A gas-filled spark gap comprising: - an insulating envelope with a hollow cylindrical shape open at two opposing ends bounding an internal housing of the gas-filled spark gap, - two sealing metal flanges assembled in an air-tight manner onto the insulating envelope respectively at the two opposing ends of this insulating envelope in order to seal in an air-tight manner the openings of the insulating envelope, each flange comprising a through-orifice, - two metal electrodes, each electrode comprising a main body extended by an external connection bar, the main body of each electrode being accommodated within the internal housing of the insulating envelope, each electrode comprising an end surface opposite to the connection bar, the end surfaces of the two electrodes bounding between them an air-gap separating the main bodies of the two electrodes in the internal housing, the external bars of the electrodes each passing through the through-orifice of one of the flanges, the flanges being assembled in an air-tight manner onto the electrodes so as to enclose the internal housing in a manner sealed to the gas, the external bars protruding to the outside of the insulating envelope beyond the flanges, and - an inert gas trapped in the internal space of the insulating envelope at a predetermined pressure, the gas-filled spark gap being characterized in that the two metal electrodes are single pieces, a peripheral portion of the end surface of each of the electrodes makes an angle with an internal face of the insulating envelope, said angle being inclined in the direction of one of the electrodes in such a manner as to deflect projections of material in the direction of said electrode, the flanges are made of a material having a coefficient of expansion whose difference with the coefficient of expansion of the material of the insulating envelope is less than 2*10 -6 K -1, and, at ambient temperature, the through-orifice of a flange has an internal diameter greater than the external diameter of the external bar which forms an expansion play so as to allow a greater thermal expansion of the external bar than the thermal expansion of the flange. - an insulating envelope with a hollow cylindrical shape open at two opposing ends bounding an internal housing of the gas-filled spark gap, - two sealing metal flanges assembled in an air-tight manner onto the insulating envelope respectively at the two opposing ends of this insulating envelope in order to seal in an air-tight manner the openings of the insulating envelope, each flange comprising a through-orifice, - two metal electrodes, each electrode comprising a main body extended by an external connection bar, the main body of each electrode being accommodated within the internal housing of the insulating envelope, each electrode comprising an end surface opposite to the connection bar, the end surfaces of the two electrodes bounding between them an air-gap separating the main bodies of the two electrodes in the internal housing, the external bars of the electrodes each passing through the through-orifice of one of the flanges, the flanges being assembled in an air-tight manner onto the electrodes so as to enclose the internal housing in a manner sealed to the gas, the external bars protruding to the outside of the insulating envelope beyond the flanges, and - an inert gas trapped in the internal space of the insulating envelope at a predetermined pressure,