User Manual

Control concept
Superposed plant controls
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Step 3: Abort sequence
On-going switch sequences are aborted when delay times are still active.
Exception: An alarm is generated when a fault occurs as part of internal
monitoring of the block. The demanded plant operating mode is determined in
this cased by the exception value [EcptVal]. If the switch sequence is active,
but not completed, it is NOT aborted, but rather is completed.
Step 4: Ramp-down sequence
The ramp-down sequence is started first for the new plant operating mode.
This shuts down all aggregates that must be switched off per the new plant
operating mode. The shut down takes place in the table sequence from right to
left, in other words, the last aggregate in the switch sequence is the shut down
first. The parameterized times for the time off delay are active during ramp
down to off. The time off delay can be activated using a fixed delay time or a
maximum timeout or deactivated using the immediate option. The length of the
delay for timeout depends on the switch off state of the monitored sequence
elements. Transition to the next sequence occurs as soon as it reports switched
off, that is, the process value of the block [PrVal] = Off. It switches after the
timeout time expires when the shut-down message is not sent.
If a sequence element with a life-safety or plant-safety priority is switched off,
the preset delay times will be ignored.
Step 5: Step-up sequence
The step-up sequence is then started for the new plant operating mode. The
remaining aggregates are switched on per the data in the function table. The
switch on takes place in the table sequence from left to right, in other words,
the first aggregate in the switch sequence is the switched on first.
The parameterized times for the time on delay is active during step-up.
The step-up delay can be activated using a fixed delay time or a maximum
timeout or deactivated using the immediate option. The length of the delay for
timeout depends on the switch on state of the monitored sequence elements.
Transition to the next sequence occurs as soon as it reports switched on, that
is, the process value of the block [PrVal] <> Off. It switches after the timeout
time expires when the switch on message is not sent.
When a sequence element with a life-safety or plant-safety priority is switched
on, the preset delay times will take effect first.
Step 6: Monitoring switch on state
A process alarm (off normal) is generated when the monitored aggregate is not
switched on after the sequence delay time expires.
The current switch sequence is immediately aborted when the current plant
operating mode is not AllLifeSafety and the exception value [EcptVal] is
selected as the operating mode.
If, however, the exception value [EcptVal] is already the plant operating mode,
the switch sequence is not aborted and the plant operating mode does not
change.
Switch on aggregates
The following figure shows the switch response and monitoring mechanism for
block CMD_CTL.
The system initially checks if 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. The next step is to run the shut-down
series, where objects 8 and 4 are switched off to the extent they have not yet
be shut down. The sequences are then switched on one after the other in the
follow-on switch on series.