Protective Relaying Methods for Reducing Arc Flash Energy

This paper reviews progress in arc flash standards and requirements and the protective relaying techniques used to reduce arc flash energy, primarily through “high-speed detection and operation”. In some cases, the high-speed zone is permanent, and in others it is switched in during maintenance or repair. The need for high-speed “backup” arc flash protection will be discussed. Using a single high-speed zone of protection, thus establishing the level of “personal protective clothing,” begs the question “what if the single high-speed zone fails”? Several arc flash clearing time examples will demonstrate this concern.