Functions
90
7UM62 Manual
C53000-G1176-C149-3
Tripping
Characteristic
The parameters for the tripping characteristic are set at the addresses
through
. The meaning of the parameters is shown in Figure 2-43. The numerical values
at the branches are the parameter addresses.
Address
I-DIFF> is the pickup value for the differential current. The pickup value
is referred to the nominal current of the generator or motor. For generators and
motors, a setting between
0.1
and
0.2
is recommended.
In addition to the pickup threshold
, a second pickup threshold is considered.
When this threshold (
) is exceeded, a trip signal is issued regardless
of the magnitude of the stabilizing current (non-stabilized high-speed tripping). This
stage must be set higher than
. Recommendation: Set a value above the
steady-state value of the transient short-circuit current, i.e.:.
With values for x
d
’ between 0.15 and 0.35, the resulting setting values for IDIFF>> are
approx. (3 to 7)
⋅
I
N, Generator
.
The tripping characteristic has two more branches (Figure 2-43). Address
determines the slope of the first branch, whose starting point is specified in
the parameter
. This branch considers current-proportional
error currents. These are mainly transformation errors of the main CTs and of the input
CTs. If the CTs are identical, the default setting of
0.25
can be reduced to
0.15
.
The second branch produces a higher stabilization in the range of high currents which
may lead to current transformer saturation. Its base point is set at address
. The slope is set at address
. The stability of the
relay during current transformer saturation can be influenced by this parameter. A
higher slope results in a higher stability. The default setting of
0.5
has proven to be a
good value.
Figure 2-43
Parameters Determining the Shape of the Tripping Characteristic
1
x
'
d
------ I
N, Generator
⋅
>
1
2
3
4
5
6
7
8
9
10 11 12
13 14 15 16 17 18
1
2
3
4
5
6
7
8
9
10
2031
I–DIFF>>
2021
I–DIFF>
2044
BASE POINT 2
BASE POINT 1
2042
Trip area
I
stab
I
NObj
---------------
I
diff
I
NObj
---------------
Block area
2043
SLOPE 2
2041
SLOPE 1
EXF–STAB
2056
Add-on stabilization
b
c
d
a
