620 Series Protection Relay Firmware Release Notes 2.1.16

This document is a release note detailing firmware update 2.1.16 for ABB's 620 series protection relays (REF620, REM620, RET620), including improvements to cyber security, supervision, control, protection, and communication. It also references improvements from the previous release 2.1.15, such as a CVE-2021-22283 fix and enhanced self-supervision.