The pickup signal is maintained for a settable seal-in time Duration of V-seal-in time, if the positive-
sequence voltage falls below a settable threshold V-seal-in threshold after an overcurrent pickup, even
if the current falls below the threshold again. If the voltage recovers before the seal-in time has elapsed, or if
the undervoltage seal-in is blocked via a binary input
>Block V-seal-in
, the signal
Pickup I>+V-seal-
in
drops out immediately.
You can switch off the undervoltage seal-in via the parameter State of V-seal-in.
Blocking of the Undervoltage Seal-in with Measuring-Voltage Failure
The Undervoltage seal-in can be blocked if a measuring-voltage failure occurs. In case of a blocking, the
pickup signal
Pickup I>+V-seal-in
drops out immediately. The following blocking options are available
for the Undervoltage seal-in:
•
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 VT miniature CB, which
links in the tripping of the voltage-transformer circuit breaker.
The parameter Blk. by meas.-volt. failure can be used to control the measuring-voltage failure
detection. The Undervoltage seal-in remains unaffected if the parameter Blk. by meas.-volt.
failure is switched off.
Application and Setting Notes
Parameter: Operate & flt.rec. blocked
•
Default setting (_:16951:2) Operate & flt.rec. blocked = no
With the parameter Operate & flt.rec. blocked, you can block the operate indication, the fault
recording, and the fault log.
Parameter: Threshold
•
Default setting (_:16951:3) Threshold = 1.350 A
The setting is mainly determined by the maximum operating current.
Pickup by overload must be excluded since the protection may trip if a short operate delay time is set. Set the
Threshold parameter for generators to a value between 20 % and 30 %, for transformers and motors
approx. 40 % above the expected peak load.
Parameter: Operate delay
•
Default setting (_:16951:6) Operate delay = 3.00 s
The parameter Operate delay must be coordinated with the time grading of the network protection to
guarantee the selectivity. Practical time delays are between 1 s to 2 s.
Parameter: Blk. by meas.-volt. failure
•
Default setting (_:16951:10) Blk. by meas.-volt. failure = yes
With the parameter Blk. by meas.-volt. failure, you can activate (yes) or deactivate (no) the
blocking by the Measuring voltage failure detection function. The recommended setting is the default
setting.
Parameter: State of V-seal-in
•
Default setting (_:16951:101) State of V-seal-in = off
With the parameter State of V-seal-in, the seal-in functionality can be activated (switched on). Siemens
recommends this setting if the excitation transformer is connected to the main lead of the generator.
6.4.5.2
Protection and Automation Functions
6.4 Voltage-Dependent Overcurrent Protection, Phases
370 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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