Functions
6-100
7SA522 Manual
C53000-G1176-C119-2
The remaining setting options are the same as for the other curves.
Figure 6-59
Logic diagram of the 3I
0P
–stage for the inverse logarithmic curve
Phase Current
Stabilization
Non-symmetrical load conditions in multiple-earthed systems or different current
transformer errors can result in a zero sequence current. This zero sequence current
could cause faulty pick-up of the earth current stages if low pick-up thresholds are set.
To avoid this, the earth current stages are stabilized by the phase current: As the
phase currents increase, the pick up thresholds are increased (Figure 6-60). The sta-
bilization factor (=slope) may be changed by means of the parameter
(setting address 3104, section 6.5.2). It applies to all stages.
Figure 6-60 Phase current stabilization
Yes
No
Reverse
Forward
Non-Directional
„1“
≥
1
&
&
inrush-
stabilization
direction-
determination
forwards
reverse
&
&
Yes
No
Yes
No
,S7HOHS%,
permissive
teleprot..
switch on
to fault
≥
1
T
0
627)7LPH'(/$<
&
&
PICKUP
DIRECT.
&
627)2S0RGH
I
E
3I
0P
t
3I
0
T
0
/2*&XUYH
&
T
0
1309 >EF BLOCK 3I0p
,S,QUXVK%ON
1357 EF 3I0p Pickup
,S627)7ULS
EF 3I0p TRIP
1369
,S6WDUWSRLQW
≥
1
>EF Inst TRIP
Inactive
3
I
0
I
N
I
Phmax
I
N
blocking of the
pick up
,(!
slope
0,1
Содержание siprotec 7SA522
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Страница 620: ...Appendix B 48 ...