What is a protection relay? What is a protection relay? Protection relay is an electrical device used to sense an abnormal condition in a power system and operate a circuit breaker or an alarm signal. Related searches: What is a protection relay? Protection relay What is the purpose of protection relay? Why is protective relay used? Relays Why relays are used in a system? Leave a Reply Cancel replyCommentEnter your name or username to comment Enter your email address to comment Enter your website URL (optional)