Siemens 7SJ82, Manual

Page: 635 / 1638

Parameter Value Description
I
2
/I
rated, obj
The negative-sequence current is referred to the rated current of the
protected object. This is a preferred normalization for electrical machines,
because the permissible limiting values are indicated exclusively referred to
the machine rated current. You can also use this normalization for other
applications.
I
2
/I
1
The normalization of the negative-sequence system to the positive-
sequence system yields a higher sensitivity. Use this normalization when
detecting interruptions in the primary system.
Set the parameter depending on the application.
Parameter:
Current limitation Imax
,
Maximum phase current
•
Default setting
(_:2311:107) Current limitation Imax
=
no
•
Recommended setting value
(_:2311:101) Maximum phase current
=
10.0 A at 1 A
If the protection function needs a maximum current limitation, set the value of the
Current limitation
Imax
parameter from
no
to
yes
. With the parameter
Maximum phase current
, you set the upper limit of
the phase current. CT saturation will cause negative-sequence current in the secondary system. To avoid over-
function due to the CT saturation, a suitable phase-current limit value is 10 times of the rated protection-
object current.
Parameter:
Release current
•
Recommended setting value
(_:2311:104) Release current
=
0.05 A at 1 A
For the safe calculation of negative-sequence currents, the current in at least one phase must be greater than
5 % of the secondary rated device current. For a 1-A device, the value of
Release current
is 0.05 A (0.25 A
for a 5-A device).
Protection and Automation Functions
6.17 Negative-Sequence Protection
SIPROTEC 5, Overcurrent Protection, Manual 635
C53000-G5040-C017-8, Edition 07.2017