Siemens 6MD85, Manual

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Measured Value
The parameter
Measured value
allows you to select whether the stage uses a measured (directly
connected) voltage or a calculated phase-to-phase voltage.
If the function Undervoltage protection with any voltage is used in a 1-phase function group, the parameter
Measured value
is not visible.
Current-Flow Criterion
The undervoltage-protection stages work optionally with a current-flow criterion. The current-flow criterion
works across all stages.
When the
Current-flow criterion
parameter is switched on, the undervoltage protection stages only
pick up when the current-flow criterion has been set to fulfilled via the binary input signal
>Current flow-
criterion
. The function reports when the current-flow criterion is fulfilled.
Figure 7-155 illustrates the influence of the current-flow criterion.
i
i
NOTE
If the
(_:2311:101) Current-flow criterion
parameter is deactivated, the device picks up imme-
diately if a missing measuring voltage is detected while the undervoltage protection is active. The param-
eter setting can be changed even when the device has picked up.
Blocking the Stage
In the event of blocking, the picked up stage will be reset. Blocking the stage is possible externally or internally
via the binary input signal
>Block stage
.
Application and Setting Notes
Parameter: Method of measurement
•
Recommended setting value
(_:571:8) Method of measurement
=
fundamental comp.
Use the
Method of measurement
parameter to define whether the tripping stage uses the fundamental
component (standard method = default setting) or the calculated RMS value.
Parameter Value Description
fundamental comp.
Select this method of measurement to suppress harmonics or transient
voltage peaks.
Siemens recommends using this parameter value as the default setting.
RMS value
Select this method of measurement if you want the stage to take harmonics
into account (for example at capacitor banks). Do not set the
threshold
value
of the tripping stage under 10 V for this method of measurement.
Parameter: Measured value
•
Default setting
(_:571:9) Measured value
=
VA measured
The
Measured value
parameter is used to specify which voltage is monitored by the stage.
The scope of setting options depends on the connection type for the voltage transformers and the routing of
the measured values to the terminals of the voltage measuring point. You can find connection examples for
voltage transformers in the Appendix.
The following setting options can be available:
•
Measured phase-to-ground voltage V
A
(
VA measured
)
•
Measured phase-to-ground voltage V
B
(
VB measured
)
•
Measured phase-to-ground voltage V
C
VC measured
)
7.17.4
Protection and Automation Functions
7.17 Undervoltage Protection with Any Voltage
820 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017