2.9 Backup Time Overcurrent Protection
117
7SD610 Manual
C53000-G1176-C145-4
Additional stage
I
ph
>>>
The I-STUB stage can be used as an additional definite time overcurrent stage since
it operates independently of the other stages. In this case, the enable input „>I-STUB
ENABLE“ (No. 7131) must be activated permanently (via a binary input or CFC).
Since the I-STUB stage has an additional enable input, it is also suitable e.g. as an
emergency stage if the remaining stages are used as backup stages. The enable input
„>I-STUB ENABLE“ (No. 7131) is then assigned the output signal „Emer. mode“
(No. 2054) (either via binary outputs and inputs or via the user-definable CFC logic
functions).
The considerations for the use of the I>>> stage as an emergency function are the
same as for the I> stages. The setting value Iph> STUB (address 2630) must here
too be higher than the maximum operational current to be expected, in order to avoid
pickup without fault. The delay T Iph STUB (address 2631), however, can be shorter
than defined in the time grading schedule, since this stage works only in emergency
operation, i.e. in case of a communication failure of the differential protection. Normal-
ly, one grading time above the base time of the differential protection is sufficient.
Accordingly, the earth current stage 3I0> STUB (address 2632) should pick up on
the smallest earth current to be expected during an earth fault and the delay T 3I0
STUB (address 2633) should exceed the base time of the differential protection by one
grading time. If only the phase currents are to be monitored, set the pickup value of
the earth current stage to ∞.
The I-STUB stage can also be accelerated by the release signal „>O/C InstTRIP“
(No. 7110), e.g. before an auto-reclosure. This is defined with parameter I-STUB
Telep/BI (address 2634). Set it to YES if the I-STUB stage is to trip without delay
while the binary input „>O/C InstTRIP“ is activated or the internal automatic reclo-
sure function is ready to operate.
Instantaneous tripping by the operational auto-reclosure should only be chosen if the
I>>> stage is set as an emergency function. If the differential protection is out of oper-
ation, this emergency stage guarantees instantaneous tripping before auto-reclosure.
Instantaneous tripping when the line is switched onto a fault is also possible with the
I-STUB stage. Set the parameter I-STUB SOTF (address 2635) to YES if instanta-
neous tripping is desired.
2.9.4 Settings
Addresses which have an appended "A" can only be changed with DIGSI, under Ad-
ditional Settings.
The table indicates region-specific presettings. Column C (configuration) indicates the
corresponding secondary nominal current of the current transformer.
Addr. Parameter C Setting Options Default Setting Comments
2601 Operating Mode ON
Only Emer. prot
OFF
ON Operating mode
2602 SOTF Time DELAY 0.00 .. 30.00 sec 0.00 sec Trip time delay after SOTF
2603A Direct. 3I0 U0/I0 or U2/I0
with U0/I0
with U2/I2
U0/I0 or U2/I0 Measurement of direction
for 3I0
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