ABB RELION REX640 - Communication settings; Ethernet ports

have all the features of the main relay, mainly containing a minimum acceptable set
of protection functions.
TC2
Same principle
as for TC1
Control +
Control -
-A1
-A1
-TO1
-A2
-TO1
-A2
-TO2
-A3
-TO1
-F1
-Q0
TC1
-A3
-TO2
-A1
-TO2
AUX. POWER
-A2
AUX. POWER
-A3
AUX. POWER
Figure 38: Redundant protection fail-safe principle, example 4
Q0 Circuit breaker (CB)
A1 Protection relay #1
A2 Protection relay #2
A3 Protection relay #3
TO# Protection relay trip output
TC1 CB trip coil 1
TC2 CB trip coil 2
F1 Miniature circuit breaker
In example 4, the fail-safe approach aims at securing circuit breaker tripping even
if one of the redundant relays fails and, in addition, no single relay alone can
cause the circuit breaker tripping. The scheme is often referred to as the 2-out-
of-3 approach. This approach allows service continuation while the failed relay is
waiting for spare parts or a complete replacement. The redundancy in this example
covers relays and circuit breaker tripping coils but it can be expanded to auxiliary
power supplies (two station batteries and isolated distribution), cabling, circuit
breaker failure protection, and so on. All three relays are similar with the same
protection functions. This principle is used in cases where the primary process
requires absolute dependability and security from the supplying feeder protection.
3.4 LED indication control LEDPTRC
Basic functions
1MRS759142 F
116 REX640
Technical Manual