Arresters

Surge arresters are devices made to protect electrical equipment from over-voltage transients caused by external or internal events. Also called a surge protection device or transient voltage surge suppressor, this class of device is used to protect equipment in power transmission and distribution systems. To protect a unit of equipment from transients occurring on an attached conductor, a surge arrester is connected to the conductor just before it enters the equipment. Surge arresters are not generally designed to protect against a direct lightning strike to a conductor, but rather against electrical transients resulting from lightning strikes occurring in the vicinity of the conductor. Transients similar to lightning-induced, such as from a high voltage system’s fault switching, may also be safely diverted to ground; however, continuous over-currents are not protected against by these devices. Because the transient is usually initiated at some point between the two ends of the conductor, most applications install a surge arrester just before the conductor lands in each piece of equipment to be protected.