CHAPTER 3: INSTALLATION
DIRECT INPUT AND OUTPUT COMMUNICATIONS
L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
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Figure 3-53: IEEE C37.94 connection to compliant digital multiplexer
The UR-series C37.94 communication module can be connected to the electrical interface (G.703, RS422, or X.21) of a non-
compliant digital multiplexer via an optical-to-electrical interface converter that supports the IEEE C37.94 standard. The
following figure shows the concept.
Figure 3-54: IEEE C37.94 connection to non-compliant digital multiplexer
In 2008, GE Grid Solutions released revised modules 76 and 77 for C37.94 communication to enable multi-ended fault
location functionality with firmware 5.60 release and higher. All modules 76 and 77 shipped since the change support this
feature and are fully backward compatible with firmware releases below 5.60. For customers using firmware release 5.60
and higher, the module can be identified with "Rev D" printed on it and is to be used on all ends of L60 communication for
two and three terminal applications. Failure to use it at all ends results in intermittent communication alarms. For
customers using firmware revisions below 5.60, it is not required to match the revision of the modules installed.
The UR-series C37.94 communication module has six switches to set the clock configuration. The following figure shows
the functions of these control switches.
Figure 3-55: Switches
For the internal timing mode, the system clock is generated internally. Therefore, set the timing switch selection to internal
timing for relay 1 and loop timed for relay 2. There must be only one timing source configured.
For the looped timing mode, the system clock is derived from the received line signal. Therefore, set the timing selection to
loop timing mode for connections to higher order systems.
The IEEE C37.94 communications module cover removal procedure is as follows:
1.
With power to the relay off, remove the IEEE C37.94 module (type 2G, 2H, 2I, 2J, 76, or 77 module) as follows. Record
the original location of the module to help ensure that the same or replacement module is inserted into the correct
slot.
2.
Simultaneously pull the ejector/inserter clips located at the top and bottom of each module in order to release the
module for removal.
3.
Remove the module cover screw.
