A connecting piece for connecting a hollow electric conductor and a coolant line includes a fluid-tight housing (1) having a hollow inner space; a hollow conductor opening (2) in the housing (1); a coolant line opening (3) in the housing (1); and an electrically insulating separating element (4). The inner space hydraulically connects the hollow conductor opening (2) and the coolant line opening (3). The housing (1) includes a coolant line-side housing part (5) and a hollow conductor-side housing part (6). The separating element (4) is arranged between the coolant line-side housing part (5) and the hollow conductor-side housing part (6), and has a coolant channel (7). The separating element (4) is formed as a ball.