3.14.4 Device Response
The response of the P634 is dependent on the type of monitoring signal. The
following responses are possible:
●
Signaling Only
If there is no malfunction associated with the monitoring signal, then only a
signal is issued, and there are no further consequences. This situation
exists, for example, when internal data acquisition memories overflow.
●
Selective Blocking
If a fault is diagnosed solely in an area that does not affect the protective
functions, then only the affected area is blocked. This would apply, for
example, to the detection of a fault on the communication module or in the
area of the PC interface.
●
Warm Restart
If the self-monitoring function detects a fault that might be eliminated by a
system restart – such as a fault caused by excessive electro-magnetic
interference –, then a procedure called a warm restart is automatically
initiated. During this procedure, as with any start-up, the computer system
is reset to a defined state. A warm restart is characterized by the fact that
no stored data and, in particular, no setting parameters are affected by the
procedure. A warm restart can also be triggered manually by control action.
During a warm restart sequence the protective functions and the
communication through serial interfaces will be blocked.
If the same fault is detected after a warm restart has been triggered by the
self-monitoring system within the set SFMON: Mon.sig. retention, then
the protective functions remain blocked but communication through the
serial interfaces will usually be possible again.
If a corrupted setting is diagnosed during the checksum test, which is part
of the self-monitoring procedure, settings are restored from an internal
back-up memory. Nevertheless, in order to get the device back to well
defined operation conditions a warm restart is executed.
For any warm restart initiated by self-monitoring, the root cause (alarm
event) is logged in the monitoring buffer.
●
Cold Restart
In case the recovery of corrupted settings failed (e.g. because of an
electrical defect of the memory chip), then a cold restart is carried out. This
is necessary because the P634 cannot identify which parameter in the
subset is corrupted. A cold restart causes all internal memories to be reset
to a defined state. This means that all the protection device settings are
also erased after a cold restart. In order to establish a safe initial state, the
default values have been selected so that the protective functions are
blocked. Both the monitoring signal that triggered the cold restart and the
value indicating parameter loss are entered in the monitoring signal
memory.
A cold restart can also be triggered manually by control action (to
intentionally erase all memories and reset the device to default settings).
3 Operation
P634
P634/EN M/R-42-A // P634‑311‑653 3-103
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