Siemens 6MD85, Manual

Page: 815 / 1256

i
i
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 is 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. 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: Pickup mode
•
Recommended setting value
(_:101) Pickup mode
=
1 out of 3
With the
Pickup mode
parameter, you specify 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
).
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
(_: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.
7.16.8
Protection and Automation Functions
7.16 Undervoltage Protection with 3-Phase Voltage
SIPROTEC 5, High-Voltage Bay Controller, Manual 815
C53000-G5040-C015-9, Edition 11.2017