ABB RDCO-04C
The ABB RDCO-04C is a differential protection relay under the ABB Relion® Protection Relay Series, specifically designed for the differential protection of power transformers, generators, busbars, and large motors. This relay detects internal faults (such as winding short circuits and ground faults) via the high-precision current differential algorithm, providing fast tripping protection to prevent equipment damage and system outages. It serves as a core component of the main protection in power systems.
Core Values of RDCO-04C
High-sensitivity fault detection: The minimum operating current can be as low as 0.1Ie (rated current), enabling the identification of minor turn-to-turn short circuits.
CT saturation resistance: Features adaptive restraint characteristics to avoid maloperation caused by CT saturation during external faults.
Multi-object protection: Supports differential protection for transformers, generators, busbars, and motors.
Product Parameters
Product Model: RDCO-04C
Manufacturer: ABB
Product Type: Differential Protection Relay
Rated Current: 1A or 5A (CT secondary side, configurable)
Differential Pickup Value: 0.1-1.0Ie (step size 0.01Ie)
Restraint Coefficient: 0.1-0.8 (adjustable slope)
Operating Time: ≤25ms (for internal faults)
Communication Protocols: IEC 61850, Modbus RTU/TCP, DNP3.0
Input/Output: 8× digital inputs, 6× relay outputs
Operating Temperature Range: -25°C to +55°C (-13°F to +131°F)
Protection Class: IP40 (panel mounting)
Mounting Method: DIN Rail or panel mounting
Certification Standards: IEC 60255, IEEE C37.90, UL 508
Structure and Composition
The RDCO-04C adopts a modular design, with main components including:
Signal Acquisition Unit: Equipped with high-precision CT interfaces (1A/5A) and supports multi-side current input (e.g., three sides of a transformer).
DSP Processing Module: Calculates differential current and restraint current in real time, and executes the proportional restraint characteristic algorithm.
Restraint Characteristic Curve: Programmable proportional restraint curve (e.g., IEEE Std C37.91).
Communication Interface Board: Includes dual Ethernet ports (for IEC 61850) and RS-485 (for Modbus RTU).
Human-Machine Interface (HMI): Features a 128×64 graphic LCD for local viewing of differential current and event records.
Test Interface: Supports secondary injection testing without disconnecting CT lines.
Key Features and Advantages
High-precision differential protection:
The proportional restraint characteristic prevents maloperation during external faults (e.g., CT saturation, inrush current).
Equipped with 2nd harmonic restraint function to distinguish between fault current and transformer inrush current.
Flexible configuration:
Select protection objects (transformer/generator/busbar) via the PCM600 software.
Supports automatic CT ratio compensation to simplify engineering configuration.
Intelligent diagnosis and recording:
Fault recording function (≥128 cycles) to record differential current waveforms.
Achieves fast tripping (≤8ms) via IEC 61850 GOOSE.
Industrial-grade reliability:
Operates in a wide temperature range of -25°C to +55°C, complying with the IEC 60068-2 environmental standard.
Built-in self-test function to monitor hardware health in real time.
Application Fields
The RDCO-04C is mainly used in the following scenarios:
Power Substations: Serves as the main protection (differential + backup protection) for 110kV/35kV transformers.
Power Plants: Provides differential protection for generator stator windings.
Industrial Power Distribution: Offers internal short-circuit protection for large motors (≥2MW).
Typical Application Case
In a 110kV substation, the RDCO-04C acts as the main transformer differential protection. It uploads operation information to the SCADA system via Modbus TCP and trips within 20ms in case of winding short circuits.
Related Products
REF615: A feeder protection device that provides transformer backup protection.
CMC256: A tester used for relay verification.
PCM600: Configuration software, available for free download.
Installation and Maintenance
Installation Key Points
Use shielded wires of ≥2.5mm² for CT secondary wires to avoid induced voltage interference.
The polarity of multi-side CTs must be consistent (pointing to the protection zone).
Maintenance Recommendations
Conduct a proportional restraint characteristic test (using CMC256) once a year.
Regularly check the software version and upgrade it via PCM600
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