The utility model relates to a circuit breaker air chamber and have two feeder cabinets of keeping apart of this circuit breaker air chamber, the upper and lower orientation in inferior officer's direct action type isolator edge sets up in the solid right side of sealing utmost point post in the box of circuit breaker air chamber, three -station isolation switch include the conductor, with the electrically conductive static contact of being connected of the generating line of every row of socket, moving contact and with moving contact fixed connection in order realizing that the major loop switches on, the screw mechanism of three kinds of functions of isolation and ground connection, this three -station isolation switch plays couple isolation with setting up generating line three -station isolation switch on the generating line jointly, lie in isolator gu seal an utmost point post to right -hand projection, arrange isolator like this, effectively utilized the solid high space of sealing utmost point post and bottom socket, and need not be in prior art will reserve out the space of installing isolator on the direction of height of box inside to reduce the height of circuit breaker air chamber, and realized the possibility at line side installation isolator.