' $ ! $!& #$"&&"! Ċ (%& !' $$ !"
6 - 12
Siemens AG ⋅ January 1999
In cases in which a transformer is directly connected
to a line, i.e. without current transformer and circuit-
breaker, an in-rush stabilization with the second harĆ
monic can be selected (addr. ). The perĆ
centage component of the second harmonic required
for stabilization can be parameterized under addr.
. A ratio I
2fN
/I
fN
of 20 % is factory set. This
is sufficient in most cases. A smaller value leads to
greater stabilization, a higher value to lower stabilizaĆ
tion.
Excceding the limit leads to blocking of the differential
protection. (The trip command is blocked whereas the
close command is not blocked.)
This block can be removed immediately when the
differential current exceeds a set current threshold
(addr. ).
A prerequisite for this, however, is that the device is
equipped with the 2nd harmonic option (model
7SD600*-*****-1, 7SD600*-*****-3).
A
1 0 I – D I F >
1 . 0 0 I N L
Y
B
Pick-up value for differential current during three-
phase symmetrical current flows referred to the rated
line current
smallest setting value: I
N line
......
largest setting value: I
N line
........
A
1 0 2 H A R M
O F F
Y
B
The in-rush stabilization with the second harmonic
restraint is
switched OFF or
O N
switched ON
A
1 0 H A R M 2 %
2 0 %
Y
B
Component of 2nd harmonic in the differential current
which only just leads to blocking in % of the fundaĆ
mental frequency component of the differential curĆ
rent
smallest setting value: %..........
largest setting value: %............
A
1 0 H A R M 2 I
5 . 0 0
Y
B
Differential current threshold for resetting the blokĆ
king by the 2nd harmonic
smallest setting value: I
N line
.........
largest setting value: I
N line
.........
The differential protection has a local current thresĆ
hold I1 ENABLE. (addr. ) which monitors
the locally flowing current and provides an additional
trip criterion. This setting value also refers to the raĆ
ted current of the line as set under addr.
(see section 6.3.3).
Tripping of the line at both ends, even during weak
infeed conditions, is achieved by setting "0".
To Next Page
Loading...
Need help?
General
