Siemens 7SJ82, Manual

Page: 370 / 1638

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