3-32 D30 Line Distance Relay GE Multilin3.3 DIRECT INPUT/OUTPUT COMMUNICATIONS 3 HARDWARE33.3.8 IEEE C37.94 INTERFACEThe UR-series IEEE C37.94 communication modules (76 and 77) are designed to interface with IEEE C37.94 compliantdigital multiplexers and/or an IEEE C37.94 compliant interface converter for use with direct input/output applications forfirmware revisions 3.30 and higher. The IEEE C37.94 standard defines a point-to-point optical link for synchronous databetween a multiplexer and a teleprotection device. This data is typically 64 kbps, but the standard provides for speeds up to64n kbps, where n = 1, 2,…, 12. The UR-series C37.94 communication module is 64 kbps only with n fixed at 1. The frameis a valid International Telecommunications Union (ITU-T) recommended G.704 pattern from the standpoint of framing anddata 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 interfaceFiber optic cable type: 50 mm or 62.5 mm core diameter optical fiberFiber optic mode: multi-modeFiber optic cable length: up to 2 kmFiber optic connector: type STWavelength: 830 ±40 nmConnection: 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 supportsthe 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 anon-compliant digital multiplexer via an optical-to-electrical interface converter that supports the IEEE C37.94 standard, asshown 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 beInternal 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 selectionshould be in Loop Timing Mode for connections to higher order systems.The C37.94 communications module cover removal procedure is as follows:842753A1.CDR
