Na7
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MiCOM P741, P742
1.5.7.5 Modem connection
For long distance communication, modems may be used in which the case the following
connections should be made.
FIGURE 17: InterMiCOM TELEPROTECTION VIA A MODEM LINK
This type of connection should also be used when connecting to multiplexers which have the
ability to control the DCD line. With this type of connection it should be noted that the
maximum distance between the Px40 relay and the modem should be 15m, and that a baud
rate suitable for the communications path used should be selected.
1.5.7.6 Functional assignment
Even though settings are made on the relay to control the mode of the intertrip signals, it is
necessary to assign InterMiCOM input and output signals in the relay Programmable
Scheme Logic (PSL) if InterMiCOM is to be successfully implemented. Two icons are
provided on the PSL editor of S1 for “Integral tripping In” and “Integral tripping out” which can
be used to assign the 8 intertripping commands. The example shown below in figure 18
shows a “Control Input_1” connected to the “Intertrip O/P1” signal which would then be
transmitted to the remote end. At the remote end, the “Intertrip I/P1” signal could then be
assigned within the PSL. In this example, we can see that when intertrip signal 1 is received
from the remote relay, the local end relay would operate an output contact, R1.
FIGURE 18: EXAMPLE ASSIGNMENT OF SIGNALS WITHIN THE PSL
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