Alstom MiCOM P545 - 1.1.5 3 to 2 terminal reconfiguration

Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546 (OP) 5-23
OP
P1008ENa
I
0
I
0
I
R2
I
R1
Digital communication channel
Relay 1
I
R1
= 0
I
R2
= I
0
I
diff
= I
0
Relay 2
I
R2
= I
0
I
R1
= I
0
I
diff
= I
0
Received Received
P1008ENa
Figure 9 Need for zero-sequence current filtering
1.1.5 3 to 2 terminal reconfiguration
The P54x rel
ays can be configured for the protection of two or three terminal lines. This
allows any of the relays to be applied to a two-ended line which may be converted to a three
terminal line at a later date. Since only the ‘configuration’ setting needs to be changed to
configure the relay for two or three terminal operation, no hardware changes are required
when the third terminal is added, provided that 2 channels of fiber optics are already fitted.
For operational reasons, it may be necessary, under certain circumstances, to switch out
one line end and its associated relay on a three terminal circuit. By altering the
‘Reconfiguration’ setting at any end of the line, an operator can command any pair of relays
to work as a two terminal system. The ‘configured out’ relay can then be switched off,
leaving the line to be protected by the other two relays. A restore command can be issued to
reconfigure the system back to three terminal operation.
Four reconfiguration settings are available:
 Three ended
 Two ended local and remote 1 (L & R1)
 Two ended local and remote 2 (L & R2)
 Two ended remote 1 and remote 2 (R1 & R2)
Before a configuration command can be successfully initiated, it is necessary to energize the
‘reconfiguration interlock’ and ‘Inhibit Current Differential’ opto isolated inputs. The latter
input will disable tripping via the current differential elements from all three relays to ensure
that the scheme will remain stable during reconfiguration.
It must be ensured that the line end to be ‘configured out‘ is open before issuing a
reconfiguration command. If this is not done, any current flowing in or out of the ‘configured
out’ end will be seen as fault current and may cause the other relays to operate.
If the new configuration setting issued to the local relay is L & R1 or L & R2, the trip outputs
of the two ‘2-ended’ relays will remain inhibited by the ‘Inhibit Current Differential’ input at the
local relay. The ‘inhibit trip/alarm outputs’ opto should be de-energized to enable the trip
outputs reconfigured scheme. If the new configuration setting is R1 & R2, the output
contacts of the two remote relays will not be inhibited as they will ignore all commands from
the local relay.
The scheme may be restored to a three terminal configuration by selecting ‘three ended‘ at
any terminal. This will occur irrespective of the status of the opto inputs but is subject to a
healthy communications channel being detected.