I. Basic Information

ABB REF545KC133AAAA is a dedicated integrated feeder protection and control terminal for REF545 series, a classic generation of intelligent relay protection IED. Designed specifically for 6kV～35kV medium-voltage distribution feeder circuits, it integrates full functions including feeder fault protection, high-precision electrical measurement, switchgear monitoring & control, logic interlocking, event logging, fault oscillography and multi-protocol communication networking. As the core automation device of medium-voltage distribution networks, this unit is widely used for power distribution of industrial & mining enterprises, municipal power grids, industrial parks and high-voltage building power supply, serving as the standard matching protection & control device for conventional medium-voltage switchgears.

II. Technical Specifications

(1) Basic Hardware Parameters

• Full Model: REF545KC133AAAA
• Brand: ABB
• Device Type: Medium-Voltage Feeder Integrated Protection & Control Terminal (IED)
• Applicable Scope: 6kV～35kV medium-voltage feeder circuits, HV distribution switchgears for industrial & mining plants, municipal distribution networks, medium-voltage power distribution systems of industrial parks
• Hardware Architecture: Dedicated power protection computing structure integrated with high-precision AD sampling unit, independent protection logic operation unit and programmable logic control unit
• Mounting: Flush panel mounting on switchgear, matching standard cutout layout of medium-voltage cabinets with compact size saving internal cabinet space
• Ingress Protection: Front face IP54 (dustproof and waterproof), rear terminals IP20, suitable for fully-enclosed switchgear operating environment
• HMI: High-definition LCD plus physical operation keys, supporting on-site parameter setting, status checking and manual breaker closing/tripping
• Net Weight: Approx. 8.0kg with rugged compact industrial construction

• Core Orientation: Fault protection for medium-voltage feeders, high-accuracy electrical parameter measurement, local/remote breaker control, distribution system networking communication, fault & event trace recording

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(2) Rated Electrical Parameters

• Control Supply Voltage: Standard DC110V/DC220V industrial DC power, compatible with conventional substation operating power supply
• Rated Input Current: Dual rating 1A/5A available, matching standard secondary transformation ratios of industrial current transformers
• Rated Input Voltage: 100/110/120VAC conforming to standard secondary output of voltage transformers
• Sampling & Measurement Accuracy: Current/Voltage ≤±0.2%, Power/Energy ≤±0.5%, Frequency ≤±0.01Hz, complying with power metering grade precision
• Protection Accuracy Class: Max. 5P20 protection class with precise fault sampling and negligible setting deviation
• Digital I/O Channels: Multi-channel DI for status acquisition and DO relay output for breaker status monitoring and switching drive

• Power Consumption: Low-power circuit design with low heat emission for long-term continuous enclosed cabinet operation

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(3) Core Protection Specifications

• Three-stage Phase Overcurrent Protection: Including instantaneous overcurrent, definite-time instantaneous overcurrent and definite-time overcurrent; setting range: 0.1In～20In, adjustable operating delay: 0～60s for rapid clearance of feeder short-circuit and overload faults
• Earth Fault Protection: Earth overcurrent protection and zero-sequence fault detection; setting range: 0.05In～5In for single-phase grounding and zero-sequence abnormality protection of medium-voltage systems
• Overload Protection: Adjustable range 0.5In～1.5In with overheat alarm and delayed tripping logic to avoid insulation ageing and line damage caused by long-term overload
• Auxiliary Protection Functions: Breaker failure protection, optional directional overcurrent protection, expandable external arc flash protection and thermal overload blocking protection

• Protection Performance: Fast fault response, accurate pickup setting and comprehensive anti-maloperation interlock to effectively prevent unnecessary tripping induced by external out-of-zone faults

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(4) Monitoring, Control & Recording Parameters

• Electrical Measurement: Real-time acquisition of full set of electrical data including 3-phase current, 3-phase voltage, active/reactive power, power factor, frequency and accumulated energy
• Equipment Control Logic: Local manual breaker operation and remote tripping/closing with complete anti-misoperation interlock logic
• Programmable Logic: Function block diagram programming to customize interlock rules, alarm logics and linkage control for non-standard field process requirements
• Fault Oscillography: Full-cycle waveform recording to store complete pre-fault and post-fault operational data for fault diagnosis

• Event Logging: Large-capacity event memory to trace full history of protection trips, equipment status changes, operation records and abnormal alarms

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(5) Communication Specifications

• Native Communication Protocols: SPA bus, LON bus, IEC 60870-5-103 standard power protocol
• Expandable Protocols: Compatible with IEC 61850, Profibus DPV1, DNP3.0, Modbus and other general industrial protocols
• Transmission Features: Low communication latency, robust message error correction, stable multi-device networking free of data loss and timing disorder

• Networking Capacity: Parallel multi-device networking within substation for seamless connection with SCADA background, dispatching platform and automation systems

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(6) Environmental Specifications

• Operating Temperature: -10℃～+55℃ standard power-grade range for regular indoor switchgear conditions
• Storage Temperature: -40℃～+70℃ suitable for equipment transportation and long-term warehousing
• Operating Humidity: 5%～95%RH (non-condensing), tolerant to humid enclosed cabinet environment
• Environmental Resistance: Designed per IEC EMC standards with high immunity to severe EMI, voltage fluctuation and thermal ageing
• Cooling Method: Passive natural convection cooling, fanless maintenance-free design eliminating mechanical failure risks
• Vibration Resistance: Adapted to switchgear vibration environment, capable of enduring long-term minor mechanical shock and vibration at distribution sites

III. Key Features

• Full-spectrum Feeder Fault Protection: Consolidates complete dedicated feeder protection functions including three-stage overcurrent, earth fault, overload and breaker failure protection, covering typical medium-voltage feeder faults such as short-circuit, overload, grounding and equipment malfunction. Mature protection algorithms and precise tripping action fully secure medium-voltage distribution feeders and switchgear assets.
• Metering-Grade High-precision Measurement: Adopts high-performance AD sampling algorithm to realize power metering-level measuring accuracy for full-range feeder electrical parameters, satisfying high-precision demands of distribution monitoring, load statistics, energy assessment and operational condition analysis.

• Flexible Expandable Programmable Logic: Supports visual function block programming enabling users to customize interlock logics, alarm criteria and linkage control strategies to meet non-standard control requirements across diverse industries and working conditions with superior adaptability and expandability.

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• Multi-protocol Compatible Networking: Natively supports mainstream power communication protocols and can be upgraded for digital communication standards to interconnect legacy SCADA systems and new-generation intelligent distribution automation platforms, ideal for networking renovation of new and old distribution systems.
• Comprehensive Anti-misoperation Control Logic: Dual operating modes of local manual control and remote supervisory control with mature built-in interlock mechanism to eliminate hazardous operations such as on-load opening and erroneous switching and guarantee safe operation of medium-voltage distribution equipment.

• Full-life-cycle Fault Data Traceability: Integrated fault oscillography, event logging and trip alarm functions fully archive fault waveforms, action sequences and operation logs to provide complete data support for fault troubleshooting, accident investigation and protection setting optimization.

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• Industrial High-reliability Long-term Operation: High front-face protection rating, strong EMI immunity and fanless maintenance-free construction enable stable 7×24-hour continuous operation under harsh cabinet conditions of enclosure, dust, humidity and intensive electromagnetic interference with extremely low failure rate.
• Convenient Installation & Wide Compatibility: Standard flush panel mounting fits mainstream medium-voltage switchgears in market and directly replaces legacy REF-series relays without extensive cabinet modification or rewiring, realizing low-cost upgrading of obsolete distribution protection systems.

IV. Working Principle

1. Power-on Initialization & Self-test: After DC control power is energized, the device automatically executes hardware circuit self-check, sampling channel calibration, protection parameter loading, communication protocol initialization and HMI self-diagnosis, and switches to steady monitoring standby mode once all tests pass.

2. Real-time High-precision Signal Collection: Continuously samples analog and digital signals including 3-phase current, 3-phase voltage and switch status of medium-voltage feeders; built-in filtering and calibration algorithms eliminate field electromagnetic noise to restore authentic distribution operating data.

1. Real-time Electrical Parameter Calculation: High-speed processing unit dynamically computes core parameters such as active/reactive power, power factor, frequency and cumulative energy to refresh feeder operating data and realize round-the-clock monitoring of distribution circuits.
2. Intelligent Protection Judgment & Tripping: Continuously compares real-time operational readings against preset protection settings. Once overcurrent, overload, earth fault or frequency deviation is detected, corresponding protection logic is instantly triggered to output trip signal for faulty circuit isolation with fault latch and alarm activation.

3. Interlock-based Equipment Control Execution: Upon receiving local keypad commands or remote control orders from upper system, the unit verifies operation validity via embedded anti-misoperation interlock logic and executes breaker switching only after compliance check to prevent improper operations.

1. Bidirectional Multi-protocol Data Exchange: Automatically matches relevant communication protocol per network configuration, uploads measured data, equipment status and fault alarms to upper management systems while downloading remote setting and control commands to realize collaborative automatic management of distribution network.
2. Fault Data Storage & Archiving: Oscillography is activated instantly upon fault inception to fully record pre/post-fault waveforms, action sequences and event information; logs and fault codes are automatically stored for subsequent fault analysis and maintenance optimization.
3. Continuous Steady Monitoring: Under normal fault-free status, the unit keeps tracking feeder operating conditions and updating real-time data with protection, control and communication links always ready to secure long-term safe power supply of medium-voltage feeders.

V. Application Scenarios

(1) Feeder Protection & Control for Medium-Voltage Switchgears

Widely deployed on 6kV～35kV medium-voltage incoming, outgoing and bus-section switch cabinets to implement core functions of fault protection, condition monitoring and switch control for feeder circuits. It serves as standardized core protection equipment for industrial, utility and park medium-voltage distribution systems to ensure independent safe operation of individual feeders.

(2) Distribution Automation System for Industrial & Mining Enterprises

Suitable for high-voltage power distribution systems of metallurgy, chemical, machinery and mining heavy industries. Designed for industrial grids featuring volatile load, complex working conditions and frequent equipment startup/shutdown, it delivers accurate and reliable feeder protection & control to avoid production line shutdown caused by distribution faults and guarantee uninterrupted industrial power supply.

(3) Municipal & Industrial Park Distribution Systems

Applied at medium-voltage distribution substations of urban power grids, industrial parks and commercial complexes to realize intelligent circuit monitoring, fast fault isolation and remote data upload, improving automation and intelligent maintenance of municipal power grids and enhancing public power supply reliability.

(4) Upgrading & Retrofit of Legacy Distribution Protection Systems

Direct replacement of outdated mechanical and semi-digital feeder relays with drop-in fit for original switchgear layout and wiring without cabinet reconstruction. It cost-effectively solves drawbacks of old devices including poor protection precision, delayed tripping, missing data traceability and no networking capability to realize intelligent upgrade of conventional distribution systems.

(5) Operation Monitoring & Dispatching of Distribution Networks