Key Features

 Comprehensive protection, control, and monitoring IED

Extensive function library and configuration flexibility

Expandable hardware design to meet specific user requirements

Suitable for:

Power transformers and autotransformers

Shunt reactors and T-connected transformers

Generator–transformer blocks

Phase-shifting transformers

Small busbar systems

Supports transformer configurations:

Two- and three-winding transformers

Up to six stabilized inputs

Single- or multi-breaker arrangements

Protection Functions

Transformer Differential Protection

Percentage bias restraint for through-fault stability

Waveform and second-harmonic restraint for inrush current detection

Fifth-harmonic restraint for overexcitation

High sensitivity for interturn fault detection

Restricted Earth-Fault Protection (REF)

For all solidly earthed or low-impedance grounded windings

Extremely fast operation with high sensitivity

Supports both high- and low-impedance REF schemes

Distance Protection (Phase-to-phase and Phase-to-earth)

Up to five protection zones

Choice of quadrilateral characteristic, modified quadrilateral, or mho characteristic

Sensitive directional earth-fault element for high-resistance grounded networks

Load encroachment logic

Power-swing detection, including additional blocking and tripping logic

Directional Power Protection

Reverse power, low forward power, active power, and reactive power protection

Phase-angle compensation

Two-stage operation (alarm / trip)

Overcurrent Protection

Directional overcurrent for each winding with four steps

Each step selectable as inverse-time or definite-time

Each step directional or non-directional

High-speed instantaneous short-circuit protection with low transient overreach

Four-step phase overcurrent protection (directional or non-directional)

Voltage, current, or dual-polarized

Steps selectable as inverse-time or definite-time

Optional blocking based on second-harmonic content

High-speed earth-fault protection with low transient overreach

Synchronization and Breaker Control

Synchronizing, Synchrocheck, and Dead-Line Check

Supports both single- and multi-breaker arrangements

Selectable energizing direction

Two functions with automatic voltage selection

Suitable for automatic and manual synchronizing with independent settings

Synchronization of asynchronous networks with configurable breaker closing time

Additional Control & System Logic

Breaker failure protection (per breaker)

Voltage protection and overexcitation protection

Monitoring and advanced control functions

Additional Monitoring & Input Functions

Sudden pressure relief / Buchholz relay input support

Transformer temperature device inputs

Binary inputs stabilized against capacitive discharges

ABB RET6701MRKO04816-AC｜Transformer Protection Relay｜