Abstract: In a surge protection device 40 (40-1 or 40-2) used for a surge protection apparatus, a gas arrester 41 is connected in series with a varister group consisting of a plurality of varisters 42-1 to 42-5 which have high withstand capacity and are connected in parallel to one another and a discharge resistor 43 is connected between both electrodes of the varister group. Besides, since the varister voltages are set higher than the peak value of the AC power supply voltage, the varisters 42-1 to 42-5 are normally insulated from a power supply circuit by the gas arrester 41. Even if an abnormal voltage is applied, since an operating voltage of the varisters 42-1 to 42-5 is set higher than a peak value of the AC power supply voltage, AC power supply current will not flow. Charges stored in the varisters 42-1 to 42-5 are released quickly through the resistor 43, making it possible to prevent the gas arrester 41 from restriking.

Abstract: In a gas-filled arrester, a pair of main electrodes and a ground electrode are air-tightly fitted to an insulating tubular member. A springy, electrically-conductive short-circuiting element having an arcuate shape is fitted around the outer wall of the ground electrode. The short-circuiting element includes extension portions extending along the outer wall of the insulating tubular member to the respective main electrodes, and these extension portions are made to face the main electrodes by utilization of spring characteristics thereof with a certain gap maintained and with a thermally-fusible spacer interposed. With this construction, if the arrester is overheated, the spacer is thermally fused by heat and therefore the extension portions electrically contact the main electrodes due to the spring characteristics thereof. Since the main electrodes are thus short-circuited to the ground electrode, the arrester is prevented from failing.