Pickup Mode
With the Pickup mode parameter, you define whether the stage picks up when there is a lower threshold-
value violation in one measuring element (1 out of 3) or when there is a lower threshold-value violation in
all 3 measuring elements (3 out of 3).
Pickup Delay
The Pickup delay parameter is only available and of relevance if you are using the current-flow criterion of
the function (parameter Current-flow criterion = on).
If the circuit breaker opens when the current-flow criterion is being used, the undervoltage detection and
current-flow dropout functions conflict with one another. Depending on the threshold value settings for
undervoltage detection and current-flow criterion, it is possible that the undervoltage is detected before the
current-flow criterion has dropped out. In this case, the stage picks up briefly. Use the Pickup delay param-
eter to prevent the stage from briefly picking up in this way when the circuit breaker opens. This is achieved
by delaying pickup by approximately 40 ms.
Current-Flow Criterion
The undervoltage protection stages work optionally with a current-flow criterion. The Current-flow
criterion works across all tripping stages.
When the Current-flow criterion parameter is activated, the undervoltage protection stages only pick
up if a settable minimum current (Threshold I>) is exceeded. A current below the minimum current blocks
the stages.
The current-flow criterion can also be set to fulfilled with the binary input signal >Current flow-crite-
rion. The function reports when the current-flow criterion is fulfilled.
Figure 6-201 illustrates the influence of the current-flow criterion.
NOTE
If the (_:2311:104) 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. The following blocking options are available for the
stage:
•
Via the binary input signal
>Block stage
from an external or internal source
•
From inside on pickup of the Measuring-voltage failure detection function (see section 9.3.2.1 Over-
view of Functions). The Blk. by meas.-volt. failure parameter can be set so that measuring-
voltage failure detection blocks the stage or does not block it.
•
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
Parameter: Method of measurement
•
Recommended setting value (_:421:8) Method of measurement = fundamental comp.
With the Method of measurement parameter, you define whether the stage uses the fundamental compo-
nent (standard method = default setting) or the calculated RMS value.
6.29.3.2
Protection and Automation Functions
6.29 Undervoltage Protection with 3-Phase Voltage
SIPROTEC 5, Overcurrent Protection, Manual 737
C53000-G5040-C017-8, Edition 07.2017
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