Technical description
3 Supporting functions
3.11 Self-supervision
VM50.EN004
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Figure 3.10-1 Combined o/c status.
The fault that can be seen in the Figure 3.10-1 was 3 times to
nominal and it started as an one phase fault L1-E. At the
moment when one of the protection stages tripped the fault was
already increased in to a two phase short circuit L1-L2. All
signals those are stated as “1” are also activated in the output
matrix. After the fault disappears the activated signals will
release.
Combined over current status can be found from vampset menu
“protection stage status 2”.
3.11.
Self-supervision
The functions of the microcontroller and the associated
circuitry, as well as the program execution are supervised by
means of a separate watchdog circuit. Besides supervising the
relay, the watchdog circuit attempts to restart the micro
controller in a fault situation. If the restarting fails, the
watchdog issues a self-supervision alarm indicating a
permanent internal fault.
When the watchdog circuit detects a permanent fault, it always
blocks any control of other output relays (except for the self-
supervision output relay).
In addition, the internal supply voltages are supervised. Should
the auxiliary supply of the relay disappear, an alarm is
automatically given because the internal fault (IF) output relay
functions on a working current principle. This means that the
IF relay is energized when the auxiliary supply is on and no
internal fault is detected.