Parameter Value Description
1 out of 3
Use this setting for protection applications or for monitoring the voltage
range.
Siemens recommends 1 out of 3 as the default setting. This reflects how
the function behaved in previous generations (SIPROTEC 4, SIPROTEC 3).
3 out of 3
Select this setting when using the stage to disconnect from the power
system (in the case of wind farms, for example).
Parameter: Pickup delay
•
Default setting (_:421:102) Pickup delay = no
The Pickup delay parameter is only available if you are using the current-flow criterion of the function
(parameter Current-flow criterion = on). If the current-flow criterion is deactivated, no pickup delay is
required.
With the Pickup delay parameter, 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 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 stage, depending on the threshold-value settings for under-
voltage pickup and the current-flow criterion. To prevent unwanted trip-
ping, 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 stage pickup.
Note that pickup is delayed by approximately 40 ms. This delay is added to
the operate time.
Parameter: Operate delay
•
Default (_:421:6) Operate delay = 3 s
The Operate delay must be set for the specific application.
Parameter: Dropout ratio
•
Recommended setting value (_:421:4) Dropout ratio = 1.05
The recommended setting value of 1.05 is appropriate for most applications. To achieve high-precision meas-
urements, the Dropout ratio can be reduced (to 1.02, for example).
Parameter: Blk. by meas.-volt. failure
•
Default setting (_:421:10) Blk. by meas.-volt. failure = yes
With the Blk. by meas.-volt. failure parameter, you control the behavior of the stage when a meas-
uring-voltage failure is detected.
A measuring-voltage failure can only be detected if one of the following two 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.
Protection and Automation Functions
6.29 Undervoltage Protection with 3-Phase Voltage
SIPROTEC 5, Overcurrent Protection, Manual 739
C53000-G5040-C017-8, Edition 07.2017
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