GE L30 Instruction Manual page 106

3.3 PILOT CHANNEL COMMUNICATIONS
IEEE standard: C37.94 for 2 × 64 kbps optical fiber interface (for 76 and 77 modules)
•
• Fiber optic cable type: 50 nm or 62.5 µm core diameter optical fiber
• Fiber optic mode: multimode
• Fiber optic cable length: up to 2 km
• Fiber optic connector: type ST
• Wavelength: 820 ±40 nm
• Connection: as per all fiber optic connections, a Tx-to-Rx connection is required
The UR-series C37.94 communication module can be connected directly to any compliant digital multiplexer that supports
the IEEE C37.94 standard shown as follows.
3
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,
shown as follows.
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 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 cus-
tomers 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, the timing switch selection should be
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, the timing selection
should be in loop timing mode for connections to higher order systems.
The IEEE C37.94 communications module cover removal procedure is as follows:
3-40 L30 Line Current Differential System
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