Metal Oxide Arrester Ratings for Rotating Machine Protection

Metal oxide arresters are ideal for protection of rotating machines against overvoltages. The absence of the gaps required in older arresters results in more consistent operation and improved protection for fast front surges. Also, the absence of gaps makes the tailoring low voltage arrester ratings to match application requirements much more practical. This paper discusses what the arrester ratings should be if they are to be established based on application requirements. After identifying arrester ratings for a wide variety of systems, a set of ratings is suggested that would provide both very good protection for the most popular machine and system voltages, and quite adequate protection for other medium voltage systems.