The present invention relates to an electrical, medium voltage, switching mechanism, which includes a casing having a gaseous or liquid insulating material filling; in the casing, between a cable connection and a bus bar, a change-over switch, which can alternately switch between a phase contact and a ground contact, follows a load disconnector, which is in the form of a vacuum switching tube, and has a fixed contact piece and an axially movable cooperating contact piece which is connected via an insulator with an actuating element.
A switching mechanism of this type operates without a separate actual grounding switch, and includes the load disconnector in the grounding effect in that after the switching of the change-over switch from the phase contact to the ground contact, the two contact portions of the load disconnector are agains joined. A locking means in the actuating mechanism assures that the change-over switch can only be actuated when the load disconnector is open. The change-over switch is therefore partially a phase disconnector which switches free of load, and partially a grounding switch which in the transmitting sense similarly switches free of load. The use of a vacuum switching tube permits a particularly large number of high-energy switching cycles. By including the casing and the insulating material filling, the switching mechanism can be free of service for a protracted period of time, and has great reliability even in a moist, dusty, or otherwise aggressive or corrosive environment.
In connection with an electrical, medium voltage switching field, according to which the entire cable connection is disposed in an air-insulated understructure to which all the phases are common, German Pat. No. 28 18 905 discloses the successive arrangement in an insulating gas filled metal casing, of a vacuum switching tube and a standard disconnector between a cable connection and a bus line. Via an insulating material plate, the vacuum switching plate is centrally disposed at the lower end of a tubular container; in contrast, the disconnector is disposed in a second container which contains the bus bar. Despite the object of wanting to be able to service the switching field in an advantageous manner, and to be able to keep the insulating gas volume of the switching field casing small, for the removal and installation of the two switches into and out of the insulating gas filled casing can only be handled in stages while consuming a lot of time, and the two lateral introductions of the switch drives or controls, in addition to requiring a complicated container shape, also require a proportionately large amount of space.
It is an object of the present invention, for an electrical, medium voltage, switching mechanism of the aforementioned general type, to provide a type of construction which has a high operating reliability but requires little space, is economical to manufacture, and can be serviced in a manner which saves time.