Power system device and method for actively interrupting fault current before reaching peak magnitude

A device for controlling fault current in an ac power system, said device comprising:

• a circuit interrupter comprising a pair of separable contacts for connection in series with said ac power system, said circuit interrupter being operable to open circuit said ac power system at zero current therethrough to thereby control the fault current;
• a first commutation circuit and a second commutation circuit connectable in parallel with said circuit interrupter, said first commutation circuit having a first commutating capacitance with a positive polarity when charged and said second commutation circuit having a second commutating capacitance with a negative polarity when charged;
• a control circuit for opening said circuit interrupter upon detection of fault current and for selecting and connecting either said first commutation circuit or said second commutation circuit in parallel with said circuit interrupter to thereby discharge into said circuit interrupter said first commutating capacitance or said second commutating capacitance, respectively, wherein said control circuit selects between said first commutation circuit and said second commutation circuit to apply across the circuit interrupter commutating capacitance of opposite polarity to a polarity of the fault current detected such that fault current in the circuit interrupter is actively driven to zero before a peak magnitude of said fault current can be reached;
• and
• wherein said first commutating capacitance and said second commutating capacitance comprise a single capacitor, said single capacitor being shared between said first commutation circuit and said second commutation circuit, said first commutation circuit and said second commutation circuit each comprising two switches, each switch of said two switches being disposed on a different side of said single capacitor for connecting said single capacitor across said circuit interrupter with either said positive polarity or said negative polarity.

A device for controlling fault current in an ac power system, said device comprising:

• a circuit interrupter comprising a pair of separable contacts for connection in series with said ac power system, said circuit interrupter being operable to open circuit said ac power system at zero current therethrough to thereby control the fault current;
• a first commutation circuit and a second commutation circuit connectable in parallel with said circuit interrupter, said first commutation circuit having a first commutating capacitance with a positive polarity when charged and said second commutation circuit having a second commutating capacitance with a negative polarity when charged;
• a control circuit for opening said circuit interrupter upon detection of fault current and for selecting and connecting either said first commutation circuit or said second commutation circuit in parallel with said circuit interrupter to thereby discharge into said circuit interrupter said first commutating capacitance or said second commutating capacitance, respectively, wherein said control circuit selects between said first commutation circuit and said second commutation circuit to apply across the circuit interrupter commutating capacitance of opposite polarity to a polarity of the fault current detected such that fault current in the circuit interrupter is actively driven to zero before a peak magnitude of said fault current can be reached;
• and
• wherein said ac power system comprises a three phase ac power system, and wherein said circuit interrupter comprises a three phase circuit interrupter and said first commutation circuit and said second commutation circuit each comprise a three phase commutation circuit.

A device for controlling fault current in a dc power system, said device comprising:

• a circuit interrupter comprising a pair of separable contacts for connection in series with the dc power system, said circuit interrupter being operable to open circuit said dc power system at zero current therethrough to thereby control the fault current;
• a commutation circuit connectable in parallel with the circuit interrupter, said commutation circuit having a commutating capacitance;
• and
• a control circuit for opening said circuit interrupter upon detection of a transient fault current in the circuit interrupter and for coupling said commutation circuit across said circuit interrupter for commutation of said transient fault current within the circuit interrupter by driving current within the circuit interrupter to zero thereby allowing said circuit interrupter to open circuit said dc power system, said control circuit comprising means for commutating the fault current within the circuit interrupter within a time interval less than approximately one-half a natural time constant of the dc power system, wherein said transient fault current is interrupted before reaching steady state magnitude.

A fast acting mechanism for mechanically opening a circuit interrupter having a pair of separable contacts connectable in series with a power system, said pair of separable contacts including a stationary contact and a moveable contact, said fast acting mechanism comprising:

• a housing having an inner chamber;
• a piston sized to reciprocate within said inner chamber of said housing, said piston having an annular groove in an outer circumference thereof;
• a split ring sized to reside within said annular groove, said split ring having a split therein;
• a key having a first end sized to reside within the split in said split ring and a second end sized to reside within an opening in said housing, said key being reciprocal transverse to a reciprocable direction of said piston;
• means for coupling said piston to said movable contact of said circuit interrupter;
• and
• means for biasing said piston to move said movable contact of said circuit interrupter to an open position, whereby when said key is moved out from engagement with said split ring, said means for biasing said piston moves said piston within said inner chamber of said housing and pulls said moveable contact from said stationary contact, thereby opening said circuit interrupter.

A device for controlling fault current in a power system, said device comprising:

• multiple circuit interrupters coupled in parallel to form an interruption circuit, each circuit interrupter comprising a pair of separable contacts, said interruption circuit being connected in series with said power system, wherein each circuit interrupter of said multiple circuit interrupters coupled in parallel conducts load current from said power system during normal operation;
• at least one circuit interrupter of said interruption circuit having a first current rating, and at least one circuit interrupter of said interruption circuit having a second current rating, said second current rating being less than said first current rating;
• and
• a control circuit for opening upon detection of fault current in the power system said at least one circuit interrupter of said second current rating prior to opening of said at least one circuit interrupter of said first current rating so that said fault current passes entirely through said at least one current interrupter of said first current rating.

A device for controlling fault current in a power system, said device comprising:

• multiple circuit interrupters coupled in parallel to form an interruption circuit, each circuit interrupter comprising a pair of separable contacts, said interruption circuit being connected in series with said power system;
• at least one circuit interrupter of said interruption circuit having a first current rating, and at least one circuit interrupter of said interruption circuit having a second current rating, said second current rating being less than said first current rating;
• a control circuit for opening upon detection of fault current in the power system said at least one circuit interrupter of said second current rating prior to opening of said at least one circuit interrupter of said first current rating so that said fault current passes entirely through said at least one current interrupter of said first current rating;
• and
• further comprising means for actively driving current in said at least one circuit interrupter of said first current rating to zero upon opening of said at least one circuit interrupter of said second current rating, said means for actively driving current comprising means for actively driving fault current in the at least one circuit interrupter of said first current rating to zero before the fault current can reach a peak magnitude.