Product Core Brief
- Model: RXEDK 2H, Full OEM part number: 1MRK000841-RA
- Brand: ABB Hitachi Energy
- Series: Classic COMBIFLEX modular secondary protection relay system
- Core Function: Microprocessor-based dual-stage voltage measuring relay, each stage configurable independently for overvoltage (59) or undervoltage (27) protection. The RA suffix version is the standard general-purpose variant without built-in third harmonic suppression filter, dedicated for conventional medium voltage busbar supervision, transformer voltage limit control, overhead line voltage monitoring and distributed generation anti-islanding protection in distribution substations. It is not designed for generator neutral displacement earth fault detection (that requires the KA filtered variant RXEDK 2H 1MRK000841-KA).
- Product Type: COMBIFLEX plug-in modular voltage protection relay
- Key Specs: 2 independent measuring protection stages; Stage 1 supports IDMT / DT time curves; Stage 2 fixed definite time delay (0–10 s adjustable); no integrated 3rd harmonic filter; ultra-low VT secondary measurement burden; high reset ratio; universal wide-range AC/DC auxiliary power; standard COMBIFLEX 19-inch rack plug-in draw-out structure
- Note: Still active production for conventional COMBIFLEX relay panel new construction and legacy substation maintenance; factory-sealed new relays and fully bench-tested surplus units are widely supplied for urban distribution substations, industrial self-generation plants and water treatment MV switchgear retrofits.
Key Technical Specifications
| Parameter | Value |
|---|---|
| Full OEM Article Code | RXEDK 2H 1MRK000841-RA |
| Measuring Stage Layout | 2 fully independent voltage measuring stages (Stage 1 + Stage 2) |
| Per-Stage Function Mode | Each stage switchable between overvoltage or undervoltage operation |
| Stage 1 Time Characteristic | Dual selectable curves: Inverse Definite Minimum Time (IDMT) / Definite Time (DT) |
| Stage 2 Time Characteristic | Fixed definite time, adjustable range: 0 s ~ 10 s |
| Built-in Filter (RA suffix) | No integrated third-harmonic suppression filter; pure fundamental frequency voltage measurement only |
| Reset Ratio | High reset ratio to avoid false operation from minor transient grid voltage fluctuations |
| VT Secondary Circuit Burden | Ultra-low burden, no extra load on voltage transformer secondary loops |
| Auxiliary Supply Range | Wide-range universal AC/DC power supply for standard substation cabinet control power |
| Output Contacts | Multiple independent Form-C changeover relay contacts for alarm and trip signal output to SCADA/DCS |
| Mechanical Mounting | Standard COMBIFLEX plug-in drawer for 19-inch rack mounting |
| Continuous Operating Ambient Temp | -10 °C ~ +55 °C inside control cabinet; storage temperature: -40 °C ~ +70 °C |
| Humidity Rating | <95% RH non-condensing, indoor control room rated |
| Compliance Standards | IEC 60255 protection relay standard, KEMA type-tested, CE certified |
Product Introduction
The RXEDK 2H 1MRK000841-RA is a standard dual-stage voltage protection relay within ABB’s COMBIFLEX modular relay family, serving as a general-purpose voltage supervision device for distribution grid bays, distinct from the KA filtered generator-specific variant.
Core Functional Characteristics
- Dual Independent Configurable Protection StagesEvery measuring stage can be separately set to overvoltage or undervoltage without mutual limitation. Stage 1 supports both inverse-time and fixed time delay curves to achieve selective backup protection coordination with upstream/downstream devices; Stage 2 adopts short fixed time delay for fast critical fault tripping, forming two-level hierarchical voltage fault protection logic.
- Fundamental Frequency Only Measurement (No Third Harmonic Filter)The RA suffix hardware removes the third-harmonic suppression filter circuit. It only measures fundamental 50/60 Hz grid voltage signals, making it suitable for standard busbar, transformer and feeder VT monitoring scenarios without generator neutral point harmonic interference. It cannot eliminate third-harmonic distortion signals from generator neutral displacement voltage, so it is not applicable for 100% stator winding earth fault protection matching REX010 injection equipment.
- Wide General Application ScopeTypical application scenarios include: medium/high voltage busbar over/undervoltage backup protection, transformer on-load tap-changer voltage limit supervision, overhead distribution line flashover voltage monitoring, distributed PV/wind generation anti-islanding voltage blocking protection, and industrial plant grid voltage stability supervision.
- Low Burden & Anti-False Operation DesignUltra-low VT secondary circuit load avoids voltage signal distortion caused by excessive VT burden. The high reset ratio suppresses false alarms triggered by normal minor grid voltage fluctuation, improving long-term stable operation of substation secondary circuits.
The plug-in COMBIFLEX drawer design enables quick unit replacement without full cabinet rewiring, fully compatible with COMBIFLEX system accessories including RXDS 4 test disconnect switches and auxiliary relay modules, forming a complete secondary measurement and protection circuit solution for standard distribution substation bays.
QA & Testing SOP (Transparency Building)
- Incoming Visual Inspection: Cross-check full part number RXEDK 2H 1MRK000841-RA and serial number against ABB power system spare parts database to reject counterfeit mismatched relays; inspect front adjustment dials, internal measuring circuit PCB, silver-plated relay output contacts and conformal coating for burn marks, corrosion or mechanical deformation; record serial numbers and production batches for full traceability.
- Full Performance Bench Test: Install the relay on standard COMBIFLEX 19-inch test rack, supply matched auxiliary power, input adjustable fundamental-frequency VT voltage signal; run 24-hour cyclic testing covering Stage 1 IDMT/DT curve switching, Stage 2 fixed time delay adjustment, overvoltage/undervoltage trigger and contact output linkage, verify no false operation under normal grid voltage fluctuation simulation, confirm no third-harmonic filtering function.
- Electrical Insulation Test: Use insulation resistance tester to confirm isolation resistance ≥ 10 MΩ between measuring voltage circuits, auxiliary power and relay output contact circuits; test chassis ground continuity resistance below 0.5 Ω.
- Setting Record Backup: Photograph front panel voltage/time adjustment dial definitions and rear COMBIFLEX plug terminal wiring pinout for field commissioning reference.
- Final QC Packaging: Wipe relay housing with anti-static microfiber cloth, cover all front adjustment terminals and rear plug connectors 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 cyclic test runtime timestamp, then pack into foam shockproof carton for long-distance substation transportation.
Installation Pitfalls & 4-Step Replacement Guide
Common Installation Hazards
❗ VT Secondary Circuit Open-Circuit Risk: Before extracting the RXEDK 2H relay, activate the VT shorting function of the matched RXDS4 test switch to avoid abnormal high voltage on VT loops during disassembly.❗ Model Variant Mismatch Risk: The RA model has no third-harmonic filter; direct replacement for generator neutral earth fault protection (originally KA variant) will cause severe measurement distortion and protection failure.❗ Auxiliary Power Polarity Reversal: Incorrect positive/negative wiring of DC auxiliary power will damage internal microprocessor and measuring circuits instantly.❗ ESD PCB Damage Risk: Wear certified anti-static wrist strap during disassembly and installation; bare hand contact with internal measuring chips leads to permanent signal processing failure.❗ Improper Stage Curve Setting: Misconfigured IDMT/DT characteristic of Stage 1 breaks protection coordination between bay primary and backup protection devices, resulting in selectivity loss during grid faults.
4-Step Plug-in Relay Replacement Guide
- Pre-install Preparation: Lock out and tag out the relay cabinet auxiliary power supply, engage VT shorting links via RXDS4 test switch, wear ESD wrist strap, photograph rear COMBIFLEX plug terminal wiring of VT measuring circuits, auxiliary power and trip/alarm output contacts.
- Removal Operation: Unlatch the COMBIFLEX plug-in drawer locking handle, pull the old RXEDK 2H relay fully out of the rack base socket (the base wiring remains fixed on the cabinet rack).
- Installation & Wiring: Insert the new RXEDK 2H 1MRK000841-RA module into the original COMBIFLEX base socket, push fully to lock the drawer handle; cross-check all VT, power and control wiring matches photographed terminal sequence without misconnection.
- Power-on Commissioning Test: Restore cabinet auxiliary power, input rated nominal VT voltage signal to verify no alarm/trip output; simulate overvoltage and undervoltage fault signals respectively, test Stage 1 time curve and Stage 2 fixed delay trigger performance, confirm stable trip/alarm signal transmission to DCS/SCADA system.
FAQ
Q: What is the core difference between 1MRK000841-RA and 1MRK000841-KA RXEDK 2H variants?
- RA suffix: Standard general-purpose version, without third-harmonic filter, only measures fundamental grid voltage; for distribution busbar, transformer and feeder voltage supervision only.
- KA suffix: Generator dedicated version, built-in third-harmonic suppression filter, compatible with REX010 injection system for 100% generator stator winding neutral-point dead zone earth fault protection.
Q: What is the difference between RXEDK 2H and single-stage RXEDK 1H relays?RXEDK 1H only has one measuring stage with single definite time characteristic, limited to simple undervoltage alarm. RXEDK 2H provides two independent protection stages with flexible time curve selection, realizing hierarchical primary trip + backup alarm logic for critical substation bay protection schemes.
Q: Can RXEDK 2H be hot-swapped under energized cabinet power?Not permitted. The relay is connected to live VT secondary measuring circuits and auxiliary power loops; extraction under energized conditions will cause abnormal voltage surge and permanent damage to internal measuring hardware. Full auxiliary power lockout and VT shorting are required before replacement.
Q: What warranty applies to stocked RXEDK 2H 1MRK000841-RA modules?Factory-new original COMBIFLEX relays carry 12-month official ABB manufacturer warranty covering measuring circuits, time delay logic and relay output contacts. Bench-tested surplus modules provide 6-month functional warranty; damage caused by VT open-circuit voltage shock, power polarity reversal or ungrounded ESD handling voids all warranty terms.
Q: Has ABB discontinued RXEDK 2H series production?No formal EOL notice issued; RXEDK 2H RA variant remains standard supply for conventional distribution substation COMBIFLEX relay panel renovation. New digital substation projects adopt REF615/RET670 series IEDs with built-in voltage protection algorithms instead of discrete COMBIFLEX relays.
Q: What typical faults indicate a defective RXEDK 2H 1MRK000841-RA relay?Common failure symptoms: Random false over/undervoltage alarms under normal grid operation, no trip output when fault threshold is reached, time delay deviation exceeding factory tolerance range, Stage 1 IDMT curve switching failure, unstable voltage measurement readings without VT or grid abnormality.
