if it has been set to Enabled during the configuration of the device
scope (address 137).
The overvoltage and undervoltage elements can detect phase-to-ground voltages, phase-to-phase voltages or
the symmetrical positive sequence system of the voltages; the symmetrical negative sequence system or the
zero sequence voltage can also be used for overvoltage. Any combination is possible. Detection procedures
that are not required are switched OFF.
Note
For overvoltage protection it is particularly important to observe the setting notes: Never set an overvoltage
element (V
Ph-N
, V
Ph-Ph
, V
1
) lower than an undervoltage element. This would put the device immediately into a
state of permanent pickup which cannot be reset by any measured value operation. As a result, operation of
the device would be impossible!
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