GE T60, Instruction Manual

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GE Multilin T60 Transformer Protection System 3-41
3 HARDWARE 3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS
3
3.3.8 IEEE C37.94 INTERFACE
The UR-series IEEE C37.94 communication modules (modules types 2G, 2H, 2I, 2J, 76, and 77) are designed to interface
with IEEE C37.94 compliant digital multiplexers or an IEEE C37.94 compliant interface converter for use with direct input
and output applications. The IEEE C37.94 standard defines a point-to-point optical link for synchronous data between a
multiplexer and a teleprotection device. This data is typically 64 kbps, but the standard provides for speeds up to 64
n kbps,
where n = 1, 2,…, 12. The UR-series C37.94 communication modules are either 64 kbps (with n fixed at 1) or 128 kbps
(with n fixed at 2). The frame is a valid International Telecommunications Union (ITU-T) recommended G.704 pattern from
the standpoint of framing and data rate. The frame is 256 bits and is repeated at a frame rate of 8000 Hz, with a resultant bit
rate of 2048 kbps.
The specifications for the module are as follows:.
• IEEE standard: C37.94 for 1 × 128 kbps optical fiber interface (for 2G and 2H modules) or C37.94 for 2 × 64 kbps opti-
cal 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.
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 T60 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.
UR-series
device
IEEE C37.94
fiber interface
up to 2 km
842755A2.CDR
Digital
multiplexer,
IEEE C37.94
compliant
UR-series
device
up to 2 km
IEEE C37.94
converter
RS422
interface
842756A2.CDR
IEEE C37.94
fiber interface
Digital
multiplexer
with EIA-422
interface