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
