Functions
6-174 7SA6 Manual
C53000-G1176-C156-2
Stub Protection When using the I STUB protection the pick-up thresholds Iph> STUB (address 2630)
and
3I0> STUB (address 2632) are usually not critical, as this protection function is
only activated when the line isolator is open which implies that every measured current
should represents a fault current. With a 1
1
/
2
–circuit breaker arrangement similar to
Figure 6-93 it is possible that large short circuit currents flow from busbar A to busbar
B or to feeder 2 via the current transformers. These currents could cause different
transformation errors in the two current transformer sets
I
A
and I
B
, especially in the
saturation range. The protection should therefore not be set unnecessarily sensitive.
If the minimum short circuit currents on the busbars are known, the pick-up threshold
Iph> STUB is set somewhat (approx. 10 %) below the minimum two phase short cir-
cuit current,
3I0> STUB is set below the minimum single-phase current.
Thetimesettings
T Iph STUB (address 2631)andT 3I0 STUB (address 2633)are
set to zero for this application, to ensure that the protection has fast operation when
the isolator is open.
For different applications similar considerations as for the other stages apply.
If the
I-Stub-stage is to trip when switching the line on to a fault with or without a
short delay,
SOTF Time DELAY (address 2680, see above and refer to Sub-section
“General”), the parameter
I-STUB SOTF (address 2635)issettoYES.Ifusingthe
stub protection, then set to
NO as the effect of this protection function only depends on
the position of the isolator.
6.11.3 Settings
Note: The indicated secondary current values for setting ranges and default settings
refer to I
N
= 1 A. For the nominal current 5 A the current values are to be multiplied
by 5.
Addr. Setting Title Setting Options Default Setting Comments
2601 Operating Mode ON
Only Active with Loss of VT
sec. circuit
OFF
Only Active with
Loss of VT sec. cir-
cuit
Operating mode
2680 SOTF Time DELAY 0.00..30.00 sec 0.00 sec Trip time delay after SOTF
2610 Iph>> 0.10..25.00 A; ∞ 2.00 A Iph>> Pickup
2611 T Iph>> 0.00..30.00 sec; ∞ 0.30 sec T Iph>> Time delay
2612 3I0>> PICKUP 0.05..25.00 A; ∞ 0.50 A 3I0>> Pickup
2613 T 3I0>> 0.00..30.00 sec; ∞ 2.00 sec T 3I0>> Time delay
2614 I>> Telep/BI NO
YES
YES Instantaneous trip via Teleprot./
BI
2615 I>> SOTF NO
YES
NO Instantaneous trip after Swit-
chOnToFault
2620 Iph> 0.10..25.00 A; ∞ 1.50 A Iph> Pickup
2621 T Iph> 0.00..30.00 sec; ∞ 0.50 sec T Iph> Time delay
2622 3I0> 0.05..25.00 A; ∞ 0.20 A 3I0> Pickup
2623 T 3I0> 0.00..30.00 sec; ∞ 2.00 sec T 3I0> Time delay
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