Product Core Brief

• Model: RXIDK 2H, Full OEM Article Code: 1MRK000838-HA
• Brand: ABB Hitachi Energy
• Series: Classic COMBIFLEX modular secondary protection relay system
• Core Function: Microprocessor-based two-stage time overcurrent protection relay for CT secondary circuits in power substations and power plants. The HA suffix variant integrates a built-in harmonic suppression filter, designed to filter magnetizing inrush harmonics from transformer/transformer-feeder bays to avoid false overcurrent trips during energization. It provides two independent measuring stages: low-set overload stage (I>) with selectable IDMT/DT curves and high-set instantaneous short-circuit stage (I>>) with fixed definite time delay, widely used as backup overload and short-circuit protection for distribution feeders, power transformers and large industrial motors.
• Product Type: COMBIFLEX plug-in modular overcurrent protection relay
• Key Specs: Dual independent measuring stages (I> overload + I>> short-circuit); I> supports multiple inverse time curves + definite time; I>> fixed definite time delay; HA built-in harmonic filter to suppress transformer inrush current; compatible with 1A / 5A secondary CT; wide universal AC/DC auxiliary supply; COMBIFLEX standard 19-inch rack plug-in drawer structure; multiple Form-C alarm/trip output contacts
• Note: Still active production for legacy COMBIFLEX relay panel renovation and new conventional substation projects; factory-sealed new relays and fully bench-tested surplus units are supplied for thermal power plants, hydropower stations, wind farm step-up transformer bays and industrial MV motor switchgear maintenance.

Key Technical Specifications

Product Introduction

The RXIDK 2H 1MRK000838-HA is a dual-stage overcurrent relay within ABB’s COMBIFLEX modular relay family, specially customized with a harmonic filter for transformer bay backup protection applications, distinct from the standard RA non-filter variant.

Core Functional Advantages

1. Two-Tier Hierarchical Overcurrent Protection LogicThe low-set I> stage handles long-term overload faults with flexible inverse-time curves to achieve selective coordination with upstream/downstream protection devices; the high-set I>> stage provides fast short-circuit instantaneous tripping to isolate severe short-circuit faults quickly, realizing hierarchical protection coordination for feeders, transformers and large motors.
2. Built-In 2nd Harmonic Filter For Transformer Inrush Suppression (HA Exclusive Feature)The integrated harmonic filter eliminates 2nd harmonic interference generated by transformer magnetizing inrush during energization, which is the core advantage of the HA variant. Standard RA versions without this filter frequently suffer false overload trips when transformers are switched on, making the HA model mandatory for transformer bay secondary circuit protection.
3. Wide General Application ScopeTypical application scenarios: Medium/high voltage distribution feeder backup overload & short-circuit protection, power transformer primary/secondary side backup protection, large thermal/hydro motor stall and overload supervision, wind farm step-up transformer bay backup protection.
4. Low Burden & High Reset Ratio DesignUltra-low CT secondary circuit load avoids current signal distortion caused by excessive CT burden. The high reset ratio prevents false operation triggered by minor transient current fluctuations under normal grid operation, greatly improving long-term protection stability.

The plug-in COMBIFLEX drawer design enables rapid unit replacement without full cabinet rewiring, fully compatible with COMBIFLEX system accessories including RXDS4 four-circuit test disconnect switches and auxiliary relay modules, forming a complete secondary measurement and protection circuit solution for conventional power substation bays.

QA & Testing SOP (Transparency Building)

1. Incoming Visual Inspection: Cross-check full part number RXIDK 2H 1MRK000838-HA and serial number against ABB power system spare parts database to reject counterfeit mismatched relays; inspect front adjustment potentiometers, internal harmonic filter circuit, silver-plated relay output contacts and conformal PCB coating for burn marks, corrosion or mechanical deformation; record serial numbers and production batches for full traceability.
2. Full Performance Bench Test: Install the relay on standard COMBIFLEX 19-inch test rack, supply matched auxiliary power, input adjustable fundamental and 2nd harmonic mixed CT current signal; run 24-hour cyclic testing covering I> IDMT/DT curve switching, I>> fixed time delay adjustment, harmonic filter inrush suppression effect, overload/short-circuit trigger and contact output linkage, verify no false operation under transformer energization simulation.
3. Electrical Insulation Test: Use insulation resistance tester to confirm isolation resistance ≥ 10 MΩ between measuring CT circuits, auxiliary power and relay output contact circuits; test chassis ground continuity resistance below 0.5 Ω.
4. Setting Record Backup: Photograph front panel current/time adjustment dial definitions and rear COMBIFLEX plug terminal wiring pinout for field commissioning reference.
5. 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 power plant transportation.

Installation Pitfalls & 4-Step Replacement Guide

Common Installation Hazards

❗ CT Open-Circuit Safety Risk: Before extracting the RXIDK 2H relay, activate the CT shorting function of the matched RXDS4 test switch to avoid lethal high open-circuit voltage on CT loops during disassembly.❗ Variant Mismatch Risk: The HA suffix integrates transformer inrush harmonic filter; direct replacement with RA non-filter variant for transformer bays will cause frequent false overcurrent trips during transformer switching.❗ Auxiliary Power Polarity Reversal: Incorrect positive/negative wiring of DC auxiliary power will damage internal microprocessor and harmonic filter 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 I>/I>> Curve Setting: Misconfigured I> inverse time characteristic breaks protection coordination between bay primary and backup protection devices, resulting in selectivity loss during grid short-circuit faults.

4-Step Plug-in Relay Replacement Guide

1. Pre-install Preparation: Lock out and tag out the relay cabinet auxiliary power supply, engage CT shorting links via RXDS4 test switch, wear ESD wrist strap, photograph rear COMBIFLEX plug terminal wiring of CT measuring circuits, auxiliary power and trip/alarm output contacts.
2. Removal Operation: Unlatch the COMBIFLEX plug-in drawer locking handle, pull the old RXIDK 2H relay fully out of the rack base socket (the base wiring remains fixed on the cabinet rack).
3. Installation & Wiring: Insert the new RXIDK 2H 1MRK000838-HA module into the original COMBIFLEX base socket, push fully to lock the drawer handle; cross-check all CT, power and control wiring matches photographed terminal sequence without misconnection.
4. Power-on Commissioning Test: Restore cabinet auxiliary power, input rated nominal CT current signal to verify no alarm/trip output; simulate overload, short-circuit and transformer inrush mixed harmonic fault signals respectively, test I> time curve and I>> fixed delay trigger performance, confirm harmonic filter suppresses inrush interference effectively, verify stable trip/alarm signal transmission to DCS/SCADA system.

FAQ

Q: What is the core difference between 1MRK000838-HA and standard 1MRK000838-RA RXIDK 2H variants?

• HA suffix: Transformer dedicated version, built-in 2nd harmonic suppression filter, eliminates magnetizing inrush false trips; mandatory for transformer bay backup overcurrent protection.
• RA suffix: General-purpose standard version without harmonic filter, only suitable for pure feeder/motor bays without transformer energization inrush interference.

Q: What is the difference between RXIDK 2H and single-stage RXIDK 1H relays?RXIDK 1H only has one single measuring stage with fixed definite time characteristic, limited to simple overload alarm. RXIDK 2H provides two independent I>/I>> protection stages with flexible inverse time curve selection, realizing hierarchical overload backup + fast short-circuit trip logic for critical transformer and feeder bay protection schemes.

Q: Can RXIDK 2H be hot-swapped under energized cabinet power?Not permitted. The relay is connected to live CT secondary measuring circuits and auxiliary power loops; extraction under energized conditions will generate abnormal high open-circuit CT voltage surge and permanently damage internal measuring hardware. Full auxiliary power lockout and CT shorting via RXDS4 are required before replacement.

Q: What warranty applies to stocked RXIDK 2H 1MRK000838-HA modules?Factory-new original COMBIFLEX relays carry 12-month official ABB manufacturer warranty covering measuring circuits, harmonic filter hardware, time delay logic and relay output contacts. Bench-tested surplus modules provide 6-month functional warranty; damage caused by CT open-circuit voltage shock, power polarity reversal or ungrounded ESD handling voids all warranty terms.

Q: Has ABB discontinued RXIDK 2H series production?No formal EOL notice issued; RXIDK 2H HA variant remains standard supply for transformer bay COMBIFLEX relay panel renovation. New digital substation projects adopt REF615/RET670 series IEDs with built-in overcurrent protection algorithms instead of discrete COMBIFLEX relays.

Q: What typical faults indicate a defective RXIDK 2H 1MRK000838-HA relay?Common failure symptoms: Random false I> overload trips during transformer energization (filter circuit failure), no trip output when overload/short-circuit threshold is reached, time delay deviation exceeding factory tolerance range, I> IDMT curve switching failure, unstable CT current measurement readings without CT or grid abnormality.