3.14.5 Monitoring Signal Memory
Depending on the type of internal fault detected the P634 will respond by trying
to eliminate the problem with a warm restart. (See above; for further details read
also about P634 behavior with problems in Chapter 11, (p. 11-1).) Whether or
not this measure will suffice can only be determined if the monitoring signal has
not already been stored in the monitoring signal memory because of a previous
fault. If it was already stored and a second fault is detected then, depending on
the type of fault detected, the P634 will be blocked after the second warm
restart.
In order to better monitor this behavior the parameter at SFMON: Mon.sig.
retention is applied. This parameter may either be set to ‘Blocked’ or to a time
duration (in hours). (It is, however, discouraged to set it to 0, because in this
case, there would be no blocking at all, so that there would be the danger of
maloperation in case of a permanent failure.)
The default for this timer stage is Blocked, i.e. blocking of the protection device
with two identical faults occurs independently of the time elapsed since the first
fault monitoring signal was issued.
The behavior caused by sporadic faults could lead to an unwanted blocking of the
P634 if the monitoring signal memory had not been reset in the interim, for
example, because the substation is difficult to reach in wintertime or reading-out
and clearing of the monitoring signal memory via the communication interfaces
was not enabled. To defuse this problem it is suggested to set the function
parameter to a specific time period so that blocking will only occur if the same
fault occurs again within this time period. Otherwise, the P634 will continue to
operate normally after a warm restart.
3.14.6 Monitoring Signal Memory Time Tag
The time when the device fault occurred last is recorded.
P634 3 Operation
3-104 P634/EN M/R-42-A // P634‑311‑653
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