High voltage electric circuit breaker including a synchronously closed resistor switch

Claim 2

In a high voltage circuit breaker for connection between bus and line portions of a polyphase AC circuit; a circuit breaker assembly for each phase comprising: means including resistor switch contacts engageable to preinsert a resistance in series with the associated phase during circuit breaker closing, means comprising main contacts of said assembly for completing a shorting circuit that shorts out said preinserted resistance during a later stage of circuiT breaker closing, and means for reducing the effective value of said preinserted resistance prior to completion of said shorting circuit, said means for preinserting said resistance comprising: closing motive means for driving said resistor switch contacts into engagement and for thereafter causing said shorting circuit to be completed through said main contacts, restraining means for blocking operation of said closing motive means until released, said closing motive means requiring a predetermined circuit breaker closing time following release of said restraining means to produce engagement of said resistor switch contacts; a closing control for the restraining means of all of said circuit breaker assemblies comprising: a. closing command means operable to provide a signal for initiating a circuit breaker closing operation; b. means permitted to operate by said signal and operable when a charge exceeding a predetermined percentage of crest voltage is trapped on the line portion of a predetermined one of said phase for releasing the restraining means of the assembly in said one phase at such an instant that the resistor switch contacts of said assembly consistently reach engagement during a voltage loop of the same polarity as the charge trapped on said line portion; and c. means for releasing the restraining means of each of said other phases in such time-staggered relationship with respect to release of the restraining means of said one phase that engagement of the resistor switch contacts in the second-toclose phase occurs 30 to 120 electrical degrees after engagement of the resistor switch contacts in said one phase.

Claim 3

In a high voltage circuit breaker for connection between bus and line portions of polyphase AC circuit; a circuit breaker assembly for each phase comprising: means including resistor switch contacts engageable to preinsert a resistance in series with the associated phase during circuit breaker closing, means comprising main contacts of said assembly for completing a shorting circuit that shorts out said preinserted resistance during a later stage of circuit breaker closing, and means for reducing the effective value of said preinserted resistance prior to completion of said shorting circuit, said means for preinserting said resistance comprising: closing motive means for driving said resistor switch contacts into engagement and for thereafter causing said shorting circuit to be completed through said main contacts, restraining means for blocking operation of said closing motive means until released, said closing motive means requiring a predetermined circuit breaker closing time following release of said restraining means to produce engagement of said resistor switch contacts; a closing control for the restraining means of all of said circuit breaker assemblies comprising: a. zero-crossing detection means operable when said circuit breaker is open for developing a first signal having a predetermined fixed time relationship with respect to passage through zero of the phase-to-ground voltage on one of said phases, measured on the bus side of said circuit breaker, said first signal having a character indicative of the direction of change of said bus-side voltage; b. trapped-charge detection means operable when said circuit breaker is open for developing a second signal in response to the phase-to-ground voltage trapped on said one phase, measured on the line side of said breaker, exceeding a predetermined value, said second signal having a character indicative of the polarity of said trapped charge; c. logic means receiving said first and second signals and operable to develop an output signal that establishes the instant that said bus-side phase-to-ground voltage crosses zero toward the polarity of said line-side trapped charge; d. timing means started by said output signal and producing a motion-initiating signal at the end of a timing period that is of such a duration that the sum of said timing period plus sAid predetermined circuit breaker closing time for the assembly in said one phase equals the time elapsing between development of said output signal and the occurrence of a voltage loop in said bus-side, phase-to-ground voltage of the same polarity as said trapped charge; e. means for releasing the restraining means of said one phase upon production of said motion-initiating signal; f. disabling means for preventing said timing means from producing an effective motion-initiating signal until a closing command signal is received by said disabling means; and g. means for releasing the restraining means of each of said other phases in such time-staggered relationship with respect to release of the restraining means of said one phase that engagement of the resistor switch contacts in the second-to-close phase occurs 30 to 120 electrical degrees after engagement of the resistor switch contacts in said one phase.

Claim 4

In a high voltage circuit breaker for connection between bus and line portions of polyphase AC circuit; a circuit breaker assembly for each phase comprising: means including resistor switch contacts engageable to preinsert a resistance in series with the associated phase during circuit breaker closing, means comprising main contacts of said assembly for completing a shorting circuit that shorts out said preinserted resistance during a later stage of circuit breaker closing, and means for reducing the effective value of said preinserted resistance prior to completion of said shorting circuit, said means for preinserting said resistance comprising: closing motive means for driving said resistor switch contacts into engagement and for thereafter causing said shorting circuit to be completed through said main contacts, restraining means for blocking operation of said closing motive means until released, said closing motive means requiring a predetermined circuit breaker closing time following release of said restraining means to produce engagement of said resistor switch contacts; a closing control for the restraining means of all of said circuit breaker assemblies comprising: a. zero-crossing detection means operable when said circuit breaker is open for developing a first signal having a predetermined fixed time relationship with respect to passage through zero of the phase-to-ground voltage on one of said phases, measured on the bus side of said circuit breaker, said first signal having a character indicative of the direction of change of said bus-side voltage; b. trapped-charge detection means operable when said circuit breaker is open for developing a second signal in response to the phase-to-ground voltage trapped on said one phase, measured on the line side of said breaker, exceeding a predetermined value, said second signal having a character indicative of the polarity of said trapped charge; c. logic means receiving said first and second signals and operable to develop an output signal that establishes the instant that said bus-side phase-to-ground voltage crosses zero toward the polarity of said line-side trapped charge; d. timing means started by said output signal and producing a motion-initiating signal at the end of a timing period that is of such a duration that the sum of said timing period plus sAid predetermined circuit breaker closing time for the assembly in said one phase equals the time elapsing between development of said output signal and the occurrence of a voltage loop in said bus-side, phase-to-ground voltage of the same polarity as said trapped charge; e. means for releasing the restraining means of said one phase upon production of said motion-initiating signal; f. disabling means for preventing said timing means from producing an effective motion-initiating signal until a closing command signal is received by said disabling means; and g. means for releasing the restraining means of each of said other phases in such time-staggered relationship with respect to release of the restraining means of said one phase that engagement of the resistor switch contacts in the second-to-close phase occurs 30 to 120 electrical degrees after engagement of the resistor switch contacts in said one phase.

Claim 5

The circuit breaker of claim 1 in which said timing period has a duration such that the sum of said timing period plus said predetermined circuit breaker closing time for the assembly in said one phase approximately equals the time elapsing between development of said output signal and the occurrence of a voltage crest in said bus-side, phase-to-ground voltage of the same polarity as said trapped charge.

Claim 6

The circuit breaker of claim 1 in which the preinserted resistance is also used for controlling the rate of rise of the recovery voltage during circuit breaker opening and is of a value less than twice the surge impedance of the energized AC circuit.

Claim 7

In a high voltage circuit breaker for connection between bus and line portions of a polyphase AC circuit; a circuit breaker assembly for each phase comprising: means including resistor switch contacts engageable to preinsert a resistance in series with the associated phase during circuit breaker closing, means comprising main contacts of said assembly for completing a shorting circuit that shorts out said preinserted resistance during a later stage of circuit breaker closing, and means for reducing the effective value of said preinserted resistance prior to completion of said shorting circuit, said means for preinserting said resistance comprising: closing motive means for driving said resistor switch contacts into engagement and for thereafter causing said shorting circuit to be completed through said main contacts, restraining means for blocking operation of said closing motive means until released, said closing motive means requiring a predetermined circuit breaker closing time following release of said restraining means to produce engagement of said resistor switch contacts; a closing control for the restraining means of all of said circuit breaker assemblies comprising: a. first sensing means responsive to the bus-side phase-to-ground voltage on one of said phases for sensing when said bus side voltage is crossing zero and the direction of change during said zero crossing; b. second sensing means responsive to the line-side phase-to-ground voltage on said one phase for sensing the polarity and magnitude of the phase-to-ground voltage trapped on said one phase on the line side of said circuit breaker; c. means controlled by said first and second sensing means and operable when said line-side trapped charge exceeds a predetermined value for developing an output signal at a fixed time relative to said bus-side voltage''s crossing zero in a predetermined direction with respect to the polarity of said line-side trapped charge; d. timing means started by said output signal and producing a motion-initiating signal at the end of a timing period that is of such a duration that the sum of said timing period plus said predetermined circuit breaker closing time for the assembly in said one phase equals the time elapsing between development of said output signal and the occurrence of a voltage loop in said bus-side, phase-to-ground voltage of the same polarity as sAid trapped charge; e. means for releasing the restraining means of said one phase upon production of said motion-initiating signal; f. disabling means for preventing said timing means from producing an effective notion-initiating signal until a closing-command signal is received by said disabling means; and g. means for releasing the restraining means of each of said other phases in such time-staggered relationship with respect to release of the restraining means of said one phase that engagement of the resistor switch contacts in the second-to-close phase occurs 30 to 120* electrical degrees after engagement of the resistor switch contacts in said one phase.

Claim 8

In a high voltage circuit breaker for connection between bus and line portions of a polyphase AC circuit; a circuit breaker assembly for each phase comprising: means including resistor switch contacts engageable to preinsert a resistance in series with the associated phase during circuit breaker closing, means comprising main contacts of said assembly for completing a shorting circuit that shorts out said preinserted resistance during a later stage of circuit breaker closing, and means for reducing the effective value of said preinserted resistance prior to completion of said shorting circuit, said means for preinserting said resistance comprising: closing motive means for driving said resistor switch contacts into engagement and for thereafter causing said shorting circuit to be completed through said main contacts, restraining means for blocking operation of said closing motive means until released, said closing motive means requiring a predetermined circuit breaker closing time following release of said restraining means to produce engagement of said resistor switch contacts; a closing control for the restraining means of all of said circuit breaker assemblies comprising: a. first sensing means responsive to the bus-side phase-to-ground voltage on one of said phases for sensing when said bus side voltage is crossing zero and the direction of change during said zero crossing; b. second sensing means responsive to the line-side phase-to-ground voltage on said one phase for sensing the polarity and magnitude of the phase-to-ground voltage trapped on said one phase on the line side of said circuit breaker; c. means controlled by said first and second sensing means and operable when said line-side trapped charge exceeds a predetermined value for developing an output signal at a fixed time relative to said bus-side voltage''s crossing zero in a predetermined direction with respect to the polarity of said line-side trapped charge; d. timing means started by said output signal and producing a motion-initiating signal at the end of a timing period that is of such a duration that the sum of said timing period plus said predetermined circuit breaker closing time for the assembly in said one phase equals the time elapsing between development of said output signal and the occurrence of a voltage loop in said bus-side, phase-to-ground voltage of the same polarity as sAid trapped charge; e. means for releasing the restraining means of said one phase upon production of said motion-initiating signal; f. disabling means for preventing said timing means from producing an effective notion-initiating signal until a closing-command signal is received by said disabling means; and g. means for releasing the restraining means of each of said other phases in such time-staggered relationship with respect to release of the restraining means of said one phase that engagement of the resistor switch contacts in the second-to-close phase occurs 30 to 120* electrical degrees after engagement of the resistor switch contacts in said one phase.

Claim 9

The circuit breaker of claim 5 in combination with: a. backup timing means started by said output signal and producing a second motion-initiating signal at the end of a second timing period that is slightly longer than that used for closing of the circuit breaker assembly in the last-to-close phase during voltage-synchronized closing; and b. means responsive to said second motion initiating signal for releasing all of said restraining means without regard to the voltage conditions sensed by the sensing means of (a) and (b) of claim 4.

Claim 10

The circuit breaker of claim 6 in which release of all of said restraining means in response to said second motion-initiating signal occurs substantially simultaneously.

Claim 11

The circuit breaker of claim 5 in which the means of (g) comprises: releasing means for the restraining means the second-to-close phase, separate timing means for the releasing means of said second-to-close phase which is started by said output signal from said logic means, said separate timing means producing a motion-initiating signal for the releasing means of said second-to-close phase at the end of a timing period longer than the timing period of the timing means of (d) by a sufficient amount to consistently produce said 30 to 120* delay in closing said second-to-close phase whenever closing is controlled by said logic means.

Claim 12

The circuit breaker of claim 5 in which said releasing means of (g) releases the third-to-close phase in such time-staggered relationship to release of the restraining means of said one phase that engagement of the resistor switch contacts in the third-to-close phase consistently occurs 30 to 120* after engagement of the resistor switch contacts in the second-to-close phase whenever closing is controlled by said logic means.

Claim 13

The circuit breaker of claim 5 in which the means of (g) comprises releasing means for the restraining means of each timing means being started by said output signal from said logic means, each of said separate timing means producing a motion-initiating signal for the releasing means of its associated phase at the end of a timing period sufficiently long that the second-to-close phase is consistently closed 30 to 120* after said one phase is closed and the third-to-close phase is consistently closed 30 to 120* after the second-to-close phase is closed whenever closing is controlled by said logic means.

Claim 14

The circuit breaker of claim 5 in which said timing period has a duration such that the sum of said timing period plus said predetermined circuit breaker closing time for the assembly in said one phase approximately equals the time elapsing between development of said output signal and the occurrence of a voltage crest in said bus-side, phase-to-ground voltage of the same polarity as said trapped charge.

Claim 15

The circuit breaker of claim 5 in which the preinserted resistance is also used for controlling the rate of rise of the recovery voltage during circuit breaker opening and is of a value less than twice the surge impedance of the energized AC circuit.