Gas circuit breaker

A gas circuit breaker comprising:

• a sealed tank filled with insulation gas;
• a pair of arc contacts that are arranged to face each other in the sealed tank and connectable and disconnectable with each other;
• a thermal puffer chamber that is provided on an outer circumferential portion of the pair of arc contacts, a part of which is formed by a partition wall;
• a mechanical puffer chamber that is provided on an outer circumference of the thermal puffer chamber and constituted by a cylinder formed in a toric shape centering around an axial line of the arc contacts;
• and
• a piston that is formed in a toric shape centering around the axial line and accommodated in the cylinder whose part is formed by the partition wall, and configured to move according to connection and disconnection of the arc contacts,
• wherein the thermal puffer chamber is formed in a toric shape so as to surround an arc generation area centering around the axial line of the arc contacts, and includes an opening along a circumferential direction on an inner circumferential surface of the thermal puffer chamber,
• the piston is a movable conducting contact that makes a conducting state when in contact with a fixed conducting contact, and
• the partition wall has at least its part being formed of an insulating material.