Siemens 6MD85, Manual

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Parameter Value Description
with effective crite-
rion
Siemens recommends keeping the default setting, because it prefers the
current as a reliable criterion for detection of an open CB and thus for
dropout of the CBFP function.
w. aux.c. and
curr.crit.
Select this setting for applications on transformers or generators (see the
preceding examples) in which the current flow is such that the current is no
longer a reliable criterion for detecting the opening of the CB.
Parameter: Retrip
•
Default setting
(_:110) Retrip after T1
=
no
Parameter Value Description
no
Where no redundant CB control is provided, a repetition of the trip signal to
the local CB is not required.
start T2 after T1
Where a redundant CB control (2nd trip coil with 2 trip circuits) is provided,
a repetition of the trip signal to the local CB makes sense.
Siemens recommends the setting
start T2 after T1
because it
provides a clear chronological separation of the processes for trip repeat
and backup tripping. Remember here that the overall fault-clearance time in
case of a failure of the local CB is the sum of T1 and T2.
parallel start T2, T1
As an alternative to the setting
start T2 after T1
, you can start
parallel start T2, T1
.
Parameter: Retrip 1-/3-pole (1/3-pole circuit breaker)
•
Default setting
(_:109)Retrip 1-/3-pole
=
3-pole
In the case of 1-phase short circuits, you can select
1-pole
or
3-pole
for retripping.
Parameter: Delay T1 for 1-pole retrip (1/3-pole Circuit Breaker), Delay T1 for 3-pole retrip
•
Default setting (3-pole circuit breaker)
(_:109) Delay T1 for 3-pole retrip
=
0.05 s
•
Default setting (1/3-pole circuit breaker)
(_:113) Delay T1 for 1-pole retrip
=
0.05 s
•
Default setting (1/3-pole circuit breaker)
(_:111) Delay T1 for 3-pole retrip
=
0.25 s
The parameters are visible only when retripping is set.
For most applications, the time delays for the 1-pole and the 3-pole (multipole) start are set equally.
The setting depends on the user's philosophy.
The following settings make sense:
•
If the minimum fault-clearing time has top priority, Siemens recommends setting the time to 0. This
setting causes initiation of the retrip immediately upon the start. The drawback is that a defect of the 1st
trip circuit is not detected.
•
With a small time delay of, for instance, 50 ms, the defect of the 1st trip circuit can be detected based on
the evaluation of the fault record.
•
With a long time delay which reliably ensures the dropout of the CBFP with the CB open, the rising edge
indication of the trip repeat
Retrip T1
is a sure signal for a fault in the 1st trip circuit. The following
example shows how this time is determined.
EXAMPLE
Determining the T1 Time that Reliably Ensures the Dropout of the CBFP with the CB Open:
Time of binary device output
(when tripping is caused by the device-internal
protection) 5 ms
Protection and Automation Functions
7.1 Circuit-Breaker Failure Protection
SIPROTEC 5, High-Voltage Bay Controller, Manual 535
C53000-G5040-C015-9, Edition 11.2017