US3183331A - Automatic reclosing circuit breaker - Google Patents

Description

May 11 P. BARKAN 3,183,331

AUTOMATIC RECLOSING CIRCUIT BREAKER Filed March 27, 1961 2 Sheets-Sheet 1 Invefitor: Philip Barkan,

PVC/born eg.

May 11, 1965 P. BARKAN AUTOMATIC RECLOSING CIRCUIT BREAKER I 2 Sheets-Sheet 2 Filed March 27, 1961 Inventor Philip Barkan,

by Attorneg.

United States Patent 3,183,331 AUTOMATIC RECLOSING CIRCUIT BREAKER Philip Barkan, Lima, Pa, assignor to General Electric Company, a corporation of New York Filed Mar. 27, 1961, Ser. No. 98,569 12 Claims. (Cl. 200-156) This invention relates to an electric circuit breaker and, more particularly, to an electric circuit breaker that is especially suited for high-speed reclosing duty.

In certain circuit breaker applications, it is important to reclose the circuit breaker within a very short time interval after the breaker has been opened to interrupt the power circuit therethrough. One problem involved in such high speed reclosing is the necessity for allowing sufficient time for the interrupter to recover its interrupting ability after the prior interrupting operation. In this regard, if heavy currents had been involved in the prior interrupting operation, a relatively large volume of arcing products would have been produced by the resulting heavy current arc. If an appreciable portion of such arcing products were still present within the interrupter when reclosing was attempted, the interrupting medium would have impaired dielectric strength and arc-extinguishing ability during this critical period. The impaired dielectric strength could result in an undesirable are being established between the contacts during closing, and the impaired arc-extinguishing ability could preclude the breaker from successfully interrupting the circuit should it be called upon to immediately reopen because of a persistent fault on the line. It will therefore be apparent that in high-speed reclosing circuit breakers, it is highly desirable that the arcing chamber of the breaker be scavenged of arcing products immediately after the interrupting operation is completed.

Accordingly, one object of my invention is to provide simple and highly efficient scavenging means that is capable of positively forcing fresh arc-extinguishing liquid into the arcing chamber and of positively forcing arcing products from the arcing chamber immediately after interruption has been completed.

Another object is to provide scavenging means of this character which derives its operating power from the pressure produced by the interrupting operation. By attaining this object it is unnecessary to rely upon the closing means of the breaker either for storing energy in the scavenging means or for actually operating the scavenging means.

Another object is to block reclosing until substantial completion of the scavenging operation and to produce reclosing immediately thereafter. A related object is to coordinate the reclosing and scavenging operations in this manner without requiring complex timers or interlocks.

Still another object is to provide a circuit breaker which can be used in a distribution system (1) to radically reduce the amounts of current that circuit breakers in the individual branches of the system will be called upon to carry and to interrupt under fault conditions and (2) to restore service over the sound portion of the distribution system immediately after the faulted portion has been isolated therefrom by one or more of the branch circuit breakers.

In carrying out my invention in one form, I provide a circuit breaker that comprises a pair of relatively movable contacts, each of which has a closed-circuit position where the contacts engage each other. Means is provided for moving one of the contacts out of the closed-circuit position to establish an arcing gap between the contacts across which an arc is established. Enclosing the arcing gap is an arcing chamber containing liquid that is adapted to react with the arc to cause high pressures to be developed in the arcing chamber. The other contact is movable out of its closed-circuit position in response to these high pressures. Biasing means is provided for returning said other contact to its closed-circuit position when the pressure in said arcing chamber subsides to a predetermined level. Piston means controlled by return movement of said other contact is provided for forcing a flow of scavenging liquid into the arcing chamber to expel arcing products therefrom. Additional biasing means is provided for returning said one contact to said closed-circuit position after said other contact has reached its closed-circuit position. The pressures present in said arcing chamber during the flow of scavenging liquid thereinto are sufficiently high to block said additional biasing means from returning said one contact into its closed-circuit position while the scavenging operation is underway.

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

FIG. 1 is a cross-sectional view of a circuit-interrupter embodying one form of my invention. The circuit interrupter of FIG. 1 is shown in its closed position.

FIG. 2 is a cross-sectional view of the circuit breaker of FIG. 1 with the breaker shown in its fully-open position.

FIG. 3 is a graphic representation of certain electrical relationships occurring during the operation of the interrupter of FIGS. 1 and 2.

FIG. 4 is a schematic illustration of counting and lockout mechanism for use with the interrupter of FIGS. 1 and 2.

FIG. 5 is a one line diagram of an electrical distribution system including the circuit breaker of FIGS. 1 and 2.

Referring now to FIG. 1, the circuit breaker 130 shown therein is similar in some respects to a circuit breaker disclosed and claimed in application S.N. 97,355, Barkan and Bogert, filed March 21, 1961, and assigned to assignee of the present invention. This circuit breaker of FIG. 1 comprises a pair of relatively movable rod-shaped contacts or electrodes 12 and 14 connected across a pair of spaced-apart terminals 16 and 18. The upper rod contact 12 is electrically connected at its upper end to a flexible conductor 19 that provides an electrical connection between one of the terminals 16 and the rod contact 12. The lower rod contact 14 is electrically connected at its lower end to a flexible conductor that provides an electrical connection between the other terminal 18 and the rod contact 14. Each of the flexible conductors 19 and 20 is shown with a conductive terminal lug suitably secured to its lower end and clamped to one of the contact rods by suitable nuts. For example, the lower terminal lug 21 is shown clamped between a pair of nuts 22, 23 threaded on an extension of the rod contact 14. The upper terminal lug 25 is shown clamped against a shou1 der on the upper rod contact 12 by means of a nut 27 threaded on an insulating operating rod 28, which forms a mechanical extension of rod contact 12. It will therefore be apparent that the circuit through the interrupter extends between terminals 16 and 18 via the conductor 19, rod contacts 12 and 14, and the conductor 20.

The circuit breaker further comprises a metallic tank 30 having a cover 32 secured thereto and supporting the terminals 16 and 18. Suitable insulating bushings 34 are provided about the conductors 19 and 20 in the region that they extend through the cover to insulate the conductors from each other and from the cover 32. The insulating operating rod 28 which is secured to rod contact 12, is relied upon for imparting circuit opening movement to the contact 12 under certain conditions soon to be described. This operating rod 28 extends freely through a slide bearing opening in the cover 32 and is surrounded by a flexible bellows 36 that permits the operating rod to be vertically reciprocated without leakage therearound so that the tank 3% can be sealed if desired.

The contacts or electrodes 12 and 14 are of the butttype and are normally maintained in abutting engagement at their opposed ends by biasing means in the form of a compression spring 3%. This compression spring 33 acts between the cover 32 and a shoulder 4% of insulating material clamped to the movable contact 12 for providing a force that urges the contact 12 in a downward closing direction. Opening of the circuit breaker is effective by driving the movable contact 12 in an upward direction away from the other contact lid against the bias of the closing spring 38.

In a preferred embodiment of our invention, the lower rod contact 14, as Well as the upper rod contact 12, is mounted for motion in a direction parallel to its longitudinal axis. The lower contact 14 is normally maintained in its position of FIG. 1 by biasing means in the form of a compression spring 37 disposed beneath a scavenging piston 39 secured to the lower end of the rod contact 14. This spring 37 bears at its upper end on the piston 3% and at its lower end, on a stationary ring ll secured to the bottom of the tank 3d and, thus, always urges the movable contact 14 in an upward direction. When the circuit breaker is in its closed position of FIG. 1, the position of the lower contact 14- is determined by a stationary shoulder 3% against which the piston 39 abuts and is maintained by the compression spring 37.

For enclosing the arcing gap that is established between the ends of contacts i2 and 14 when the contact 12 is driven upwardly during a circuit opening operation, an arcing chamber 42 suitably fixed to the tank 30, as by insulating screws 40a, is provided. This arcing enclosure 42 comprises a relatively thick-walled outer cylinder :3 made preferably of a high strength non-magnetic metal, such as a non-magnetic steel. 43 is a lining 45 of insulating material, preferably made in several parts to facilitate assembly and manufacture. In the illustrated embodiment of the invention, this lining 45 is shown clamped in place against an internal shoulder on the outer cylinder 43 by means of a heavy insulating nut 43. The nut 48 has external threads that mesh with suitable internal threads formed in the cylin der 43. This composite enclosure 42 defines internally thereof an arcing chamber 49 in which arcing between the contacts takes place during a circuit-interrupting operation. As will soon be pointed out in greater detail, the arcing enclosure 42 serves to confine the high pressure developed in the arcing chamber during arcing. The insulating lining 45 protects the metallic outer cylinder 43 from the arc by preventing the arc from contacting the cylinder 43.

The two rod contacts or electrodes 12 and 14 are slidably mounted within the arcing enclosure 42 by means of suitable slide bearings closely surrounding the rod contacts at locations spaced from their abutting ends. The slide bearing for the lower rod contact 14 is formed in the insulating lining 45 at d, and the slide bearing for the upper rod contact 12 is formed in the nut 48 at 52.

Since the slide bearing 5%, 52 and the lining 45 are of electrical insulating material, it will be apparent that these parts serve the additional function of insulating the two contacts from each other and from the metallic cylinder 4? when the contacts are in their separated, or opened, position.

For reacting with the arc to provide the pressures and Within this outer cylinder til tacts 12 and 14 so as to be available for immediate reaction with the arc.

F or directing the flow of arc-extinguishing fluid through the region between the contacts 12 and ll l during interruption, an exhaust passage 60 extending longitudinally of the rod contact 12 is provided. This exhaust passage extends from the arcing chamber 453 to an expansion chamber 62 surrounding the rod contact 12 outside of the arcing chamber 49. Preferably the exhaust passage is provided with a pair of diametrically opposed exhaust ports 6d at its upper end leading to the expansion charm: her 62.. The walls of the expansion chamber 62 are defined by a recess formed in nut 48 and by a movable piston 65 secured to the contact 12. The recess in the nut 48, in effect, constitutes a cylinder in which the piston as is slidable. When the contacts 12 and 14 are in their closed position ofPlG. l, the piston 65 telescopes'into the cylinder a short distance so as to block the egress of fluid trorn the expansion chamber 62 until the piston 65 is moved out of the cylinder. Thus, when the fluid is forced through the exhaust passage as into the expansion chamber 62, it exerts an upward contact-opening force on the piston s5. Since the pressurized fluid is prevented from leaving the expansion chamber until the piston 65 is moved upwardly a short distance, it will be apparent that the piston 65, constitutes a restriction flow through the exhaust passage oil which accelerates pressure buildup in the arcing chamber 49. I a

The interrupter as described up to this point is substantially the same as the interrupter described and claimedin the aforementioned Barltan and Bogert application SN. 97,355. As pointed out in the Barkan and Bogart application, this interrupter is capable of interrupting short circuit currents in a conventional 60 cycle alternating current circuit with a current-limiting action. That is, the interrupter limits the maximum instantaneous peak value of current whichthe interrupter permits to ilow (maximum let-through current) under short circuit conditions to a value considerably lower than the maximum available current, i.e., the maximum instantaneous peak value of current that would have been carried by the device had it retained its normal closed circuit impedance value. The interrupter accomplishes this current-limiting action by sensing the presence of'a short circuit, then opening its contacts in response to the short circuit, and

then building up an arc voltage approaching line voltage,

all'within the extremely short period of about two milliseconds.

For sensing the presence of a short circuit and then initiating contact-separation in response to the short circuit, all within the extremely short time available to produce current-limiting action, the disclosed interrupter relies upon popping apart of the contacts. In this regard,

there is developed in the abutting regions of the contacts a force dependent upon the magnitude of the current flowing through the contacts, which acts to drive the con tacts apart under high current conditions. One component of this force is a magnetic repulsion force between the contacts produced by the current distribution in the abutting regions of the contacts. T he other component is a contact-separating force resulting from local heating at the point of contact that produces vaporization that, in turn, produces pressures tending to separate the contacts.

' These two components of contact-separating force increase sharply as the current increases; and in the disclosed interrupter the sum of these contact-separating force components exceeds the biasing iorc'e of the spring 33 at values of short circuit current well within the interrupting rating of the circuit breaker. Whenthis total contactseparating force exceeds the opposing ,force of the spring 32;, the contacts separate or pop apart. The sum of these force components tending to drive the contacts apart at a given current is referred to hereinafter as the contact popping force; p v p Immediately after the contacts separate in response to the above-described popping action, an arc is drawn between the contacts, and this are immediately vaporizes more surrounding liquid and thus creates additional pressure tending to force the contacts open. The arcing chamber, being essentially imperforate except for the exhaust passage 60, confines this pressure and thus tends to accelerate additional pressure build-up. Not only does this high pressure act directly on the lower end of the movable contact 12 to accelerate the cont-act toward open position, but it also acts upon piston 65 at the upper end of the contact 12 to provide still additional force for accelerating the movable contact 12 toward open position. In this regard, the high pressures developed within the arcing chamber 49 force fluid through the exhaust passage 60 thus pressurizing the fluid in expansion chamber 52. Since the piston 65 telescopes into the cylinder forming the peripheral wall of the expansion chamber and since there is little clearance between the piston 65 and the cylinder 48, the increased pressure in the expansion chamber is transmitted to the piston 65, thus producing additional force for accelerating the movable contact toward its fully open position.

The piston 65 serves not only as a means for magnifying the contact accelerating force by providing extra area on which the arcing pressure can act, but it serves also to accelerate the pressure build-up within the arcing chamber 49 since it severely restricts the flow of fluid through exhaust passage 60 until the piston emerges from its surrounding cylinder 48. Since this passage 6b is the only significant exhaust passage leading from the otherwise imperforate arcing chamber 49, extremely high pressures are built up within the arching chamber 49 while the exhaust passage is maintained restricted by the piston. The fact that these pressures are extremely high, e.g., on the order of 500 to 1000 p.s.i. for maximum let-through currents of 50,000 amperes, contributes in an important manner to the high speeds at which contact separation occurs.

It is to be noted, with regard to the interval in which the piston is still within the cylinder 48, that some flow, though limited, is even then taking place through the flow passage 60. Although this limited flow has only a moderate eflect in reducing the rate of pressure build'up within the arcing chamber 49, it does serve the important purpose of accelerating arc cooling and in this way accelerating the buildup of arc voltage as will appear more clearly hereinafter.

As the piston 65 emerges from its surrounding cylinder 48, it no longer severely restricts flow through the exhaust passage 60. Accordingly, the high pressure developed in the arcing chamber 49 then becomes free to drive fluid at a much higher rate of flow from the arcing chamber 49 through the exhaust passage 60 via the paths indicated by the arrows 69 of FIG. 2. This blast of fluid cuts radially and axially across the arcing region, turbulently mixing with the arc plasma and subjecting the arc to an intense cooling action. This combined mixing and cooling action rapidly builds up an arc voltage that approaches the instantaneous line voltage, and this high are voltage limits the maximum let-through current to a value considerably lower than the maximum available current. After the current through the breaker has reached its peak, or maximum let-through, value, the arc voltage is able to quickly force the current down toward zero, with the zero current point being reached considerably ahead of the natural current zero. No reignition of the arc occurs thereafter so that interruption is consistently completed by the time the first current zero is reached.

The pattern of flow that results from locating the exhaust passage 60 in its disclosed position, i.e., leading from the arcing gap through the contact 12 in a direction generally parallel to the direction of movement of the contact, is exceptionally effective in producing intense cooling of the arc because the cooling fluid is able to envelop the are about substantially its entirep eriphery.

In other words, the fiow of cooling fluid is radially-inward about substantially the entire periphery of the arcing gap. The fact that the cooling fluid envelops the arc about its entire periphery is also advantageous from the standpoint of preventing radially-outward expansion of the arcing products and of maintaining the arc centered in the arcing chamber 49 and out of direct contact with the walls of the arcing chamber. This enables us to use a smaller arcing chamber than would be otherwise required without exposing the walls of the chamber to damaging arcing. The smaller this arcing chamber, the more easily it can be made strong enough to safely withstand the high pressures developed during interruption.

The current-limiting action described hereinabove is graphically illustrated in FIG. 3, where the available current is depicted in dotted lines D, and the actual current is depicted in solid lines I. When a fault occurs at a point A, the current flowing through the breaker will increase extremely rapidly toward a maximum available value M, that may be hundreds of times greater than the normal continuous current through the breaker. Due to the contact-popping action described hereinabove, the breaker will part its contacts in response to this sudden rise in current at a point B and will immediately begin developing an arc voltage that limits the actual current to a maximum let-through value Im that is considerably less than the maximum available value M depicted on the dotted line curve. The current is thereafter driven down to Zero considerably ahead of the natural current zero occurring at point C.

Actual interrupting tests made with an interrupter corresponding in design to that of FIGS. 1 and 2 have demonstrated that this interrupter can consistently interrupt short-circuit currents with current-limiting action such as depicted in FIG. 3. For example, in 600 volt alternating-current circuit, the interrupter has interrupted currents having a maximum available value of between 35,000 and 100,000 amperes with such current-limiting action. These figures are given merely by way of example, it being understood that the interrupter can be applied to lower voltage circuits and, with minor modifications, to higher voltage circuits. In the above-mentioned tests made on a 600 volt circuit, only short contact separations, less than /4 inch, were required to interrupt the circuit with current-limiting action.

For limiting the length of the arc during interruption, a probe 70, preferably of tungsten, is provided in the center of the exhaust passage 60. The above-described blast action that occurs through the exhaust passage 60 during interruption forces the upper terminal of the are into the exhaust passage and on to the probe '70 where it is maintained during the remainder of the interrupting operation.

During heavy current interruptions, the lower contact 114, as Well as the upper contact 12, is moved in a contact separating direction. In this regard, the pressures generated inside the arcing chamber by a heavy current are act on the exposed top surface of contact 14 to drive this contact rapidly downward against its biasing spring 38 until the piston 39 engages a stop '71. This downward motion of the lower contact 14 contributes to increased arc lengths, and, hence, increased arc voltages and thus facilitates the current-limiting action of the breaker. This downward motion of the lower contact 14 also plays an important part in the scavenging and reclosing operations that take place immediately after interruption, as will soon appear more clearly.

' With regard to reclosing, in certain circuit breaker applications it is desirable to quickly reclose the circuit breaker after an interrupting operation so that the electric service continuity can be maintained in the event that the fault has been cleared or has cleared itself after the interrupting operation. The disclosed circuit breaker is especially suited for such duty inasmuch as the two movable contacts 12 and 14 can return to their closed 2" circuit position under the influence of their respective springs 38 and .37 after the pressure in arcing chamber 49 decays to predetermined values.

The circuit breaker of KG. 1 is so constructed that the lower contact 14 will return to its position of FIG. 1 before the upper contact returns. This follows primarily from the fact that the lower spring 37 is considerably heavier than the upper spring 323 and is thus able to drive the lower contact into its closed position of FIG. 1 while the pressure in the arcing chamber 49 is still above a value that would allow the upper contact 12 to return.

The disclosed circuit breaker utilizes this upward motion of the lower contact 14 to produce a scavenging action that scavenges the arcing chamber 49 or any gases remaining after interruption. in this connection, when the lower contact 14 moves downwardly during an opening operation, fresh liquid is forced into a scavenging chamber '75 located above the piston 39 through ports 76 extending through the piston. FIG. 2 depicts the parts of the interrupter when the piston has reached its lowermost position and the scavenging chamber has been filled with fresh liquid. When the spring 33 returns piston 39 from its position of FIG. 2 to its upper position of PEG. 1 after interruption, the fresh liquid trapped in the scavenging chamber '75 is positively forced upwardly through a passage '77 extending through the movable contact 14 past a spring-loaded check valve fit into the arcing chamber. This flow of liquid into the arcing chamber drives any gases remaining therein out or" the arcing chamber through the exhaust port db and through small bleed opening '79 provided about the upper contact 12. Suitable spring-loaded check valves Stl prevent the scavenging liquid from flowing back through the port '76 during this scavenging operation.

The bleed evenin s 79 throu h which ases are forced from the arcing chamber 49 during scavenging are so located that they are opened only at the end of the opening stroke of the upper contact 12., and thus their presence does not detract from the essentially imperforate character of the arcing chamber 49 during the earlier and more critical stages of the interrupting operation. These bleed openings 79 can be quite small inasmuch as they serve primarily for the exhaust of gases rather than liquids. Inasmuch as gases have an extremely low viscosity com pared to liquids, an opening small enough to substantially block liquid flow therethrough will allow an appreciable volume of gases to pass therethrough. lit is also to be noted that the check valve 78 in the passage 77 blocks any flow out of the arcing chamber and allows flow only into the arcing chamber, and thus its presence does not detract from the essentially imperforate character of the arcing chamber during interruption.

The above-described scavenging action maintains the pressure in the arcing chamber at a high enough level to prevent the upper contact 12 from returning to its fully closed position of MG. 1 until the lower contact 14 has substantially reached its'closed position of FIG. 1. When the lower contact 14 reaches its position of FIG. 1, the scavenging ceases and the pressure in arcing chamber 4h drops sharply, allowing the upper spring 33 to immediately return the upper contact 12 to its closed position of FTG; l. If. the electric fault is then cleared, upper contact 12 will remain in its closed position, thus allowing service to be continued through the then-closed circuit breaker. 1

If, however, the fault has not cleared when the upper contact 12 returns to its position of FIG. 1, another opening operation, essentially identical to the opening operation described hereinabove, will occur. The abovedescribed scavenging action and the fact that this scaven ing. action is essentially completed prior to closing of the upper contact 12 are important factors in assuring V a that no significant quantity of gases will be present in the arcing chamber 49 to interfere with the pressurebuildly completed. Only when scavenging has been substantially completed does the pressure within the? arcing chamber 49 decay to a level which permits the spring 38 to reclose contact 12. Minor variations in the time required for scavenging do not impair this highly desirable sequencing since the reclosing means 3% for actuating the upper contact 1?. responds to completion of this scavenging action, irrespective of minor variations in the time required for completion. In other words, the reclosirig means automatically compensates for minor variations in the time required for scavenging. it will be apparent that this highly desirable sequencing and compensatingaction are obtained in a simple manner without reliance on any special or complex timers or interlocks.

To aid the scavenging means in maintaining the pressure in the arcing chamber high enough to block reclosing of contact 12 during scavenging, it is desirable that the minimum cross-sectional area of the scavenging pas' sage '77 be relatively large in comparison to the clearance area between piston 65 and cylinder as so that a substantial portion of the pressure drop in scavenging fluid flowing through the interrupter occurs in the exhaust area about piston as. This region of minimum crosssection in the scavenging passage '77 is located in the region of check valve 7?).

It will be apparent that my scavenging means 39, 37 derives its operating power from the pressures produced by the interrupting operation since it is these pressures which produce the force for charging spring 37. It is unnecessary to rely upon the closing means 38 of the breaker either for storing energy in the scavenging means or for actually operating the scavenging means. The closing means 38 is thus free to close the circuit breaker at the desired high rate without any impedance from the scavenging means 37, 39. 7

Another feature of my interrupter is its compactness. Since piston 39 is secured directly to one of the contacts lid, it is unnecessary to rely upon any special pump separate from the contacts to effect the desired scavenging operation.

If the circuit interrupter does not remain closed for a predetermined time after one or more reclosures, it is desirable to prevent additional reclosures, i.e., to lock out the circuit interrupter. For performing this lockout function, I provide a lockout mechanism d5 schematically depicted in FIG. 4. This lockout mechanism comprises a lockout lever 86 that is pivotally supported on a stationary pivot 87 and is biased in a counterclockwise direction about the pivot 87 by means of a lockout spring 8%. When the circuit breaker is closed, the lockoutlever 36. is held in its closed position of FIG. 4 by means of a conventional trip-latch 9b. This trip-latch 9t) engages a latch roller 92 that is rotatably mounted on the lockout lever 86 at its outer end by means of a'shatt 93 fixed to the lockout lever. When the trip latch 96) is rotated in a clockwise direction about its stationary pivot M, the restraint of latch 9% is removed from the lockout lever $6, and the lockout spring 83 becomes tree to drive the lock' out lever ina counterclockwise direction towardits dotted line locked-out position. When this occurs, the contact 12 is at or near its fully open position, as will soon be desiderably stronger than closing spring 3%, acts through 7 this shoulder 2th: to apply force to the operating rod 28 greater than the closing force applied'by closing spring 3%.

Thus, the contact 12 is maintained in its open position when the latch Wis tripped.

The above-described tripping of the trip-latch 90 is effected by means of a suitable cam 100 after the interrupter has opened two times in close succession. This cam 100 is fixed to the rod of a counting piston 101, that is advanced a predetermined distance upwardly in response to each opening operation in a series of closely successive operations. The first of these opening operations advances the cam 100 an insufiicient distance to trip the latch 90, but the second of these opening operations advances the cam 100 through an additional increment sufficient to drive the rod 102 to the right to trip the latch 90.

For advancing the counting piston 101 a predetermined distance in response to each of the opening operations in a series of closely successive operations, a pawl 105 is provided pivotally mounted on the operating rod 28. This pawl 105 is biased in a counterclockwise direction about a pivot 104 carried by the operating rod 28 by means of a spring 109. The pawl 105 is adapted to engage ratchet teeth 106 carried by the counting piston 101. A stationary pin 108 normally holds the pawl 105 out of engagement with the ratchet teeth 106, but when the operating rod 28 moves upwardly during an opening operation the pin 108 is no longer capable of holding the pawl out of engagement with the ratchet teeth 106 and the spring 109 forces the pawl clockwise about its pivot 104 into a position to engage the ratchet teeth 106. This enables upward motion of the operating rod 28 and pawl 105 to drive the counting piston 101 upwardly through one step. This motion is transmitted to the counting piston through the upper ratchet tooth 106.

When the operating rod 28 is returned to its closed position immediately after the first opening operation, the counting piston 101 remains in its advanced position temporarily. A suitable reset spring 111 disposed thereabove urges the counting piston 101 to slowly return to its original position. If, however, the movable contact 12 and, hence, operating rod 28 should immediately reopen after closing, the reset spring 111 would not have had an opportunity to produce any significant return movement of the counting piston. No return movement of counting piston 101 having occurred, the pawl 105 would then be in a position to engage the lower one of the ratchet teeth 106 when the operating rod 28 moved upwardly during the second operation. With the pawl 105 in engagement with the lower ratchet tooth 106, the cam 100 would cause the rod 102 to move to the right to trip the latch 90. This would produce lockout of the circuit breaker after the second opening operation in the manner described hereinabove.

The counting piston 101 operates within a liquid filled cylinder 114, but upward motion of the counting piston 101 occurs without significant retardation due to a large passage 115 provided through the counting piston 101. Liquid can flow freely through this passage 115 from top to bottom of the piston during upward motion of the piston 101. This lack of retardation of piston 101 cuables the contact 12 to open without significant retardation from the counting device. Return motion of contact 12 also occurs without retardation from the counting device inasmuch as the pawl 105 simply slides over the ratchet teeth 106 during such return motion. Return motion of the counting piston 101 is retarded, however, by virtue of a check valve provided in the passage 115 which blocks the flow of liquid through the passage 115 during downward motion of the counting piston 101. A small metering passage 116 in the counting piston 101 controls this rate of return motion.

If the contact 12 remains closed after the first reclosing operation, the counting piston 101 will slowly reset to its position of FIG. 1. After this resetting has been completed, two closely successive opening operations would be necessary before lockout of the circuit interrupter would occur.

For enabling the counting piston 101 to reset after a lockout operation, a stationary pin 120 is provided for releasing the pawl 105 from the lower ratchet tooth 106 at the end of an opening operation. This pin engages a tail portion of the pawl 105 to pivot the pawl 105 counterclockwise out of driving engagement with the ratchet tooth 106. The reset spring 111 above the counting piston 101 then becomes effective to reset the counting piston 101 to its position of FIG. 4. Accordingly, when the lockout lever 86 is afterwards returned to its solid-line position of FIG. 4 to permit the circuit interrupter to reclose under the influence of its spring 38, the latch 90 is then free to fall in place behind the lookout lever 86. This holds the lockout lever in its position of FIG. 4 when closing force is removed from the lockout lever, thus assuring that the breaker will remain closed if no fault is then present.

For selectively opening the interrupter at any desired instant, a suitable tripping rod coupled to trip latch 90 is provided. This trip rod 125 can be moved to the right either manually or by means of a suitable solenoid 126 to trip the latch 90 and thereby effect opening and lockout of the circuit interrupter.

The disclosed circuit breaker can be used in a wide variety of different circuit applications, but there is one particular application for which it is exceptionally well suited. This application is illustrated in the one-line circuit diagram of FIG. 5, where the circuit breaker of the present invention, designated 130, is shown located at the head of a distribution system including branch circuits 132, 133, and 134 for supplying power to suitable loads L. Each of these branch circuits 132, 133, and 134 is connected to a secondary bus 136 which, in turn, is connected to a main bus 138 through a tie line 140.

The current-limiting circuit breaker of the present invention is connected in the tie line 140, and suitable low capacity circuit breakers, or contactors 142, 143, and 144 are connected in the branch circuits 132, 133, and 134, respectively. Each of the low capacity branch circuit breakers are of a conventional type that includes suitable current responsive means for automatically opening the branch circuit breaker within, say, two cycles after the inception of a fault on the circuit which the breaker protects. The current-limiting circuit breaker 130, however, is a much quicker acting circuit breaker and is capable of interrupting current flow therethrough within a fraction of a half cycle after the inception of a fault, as was described hereinabove. The current-limiting circuit breaker 130 is also capable of accommodating the maximum available current from the main bus 138 and of limiting the peak current flowing through tie line 140 to a value substantially below the maximum available current.

Assume now that a short circuit develops on branch circuit 132. Current-limiting circuit breaker 130 opens in response to this fault and limits the fault current to a value substantially below the maximum available current. However, during the time (say four milliseconds) required for the current-limiting circuit breaker 130 to interrupt the fault, the trip device of breaker 142 is also energized. This breaker 142 will also open, but in about two cycles after the inception of the short circuit. However, since the current-limiting circuit breaker 130 has already interrupted the tie-line 140, breaker 142 opens against only the relatively small currents, if any, contributed from the branch circuits 133 and 134. This small current the breaker 142 can readily interrupt, even though it is completely incapable of interrupting current anywhere near the maximum available current from bus 138. After the branch circuit 132 has been thus opened by the branch circuit breaker 142, the current-limiting circuit breaker 130 immediately and automatically recloses (in about three or four cycles after fault inception). This reenergizes the sound branch circuits 133 and 134, and such circuits continue operating normally. Assuming that branch circuit breaker 142 had successfully interrupted the small amount of current flowing therethrough, no further current is supplied to the faulted branch cirill.

cuit 132 inasmuch as its circuit breaker 142 is then open and isolating circuit 132 from the secondary bus res.

The minimum reclosing time for the main circuit breaker 13b is dictated by the opening speed of the branch breakers 142-1144. In this regard, if the branch breakers can separate their contacts in one cycle after fault inception, then the main circuit breaker 139 can completely reclose in as short a time as 1 /2 cycles after fault inception. Tests made with circuit breakers similar to that disclosed hereinabove indicate that this breaker can be readily designed to provide reclosing times as short as 1 or 1 /2 cycles. The maximum reclo'sing time should be about six cycles in order to lessen to a non-objectionable extent the falling back in phase position of the rotors of synchronous motor. loads.

Had the circuit breaker 1142 failed to interrupt the current fed therethrough, the current-limiting circuit breaker 13%? would immediately reopen after reclosing and would be locked out in the manner described hereinabove.

It will be apparent that inclusion of the high speed reclosing circuit breaker 136* in the system of PEG. allows the circuit breakers 142, i143, and 1 24 to be of a much smaller capacity than would otherwise be required since these branch circuit breakers are never called upon to interrupt currents anywhere near. the maximum available current, and, as a matter of fact, are not even required to conduct such currents when closed due to the currentlimiting action of the main circuit breaker 130. Being able to use branch circuit breakers with greatly reduced interrupting capacity permits these breakers to be of a much less expensive construction period.

Had a current-limiting fuse instead of a current-limiting circuit breaker been used in the tie-line 338, it would have been impossible to maintain service continuity over the sound branch circuits due to the inability of a fuse to automatically reclose after a circuit interrupting operation.

The system of FIG. 5 is shown and claimed in divisional application SN. 363,525, filed April 29, 1964, and assigned to the assignee of the present invention.

Although I have illustrated the reclosing and scavenging features of my invention in connection with a currentlimiting type of circuit breaker, it is to be understood that these features can also be utilized with other suitable types of breakers having no current-limiting action. 'The invention in its broader aspects is therefore not restricted to current-limiting type circuit breakers.

It will be obvious to those skilled in the art that various other changes and modifications may be made without departing from my invention in its broader aspects, and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. An electric circuit breaker comprising a pair of relatively movable contacts, each having a closed-circuit position in which said contacts engage each other, means for moving one of said contacts out of said closed-circuit position to establish an arcing gap between said contacts across which an arc is established, an arcing chamber enclosing said arcing gap and containing liquid that is ada ted to react with said are tocause h ressures Cir 2. The circuit breaker of claim l'in which operation of said piston means maintains the pressure in said arcing chamber sufficiently high to block return motion of said one contact into its closed-circuit position until said other contact has returned substantially to its closed-circuit position.

'3. The circuit breaker of claim 1 in which a passageway extending through said other contact is provided for conducting liquid from said scavenging chamber into said arcing chamber, and in which an exhaust passage extending through said one contact is provided for conducting arcing products from said arcing chamber.

4-. An electric circuit breaker comprising a pair of relatively movable contacts, each having a'closed-circuit position in which said contacts engage each other, means for moving one of said contacts out of said closed-circuit position to establish an arcing gap between said contacts across which an arc is established, an arcing chamber enclosing said arcing gap and containing liquid that is adapted to react with said are to cause high .pressures to be developed in said arcing chamber, said other contact being movable out of its closed-circuit position in response to said high pressures developed within said arcing chamber during arcing, biasing means for returning said other contact to said closed-circuit position when the pressure in said arcing chamber subsides'to a predetermined level, piston means coupled to said other contact for movement in one direction during movement of said other contact out of said closed-circuit position and for movement in an opposite direction during return movement of said other contact into closed-circuit position, a scavenging chamber in which said piston means operates, means controlled by motion of said piston means in said one direction for admitting scavenging liquid into said scavenging chamber during motion of said other contact out of closed-circuit position, a passageway leading from said scavenging chamber into said arcing chamber ans containing check valve means for permitting fluid to iiow through said passageway only in a direction into said arcing chamber, said piston means acting during movement in said opposite direction to force scavenging liquid from said scavenging chamber into said arcing chamber via said passageway, an exhaust passage leading from said arcing chamber through which arcing products are forced from said arcing chamher by liquid forced into said arcing chamber by said piston means, and mean for returning said one contact to said closed-circuit position after said other con tact has been returned to said closed-circuit position.

5. The circuit breaker of claim 4 in which operation of said piston means in said opposite direction maintains turning said other contacts to said closed-circuit position when the pressure in said arcing chamber subsides to a predetermined level, piston means controlled byreturn movement of saidother contact for forcing a flow of scavenging liquidinto said arcing chamber to expel arcing products therefrom, and biasing means for returning said one contact to said closed-circuit position after said other contact has reached said closed-circuit position.

the pressure in said arcing chamber suiiiciently high to block return motion of said one contact into its closedcircuit position until said other contact has returned substantially to its closed circuit position.

6. An electric circuit breaker comprising a pair of relatively movable contacts, each having a closed-circuit position in which said contactsengage' each other, means for moving one of said contacts out of said closed-circuit position to establish an arcing gap between said con' tacts across which an arc is established, an arcing chamber enclosing said arcing gap and containing liquid that is adapted to react with said are to cause high pressures to be developed in said arcing chamber, said other contact being movable out of its closed-circuit position in response to said high pressures developed within said arcing chamber during arcing, biasing means for returning said other contact to said closed-circuit position after interruption in response to a drop in the pressure in said arcing chamber to a first predetermined value, piston means controlled by said return movement of said other contact for forcing a flow of scavenging liquid into said arcing chamber to expel arcing products there! from, biasing means for-returning said one contact to closed-circuit position in response to adrop in, the pres- 13 sure in said arcing chamber to a second predetermined value that is substantially less than said first predetermined value.

7. A current-limiting circuit breaker for an alternating current circuit rated in the general neighborhood of 600 volts comprising a pair of relatively movable contacts, means responsive to the flow of fault current through said contacts for separating said contacts to establish an arcing gap therebetween and means including an arcing chamber for developing across said arcing gap an arc voltage on the order of magnitude of the instantaneous line voltage, all within about two milliseconds of fault inception, thereby to interrupt said circuit with a current limiting action; means for returning said contacts to closed circuit position after circuit interruption and within a period of between one and six cycles after fault inception, and means for freeing said arcing chamher from the ionized products of said first interruption prior to said return of said contacts to closed position.

8. A current-limiting circuit breaker for an alternating current circuit comprising a pair of relatively movable contacts having a closed-circuit position of engagement; means responsive to the flow of current through said contacts for separating said contacts to establish an arcing gap therebetween and for developing across said arcing gap an arc voltage on the order of magnitude of the instantaneous line voltage, all within about two milliseconds of fault inception; said means for developing said arc voltage comprising an arcing chamber enclosing said gap and containing liquid that is adapted to react with said arc to cause high pressures to be developed in said arcing chamber; exhaust passage means for providing a path through which a blast of arc-extinguishing fluid is forced during interruption and for relieving the pressures developed within said arcing chamber, and biasing means operable in response to a drop in the pressure within said arcing chamber to return one of said contacts into a position of engagement with the other of said contacts immediately after said arc has been extinguished.

9. The circuit breaker of claim 8 in combination with scavenging means operable in response to a pressure drop in said arcing chamber for forcing a flow of scavenging liquid through said arcing chamber before said one contact reengages said other contact upon reclosing.

-10. An electric circuit breaker comprising a pair of relatively movable contacts having a closed-circuit position of engagement, means vfor moving one of said contacts out of its closed-circuit position to establish an arcing gap between said contacts across which :an arc is established, an arcing chamber enclosing said arcing gap and containing liquid that is adapted to react with said arc to cause high pressures to be developed in said arcing chamber, scavenging means comprising a piston occupying a normal position when said contacts are in closed circuit position, means for driving said piston out of its normal position in response to said high pressure developed within said arcing chamber during arcing, a scavenging chamber in which said piston operates, means for supplying scavenging liquid from outside of said arcing chamber to said scavenging chamber when said piston moves out of its normal position, biasing means \for returning said piston to said normal position when the pressure in said arcing chamber subsides to a predetermined level, means controlled by said return movement of said piston for directing liquid from said scavenging chamber into said arcing chamber to expel arcing products therefrom, and biasing means responsive to the pressure in said arcing chamber -for returning said one contact to said closed-circuit position when said piston means has substantially returned to its normal position.

11. A current-limiting circuit breaker for an alternating current circuit comprising a pair of relatively movable contacts having a closed-circuit position of engagement; means responsive to the flow of current through said contacts for separating said contacts to establish an arcing gap therebetween and for developing across said arcing gap an arc voltage on the order of magnitude of the instantaneous line voltage, all within about two milliseconds of fault inception; said means vfor developing said are voltage comprising an arcing chamber enclosing said gap and containing liquid that is adapted to react within said are to cause high pressures to be developed in said arcing chamber; exhaust passage means for providing a path through which a blast of arc-extinguishing fluid is forced during interruption and for relieving the pressures developed within said arcing chamber, and biasing means for returning one of said contacts to closed-circuit position when the pressure in said arcing chamber subsides to a predetermined level, piston means controlled by return movement of said one contact for forcing a flow of scavenging liquid into said arcing chamber to expel arcing product therefrom, and additional biasing means for returning said other contact to said closed-circuit position when said one cont-act has reached its closed-circuit position, the pressure in said arcing chamber during the flow of scavenging liquid thereinto being sufficiently high to block return of said other contact into said closed-circuit position until said one contact has substantially reached its closed-circuit position.

12. The circuit breaker of claim 7 in which said contacts are returned to closed position within a period of between one and tour cycles after fault inception.

References Cited by the Examiner UNITED STATES PATENTS 2,365,602 '12/44 Slepian 200- 2,442,477 6/ 48 Wallace et a1. 200-89 2,548,625 4/51 Seeley 317-26 2,816,974 12/57 Gibson et -al 200-89 2,919,330 12/59 Gantenbein 200-150 2,920,241 1/ 60 Jacobs et al. 317-26 2,977,439 3/61 Matthews 200-89 3,002,073 9/61 Cobine 200-150 FOREIGN PATENTS 347,007 4/ 31 Great Britain. 1,187,184 3/59 France.

BERNARD A. GILHEANY, Primary Examiner. MAX L. LEVY, ROBERT K. SCHAEFER, Examiners.

Claims (1)

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING A PAIR OF RELATIVELY MOVABLE CONTACTS, EACH HAVING A CLOSED-CIRCUIT POSITION IN WHICH SAID CONTACTS ENGAGE EACH OTHER, MEANS FOR IN WHICH SAID CONTACTS ENGAGE EACH OTHER, MEANS POSITION TO ESTABLISH AN ARCING GAP BETWEEN SAID CONTACTS ACROSS WHICH AN ARC IS ESTABLISHED, AN ARCING CHAMBER ENCLOSING SAID ARCING GAP AND CONTAINING LIQUID THAT IS ADAPTED TO REACT WITH SAID ARC TO CAUSE HIGH PRESSURES TO BE DEVELOPED IN SAID ARCING CHAMBER, SAID OTHER CONTACT BEING MOVABLE OUT OF ITS CLOSED-CIRCUIT POSITION IN RESPONSE TO SAID HIGH PRESSURES DEVELOPED WITHIN SAID ARCING CHAMBER BEING ARCING, BIASING MEANS FOR REARCING SAID OTHER CONTACTS TO SAID CLOSED-CIRCUIT POSITION WHEN THE PRESSURE IN SAID ARCING CHAMBER SUBSIDES TO A PREDETERMINED LEVEL, PISTON MEANS CONTROLLED BY RETURN

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