615 Series Protection Relay Firmware Update Release Notes 5.1.24

This document details firmware update release 5.1.24 for ABB's 615 series IEC protection relays (including REF615, REM615, RET615, and others), along with cumulative improvements from previous releases 5.1.23 and 5.1.22. It covers enhancements to self-supervision, RAM testing, frequency protection, PTP time synchronization, cyber security, and communication protocols, with specific instructions for identifying relay versions and order codes.