Functions
2.2 Phase Comparison Protection and Ground Differential Protection
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
67
Time Delays
The ground fault is detected and reported only when the displacement voltage has applied for at least the time
87N L:TD-F.det. (address 1230). This stabilizing time also takes effect when ground fault conditions
change (e.g. change of direction).
The tripping can be delayed via the time delay 87N L:TripDelay (address1231).
With the inrush current restraint activated, the time delay 87N L:TripDelay must be at least 20 ms for the
blocking by the inrush current restraint to be effective.
2.2.5 Differential Protection Pickup Logic and Tripping Logic
2.2.5.1 Description
Pickup Logic
Once the differential protection function has reliably registered a fault within its tripping zone, the signal
“87(N)L Gen.Flt.“ (general pickup of the differential protection) is generated. For the differential protection
function itself, this pickup signal is of no concern since the tripping conditions are available at the same time.
This signal, however, is required to initiate the internal or external supplementary functions, e.g. fault recording,
automatic reclosing.
Figure 2-15 General pickup
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