Description
Product Overview
1MRK002122-AB is the short-range optical line data communication module of ABB’s Relion 670 family — the board that ABB’s own product guide names “Optical short range LDCM” and that carries the factory designation 670LDCM02 SHORT. It installs in a remote-communication position inside a RED670, REG670, REL670, RET670 or REC670 terminal, and converts one duplex multimode fiber pair into a synchronous channel over which two ends of a protected line exchange their sampled currents.
What travels through that channel is what makes the board a protection component rather than a data link. Every 5 ms a telegram leaves carrying the three-phase current samples, the time reference that keeps both ends in step, trip, block and alarm flags, and eight binary signals available for transfer trip or interlocking. The differential algorithm is only as dependable as the alignment of those samples, so the channel’s stability, framing and clock behaviour become part of the protection settings rather than a background IT concern.
The engineering decision that follows from this is optical budget. On 62.5/125 µm graded-index fiber the module offers 13 dB of budget and about 3 km of reach; on 50/125 µm, 9 dB and roughly 2 km. Launch power is −17 dBm at minimum against −30 dBm receiver sensitivity, and a selectable high-power setting contributes about 3 dB of extra headroom. Those numbers, together with the stated assumptions of 3 dB/km fiber loss, 1.5 dB per ST connector and 0.5 dB per repair splice, let a route be judged on paper before any hardware is ordered.
Technical Specifications
| Parameter | Value |
|---|---|
| Model | 1MRK002122-AB (revision r00) |
| Manufacturer | ABB, Sweden |
| Product type | Line data communication module, optical short range, IED plug-in board |
| Optical connector | ST duplex, transmit and receive pair |
| Fiber type | Graded-index multimode 62.5/125 µm as standard; 50/125 µm accepted with lower budget |
| Wavelength | 820 nm peak emission, 865 nm nominal, 792 nm minimum |
| Optical budget | 13 dB on 62.5/125 µm, 9 dB on 50/125 µm |
| Working distance | About 3 km and 2 km respectively, confirmed by link calculation |
| Launch and sensitivity | −17 dBm minimum output on 62.5/125 µm, −30 dBm receiver sensitivity |
| Protocol | IEEE C37.94 synchronous, HDLC framing |
| Data rate | 64 kbit/s default, 2 Mbit/s mode selectable |
| Telegram payload | Three-phase current samples each 5 ms, time information, trip/block/alarm, eight binary signals |
| Channels per IED | Up to four remote communication interfaces |
| Supply | From the IED backplane, no separate power feed |
| Slot positions | P30:5, P30:6, P31:3, P32:2, P32:3 depending on chassis model |
| Standards | IEC 60255-26 for EMC, IEC 60255-1 and IEC 60255-27 for the parent IED |
1MRK002122-ABr01
Key Features and Advantages
The telegram defines the product, not the connector
Eight binary signals ride inside the same telegram as the currents, which is why a scheme built on 1MRK002122-AB needs no second path for transfer trip, interlocking or status exchange. One fiber pair replaces what would otherwise be a differential channel plus a separate teleprotection link with its own terminal equipment and its own failure modes.
Budget-led reach keeps single-mode out of the picture
Where the two ends sit within a compound or an industrial site, the 13 dB multimode budget covers the route and the cost of single-mode optics, FC/PC terminations and fusion splicing disappears from the project. The low and high power settings let one board type serve a 200 m intra-station patch and a 2.5 km inter-substation run without attenuators on the short span.
Redundancy from module count rather than added hardware
A chassis accepts up to four modules, so a main and standby channel pair, or the two links of a three-ended line, are configured by populating positions and assigning them in the signal matrix. 1MRK002122-AB therefore covers redundant topologies without a second communication processor or an external changeover device.
Clock discipline shared between the two ends
One end generates the timing and the other derives it from the received signal, a relationship set at commissioning rather than negotiated at runtime. The 2 Mbit/s mode extends this to link forwarding, where a mid-route terminal passes both local and received remote currents onward so that a chain behaves as a single differential zone.
Applications
Station pairs inside one compound account for most deployments: a 400 kV yard and its 110 kV counterpart sharing a fence line, a hydro plant switchyard and the adjacent grid substation, or two bays protecting a short interconnecting feeder. The physical span is small, the protection requirement is identical to a long overhead line, and 1MRK002122-AB provides unit protection without entering the single-mode domain.
Along a river cascade, generating stations often sit a kilometer or two apart, and the same module links successive REG670 terminals for unit and line differential functions without leasing a telecom circuit. Urban cable networks use it between adjacent distribution substations, where the cable route is short but the consequence of an uncleared fault is measured in customer minutes.
Industrial captive grids form a third family — mine feeder lines, steel works interties, refinery internal transmission, airport and data-centre HV distribution — where a private network of a few kilometers needs the same unit protection as a utility line. Binary signal transfer is the fourth: interlocking between busbar and line protection, transfer trip from external relays, or status exchange for a sequential black-start, all carried on the same supervised pair of fibers.
Commissioning benches and training facilities make up the fifth, where two IEDs are connected back-to-back over a short multimode patch cord to exercise the differential function end to end before the scheme goes live.
Related Products
1MRK002311-AA — medium range LDCM on single-mode 9/125 µm at 1310 nm with FC/PC connector, 22 dB budget for the 60 to 80 km class of route. 1MRK002311-BA — long range LDCM at 1550 nm, 26 dB budget, for links in the 110 to 130 km range. 1MRK005500-AA — Ethernet SFP module with optical LC connector, used for station bus traffic rather than the protection channel. 1MRK005500-BA — Ethernet SFP module with RJ45 connector, the copper alternative for the same station-bus function. 1MRK002266-EA — optical Ethernet module for IEC 61850 station communication. 1MRK001608-AB / 1MRK001608-BB / 1MRK001608-CB — serial SPA, LON, DNP and IEC 60870-5-103 modules in plastic, plastic-glass and glass versions, the option when the far end is reached over serial telecontrol. 1MRK002309-AA — galvanic RS485 module for short copper connections between devices in the same station. 1MRK007002-AA — GPS time module, specified where differential protection relies on a global clock rather than derived channel timing. 1MRK002282-AB — IRIG-B time synchronization module, the other external time base for the same schemes. RED670 / REG670 / REL670 — the terminals that host 1MRK002122-AB in line, generator and distance protection applications.
Installation and Maintenance
Before installation: check which remote-communication positions the installed chassis actually offers, because the slot map differs between case sizes and a module cannot simply be dropped into any free opening. Count the channels the scheme needs before ordering fiber — one for a two-ended line, two per end for a three-ended line, a main plus standby for redundancy. Sweep the route with an optical time-domain reflectometer, compare the measured loss against the 13 dB budget, and decide the low or high power setting from the resulting margin; low applies up to about 1 km, high beyond. De-energize the IED before fitting 1MRK002122-AB, and keep patch cords to the same fiber specification as the installed route.
Maintenance practice: clean each ST ferrule before mating and after any intervention at the distribution panel, since one contaminated end face can consume more budget than the entire long-term aging allowance. Record launch power and received level at commissioning, then re-measure annually; a drift of 2 to 3 dB indicates connector degradation, not a failing board. Verify after every board change that one end is clock master and the other slave, then run a loop-back test and read the channel supervision counters before the protection is returned to service. Store spares with optical port caps fitted and the revision level marked on the label.
Warranty and Quality
1MRK002122-AB is supplied as a plug-in module with the revision level confirmed against the position it will occupy, and every unit passes a fiber loop-back bench check covering launch power, received level, C37.94 framing lock and channel status, with the record issued alongside the packing list. A 12-month warranty applies under standard substation-automation practice, covering repair or replacement of quality-related failures. Where a scheme depends on two or three modules at once, the set is checked for revision consistency before dispatch, because mixed revisions inside one chassis complicate later diagnosis. Technical support covers slot mapping, master/slave clock configuration, optical budget review from route survey data, and the low versus high power decision.
