A switching apparatus for medium voltage electric systems, said switching apparatus comprising one or more electric poles, wherein, for each electric pole, said switching apparatus comprises: - a first pole terminal, a second pole terminal and a ground terminal, said first pole terminal being electrically couplable to a first conductor of an electric line, said second pole terminal being electrically couplable to a second conductor of said electric line and said ground terminal being electrically couplable to a grounding conductor; - a plurality of fixed contacts spaced apart one from another, said plurality of fixed contacts comprising a first fixed contact electrically connected to said first pole terminal, a second fixed contact electrically connected to said second pole terminal, a third fixed contact electrically connected to said ground terminal and a fourth fixed contact; - a movable contact reversibly movable about a corresponding rotation axis according to opposite first and second rotation directions (R1, R2), so that said movable contact can be coupled to or uncoupled from said fixed contacts (5, 6, 7, 8); - a vacuum interrupter comprising a fixed arc contact electrically connected to said first pole terminal, a movable arc contact electrically connected to said fourth fixed contact and reversibly movable along a corresponding translation axis between a coupled position with said fixed arc contact and an uncoupled position from said fixed arc contact, and a vacuum chamber, in which said fixed arc contact and said movable arc contact are enclosed and can be coupled or decoupled; - a motion transmission mechanism operatively coupled to said movable arc contact, said motion transmission mechanism being actuatable by said movable contact to cause a movement of said movable arc contact along said translation axis, when said movable contact moves about said rotation axis; characterized in that said motion transmission mechanism comprises a slider member solidly coupled to said movable arc contact in such a way to move translationally together with said movable arc contact, said slider member being reversibly movable between a first position, which corresponds to the coupled position of said movable arc contact, and a second position, which corresponds to the uncoupled position of said movable arc contact, wherein said slider member is configured to be actuated by said movable contact, during an opening manoeuvre of said switching apparatus, said slider member moving from said first position to said second position, when said slider member is actuated by said movable contact, wherein said motion transmission mechanism comprises a blocking member configured to block said slider member in said second position, when said slider member reaches said second position upon actuation by said movable contact. - a first pole terminal, a second pole terminal and a ground terminal, said first pole terminal being electrically couplable to a first conductor of an electric line, said second pole terminal being electrically couplable to a second conductor of said electric line and said ground terminal being electrically couplable to a grounding conductor; - a plurality of fixed contacts spaced apart one from another, said plurality of fixed contacts comprising a first fixed contact electrically connected to said first pole terminal, a second fixed contact electrically connected to said second pole terminal, a third fixed contact electrically connected to said ground terminal and a fourth fixed contact; - a movable contact reversibly movable about a corresponding rotation axis according to opposite first and second rotation directions (R1, R2), so that said movable contact can be coupled to or uncoupled from said fixed contacts (5, 6, 7, 8); - a vacuum interrupter comprising a fixed arc contact electrically connected to said first pole terminal, a movable arc contact electrically connected to said fourth fixed contact and reversibly movable along a corresponding translation axis between a coupled position with said fixed arc contact and an uncoupled position from said fixed arc contact, and a vacuum chamber, in which said fixed arc contact and said movable arc contact are enclosed and can be coupled or decoupled; - a motion transmission mechanism operatively coupled to said movable arc contact, said motion transmission mechanism being actuatable by said movable contact to cause a movement of said movable arc contact along said translation axis, when said movable contact moves about said rotation axis; characterized in that said motion transmission mechanism comprises a slider member solidly coupled to said movable arc contact in such a way to move translationally together with said movable arc contact, said slider member being reversibly movable between a first position, which corresponds to the coupled position of said movable arc contact, and a second position, which corresponds to the uncoupled position of said movable arc contact, wherein said slider member is configured to be actuated by said movable contact, during an opening manoeuvre of said switching apparatus, said slider member moving from said first position to said second position, when said slider member is actuated by said movable contact, wherein said motion transmission mechanism comprises a blocking member configured to block said slider member in said second position, when said slider member reaches said second position upon actuation by said movable contact.