615 Series CN Protection Relays Firmware Update Release Notes 5.1.5

This document is a release note detailing firmware update 5.1.5 (and prior update 5.1.4) for ABB’s 615 series CN protection relays, including models RED615, REF615, REG615, REM615, RET615, REU615, and REV615. It outlines implemented improvements in cyber security, communication protocols (MMS, PTP, TLS 1.2), supervision, and protection functions, along with instructions for identifying compatible relay versions.