Overview

The ABB RET521 is a numerical transformer protection relay designed to deliver advanced protection and control for power transformers in utility substations and industrial power systems. It consolidates multiple standalone relays by integrating differential protection, overcurrent protection, voltage supervision, and breaker control into a single device.
This model supports multi-breaker arrangements and does not require interposing CTs, simplifying system design and reducing installation complexity.

Technical Data

Key Features

• Differential protection for two- and three-winding transformers

• Integrated breaker control and switchgear management

• Wide and flexible frequency range for diverse grid conditions

• Event logs and disturbance recording for fault analysis

• IEC 61850 compliance for digital substations

• No interposing CTs required, simplifying installation

Typical Applications

• Utility substations: Protection for power transformers and generator-transformer blocks

• Industrial power systems: Reliable protection for critical plant transformers

• Renewable energy plants: Advanced detection and control for grid-connected transformers

• Reactors & multi-breaker arrangements: Supports complex transformer configurations

FAQ

Q1: What is the primary function of the ABB RET521?
A1: To provide protection, control, and monitoring for power transformers, integrating multiple protective functions into one device.

Q2: Can the RET521 handle three-winding transformers?
A2: Yes, it supports both two-winding and three-winding transformer applications.

Q3: What communication protocols does it support?
A3: IEC 61850, Modbus, and DNP3.

Q4: Does the RET521 require interposing CTs?
A4: No, it eliminates the need for interposing CTs, simplifying installation.

Q5: Where is the RET521 typically used?
A5: In utility substations, industrial facilities, renewable energy plants, and systems requiring advanced transformer protection.