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Functions
2.3 Differential Protection
Tripping logic of the differential protection
The tripping logic of the differential protection combines all decisions of the differential stages and forms output
signals which are also influenced by the central tripping logic of the entire device (Figure 2-32).
The pickup signals that identify the concerned stages of the differential protection stages can be delayed via
the time stage T-DELAY I-DIFF>. Independently of this condition, a single-phase pickup can be blocked for
a short time in order to bridge the transient oscillations on occurrence of a single earth fault in a resonant-
earthed system.
The signals thus processed are linked with the output signals „Diff. Gen. TRIP", „Diff TRIP 1p L1",
„Diff TRIP 1p L2", „Diff TRIP 1p L3", „Diff TRIP L123" in the tripping logic of the device. The
single-pole information implies that tripping will actually take place single-pole only. The actual generation of
the commands for the tripping (output) relay is executed within the tripping logic of the entire device (see
Section 2.25.1).
Figure 2-32
Tripping logic of the differential protection
102
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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