Electrical switching system and method to switch this system

A method of operating an electrical switching system, particularly a medium voltage switching system, for a plurality of input and output terminals, of the type including a main bus bar, an auxiliary bus bar, a coupling switch means, electrically connected between said bus bars, for performing the connections of loads and power for said plurality of input and output terminals, and disconnect switch means for selectively connecting each of said terminals with said bus bars, and wherein said disconnect switch means includes a respective single multiposition disconnect switch connected to each of said terminals for selectively connecting same to said bus bars, with each of said multiposition disconnect switches being of the same basic configuration and having a normal ON-position wherein it forms a direct electrical connection between the respective associated one of the said terminals and only said main bus bar, a further ON position wherein it forms a direct electrical connection between the respective associated one of said terminals and only said auxiliary bus bar, an intermediate ON-position which is intermediate said normal ON-position and said further ON-position and in which the associated respective one of said terminals is connected with both said main and said auxiliary bus bars, an OFF-position wherein the associated respective one of said terminals is disconnected from both said main and said auxiliary bus bars, and means for effecting, during switching the transition of current from said main bus bar to said auxiliary bus bar without interruption of the current, and wherein the respective said terminals are in direct electrical connection with only said main bus bar via the respective said multiposition disconnect switches during normal operation and are connected with said auxiliary bus bar only during respective connect and disconnect processes;

• said method comprising:
• before and after a switching process to connect or disconnect a respective one of said terminals, causing all of said multiposition disconnect switches associated with a current flowing through a respective said terminal to be in their correspnding said normal ON-position so that all currents flowing in said plurality of terminals flow through said main bus bar, and said auxiliary bus bar is without current:
• and synchronizing the actuation of said coupling switch means and of said multiposition disconnect switch to assure the proper time sequence of the switching actions.

A method of operating an electrical switching system, particularly a medium voltage switching system, for a plurality of input and output terminals including a main bus bar, an auxiliary bus bar, a normally closed coupling switch electrically connected between said bus bars for performing the connections of loads and power for said plurality of terminals, and a single respective multiposition disconnect switch for each said terminal and having a moveable contact connected to the respective said terminal;

• and wherein during normal operation said terminals are all interconnected via direct connections between their respective said multiposition disconnect switches and said main bus bar to cause current flow;
• said method of comprising the step of disconnecting one of said terminals from said main bus bar to interrupt the current flowing through said one terminal by:
• moving said moveable contact of the corresponding one of said multiposition disconnect switches so as to cause same to simultaneously contact both said main bus bar and said auxiliary bus bar and subsequently to contact only said auxiliary bus bar whereby the current flowing through said one terminal commutates without interruption, to said auxiliary bus bar via said closed coupling switch;
• while said moveable contact is contacting only said auxiliary bus bar, opening said coupling switch to interrupt the current flowing through said one terminal;
• and thereafter moving said moveable contact to an open position wherein it is disconnected from both of said bus bars and then closing said coupling switch.

An electrical switching system, particularly a medium voltage switching system, for selectively connecting and disconnecting a plurality of power input and output load terminals to and from each other via a bus bar, said system comprising in combination:

• a main bus bar;
• an auxiliary bus bar;
• a single normally closed coupling switch means, electrically connected between said bus bars, for selectively permitting and interrupting a flow of current between said bus bars;
• a respective multiposition switch connected to each of said terminals with each said multiposition switch having a first ON-position wherein it directly connects a respective one of said terminals with only said main bus bar, a second ON-position wherein it directly connects said one terminal with both of said bus bars, a third ON position wherein it directly connects said one of said terminals with only said auxiliary bus bar, and a fourth OFF position wherein said one of said terminals is disconnected from both of said bus bars;
• drive means for sequentially moving a respective one of said switches from said fourth to said first position and vice versa to respectively connect or disconnect a respective one of said terminals to said main bus bar and thus to another of said terminals connected to said main bus bar;
• and means for selectively opening and closing said coupling switch means in synchronism with said drive means to open said coupling switch means only when one of said switches is in said third position during a disconnect sequence, and to open said coupling switch means when a respective switch is in said fourth position and to close said coupling switch means in said third position during a connect sequence.