Functions
2.8 Earth Fault Protection in Earthed Systems (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
244
Inrush restraint
The inrush restraint is only required if the device is applied to transformer feeders or on lines that end on a
transformer; in this case also only for such stages that have a pickup threshold below the inrush current and
have a very short or zero delay. The parameters 3I0>>>InrushBlk (address 3115), 3I0>> InrushBlk
(address 3125), 3I0> InrushBlk (address 3135) and 3I0p InrushBlk (address 3150) can be set to YES
(inrush restraint active) or NO (inrush restraint inactive) for each stage. If the inrush restraint has been disabled
for all stages, the following parameters are of no consequence.
For the recognition of the inrush current, the portion of second harmonic current content referred to the funda-
mental current component can be set in address 3170 2nd InrushRest. Above this threshold the inrush
blocking is effective. The preset value (15 %) should be sufficient in most cases. Lower values imply higher
sensitivity of the inrush blocking (smaller portion of second harmonic current results in blocking).
In applications on transformer feeders or lines that are terminated on transformers it may be assumed that, if
very large currents occur, a short-circuit has occurred before the transformer. In the event of such large cur-
rents, the inrush restraint is inhibited. This threshold value which is set in the address 3171 Imax
InrushRest, should be larger than the maximum expected inrush current (RMS value).
2.8.3 Settings
Addresses which have an appended "A" can only be changed with DIGSI, under Additional Settings.
The table indicates region-specific presettings. Column C (configuration) indicates the corresponding second-
ary nominal current of the current transformer.
Addr. Parameter C Setting Options Default Setting Comments
3101 FCT EarthFltO/C ON
OFF
ON Earth Fault overcurrent
function
3102 BLOCK for Dist. every PICKUP
1phase PICKUP
multiph. PICKUP
NO
every PICKUP Block E/F for Distance pro-
tection
3103 BLOCK 1pDeadTim YES
NO
YES Block E/F for 1pole Dead
time
3104A Iph-STAB. Slope 0 .. 30 % 10 % Stabilisation Slope with
Iphase
3105 3IoMin Teleprot 1A 0.01 .. 1.00 A 0.50 A 3Io-Min threshold for Tele-
prot. schemes
5A 0.05 .. 5.00 A 2.50 A
3105 3IoMin Teleprot 1A 0.003 .. 1.000 A 0.500 A 3Io-Min threshold for Tele-
prot. schemes
5A 0.015 .. 5.000 A 2.500 A
3109 Trip 1pole E/F YES
NO
YES Single pole trip with earth
flt.prot.
3110 Op. mode 3I0>>> Forward
Reverse
Non-Directional
Inactive
Inactive Operating mode
3111 3I0>>> 1A 0.05 .. 25.00 A 4.00 A 3I0>>> Pickup
5A 0.25 .. 125.00 A 20.00 A
3112 T 3I0>>> 0.00 .. 30.00 sec; ∞ 0.30 sec T 3I0>>> Time delay
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