VAMP Ltd
Overcurrent and earth-fault relay
Technical description
VAMP 140
VM140.EN011
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25
2.7.
Self-supervision
The functions of the micro controller 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 because of a
permanent relay fault.
When the watchdog circuit detects a permanent fault it always
blocks any control of the other output relays, except for the self-
supervision output relay.
Also the internal supply voltage is supervised. Should the
auxiliary supply of the relay disappear, an IF alarm is
automatically given. The IF relay contact is normally closed
type of contact. This means that the IF relay contact is closed,
when there is an internal fault or there is no auxiliary power
supply. If the relay is fully operational with the auxiliary power
supply, the IF contact is on the open position.