Alstom MiCOM P54 Series, Technical Manual, Page: 295 / 1024

Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546
(OP) 5-121
OP
2.3.1.3 InterMiCOM
64
and differential communications
The Differential function can be globally enabled or disabled using the CONFIGURATION
/Phase Diff/ Enabled-Disabled setting.
If the Differential function is enabled, communication messages between the relays will have
the complete differential format including currents and additional bias. In addition, the
GROUP X/PHASE DIFF/Enabled-Disabled setting will be displayed allowing the differential
functionality to be enabled or disabled on a per group basis.
If the Differential function is disabled in Configuration column, a
CONFIGURATION/InterMiCOM
64
/Enabled-Disabled setting will be displayed. The
InterMiCOM
64
function could be enabled and the communication messages between the
relays will have a different format compared with those of the differential function. The
message format will include digital signals only and will be shorter and faster.
If differential protection in group is disabled, the InterMiCOM
64
function can work with the
differential message format or with an inherent stand-alone format where only digital signals
are transmitted. The stand-alone message format has a pass though feature and is slightly
faster than using the InterMiCOM
64
function with the differential message format.
2.3.2 Permissive Intertrip
The P54x relays include a facility to send a permissive intertrip command over the protection
communication channel, as shown in Figure 79.
P10 2 1ENa
D ata m essage
P 5 xx P 5 xx
Figure 79 Permissive intertrip
An opto input can be assigned for this purpose. When the associated opto input is
energized at END B, the PIT flag is set in the communication message. Upon receipt of this
message, the relay at END A initiates the PIT timer which times out and trips the circuit
breaker, providing that the Remote or Local current (according to setting PIT I selection/
Remote or Local ) remains above its basic current threshold setting (

s1), times out, the relay
closes it’s three phase differential trip contacts. The remote relay provides indication of the
permissive intertrip.
The permissive intertrip timer is settable between 0 and 200 ms. This time should be set to
provide discrimination with other protection. For example, in Figure 79
, the time delay
should be set to allow the busbar protection to clear the fault in the event of a genuine
busbar fault. A typical setting may be 100 - 150 ms.