GE L30 Instruction Manual page 96

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: multi-mode
• 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 as shown below.
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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, as
shown below.
In 2008, GE Digital Energy 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 communi-
cation 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 that are used to set the clock configuration. The functions
of these control switches are shown below.
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:
1. With power to the relay off, remove the IEEE C37.94 module (type 76 or 77 module):
3-38 L30 Line Current Differential System
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