With the parameter Pickup delay you set whether pickup of the stage is to be delayed by approximately
40 ms or not. The delay avoids possible brief pickup of the stage when the circuit breaker opens.
Parameter Value Description
no
Use this setting if you definitely do not want tripping-stage pickup to be
subject to a time delay in the event of a fault. This setting results in pickup
and, where applicable, tripping being performed as quickly as possible.
Note that switching procedures (opening of the CB) can result in brief
pickup of the tripping stage, depending on the threshold-value settings for
undervoltage pickup and the current-flow criterion. To prevent unwanted
tripping, you must set a minimum tripping delay of 50 ms.
yes
Use this setting when switching procedures (opening of the CB) are not
permitted to result in tripping-stage pickup.
Note that pickup is delayed by approximately 40 ms. This delay is added to
the operate time.
Parameter: Operate delay
•
Default setting (_:481:6) Operate delay = 3 s
The Operate delay must be set for the specific application.
Parameter: Dropout ratio
•
Recommended setting value (_:481:4) Dropout ratio = 1.05
The recommended setting value of 1.05 is sufficient for many applications. To obtain extremely accurate indi-
cations, the Dropout ratio can be reduced.
Parameter: Blk. by meas.-volt. failure
•
Default setting (_:481:10) Blk. by meas.-volt. failure = yes
You use the Blk. by meas.-volt. failure parameter to control the behavior 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 supervision function Measuring-voltage failure detection is configured and
switched on.
•
The binary input signal >Open of the function block VTCB is connected to the voltage-transformer circuit
breaker (see chapter 9.3.4.1 Overview of Functions).
Parameter Value
Description
yes
The protection stage is blocked (= default setting). Siemens recommends
using the default setting.
no
The protection stage is not blocked.
Parameter: Current-flow criterion
•
Recommended setting value (_:2311:104) Current-flow criterion = on
Depending on the system, the voltage transformers can be located on the supply or the output side. These 2
possible voltage transformer locations induce a different behavior of the function after tripping and opening
of the circuit breaker:
•
If they are located on the supply side, the voltage still exists.
•
If they are located on the output side, the voltage does not exist.
Parameter Value
Description
on
If the voltage transformers are located on the output side, you can use the
current-flow criterion to make the pickup drops out when the current falls
below a minimum value (parameter Threshold value I>).
Protection and Automation Functions
6.30 Undervoltage Protection with Positive-Sequence Voltage
SIPROTEC 5, Overcurrent Protection, Manual 753
C53000-G5040-C017-8, Edition 07.2017
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