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3-34 L60 Line Phase Comparison Relay GE Multilin
3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE
3
3.3.9 C37.94SM INTERFACE
The UR-series C37.94SM communication modules (2A and 2B) are designed to interface with modified IEEE C37.94 com-
pliant digital multiplexers and/or IEEE C37.94 compliant interface converters that have been converted from 820 nm multi-
mode fiber optics to 1300 nm ELED single-mode fiber optics. 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 C37.94SM communication module is 64 kbps
only with n fixed at 1. 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 result-
ant bit rate of 2048 kbps.
The specifications for the module are as follows:
Emulated IEEE standard: emulates C37.94 for 1 × 64 kbps optical fiber interface (modules set to n = 1 or 64 kbps)
Fiber optic cable type: 9/125
μ
m core diameter optical fiber
Fiber optic mode: single-mode, ELED compatible with HP HFBR-1315T transmitter and HP HFBR-2316T receiver
Fiber optic cable length: up to 10 km
Fiber optic connector: type ST
Wavelength: 1300 ±40 nm
Connection: as per all fiber optic connections, a Tx to Rx connection is required.
The UR-series C37.94SM communication module can be connected directly to any compliant digital multiplexer that sup-
ports C37.94SM as shown below.
It can also can be connected directly to any other UR-series relay with a C37.94SM module as shown below.
The UR-series C37.94SM communication module has six (6) switches that are used to set the clock configuration. The
functions 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.
The C37.94SM communications module cover removal procedure is as follows:
1. Remove the C37.94SM module (modules 2A or 2B):
UR-series
relay
Digital
Multiplexer
C37.94SM
C37.94SM
Fiber Interface
up to 10 km
UR-series
relay
C37.94SM
Fiber Interface
up to 10 km
UR-series
relay
842753A1.CDR