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3-32 L60 Line Phase Comparison Relay GE Multilin
3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE
3
3.3.8 IEEE C37.94 INTERFACE
The UR-series IEEE C37.94 communication modules (76 and 77) are designed to interface with IEEE C37.94 compliant
digital multiplexers and/or an IEEE C37.94 compliant interface converter for use with L90 and L90 direct inputs/outputs on
version 3.20 and direct input/output applications for firmware revisions 3.30 and higher. 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
module is 64 kbps only with n fixed at 1. The frame is a valid International Telecommunications Union (ITU-T) recom-
mended 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 × 64 kbps optical fiber interface
Fiber optic cable type: 50 mm or 62.5 mm core diameter optical fiber
Fiber optic mode: multi-mode
Fiber optic cable length: up to 2 km
Fiber optic connector: type ST
Wavelength: 830 ±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.
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.
The UR-series C37.94 communication module has six (6) switches that are used to set the clock configuration. The func-
tions of these control switches is 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.
UR series
relay
Digital
Multiplexer
IEEE C37.94
compliant
IEEE C37.94
Fiber Interface
up to 2 km
UR series
relay
Digital
Multiplexer
with EIA-422
Interface
IEEE C37.94
Fiber Interface
up to 2 km
IEEE C37.94
Converter
RS422
Interface
842753A1.CDR