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Functions
2.20 Auxiliary Functions
Figure 2-100
Diagram of CB maintenance procedures
The ΣI procedure is always present and active as a basic functionality. However, the other procedures (ΣI
2
and I
t) can be selected via a common configuration parameter.
As the load on the switch depends on the current amplitude and duration of the actual switching action, includ-
ing arc deletion, determination of the start and end criteria is of great importance. The procedures ΣI
2
I
t make use of the same criteria for that purpose. The logic of the start and end criterion is illustrated in Figure
2-101.
The start criterion is fulfilled by an internal protective tripping initiated by the group indication "device TRIP".
Trips initiated via the internal control function are taken into consideration for the circuit breaker maintenance
if the respective command is indicated via the parameter 265 Cmd.via control. An externally initiated trip
command can be taken into consideration if the message „>52 Wear start" is sent simultaneously via a
binary input. The edge of the sent message „>52-a" can also be used as a further criterion as this signals
that the mechanism of the circuit breaker is put in motion in order to separate the contacts.
As soon as the start criterion has been fulfilled, the parameterized opening time of the circuit breaker is started.
The time of commencement of separation of the circuit breaker contacts is thus determined. The end of the trip
procedure, including arc deletion is determined via another given parameter (CB tripping time) supplied by the
manufacturer of the circuit breaker.
In order to prevent an incorrect calculation procedure in case of circuit breaker failure, the current criterion 212
BkrClosed I MIN verifies whether the current actually returned to zero after two additional cycles. When the
phase-selective logic release is fulfilled by the current criterion, the calculation and evaluation methods of the
respective procedures are initiated. After these have been completed, the end criterion of the circuit breaker
maintenance is fulfilled and ready for a new initiation.
Please note that CB maintenance will be blocked if parameter settings are made incorrectly. This condition is
indicated by the message „52 WearSet.fail", „52WL.blk n PErr" or „52WL.blk I PErr" (see
Section 2.1.6.2, „Power System Data 2"). The latter two indications can only take effect if the 2P-procedure was
configured.
264
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
x
, 2P
x
, 2P and
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