Siemens Siprotec 7UM611, Руководство пользователя

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2.28 Measurement Supervision
167
7UM61 Manual
C53000-G1176-C127-3
Measurement Value
Acquisition – Cur-
rents In the current paths there are three input transformers; the digitized sum of the trans-
former currents of one side must be almost zero for generators with isolated starpoint
during 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 programmable settings. The component
Σ I
FACTOR
· Imax takes into account the admissible current-proportional transformation
error of the input transformer, which can occur particularly when high fault current
levels are present (see the following figure). The dropout ratio is about 95 %.
This malfunction is signaled as
“Failure Σ I”
.
The current sum monitoring is not executed if the starpoint was set as
273
at Power
System Data 1 (address
low-resist.
).
Figure 2-62 Current sum monitoring
Measured Value Ac-
quisition Voltages Four measuring inputs are available in the voltage path: 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
| >
SUM.thres. U
+
SUM.Fact. U
x U
max
Here
SUM.thres. U
and
SUM.Fact. U
are parameter settings, and U
max
is the
highest of the phase-earth voltages. Factor k
U
considers the transformation ratio dif-
ferences between the displacement voltage input and the phase voltage inputs (pa-
rameter k
U
=
Uph / Udelta
Address
225
). The
SUM.Fact. U
x U
max
component
considers admissible voltage-proportional transformation errors of the input transduc-
ers, which can be especially large in the presence of high voltages (see the following
figure).
This malfunction is reported as
“Fail Σ U Ph-E”
.
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