ABB Relion ® RET620 Transformer Protection and Control Device

ABB Relion ®  RET620 Transformer Protection and Control Device

Product positioning and functional architecture

RET620 is an intelligent electronic device (IED) designed specifically for medium voltage power grid transformers, belonging to Relion ®  The 620 series supports protection, monitoring, and control of dual winding/triple winding transformers, autotransformers, and generator transformer groups. Its core features include:

Modular design: adopting a plug-in hardware architecture, supporting standard/wide size chassis, and adapting to different scene requirements.

Multi protocol communication: compatible with IEC 61850, Modbus, DNP3, supports GOOSE/SMV messages and IEEE 1588 time synchronization.

Pre configured Function Package: Provides two types of configurations: A (basic protection) and B (including RTD temperature protection), covering core functions such as differential, overcurrent, voltage/frequency protection, etc.

Core protection function

Differential protection

Three winding differential (87T): automatic CT ratio matching and vector group compensation, supporting six constraint CT input, including second harmonic/fifth harmonic braking to prevent excitation inrush current.

Low impedance grounding fault protection (87LOZREF): for winding grounding faults, including zero sequence current direction criterion, with sensitivity up to 5% of rated current.

Overcurrent and grounding protection

Multi stage overcurrent protection: supports three-stage phase overcurrent (51P) and six stage quick break overcurrent (50P), with configurable directional characteristics.

Ground fault protection: including four segment zero sequence overcurrent (51N) and three segment quick break zero sequence (50N), supporting negative sequence polarization direction criterion.

Voltage and frequency protection

Overvoltage/undervoltage protection: two-stage phase voltage protection (59/27) and residual voltage protection (59N/59G), suitable for system abnormal voltage monitoring.

Overexcitation protection (24): Based on U/f ratio monitoring, it prevents transformer core saturation damage.

Frequency protection (81): including over/under frequency protection and frequency change rate (df/dt) detection, supporting load shedding.

Auxiliary protection

Circuit breaker failure protection (50BF): Quickly trip adjacent circuit breakers when detecting circuit breaker refusal to move.

Thermal overload protection (49T): Dual time constant model, monitors winding temperature and triggers alarm/trip.

Monitoring and control functions

measurement and metrology

Real time monitoring of three-phase current/voltage, power, frequency, and sequence components, supporting harmonic analysis and load curve recording.

Disturbance Recorder (DFR): Stores waveforms before and after faults in COMTRADE format, supporting 12 analog signals and 64 switch signals.

Control and regulation

On load tap changer control (OLATC): Automatic voltage regulation, supporting parallel operation of single or multiple transformers.

SESRSYN: Monitor voltage phase, frequency, and amplitude during grid connection to ensure safe closing.

Condition monitoring

Trip Circuit Supervision (TCS): Real time monitoring of the integrity of the circuit breaker trip circuit.

CT/PT fault detection: Identify current/voltage circuit breaks or fuse faults.

Hardware and Interface

hardware module 

Power module (PSM): Supports 48-250V DC/80-240V AC input, including fault output contacts.

Binary Input/Output Module (BIM/BOM): Up to 16 inputs/24 outputs, supporting high-speed pulse counting.

Analog Input Module (AIM): Supports 3-phase current (1A/5A) and voltage input, compatible with Rogowski coils.

communication interface

Ethernet interface: 100BASE-FX (fiber optic)/100BASE-TX (twisted pair), supporting IEC 61850-8-1 GOOSE.

Serial port module: RS-485/RS-232, compatible with Modbus/DNP3 protocol.

Application advantages

Overview of Multi Protocol Communication Function: RET620 supports multiple communication protocols, including IEC 61850, Modbus, DNP3, etc. Among them, IEC 61850 is an international standard for substation communication and modeling protocol, and RET620's support for it covers Edition 1 and 2, including High availability Seamless Redundancy (HSR) and PRP（Parallel Redundancy Protocol）、GOOSE（Generic Object Oriented Substation Event） Messages and IEC 61850-9-2 LE enable simpler wiring and supervised communication. Meanwhile, Modbus and DNP3 protocols also provide extensive compatibility for RET620, enabling it to communicate with devices from different manufacturers. In addition, the device also supports IEEE 1588 V2 Precision Time Protocol for high-precision time synchronization, ensuring precise and unified time between devices.

Advantages of application in the power system

Enhance system integration: The multi protocol communication function enables RET620 to seamlessly integrate with devices from different manufacturers and types in the power system. In a complex substation environment, there may be devices from multiple suppliers. With its support for multiple protocols, RET620 can effectively exchange data with these devices, achieve unified monitoring and management of the entire power system, and improve the system's integration and collaborative work capabilities.