615 Series CN Protection Relays Firmware Update 5.1.6 Release Notes

This document is a release note detailing firmware update 5.1.6 (and prior versions 5.1.5 and 5.1.4) for ABB's 615 series CN protection relays, including models RED615, REF615, REG615, REM615, RET615, REU615, and REV615. It describes implemented usability improvements, cyber security fixes (including CVE-2021-22283), communication enhancements (MMS, PTP, FTPS), and protection function updates such as enhanced RMS measurement stabilization and improved earth-fault protection.