GE L30 Instruction Manual page 99

CHAPTER 3: INSTALLATION
Figure 3-45: 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 the module and is to be used on all ends of L30
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.
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 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.
4. Remove the top cover by sliding it towards the rear and then lift it upwards.
5. Set the timing selection switches (channels 1 and 2) to the required timing modes (see description earlier).
6. Replace the top cover and the cover screw.
7. Re-insert the IEEE C37.94 module. Take care to ensure that the correct module type is inserted into the correct slot
position. The ejector/inserter clips located at the top and at the bottom of each module must be in the disengaged
position as the module is inserted smoothly into the slot. Once the clips have cleared the raised edge of the chassis,
engage the clips simultaneously. When the clips have locked into position, the module is inserted fully.
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
Figure 3-46: Switches
PILOT CHANNEL COMMUNICATIONS
3
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