A device designed to protect transmission lines and electrical distribution equipment against damage from sudden voltage increases (line surges) caused by lightning, erratic system conditions, faulty insulation, crossed power lines and other mishaps. The device functions in a similar fashion to a lightning rod by routing excess energy to ground. Unlike a lightning rod, an arrester only bleeds voltage to ground when voltage exceeds specified limits for that part of the system.
Surge arresters are designed to protect the energy transmission and distribution system. Protection of end-user electrical devices is normally the responsibility of the consumer. Surge arresters can and do bleed away most excess voltage, but they do not necessarily provide significant protection against sudden, massive surges such as lightning strikes. Additional protection, such as a surge suppressor in an electrical outlet (power) strip, will often provide significantly more protection for sensitive equipment such as computers and household electronics.
See also:line surge, surge suppressor, ground