Product Core Brief
- Model: RXIIK 4, Full OEM part code: 1MRK001643-AA
- Brand: ABB Hitachi Energy
- Series: ABB COMBIFLEX modular secondary measurement relay system
- Core Function: Four-channel independent low-burden CT current measuring relay designed to collect and sum multiple secondary CT currents for residual earth fault supervision, transformer differential auxiliary current matching, and multi-winding generator current balance monitoring. It receives signals from up to four separate CT secondary loops, calculates vector-sum residual current, and outputs analog measured signals to overcurrent/earth fault protection relays (RXIDK, RET670, REG series). The AA variant is the standard universal version compatible with both 1A and 5A CT secondary ratings without extra hardware modification.
- Product Type: COMBIFLEX plug-in multi-channel current summation measuring relay
- Key Specs: 4 galvanically isolated CT input channels; software selectable 1A / 5A CT secondary; ultra-low measurement burden on CT circuits; linear summation of multi-path currents; multiple Form-C auxiliary output contacts for residual current alarm; standard COMBIFLEX 19-inch rack plug-in drawer; wide-range AC/DC auxiliary supply
- Note: Mature COMBIFLEX platform component still in active production for conventional power plant and distribution substation relay panel retrofits; factory-sealed new units and fully bench-tested surplus relays are widely supplied for thermal power main generator bays, two/three-winding transformer bays and large feeder secondary circuit maintenance.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Full OEM Article Code | RXIIK 4 1MRK001643-AA |
| Number of CT Measuring Channels | 4 fully independent galvanically isolated current input circuits |
| CT Secondary Compatibility | Software switchable 1 A or 5 A rated secondary CT signals |
| Measurement Principle | Linear vector summation of 4 input currents for residual residual earth current calculation |
| CT Circuit Burden | Extremely low burden, avoids saturation and signal distortion of miniature CTs |
| Auxiliary Supply Range | Universal wide AC/DC voltage input for substation cabinet control power |
| Output Contacts | Multiple independent Form-C changeover relay contacts for residual overcurrent alarm signaling to DCS/SCADA |
| Front Panel Status Indicators | Green RUN LED, yellow measuring signal active LED, red residual current alarm LED |
| Mechanical Structure | Standard COMBIFLEX plug-in drawer for 19-inch rack mounting, compatible with RXDS4 test disconnect switches |
| Continuous Operating Ambient Temp | -10 °C ~ +55 °C inside control cabinet; storage temperature: -40 °C ~ +70 °C |
| Humidity Resistance | <95% RH non-condensing, indoor substation control room grade |
| Overall Dimensions | Standard COMBIFLEX module size 120 W × 177 H × 145 D mm |
| Net Weight | Approx. 430 g |
| Compliance Standards | IEC 60255 measuring relays, KEMA type-tested, CE certified |
Product Introduction
The RXIIK 4 1MRK001643-AA is a dedicated multi-channel CT current summation relay in the COMBIFLEX product line, solving the limitation of single/dual-channel current relays that cannot handle multi-winding transformer or multi-branch generator residual current measurement.
Core Functional Advantages
- Four Independent Galvanic CT Input LoopsIt supports four separate CT secondary circuits simultaneously, which is ideal for: three-phase transformer winding CT plus neutral residual CT, dual parallel feeder combined residual current monitoring, or generator stator three-phase CT plus neutral injection CT matching REX010 systems. Each channel features independent galvanic isolation to eliminate cross-interference between different measuring branches.
- Universal 1A/5A CT CompatibilityThe AA standard variant supports software switching between 1A and 5A CT secondary ratings without hardware replacement, adapting to different transformer and generator CT configurations in various power plants, greatly reducing spare part inventory types for maintenance teams.
- Ultra-Low CT Burden DesignLow impedance measuring circuits minimize load on CT secondary windings, preventing CT saturation during high fault current transients and ensuring accurate residual current calculation for sensitive restricted earth fault (REF) protection logic.
- Residual Current Alarm OutputAfter summing four current vectors, the relay continuously monitors residual unbalance current. If residual current exceeds the adjustable threshold, it triggers dedicated alarm contacts to warn operators of winding insulation degradation, loose CT wiring or earth fault risks before severe equipment damage occurs.
The plug-in COMBIFLEX drawer structure enables fast replacement without full cabinet rewiring, perfectly matched with RXDS4 test switches for safe offline secondary injection testing of CT loops, and works cooperatively with RXIDK overcurrent relays and RXEDK voltage relays to form a complete secondary protection system for transformer and generator bays.
QA & Testing SOP (Transparency Building)
- Incoming Visual Inspection: Cross-check full part number RXIIK 4 1MRK001643-AA and serial number against ABB power system spare parts database to reject counterfeit mismatched relays; inspect rear CT input terminals, internal summation PCB, silver-plated alarm relay contacts and conformal coating for burn marks, corrosion or deformation; record serial numbers and production batches for full traceability.
- Full Multi-Channel Linkage Bench Test: Mount RXIIK4 on standard COMBIFLEX 19-inch test rack, supply rated auxiliary power, inject independent adjustable 1A/5A simulated CT current signals into each of the four channels; run 24-hour cyclic testing to verify accurate vector summation of multi-channel currents, residual current threshold alarm trigger, and cross-channel isolation performance without signal crosstalk.
- Electrical Insulation Test: Use insulation resistance tester to confirm isolation resistance ≥ 10 MΩ between each CT measuring channel, auxiliary power circuit and relay output contacts; test chassis ground continuity resistance below 0.5 Ω.
- Parameter Record Backup: Photograph front panel CT rating selector switch and residual current threshold adjustment dial, document rear COMBIFLEX plug terminal pin definitions for field wiring reference.
- Final QC Packaging: Wipe relay housing with anti-static microfiber cloth, cover all rear CT plug terminals with insulating dust caps, place the unit into independent ESD shielding bag, attach unified printed QC test tag with technician ID and full 24-hour multi-channel test runtime timestamp, then pack into foam shockproof carton for long-distance power plant transportation.
Installation Pitfalls & 4-Step Replacement Guide
Common Installation Hazards
❗ Lethal CT Open-Circuit Risk: Before pulling the RXIIK4 plug-in relay out of the rack base, fully activate the CT shorting links of the matched RXDS4 test switch; unshorted CT secondary terminals generate dangerous high voltage and arc flash hazards.❗ Mismatched CT Rating Setting: Failure to toggle the internal selector switch between 1A and 5A will lead to residual current calculation deviation, causing false earth fault alarms or missed fault detection.❗ CT Channel Cross-Wiring: Misconnecting phase CT and neutral residual CT to different input channels breaks vector summation logic and invalidates REF protection; take clear photos of original wiring before disassembly.❗ Auxiliary Power Polarity Reversal: Reverse DC auxiliary power wiring will burn the internal summation processing circuit instantly.❗ ESD Damage Risk: Wear certified anti-static wrist strap during all disassembly and installation work; bare hand contact with PCB measuring chips permanently impairs multi-channel current summation accuracy.
4-Step Plug-in Relay Replacement Guide
- Pre-install Preparation: Lock out and tag out the relay cabinet auxiliary power supply, engage all CT shorting links via RXDS4 test switch, wear ESD wrist strap, photograph rear COMBIFLEX plug wiring of four CT measuring circuits, auxiliary power and residual alarm output contacts.
- Removal Operation: Unlatch the COMBIFLEX drawer locking handle, pull the old RXIIK 4 relay fully out of the fixed rack base socket (base wiring remains hardwired to cabinet secondary circuits).
- Installation & Wiring: Insert the new RXIIK 4 1MRK001643-AA module into the original COMBIFLEX base socket and lock the drawer handle; adjust the internal CT rating selector switch to match on-site 1A or 5A CT specifications; re-terminate all four CT channels, auxiliary power and alarm wiring strictly following photographed terminal sequences.
- Power-on Commissioning Test: Restore cabinet auxiliary power, input balanced nominal CT current signals to all four channels and confirm zero residual current reading; inject unbalanced single-channel fault current to trigger residual current alarm, verify stable alarm signal transmission to DCS/SCADA system, and confirm no cross-channel signal interference.
FAQ
Q: What is the difference between RXIIK 4 and RXIIK 2 relays?RXIIK 2 only supports 2 CT input channels, limited to simple single-feeder residual current measurement. RXIIK 4 provides four independent CT loops, suitable for multi-winding transformers, generators and dual parallel feeder bays that require simultaneous summation of multiple current branches.
Q: Can RXIIK 4 directly execute fault trip protection?No. RXIIK4 is only a measuring and summation auxiliary relay without independent overcurrent/earth fault trip logic. It outputs residual current analog signals to dedicated protection relays like RXIDK or main IEDs (RET670, REG series) to complete fault tripping functions.
Q: Can the plug-in RXIIK4 be hot-swapped with cabinet auxiliary power energized?Forbidden. The relay connects directly to live CT secondary circuits. Extraction without pre-shorting CT loops will create fatal open-circuit high voltage. Full auxiliary power lockout and CT shorting via RXDS4 are mandatory before replacement.
Q: What warranty applies to stocked RXIIK 4 1MRK001643-AA modules?Factory-new original COMBIFLEX relays carry a 12-month ABB official warranty covering multi-channel measuring circuits, summation logic and alarm relay contacts. Bench-tested surplus units come with a 6-month functional warranty; damage caused by CT open-circuit surges, power polarity reversal or ungrounded ESD handling voids all warranty coverage.
Q: Has ABB discontinued RXIIK 4 production?No formal EOL notice has been released. remains standard supply for conventional COMBIFLEX transformer/generator relay panel renovation. Modern digital substations adopt multi-input REF630/RET670 IEDs with integrated multi-channel CT summation functions instead of discrete RXIIK modules.
Q: What typical faults indicate a defective RXIIK 4 relay?Common failure symptoms: Persistent false residual current alarms with balanced CT currents, inconsistent summation readings between channels, no alarm output when obvious unbalance current occurs, single CT channel signal loss without CT circuit faults, unstable measuring values fluctuating randomly under normal operating conditions.
