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2 Functions
is issued. 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, how-
ever, is necessary for the initiation of internal or external supplementary functions (e.g.
fault recording, automatic reclosure).
Tripping logic of the
The tripping logic of the differential protection combines all decisions of the differential
differential
stages and forms output signals which are also influenced by the central tripping logic
protection
of the entire device (Figure 2-22).
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 output signals generated by the stages are combined to 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. The single-pole information implies
that tripping will 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 2.16.1).
Figure 2-22
Tripping logic of the differential protection
2.3.2
Setting Notes
The differential protection can be switched 1201 or STATE OF DIFF. in address ON
General
OFF. If a device is switched off at any end of the protected object, a calculation of mea-
sured values becomes impossible. The entire differential protection system of all ends
is then blocked.
70
7SD610 Manual
C53000-G1176-C145-4
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