ABB RET670 Numerical Transformer Protection Relay

Description

Real-World Use & Application Scenarios

At the heart of an electrical transmission substation, where hundreds of megawatts of power flow and system stability is paramount, the protection of the power transformer is one of the most critical tasks. A fault within a transformer is not just a local issue; it can destabilize a regional grid, leading to widespread blackouts and causing damage that takes months and millions of dollars to repair. The ABB RET670 is the dedicated guardian engineered for this mission. This relay is deployed to protect critical assets like large power transformers, autotransformers, and generator step-up units in utilities, heavy industry, and large-scale renewable integration facilities. It addresses complex challenges such as detecting internal winding faults using differential protection, managing inrush currents during transformer energization to prevent false trips, and monitoring for incipient thermal faults. By providing a comprehensive and highly secure suite of protection and control functions, the ABB RET670 ensures that these high-value, difficult-to-replace assets are isolated only during genuine faults, maintaining the overall integrity and reliability of the electrical power system.

Product Introduction & Positioning

The ABB RET670 is a bay controller and protection relay, specifically designated as a transformer protection terminal within ABB’s renowned Relion® 670 series. It functions as the primary Intelligent Electronic Device (IED) for a transformer bay, integrating all necessary protection, control, measurement, and monitoring functions into a single, sophisticated unit. Its role extends far beyond simple fault detection; it is a local intelligence hub that manages tap changer control, provides comprehensive metering data, and enforces interlocking logic. For protection engineers and system integrators, the value of the ABB RET670 lies in its application-specific design and unparalleled integration capabilities. It is pre-configured with transformer-specific protection schemes, which drastically reduces engineering time and validation efforts compared to building a system from generic components. Its seamless support for the IEC 61850 standard makes it a foundational component of the modern digital substation, enabling powerful communication and interoperability that enhances both situational awareness and operational efficiency.

Key Technical Features & Functional Benefits

The ABB RET670 delivers its core protective functions with a focus on security, dependability, and advanced analysis. Its flagship feature is the high-impedance differential protection, which provides extremely fast and secure operation for internal transformer faults. The relay incorporates advanced harmonic restraint and blocking techniques, which allow it to reliably distinguish between a true fault and the magnetizing inrush current that occurs when a transformer is energized—a classic cause of nuisance tripping for less sophisticated devices. This ensures that the transformer remains online during safe switching operations while being protected against genuine internal faults.

From a system and hardware perspective, the ABB RET670 is built for the long-term demands of a high-voltage environment. It features a robust, modular chassis designed for flexible I/O configuration and easy maintenance. A key benefit is its powerful Condition Based Monitoring functionality. The relay doesn’t just trip; it continuously analyzes the health of the transformer itself, calculating key parameters like winding temperature using advanced thermal models and monitoring dissolved gas analysis (DGA) trends from external sensors. This data, combined with detailed event and disturbance records, provides invaluable insight for predictive maintenance strategies. Coupled with its native support for IEC 61850 process bus, which allows it to communicate with non-conventional instrument transformers, the ABB RET670 represents a complete, future-proof solution for transformer management, merging primary protection with deep asset intelligence.

Detailed Technical Specifications

Related Modules or Compatible Units

REF670 – Feeder protection terminal, often used on the incoming or outgoing lines connected to the transformer.
REC670 – A generator protection terminal, used in conjunction with the ABB RET670 for complete unit protection.
REG670 – A bay controller for applications requiring more extensive automation and interlocking logic.
REQ650 – A dedicated voltage and power quality controller.
CMC 256 Plus – A universal test system used for comprehensive commissioning and periodic testing of the ABB RET670.

Installation Notes & Maintenance Best Practices

Proper installation of the ABB RET670 is a meticulous process that begins with system design. The relay must be mounted in a well-ventilated, clean section of the control panel or rack. The most critical aspect is the correct wiring and configuration of the Current Transformer (CT) and Voltage Transformer (VT) circuits. It is imperative that the CT connections for differential protection are phased correctly according to the transformer vector group; a wiring error here can render the primary protection scheme inoperative or cause false tripping. All CT and VT circuits must be securely grounded at a single point for safety and to prevent circulating currents that can affect measurement accuracy. A dedicated, high-integrity DC control power source is essential to ensure the relay remains operational during AC system faults.

Maintenance for the ABB RET670 is heavily reliant on its advanced diagnostic and data management capabilities. The relay requires no routine calibration. The primary maintenance activity involves analyzing its extensive recorded data. After any operation or alarm, engineers should download and meticulously review the sequence of events (SOE) and detailed disturbance fault records to verify the relay’s response and analyze the nature of the system event. During planned transformer outages, a secondary injection test using a modern test set is recommended to verify the health and accuracy of the entire protection chain, from the relay’s firmware logic down to its binary output contacts. Regularly archiving the relay’s configuration and keeping its firmware up to date are also key best practices for long-term reliability and security.