Hybrid Switching Apparatus for Electric Grids

An electric grid comprising at least one switching apparatus, the at least one switching apparatus comprising:

• first and second electric terminals for electrical connection with corresponding grid portions;
• a first electric branch comprising one or more switching devices of electromechanical type, each having electric contacts that can be mechanically coupled or separated to conduct or block a current, respectively;
• a second electric branch comprising a plurality of switching devices (41, 42) of solid-state type, each including one or more switching components based on semiconductor materials (41A, 41B, 42A, 42B) and being adapted to switch between an on-state, at which said switching device conducts a current, and an off-state, at which said switching device blocks a current, said second electric branch being electrically connected in parallel with said first electric branch between said first and second electric terminals;
• wherein said second electric branch comprises:
• a current blocking circuit adapted to block a current flowing along said second electric branch, said current blocking circuit including a first switching device of solid-state type and a first electronic circuit electrically connected in parallel to said first switching device of solid-state type;
• a current limiting circuit adapted to limit a current flowing along said second electric branch, said current limiting circuit being electrically connected in series with said current blocking circuit and including a second switching device of solid-state type and a second electronic circuit electrically connected in parallel to said second switching device of solid-state type.

A switching group comprising a switching apparatus, the switching apparatus comprising:

• first and second electric terminals for electrical connection with corresponding grid portions;
• a first electric branch comprising one or more switching devices of electromechanical type, each having electric contacts that can be mechanically coupled or separated to conduct or block a current, respectively;
• a second electric branch comprising a plurality of switching devices (41, 42) of solid-state type, each including one or more switching components based on semiconductor materials (41A, 41B, 42A, 42B) and being adapted to switch between an on-state, at which said switching device conducts a current, and an off-state, at which said switching device blocks a current, said second electric branch being electrically connected in parallel with said first electric branch between said first and second electric terminals;
• wherein said second electric branch comprises:
• a current blocking circuit adapted to block a current flowing along said second electric branch, said current blocking circuit including a first switching device of solid-state type and a first electronic circuit electrically connected in parallel to said first switching device of solid-state type;
• a current limiting circuit adapted to limit a current flowing along said second electric branch, said current limiting circuit being electrically connected in series with said current blocking circuit and including a second switching device of solid-state type and a second electronic circuit electrically connected in parallel to said second switching device of solid-state type;
• and
• a disconnector electrically connected in series with the first and second electric branches.

A method for protecting an electric grid, said electric grid comprising a plurality of switching groups for electrically connecting or disconnecting different grid portions of said electric grid, wherein each switching group comprises:

• a switching apparatus configured to control bi-directional currents, said switching apparatus being capable of switching in a closed state, in which said switching apparatus conducts a current, or in an open state, in which said switching apparatus blocks a current, or in a current limiting mode, in which said switching apparatus limits a current commuted from a first electric branch to a second electric branch;
• a disconnector electrically connected in series with said switching apparatus, said disconnector being configured to switch between a closed state, in which said disconnector conducts a current, and an open state, in which said disconnector blocks a current;
• wherein each switching group is configured to switch to a closed state, in which said switching apparatus is in a closed state and said disconnector is in a closed state, and an open state, in which said switching apparatus is in an open state and said disconnector is in an open state, or in a current limiting mode, in which said switching apparatus is in a current limiting mode and said disconnector is in a closed state,
• wherein the method includes:
• when there is an electric fault in said electric grid, switching said switching groups in a current limiting mode;
• switching the switching group, which is closest to said electric fault, in an open state and maintaining the remaining switching groups of said electric grid in a current limiting mode;
• when said electric fault is electrically isolated within a predefined period of time when the switching group, which is closest to said electric fault, is in an open state:
• maintaining the switching group, which is closest to said electric fault, in an open state and switching the remaining switching groups of said electric grid back to the closed state;
• when said electric fault is not electrically isolated within said predefined period of time and when the switching group, which is closest to said electric fault, is in an open state:
• switching all the switching groups of said electric grid in an open state.