Measuring-Element Release
When the controlling voltage drops below the setting
Undervoltage threshold
, the respective measuring
element is released.
The release of the measuring elements is carried out phase-selectively. The assignment of voltages to current-
carrying phases is shown in
.
Blocking of the Stage with Measuring-Voltage Failure
The stage can be blocked if a measuring-voltage failure occurs. In case of a blocking, the picked up stage is
reset. The following blocking options are available for the stage:
•
From an internal source upon pickup of the Measuring-voltage failure detection function
•
From an external source via the binary input signal
>Open
of the function block
Volt.-transf. c.
b.
, which links in the tripping of the voltage-transformer circuit breaker
The
Blk. by meas.-volt. failure
parameter can be set so that measuring-voltage failure detection
blocks the stage or does not block it.
Application and Setting Notes
This stage is structured in the same way as the Inverse-time overcurrent, voltage-dependent stage. The
only differences are the conditions for the pickup and the influence on the operate curve. This chapter only
provides the application and setting notes for the setting
Blk. by meas.-volt. failure
and
Under-
voltage threshold
. For guidance on the other parameters of this stage, refer to chapter
.
Parameter:
Blk. by meas.-volt. failure
•
Recommended setting value
(_:10) Blk. by meas.-volt. failure
=
yes
You can use the
Blk. by meas.-volt. failure
parameter to control the response of the stage when a
measuring-voltage failure is detected.
A measuring-voltage failure can only be detected if one of the following 2 conditions is met:
•
The device-internal Measuring-voltage failure detection function is configured and switched on.
•
The binary input signal
>Open
of the function block Voltage-transformer circuit breaker is connected to
the voltage-transformer circuit breaker.
Parameter Value
Description
no
The overcurrent-protection stage is not blocked when a measuring-voltage
failure is detected.
yes
The overcurrent-protection stage is blocked when a measuring-voltage
failure is detected. Siemens recommends using the default setting, as
correct operation of the stage cannot be guaranteed if a measuring-voltage
failure occurs.
Parameter:
Undervoltage threshold
•
Default setting
(_:104) Undervoltage threshold
=
75.0 V
When the controlling voltage is below the set value, the Inverse-time overcurrent protection stage is
released.
The parameter is set to a value just below the lowest phase-to-phase voltage admissible during operation, for
example, from 75 % to 80 % of V
rated
.
7.12.4.2
Protection and Automation Functions
7.12 Voltage-Dependent Overcurrent Protection
SIPROTEC 5, High-Voltage Bay Controller, Manual
781
C53000-G5040-C015-9, Edition 11.2017
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