•
Measured phase-to-phase voltage V
AB
(VAB measured)
•
Measured phase-to-phase voltage V
BC
(VBC measured)
•
Measured phase-to-phase voltage V
CA
(VCA measured)
•
Calculated phase-to-phase voltage V
AB
(VAB calculated)
•
Calculated phase-to-phase voltage V
BC
(VBC calculated)
•
Calculated phase-to-phase voltage V
CA
(VCA calculated)
•
Calculated voltage V0 (V0 calculated)
The selection depends on the corresponding application.
NOTE
From V7.30 on, the value VN measured is no longer provided. If you have selected this value in earlier
versions, you can select the value V0 calculated instead after upgrading the configuration to V7.30 or a
later version.
If the function Undervoltage protection with any voltage is used in a 1-phase function group, the param-
eter Measured value is not visible.
Parameter: Threshold
•
Default setting (_:571:3) Threshold = 80 V
Specify the Threshold (pickup threshold) for the specific application.
Depending on the Measured value, the Threshold is set either as measured voltage or as a phase-
to-phase variable.
NOTE
If the function is used in a Voltage-current 1-phase function group connected to the 1-phase voltage
measuring point with the voltage type VN broken-delta, you set the threshold value based on the
equivalent zero-sequence voltage.
Calculate the equivalent zero-sequence voltage V
0 equiv. sec
from the measured voltage V
N sec
with the
following formula:
You can find more information about the Matching ratio Vph / VN parameter in chapter 5.1.4 Appli-
cation and Setting Notes for Measuring Point Voltage 3-Phase (V-3ph).
Parameter: Operate delay
•
Default setting (_:571:6) Operate delay = 3 s
The Operate delay must be set for the specific application.
Parameter: Dropout ratio
•
Recommended setting value (_:571:4) Dropout ratio = 1.05
The recommended set value of 1.05 is appropriate for most applications. To achieve high measurement preci-
sion, the Dropout ratio can be reduced to 1.02, for example.
Parameter: Current-flow criterion
•
Recommended setting value (_:2311:101) Current-flow criterion = on
Protection and Automation Functions
7.17 Undervoltage Protection with Any Voltage
SIPROTEC 5, High-Voltage Bay Controller, Manual 821
C53000-G5040-C015-9, Edition 11.2017
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