ABB 1MRK002247-AH Transformer Module – Auxiliary Current Transformer (Interposing CT) for ABB RET/REG/RED IED Cubicles

Technical Specifications

Main Features and Advantages

AH suffix = ratio + burden + tap, not optional.​ The ABB 1MRK002247-AH​ is useless without knowing what the AH suffix encodes for your cubicle. The 1MRK002247 base spans AA through (at least) AH and beyond, and each suffix changes the primary/secondary ratio, the VA burden class, the tap positions, and sometimes the terminal-function map (summation 3→1 vs. REF core vs. 1:1 buffer). For a RET620 cubicle, the AH might be a 300/5 → 1A REF core; for a REG670, the same base number with a different suffix might be a 1:1 5VA neutral buffer. The buying rule — same as the 1MRK PWAs in this catalog — is: photograph the removed 1MRK002247-AH​ label, match the full suffix, order. If your BOM just says “1MRK002247” without suffix, you’re guessing, and CT guessing in a protection cubicle is how you get relay ratio alarms on commissioning.Magnetic, not electronic — different failure mode, different spare logic.​ Unlike the AAR01 and BDR02 PWAs (DSP/FPGA/logic, fail by corruption or EMI), the ABB 1MRK002247-AH​ fails by core saturation, winding insulation breakdown, or potting hygroscopy after a decade-plus in a cubicle that sees humidity cycles. Symptoms are subtle: relay logs “CT ratio error,” “diff spill at load,” or “REF element unstable during switching” — all traceable to the aux CT if you know the cubicle schematic. The 1MRK002247-AH​ has no LEDs, no firmware, no self-diag — it’s a passive magnetic, and that’s exactly right for a component that sits between a 5A site CT secondary and a relay input. Passive also means it survives the cubicle’s EMI environment (thyristor cubicle next door, VFD bay upstairs) without the headaches a small PWA would have in the same spot.Potted encapsulation for cubicle environments.​ The ABB 1MRK002247-AH​ is potting-filled, not open-frame, because protection cubicles — especially in hydro, coastal, paper-mill, and untreated MCC rooms — see humidity, salt-mist, and chemical vapour that would corrode bare CT tappings in five years. The potting also damps vibration from cubicle cooling fans and from the switchyard-side circuit-breaker operation that rattles the bay floor. For a CT that may not move for twenty years, that potting is the difference between “still within ratio” and “core laminations walking.”Screw-terminal, DIN or panel — cubicle-flexible.​ The 1MRK002247-AH​ ships with screw-clamp terminals (CT secondaries must be screw-clamp or stud, not spring-wire meant for electronics — CT secondary open = kV on the open terminal). Mounting is typically DIN-rail clip or panel-foot screws per the cubicle BOM, so the same AH module drops into a RELION IED flush-cubicle DIN row or a SAM freestanding cubicle panel without adapter hardware. For MRO electricians this means the swap is: LOTO the CT secondary (keep it shorted until the last second), unscrew 4–6 terminals, unclip, clip new ABB 1MRK002247-AH, re-land, torque, un-short — 15 minutes.Pairs with the 1MRK PWA siblings in the same cubicle.​ In a RET620 or REG670 cubicle the 1MRK002247-AH​ often shares the cubicle with the 1MRK000161-AAR01​ (regulation/control PWA in excitation cousin-cubicles) or with the IED’s own processor/communication boards — different product class, same 1MRK catalog umbrella, same “suffix-discipline” buying logic. For MRO planners standardising a bay’s spare set, the AH aux-CT belongs on the shelf alongside whatever 1MRK PWAs the same cubicle carries, because a “RET620 bay #3” requisition should pull ratio-matched CT + any 1MRK PWA + the IED’s own spare COM/processor module as a kit, not as a scavenger hunt.

Application Field

The ABB 1MRK002247-AH​ lives inside ABB protection relay cubicles rather than in open-panel builds, so its application field clusters in utilities and heavy-process plants where ABB RET/REG/RED/REF RELION or SAM cubicles were specified. Hydroelectric unit bays — generator protection (REG670) with neutral CT adaptation, transformer protection (RET620) with wye-side REF CT and delta-sum CT — are dense users of the 1MRK002247-AH​ because every RET620 cubicle typically carries 2–4 aux CTs (high-side sum, low-side sum, wye-neutral REF, sometimes delta-tertiary REF on three-winding units), and the AH suffix pins which ratio goes where. Steam-turbine genset bays in cogen and utility thermal using REG670 for generator diff + stator earth + REF use the same aux-CT class for neutral and restricted-earth paths. Substation line bays (RED670 / REF670) use the ABB 1MRK002247-AH​ as 3-phase summation CTs for the earth-fault overcurrent element, especially on non-homogeneous CT secondary sets (e.g., two phases at 600/5, one at 1200/5 — sum them to a common 1A for the relay).Industrial plants — refinery switchyards, mine concentrator substations, pulp-mill main-incomer bays, data-centre medium-voltage genset-paralleling switchgear — that standardised on ABB SAM or RELION cubicles during the original build also surface the 1MRK002247-AH​ during mid-life refresh, often alongside the cubicle’s IED processor spare and any 1MRK PWA spares. Across all these, the problem pattern is the same: the site CT secondary doesn’t match what the IED wants, or the protection scheme (diff, REF, summation) needs a CT core that isn’t on the primary breeaker/CT deck, and the 1MRK002247-AH​ is the cubicle-internal fix. For MRO buyers the caution is consistent with the rest of this 1MRK catalog subset: confirm host BOM, confirm AH suffix (ratio/burden/tap), then buy — the 1MRK002247 base is broad, and the magnetic details move with the two-letter suffix.