ABB REX 521, Technical Reference Manual, Standard Configurations

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1MRS751802-MUM Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
Fig. 4.4.1.-3 The other option how to use the lockout function
Note that when the lockout function is in use and an auxiliary power failure occurs,
the output relays return to off-state. The same happens in a situation where external
lockout is used with the output relays PO1, PO2, PO3, SO1
1
and SO2
1
and the
auxiliary power failure occurs. When the protection relay has been powered up
again, the output relay states are restored to the state before the power failure and the
output relay used for the lockout function is energized. If the lockout function is used
with the HSPO1 relay, the control of the breaker could be possible when the
auxiliary power of the protection relay is not connected.
To ensure maximum safety when using the lockout function, it is recommended to
use a battery unit as an auxiliary power. Then the fault in the protected object does
not effect the auxiliary supply of the protection relay and the state of the lockout
function is safely stored in the protection relay’s memory.
1. Change-over contact
+
Lockout
(Normally closed)
Close command
Trip signal
Lockout reset
Lockout
S
R
Q
1
Lockout2