Abstract: A secondary surge arrester has a line conductor and a ground conductor extending through a casing. A nonlinear voltage dependent resistive element and a fault current limiting fuse are connected between the conductors and are disposed within the casing. The fault current limiting fuse includes a fusible material surrounded by sand. The sand also surrounds the nonlinear voltage dependent resistive element. A heat sensitive material is disposed in close proximity to the fusible material and is viewable through a transparent cover. In the event of a failure of the nonlinear voltage dependent resistive element causing arcing, the fusible material fuses to open the current path between the conductors, and the sand absorbs energy by transforming state. Thus, the fault current limiting fuse limits current flow through the surge arrester and extinguishes the arc within the surge arrester so as to prevent violent fragmentation of the casing.

Abstract: A high voltage surge arrester includes first, second and third terminals. Arrester components, including one or more arrester valve blocks, are serially disposed in an insulating arrester housing between the first and second terminals. A first current carrying conductor is connected between the second and third terminals by way of a disconnector. If the arrester fails, the disconnector will disengage the first current carrying conductor to provide a visible indication that the arrester has failed. At the same time, a second current carrying conductor then reestablishes the connection between the second and third terminals. Thus, a current carrying conductive path is maintained between the first and third terminals.

Abstract: A voltage limiting composition, actually a nonlinear resistor, especially suitable for use in a gapless surge arrester is disclosed herein. This composition includes a predetermined amount of zinc oxide as its primary ingredient and one or more specifically selected additives. All of these constituents are combined and sintered so that the composition displays a nonlinear exponent .alpha. at least equal to about 35 over the current range of 1 ma to 5000 amps and such that its energy absorption capability is at least equal to about 50 joules/cm.sup.3.

Abstract: A gapless surge arrester is disclosed herein and includes a porcelain outer casing and a stack of zinc oxide discs located within the casing for passing surge currents therethrough. Silicon dioxide, preferably sand, is provided between this stack in the casing for transferring heat from the discs to the porcelain outer casing as a result of the surge current and for absorbing fault energy where necessary by changing states.

Abstract: A spark gap assembly of a stack of insulating plates which have on one surface thereof a pair of electrodes preassembled and affixed thereto with a defined spark gap therebetween and a piece of ionizing material disposed on and affixed to each of the plates between the pair of electrodes. The plates are stacked with mating surfaces joined together and with a center plate bearing no electrodes that is joined with mating surfaces of each of two symmetrical groups of electrode bearing plates, and an electromagnetic coil is disposed around the periphery of the center plate.