Abstract: An improved high-voltage, single-shot circuit-protector device, having fuse-like characteristics, and having a chemical operating mechanism, is provided to protect, at low-cost, transmission-line circuits. Preferably, the device contemplates the use of a single-pressure puffer-interrupter having a driving piston attached to the movable contact structure and operated by a chemical operator having an explosive element. Also, preferably, the aforesaid device is self-contained and self-operable, utilizing, preferably, a current-transformer, which triggers a self-contained static control circuit, the latter effecting the "firing" of the explosive element of the chemical operator to thereby generate gas pressure very quickly, and thus effect an opening operation of the contact-operating piston and the attached movable contact structure. For repetitive use, a manual reset lever is preferably provided which is capable of manual hook-stick operation.