Abstract: A protective device for use with a surge arrester to prevent fracturing of the porcelain body of a failed arrester includes a fast-operating switch which shunts a current-limiting fuse. The switch is operated by ignition of a chemical propellant charge, thereby rapidly diverting fault current to the fuse and additionally isolating the arrester from ground. The switch has a moving contact in the form of a gas-driven piston which strikes a separable terminal connected to a ground lead.