Siemens siprotec 7SA522 User Manual

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 ,SK67$%
6ORSH(setting address 3104, section 6.5.2). It applies to all stages.
Figure 6-60 Phase current stabilization

Yes
No
Reverse
Forward
Non-Directional
„1“
≥1
&
&
inrush-
stabilization
direction-
determination
forwards
reverse
&
&
Yes
No

Yes
No
,S7HOHS%,
permissive
teleprot..
switch on
to fault
≥1
T0
 627)7LPH'(/$<
&
&
PICKUP
PICKUP+DIRECT.

&
627)2S0RGH
I
E
3I
0P


t
3I
0

T0
 /2*&XUYH

&

T0

1309
>EF BLOCK 3I0p
,S,QUXVK%ON
1357
EF 3I0p Pickup
,S627)7ULS

EF 3I0p TRIP
1369
,S6WDUWSRLQW

≥1
>EF Inst TRIP
,S3,&.83
2SPRGH,S
$GG7'(/$<
,S0LQ7'(/$<
Inactive
,S0D[7'(/$<
,S7LPH'LDO
3I
0
I
N
I
Phmax
I
N
blocking of the
pick up
,(!
slope
0,1

Siemens siprotec 7SA522 Specifications

General

Brand	Siemens
Model	siprotec 7SA522
Category	Protection Device
Language	English