User Manual

Control concept
Superposed plant controls
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service [OoServ]. The state monitoring of the plant cannot operate correctly, since [PrVal] no longer
reflects the actual state of the aggregate.
To reduce the frequency with which aggregates are switched on and off, it is possible to define a minimum
switch-off time [TiOffMin] in the aggregates. The look-ahead mechanism in the CMD_CTL block prevents
the switching of the whole sequence if the minimum off-time in one aggregate with active state-monitoring
has not yet expired. The output [TraSta] shows the transitional state and [PrVal] remains unchanged, at
the last value. The new plant operating mode will be implemented only when all the aggregates to be
enabled in the switching sequence can actually be enabled.
A minimum off-time should always be set for aggregates incorporating a rotating mass (e.g., fans).
Operating mode changeover
The following figure shows a changeover from operating mode Stage Y to Night cooling.
All objects were switched on in Stage Y. During the changeover to Night Cooling, the system initially checks
whether the new plant operating mode is an AllLifeSafety mode. The Look Ahead check takes place in the
second step; followed by the check and abort of on-going sequences.
In the next step, the switch off series is conducted where the sequence elements of switch off sequence 1
are switched off in parallel. It transitions to the second sequence after the delay time expires. Object 5 is
commanded to Off with plant safety, priority 5. For plant safety or life safety (priority 2), the delay times or
timeouts have no effect. The transition to switch-off sequence is immediately since object 4 is already
switched on.
Objects 3 and 2 are switched at the same time as object 5. Object 1 remains switched on.
Alarm management
Block CMD_CTL is alarmable and differentiates process from system alarms.
02:00
01:00
00:30
1 2 3 4 5 6 7 8
4
1
Object nr.
State monitoring
Switch-on mode
Switch-off delay
Switch-off mode
Operating states
Priority
None None None
None
Delayed
Delayed
Delayed
Delayed
On On
Spec. cmd
Spec. cmd
Spec. cmd
Spec. cmd
Spec. cmd
Spec. cmd
Spec. cmd
Spec. cmd
Switch-off 7Switch-off 8 Switch-off 6
Switch-off 2Switch-off 3
Sequence 1Sequence 2Sequence 3
Objects 8, 7 and 6 are switched off in parallel.
The transition to sequence 2 occurs as
soon as the 30 sec. delay has expired.
Object 4 remains on, object 5 is
switched off at priority level 5. The transition
to sequence 1 occurs immediately
without delay.
Objects 3 and 2 are switched off in parallel.
Object 1 remains on.
Sequence 1
Sequence 2
Sequence 3
00:30 01:00 02:00
Switch-off 5
Delayed 0:30
Delayed 1:00
Delayed 2:00