US3624324A

US3624324A - Circuit breaker actuated by extra-high speed electrohydraulically operated piston

Info

Publication number: US3624324A
Application number: US873938A
Authority: US
Inventors: Philip Barkan; Edward C Schrom
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1969-11-04
Filing date: 1969-11-04
Publication date: 1971-11-30
Anticipated expiration: 1988-11-30
Also published as: CA922763A

Abstract

Discloses an extra-high speed circuit breaker in which the force for initial contact-separation is supplied by an electrohydraulic shock wave generator. A follow-up operator is triggered into operation by the electrohydraulic operator to continue contact-separation after the electrohydraulic operator has lost its initial effectiveness.

Description

United States Patent lnventors Philip Barkan Media, Pa.;

Edward C. Schrom, Latham, NY. 873,938

Nov. 4, 1969 Nov. 30, 1971 General Electric Company Appl. No. Filed Patented Assignee CIRCUIT BREAKER ACTUATED BY EXTRA-HIGH SPEED ELECTROI-IYDRAULICALLY OPERATED PISTON 8 Claims, 3 Drawing Figs.

US. Cl 200/82 R, 200/144 B, 313/232 Int. Cl 01h 3/24, HOlh 35/38, H01h 33/66 Field of Search 200/82 R,

144 B,61.01, 8l;337/401,409, 30, 326, 315; 313/232, 23l;340/15 [56] References Cited UNITED STATES PATENTS 3,141,296 7/1964 Jacobs,Jr. et a1 313/232 X 3,190,990 6/1965 Perry 200/82 X 3,334,348 8/1967 Alfano, Jr.. 200/82 X 3,377,511 4/1968 Richtr et a1. 200/82 X 3,486,062 12/1969 Schrom 313/231 X FOREIGN PATENTS 1,118,868 12/1961 Germany ZOO/61.01 1,287,677 1/1969 Germany 200/82 Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorneys-J. Wesley Haubner, William Fredman, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Discloses an extra-high speed circuit breaker in which the force for initial contact-separation is supplied by an electrohydraulic shock wave generator. A follow-up operator is triggered into operation by the electrohydraulic operator to continue contact-separationafter the electrohydraulic operator has lost its initial effectiveness.

CIRCUIT BREAKER ACTUATED BY EXTRA-HIGH SPEED ELECTROI-IYDRAULICALLY OPERATED PISTON This invention relates to an electric circuit breaker that opens at extra-high speeds and relates more particularly to a circuit breaker in which the force for initial contact-separation is supplied by an electrohydraulic shock wave generator.

In certain circuit breaker applications, it is important that the circuit breaker be opened at extreme high speeds. For example, in the alternating current circuit breaker disclosed in application Ser. No. 806,19l-Kotos, filed Mar. 1 1, I969, and assigned to the assignee of the present invention, it is required that the opening operation be initiated and substantially completed after the instant of peak current and during the short period of a few milliseconds immediately preceding a natural current zero. The shorter the period in which such an opening operation can be completed, the more its initiation can be delayed after passage through peak current and, accordingly, the less severe will be the interrupting duty on the circuit breaker.

Accordingly, an object of our invention is to provide an extra-high speed circuit breaker operator which can separate the contacts of the circuit breaker by an effective distance of one-half inch within 1 or 2 milliseconds following delivery of a tripping signal to the operator.

In attaining this object, we use an operator that relies upon the principle of electrohydraulics for generating a shock wave that supplies the energy for initiating the opening operation. As pointed out in application Ser. No. 814,478-Schrom, filed Jan. 13, 1969 now US. Pat. No. 3,486,062, issued Dec. 23, 1969, and assigned to the assignee of the present invention, an electrohydraulic shock wave generator derives its energy from an electric are initiated under liquid and into which a large amount of electrical energy is rapidly discharged. A shock wave or step pressure gradient is transmitted from the are through the-liquid and is appropriately focused onto the object being worked upon. In carrying out our invention, we focus this shock wave onto a piston coupled to the movable contact of the circuit breaker, and the piston responds to receipt of the shock wave by rapidly moving the contact through the initial portion of an opening stroke.

The force pulse derived from such an electrohydraulic operator, though rising very rapidly to a very-high peak value, is of relatively short duration and quickly loses its effectiveness after passing through its peak. Another object of our invention is to provide an operating mechanism which can continue the rapid contact separation begun by the electrohydraulic operator immediately after this force pulse loses its effectiveness.

In further carrying out the invention in one form, we provide a followup operator for continuing separation of said contacts after the shock wave from said electrohydraulic operator has begun contact-separating motion of said piston. Restraining means prevents the followup operator from operating prior to operation of the electrohydraulic operator. Releasing means responsive to operation of the electrohydraulic operator is provided for releasing the restraining means to cause said followup operator to continue separation of said contacts after said electrohydraulic operator has lost its initial effectiveness.

For a better understanding of the invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. I is a schematic view of a circuit breaker embodying one form of the invention. In FIG. I the circuit breaker is shown in closed position.

FIG. 2 shows a portion of the circuit breaker of FIG. 1 near the end of an opening operation but prior to a resetting operation.

FIG. 3 shows the components of FIG. 2 in a position occupied when the circuit breaker is fully open and the components reset.

INTERRUPTER Referring now to FIG. I, there is shown a high-voltage power line 9 in which an electric circuit interrupter 10 is connected for controlling the current therethrough. The illustrated interrupter I0 is a conventional vacuum-type circuit interrupter that comprises a highly evacuated housing ll. Housing I1 comprises a tubular casing of insulating material and a pair of

metal end caps

12 and 13 sealed to the casing at its opposite ends. Located within evacuated housing 11 are two separable contacts 15 and 16. Contact 16 is a stationary contact that is supported on the lower end of a conductive stationary rod 18 projecting through the upper end cap 12. Contact I5 is a movable contact supported on the upper end of a movable contact rod 20 that projects through the lower end cap of housing 11. A suitable flexible metallic bellows 21 forms a seal around movable contact rod 20 and allows reciprocation thereof without permitting air leakage into housing 11.

The portion of power line 9 on one side of the interrupter is suitably connected to the movable contact rod 20, and the portion on the opposite side is suitably connected to stationary contact rod 18. Thus, the circuit through the interrupter extends through conductive parts I8, l6, l5 and 20. When movable contact rod 20 is driven downwardly from its position of FIG. I, it separates the movable contact 15 from stationary contact 16 to draw an arc therebetween. When the arcing current passes through zero, the arc is prevented from reigniting by the high-dielectric strength of the vacuum, thus completing the interrupting operation. A significant characteristic of a vacuum interrupter is its ability to complete an interrupting operation with only a very small contact separation, e.g., onehalf to three-fourth inches.

ELECTROI-IYDRAULIC OPERATOR For separating the contacts at extreme-high speeds, we provide an electrohydraulic operator 25. The operator 25, in many respects, is similar to the hydraulic shock wave generating apparatus shown and claimed in the aforesaid application Ser. No. 814,478-Schrom. As such, it comprises a chamber 26 that is filled with a suitable liquid, such as water with insoluble electrically conductive particles suspended therein. Such a fluid system is disclosed and claimed in US. Pat. No. 3,225,252-Schrom et al., assigned to the assignee of the present invention. At the right-hand end of the illustrated chamber is a cylindrical bore 27 in which a piston 28 is slidably mounted. In the illustrated embodiment, the internal surfaces of chamber 26 are constituted by a director surface 30 of generally hemispherical form at the left-hand side of the chamber and a collimator surface 32 of frustoconical form disposed between the hemispherical surface and the bore and converging toward the bore.

In the center of the hemispherical surface is an opening into which suitable electrode structure 35 extends. This electrode structure is preferably of the type shown and claimed in U.S. Pat. No. 3.354,344-Schrom, assigned to the assignee of the present invention. As such, it comprises an outer electrode 36 and an inner electrode 38 concentric therewith and electrical insulation 39 disposed between the two electrodes. The electrodes have exposed metal tips that are disposed substantially flush with the hemispherical surface 30.

When a sufficiently high-voltage is applied between these

electrodes

36 and 38, an electric arc is initiated between the exposed metal tips of the electrodes Through this arc a sharply rising pulse of current having a duration of about 10 microseconds is caused to flow in a manner soon to be described. The arc reacts with the liquid in the chamber 26, vaporizing a portion of the liquid and generating a shock wave which is rapidly propagated through the liquid into sharp impact with the exposed left-hand surface of piston 28. This impact drives piston 28 at extreme-high speed toward the right, thereby extremely rapidly separating contact 15 from contact 16, as will soon be described.

The hemispherical surface 30 directs the shock wave into the liquid and the conical surface 32 concentrates the energy of the shock wave into a path leading toward the piston 28. The shape of these surfaces can be varied to change the shape and distribution of the force pulse output from the electrohydraulic operator. But in a preferred form of the invention, we use a director surface that is a divergent surface of revolution having its axis of revolution substantially coincident with the electrode region in which the arc is initiated.

For terminating motion of the piston 28 without excessive shock, dashpotting action is provided by means of an annular shoulder 40 on the bore 27 coacting with an enlarged portion 28a of the piston rod. When the piston 28 moves to the right, it forces liquid ahead of it into an overflow chamber 4]. Initially this liquid flows freely into the overflow chamber 41, but when the enlarged portion 28a enters the region of the annular shoulder 40, a restricted flow passage is present around the enlarged portion, and the impedance of this restricted passage imposes a high-decelerating force on piston 28.

A suitable piston reset spring 43 biases the piston 28 to the left and returns it to its illustrated position of FIG. 1 after the piston has moved through its above-described working stroke. Any gases then present in the liquid to the left of the piston are vented through a restricted bleed passage 45. This bleed passage is sufficiently restricted that it does not significantly interfere with pressure build up in chamber 26 during a normal working operation of the electrohydraulic operator 25.

IN ITIATING OPERATION OF THE ELECTROI-IYDRAULIC OPERATOR For initiating the aforementioned are between

electrodes

36 and 38 of the electrohydraulic operator, we provide the series combination of a high-voltage capacitor 50 and a normally open, turn-on switch 52 connected across the electrodes. The capacitor 50 is charged from a suitable separate source (not shown) via conductors 51. When switch 52 is open, insufficient voltage is present between the

electrodes

36 and 38 to initiate an arc therebetween. But when the switch 52 is closed, the full capacitor voltage is available across the electrodes, thus producing the desired arc-over therebetween. The capacitor rapidly discharges through this arc to produce a sharply rising current pulse. The inductance of the capacitor discharge circuit is held to a minimum value in order to maximize the rate of rise of this current pulse.

The turn-on switch 52 can be of any suitable conventional form. It is schematically shown as a normally nonconducting gap device having a trigger electrode 54 disposed between an anode and a cathode. When a sufficient trigger voltage is applied between the trigger electrode and the cathode of the gap device, the gap device becomes conducting, in effect, closing.

For turning on the switch 2, any suitable control circuit can be used. In the illustrated embodiment, we have shown an overcurrent sensitive control circuit 56. The circuit 56 comprises a current transformer having a secondary winding 57 magnetically coupled to the power line 9 and a bridging rectifier 58 connected across the secondary winding 57. The output terminals of the bridging rectifier are connected across a potentiometer type resistor 59. The previously described trigger electrode 54 is connected to a suitable tap on resistor 59 so that when the voltage across resistor 59 reaches a predetermined threshold value, sufficient voltage is present between the trigger electrode and the cathode of the gap device 52 to fire the gap device. Since the voltage across resistor 59 is directly dependent upon the current in line 9, it will be apparent that the gap device 52 will be fired in response to a predetermined current through line 9.

Another suitable control circuit is that shown in the aforementioned Kotos application, where a tripping pulse is generated at a preselected point on the current wave just prior to current zero. When such a circuit is used, this tripping pulse is applied to the trigger electrode 54 to turn on the switch 52 and initiate opening.

OPERATING MECHANISM For transmitting opening force from the piston 28 to the movable contact 15, we provide a bellcrank 60 which is pivotally mounted on a stationary pivot 62. One arm of the bellcrank is pivotally joined to the movable contact rod 20. The other arm of the bellcrank is positioned to receive the rightward impact of piston 28. Thus, when piston 28 is driven to the right, it pivots bellcrank 60 counterclockwise about its stationary pivot 62, thereby driving rod 20 and movable contact l5 rapidly downward, thus opening the interrupter. A compression spring 64, disposed between the bellcrank 60 and a portion of frame member 68, biases the contacts 15 and 16 together and tends to oppose contact-separating motion by piston 28. But the rapidly rising force from piston 28 quickly overcomes the opposing bias of the spring 64 to initiate operation.

Frame member 68 is pivotally mounted on stationary pivot 62, but normally during the above-described operation of the electrohydraulic operator, it remains stationary. For holding the frame stationary during this period, a releasable latch 70 is relied upon. A portion of this latch is coupled to an actuating rod 72, which, in turn, is pivotally connected to the frame member 68, as by a suitable pin and slot connection. So long as the latch is in its position of FIG. 1, the actuating rod 72 and the frame member 68 remain fixed When latch 70 is released (to initiate a resetting operation, as will soon be described) a spring 74 drives the rod 72 to the right, pivoting the frame member 68 counterclockwise into its position of FIG. 3.

The force derived from the electrohydraulic operator, though it rises very rapidly, if of a relatively short duration and can carry the movable contact at the desired high-speed through only a portion of its complete opening stroke. To complete the high-speed opening stroke, we rely upon a mechanism which is slower in starting but can provide a sustaining force that continues the opening operation after the force pulse from the piston has lost its effectiveness. This latter mechanism comprises an actuating lever pivotally mounted on a fulcrum 81 carried by frame member 68. A compression spring 84 biases lever 80 in a counterclockwise direction about fulcrum 81 but is normally prevented from driving the lever 80 in this direction by the lower end of bellcrank 60. But when bellcrank 60 is forced counterclockwise a short distance by motion of piston 28, the spring 84 drives actuating lever 80 counterclockwise into its position of FIG. 2 against a stop 86 on frame member 68. In so moving, the actuating lever acts through a roller 87 and cam 88 to force the bellcrank counterclockwise into its position of FIG. 2. Roller 87 is carried on the actuating lever 80, and cam 88 is formed on the lower end of bellcrank 60. The length of the opening stroke can be increased by an appropriate change in the shape of cam 88.

The spring 84 and lever 80 may be thought of as constituting a stored-energy followup operator. Cam 88 and roller 87 may be thought of as releasable restraining means for holding the

operator

84, 80 in its charged condition. The lower arm of bellcrank 60 may be thought of as releasing means for releasing the restraining means in response to operation of the electrohydraulic operator 25.

An electrohydraulic operator similar to that illustrated has demonstrated that it can separate contacts by about thirteensixteentli inch in the extremely short time of 2 milliseconds. Only about 1.2 milliseconds was required for a l-inch contact-separation. In these tests, the mass of the movable contact structure was 0.4 pounds, and the arcing energy was obtained from a capacitor of 8.5 microfarads precharged to a voltage of l2 KV. Even higher speeds can be obtained by precharging the capacitor to a higher level.

RESE'ITING OF THE OPERATING MECHANISM For resetting the actuating lever 80 to its original position with respect to bellcrank 60 and frame member 68, the reset latch 70 is tripped to allow reset spring 74 to drive frame member 68 counterclockwise into the position of FIG. 3. This counterclockwise motion of frame member 68 drives a tail 89 on the actuating lever 80 into engagement with a stationary stop 90. Thereafter, as frame member 68 continues moving counterclockwise, this engagement of tail 89 with stop 90 causes actuating member 80 to pivot in a clockwise direction about its fulcrum 81, thus returning the actuating lever 80 to its original position with respect to the bellcrank 60 and frame member 68, as shown in FIG. 3. Such return movement of actuating lever 80 also recharges the opening spring 84. When actuating member 80 is moved through its resetting stroke into the position of FIG. 3, it no longer holds bellcrank 60 in its operated position; but a stop 92 carried by frame member 68 engages bellcrank 60 to continue holding the bellcrank in open position against the bias of spring 64.

For releasing latch 70 to effect the above-described resetting action, a tripping solenoid 100 is provided. This solenoid is connected in an operating circuit 102 that includes a nonnally open switch 104. When the movable contact moves through a predetennined point in its opening stroke, the normally open switch 104 is closed to complete circuit 102, thereby operating the solenoid to trip latch 70 and initiate resetting. A mechanical linkage (not shown) between latch 70 and movable contact rod 20 could alternatively be used for releasing latch 70 in response to opening movement of contact rod 20.

ADDITIONAL MEANS FOR INITIATING AN OPENING OPERATION If it is desired to open the circuit breaker at will or in response to conditions not requiring extreme-high speed opening, the operating circuit 102 is completed by closing a switch 106, which may be manually operable or automatically operable in response to preselected conditions. Switch 106 is normally open but when closed completes an energizing circuit for solenoid 100 to trip latch 70. Reset spring 74 responds to tripping of latch 70 by driving frame member 68 counterclockwise from its position of FIG. 1 into its position of FIG. 3, as explained hereinabove. The pin 92 on frame member 68 engages bellcrank 60 to drive bellcrank 60 counterclockwise about pivot 62 to open the interrupter. The electrohydraulic operator 25 remains inactive during such an opening operation.

If an extra-high speed opening operation is desired, a manually controlled switch 108 in parallel with gap device 52 can be operated to discharge capacitor 50 and cause the electrohydraulic operator to initiate the opening operation. The opening operation thereafter continues in the same manner as described hereinabove.

CLOSING OF THE CIRCUIT BREAKER Closing of the circuit breaker is effected by driving the reset rod 72 to the left from its position of FIG. 3 into its position of FIG. 1. This causes frame member 68 to pivot clockwise about its stationary pivot 62; and such motion is transmitted to bellcrank 60 through spring 64, thus driving the bellcrank counterclockwise about pivot 60 with the frame member 68. This counterclockwise movement of bellcrank 60 drives movable contact rod 20 upwardly to reengage contacts and 16.

The electrohydraulic operator 25 is reset to its position of FIG. 1 prior to the initiation of a closing operation and is therefore in readiness to reinitiate another opening operation as soon as the contacts enter their engaged position should such opening be necessary, as a result, for example, of closing the circuit breaker on a faulted line. The electrohydraulic operator performs such an opening operation simply by driving piston 28 to the right to pivot bellcrank 60 counterclockwise to separate the contacts and release followup operator 84 to complete the contact-separating operation. All of these opening operations can be performed even though a leftward closing force is then being applied to the actuating rod 72 inasmuch as the frame member 68 may remain stationary while all these opening operations are taking place. When the closing force is discontinued after such a close-open operation, spring 74 will return reset rod 72 to its position of FIG. 3

to reset the mechanism.

While we have shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that the various changes and modifications may be made without departing from our invention in its broader aspects; and we, therefore, intend herein to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high speed electric circuit breaker comprising:

a. a pair of separable contacts,

b. an electrohydraulic operator for producing extreme-high speed separation of said contacts,

c. said electrohydraulic operator comprising a chamber containing liquid, means for developing an electric are within said liquid to generate a shock wave in said liquid, a piston exposed to said liquid and movable at high-speed in response to said shock wave impacting against said piston,

d. linkage means mechanically connecting said piston to one of said contacts for imparting contact-separating force and motion from said piston to said one contact when said piston moves in response to receipt of said shock wave,

. said means for developing an are within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-on switch in circuit with said capacitor and said electrodes for initiating said are and for causing said capacitor to rapidly discharge therethrough,

f. only one are being initiated within said liquid per contactseparating operation,

g. a followup operator for continuing separation of said contacts after said shock wave has begun contact-separating motion of said piston,

. restraining means for preventing said followup operator from operating prior to operation of said electrohydraulic operator,

. and releasing means responsive to operation of said electrohydraulic operator for releasing said restraining means to cause said followup operator to continue separation of said contacts after said electrohydraulic operator has lost its initial effectiveness.

2. The circuit breaker of claim 1 in which: said restraining means and said releasing means comprise a cam member and a follower member, one of which is coupled to said linkage and the other of which is coupled to said followup operator, said one member normally restraining said followup operator from operating but moving in response to operation of said electrohydraulic operator into a position wherein it is effective to restrain said followup operator from operating, said followup operator acting thereafter through said cam and follower to impart contact-opening motion to said linkage.

3. The circuit breaker of claim 1 in which:

a. said followup operator is a stored energy device,

b. said restraining means holds said stored energy device in a charged condition during initial operation of said electrohydraulic operator,

0. and said releasing means is coupled to said linkage means for releasing said restraining means in response to operation of said electrohydraulic operator.

4. The circuit breaker of claim 1 in which:

a. said electrodes of the electrohydraulic operator are disposed in substantially coaxial relationship and insulation is provided therebetween,

b. said electrodes terminate in exposed portions between which said arc is initiated and which are located closely adjacent a wall of said chamber.

5. The circuit breaker of claim 1 in which:

a. said electrodes have exposed metal portions between which said arc is formed, and

b. means is provided for directionally controlling the shock wave produced by said are comprising a surface immediately adjacent said exposed electrode portions which is a divergent surface of revolution having an axis of revolution immediately adjacent which said exposed electrode portions are located.

6. The circuit breaker of claim 1 in which said electrodes are spaced apart and insulated from each other prior to the formation of said are therebetween.

7. A high-speed electric circuit breaker comprising:

a. a pair of separable contacts,

b. an electrohydraulic operator for producing extreme highspeed separation of said contacts,

e. said means for developing an arc within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-on switch in circuit with said capacitor and said electrodes for initiating said are and for causing said capacitor to rapidly discharge therethrough,

a followup operator for continuing separation of said contacts after said shock wave has begun contact-separating motion of said piston,

g. restraining means for preventing said followup operator from operating prior to operation of said electrohydraulic operator,

h. releasing means responsive to operation of said electrohydraulic operator for releasing said restraining means to cause said followup operator to continue separation of said contacts after said electrohydraulic operator has lost its initial effectiveness,

i. said followup operator being a stored energy device,

j. said restraining means holding said stored energy device in a charged condition during initial operation of said electrohydraulic operator,

k. said releasing means being coupled to said linkage means for releasing said restraining means in response to operation of said electrohydraulic operator,

1. and reset means provided for recharging said stored-energy followup operator and restoring said restraining means to a reset condition for holding said stored energy followup operator charged,

m. said reset means comprising a stored-energy reset operator, means responsive to a condition which initiates circuit breaker opening for causing said reset operator to discharge and supply energy for resetting, and means operated by said reset operator for recharging said stored-energy followup device and restoring said restraining means to said reset condition.

A high-speed electric circuit breaker comprising:

a. a pair of separable contacts,

c. said electrohydraulic operator comprising a chamber containing liquid, means for developing an electric arc within said liquid to generate a shock wave in said liquid a piston exposed to said liquid and movable at high-speed in response to said shock wave impacting against said piston,

d. linkage means mechanically connecting said piston to one of said contacts for imparting contact-separating force and motion from said piston to said one co'ntact when said piston moves in response to receipt of said shock wave,

e. said means for developing an are within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-o n switch in circuit with said capacitor and said electrodes for initiating said arc and for causing said capacitor to rapidly discharge therethrough,

. followup operating means for continuing separation of said contacts after said shock wave has begun contactseparating motion of said piston, and

g. reset means operable in response to a condition which initiates circuit breaker opening for resetting said followup operating means to a state of preparedness for another operation following a first operation by said followup operating means.

Claims

1. A high speed electric circuit breaker comprising: a. a pair of separable contacts, b. an electrohydraulic operator for producing extreme-high speed separation of said contacts, c. said electrohydraulic operator comprising a chamber containing liquid, means for developing an electric arc within said liquid to generate a shock wave in said liquid, a piston exposed to said liquid and movable at high-speed in response to said shock wave impacting against said piston, d. linkage means mechanically connecting said piston to one of said contacts for imparting contact-separating force and motion from said piston to said one contact when said piston moves in response to receipt of said shock wave, e. said means for developing an arc within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-on switch in circuit with said capacitor and said electrodes for initiating said arc and for causing said capacitor to rapidly discharge therethrough, f. only one arc being initiated within said liquid per contactseparating operation, g. a followup operator for continuing separation of said contacts after said shock wave has begun contact-separating motion of said piston, h. restraining means for preventing said followup operator from operating prior to operation of said electrohydraulic operator, i. and releasing means responsive to operation of said electrohydraulic operator for releasing said restraining means to cause said followup operator to continue separation of said contacts after said electrohydraulic operator has lost its initial effectiVeness.

3. The circuit breaker of claim 1 in which: a. said followup operator is a stored energy device, b. said restraining means holds said stored energy device in a charged condition during initial operation of said electrohydraulic operator, c. and said releasing means is coupled to said linkage means for releasing said restraining means in response to operation of said electrohydraulic operator.

4. The circuit breaker of claim 1 in which: a. said electrodes of the electrohydraulic operator are disposed in substantially coaxial relationship and insulation is provided therebetween, b. said electrodes terminate in exposed portions between which said arc is initiated and which are located closely adjacent a wall of said chamber.

5. The circuit breaker of claim 1 in which: a. said electrodes have exposed metal portions between which said arc is formed, and b. means is provided for directionally controlling the shock wave produced by said arc comprising a surface immediately adjacent said exposed electrode portions which is a divergent surface of revolution having an axis of revolution immediately adjacent which said exposed electrode portions are located.

6. The circuit breaker of claim 1 in which said electrodes are spaced apart and insulated from each other prior to the formation of said arc therebetween.

7. A high-speed electric circuit breaker comprising: a. a pair of separable contacts, b. an electrohydraulic operator for producing extreme high-speed separation of said contacts, c. said electrohydraulic operator comprising a chamber containing liquid, means for developing an electric arc within said liquid to generate a shock wave in said liquid, a piston exposed to said liquid and movable at high-speed in response to said shock wave impacting against said piston, d. linkage means mechanically connecting said piston to one of said contacts for imparting contact-separating force and motion from said piston to said one contact when said piston moves in response to receipt of said shock wave, e. said means for developing an arc within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-on switch in circuit with said capacitor and said electrodes for initiating said arc and for causing said capacitor to rapidly discharge therethrough, f. a followup operator for continuing separation of said contacts after said shock wave has begun contact-separating motion of said piston, g. restraining means for preventing said followup operator from operating prior to operation of said electrohydraulic operator, h. releasing means responsive to operation of said electrohydraulic operator for releasing said restraining means to cause said followup operator to continue separation of said contacts after said electrohydraulic operator has lost its initial effectiveness, i. said followup operator being a stored energy device, j. said restraining means holding said stored energy device in a charged condition during initial operation of said electrohydraulic operator, k. said releasing means being coupled to said linkage means for releasing said restraining means in response to operation of said electrohydraulic operator, l. and reset means provided for recharging said stored-energy followup operatOr and restoring said restraining means to a reset condition for holding said stored energy followup operator charged, m. said reset means comprising a stored-energy reset operator, means responsive to a condition which initiates circuit breaker opening for causing said reset operator to discharge and supply energy for resetting, and means operated by said reset operator for recharging said stored-energy followup device and restoring said restraining means to said reset condition.

8. A high-speed electric circuit breaker comprising: a. a pair of separable contacts, b. an electrohydraulic operator for producing extreme-high speed separation of said contacts, c. said electrohydraulic operator comprising a chamber containing liquid, means for developing an electric arc within said liquid to generate a shock wave in said liquid, a piston exposed to said liquid and movable at high-speed in response to said shock wave impacting against said piston, d. linkage means mechanically connecting said piston to one of said contacts for imparting contact-separating force and motion from said piston to said one contact when said piston moves in response to receipt of said shock wave, e. said means for developing an arc within said liquid comprising a normally charged capacitor, a pair of electrodes between which said arc is adapted to be formed, and means comprising a turn-on switch in circuit with said capacitor and said electrodes for initiating said arc and for causing said capacitor to rapidly discharge therethrough, f. followup operating means for continuing separation of said contacts after said shock wave has begun contact-separating motion of said piston, and g. reset means operable in response to a condition which initiates circuit breaker opening for resetting said followup operating means to a state of preparedness for another operation following a first operation by said followup operating means.