Functions
242
7UM62 Manual
C53000-G1176-C149-3
Measured Value
Acquisition -
Currents
In the current path, there are three input transformers each on side 1 and side 2; the
digitized sum of the outputs of these on one side must be almost zero for generators
with isolated starpoint and earth-fault-free operation. A current circuit fault is detected
if
I
F
= |
I
L1
+
I
L2
+
I
L3
|
>
Σ
I THRESHOLD
·
I
N
+
Σ
I FACTOR
·
I
max
Σ
I THRESHOLD
and
Σ
I FACTOR
are settings that are available individually for side 1
and side 2. The component
SUM.Fact.I
·
I
max
takes into account permissible current
proportional transformation errors in the input converters, which can be especially
large when high fault current levels are present (Figure 2-116). The dropout ratio is
about 95%.
This error is reported separately for side 1 and side 2 by ”
Fail
Σ
I
”.
The current sum monitoring is only effective for the side for which the starpoint has
been configured as
Isolated
in the power system data (addresses
/
Figure 2-116 Current Sum Monitoring
Measured Value
Acquisition -
Voltages
In the voltage path, there are four input transformers: If three of them are used for
phase-earth voltages, and one input for the displacement voltage (e–n voltage from
the broken delta winding or neutral transformer) of the same system, a fault in the
phase-earth voltage sum is detected if
|U
L1
+ U
L2
+ U
L3
+ k
U
· U
E
|
>
+
x U
max
and
are parameter settings, and U
max
is the highest
of the phase-earth voltages. The factor k
U
considers the transformation ratio
differences between the displacement voltage input and the phase voltage inputs
(parameter k
U
=
address
). The
x U
max
component considers permissible voltage-proportional transformation errors, which
can be especially large in the presence of high voltages (Figure 2-117).
This malfunction is reported as ”
I
F
I
N
I
max
I
N
Σ
I THRESHOLD
Slope:
Σ
I FACTOR
