US2554974A - Electric circuit breaker - Google Patents

Description

y 1951 J. w. BEATTY 2,554,974

- ELECTRIC CIRCUIT BREAKER Filed April 6, 1948 Inventor: John W.Beatty,

His Attobney.

\time as at any other. [that the interrupting blast be maintained until the series isolating switch has achieved a subi'stantial fraction of its full contact separation. As the series switch must not separate its con- "tacts'before the arc is extinguished, this means Patented May 29, 1951 UNITED STATES PATENT oF ics ELECTRIC CIRCUIT BREAKER John W, Beatty, Lansdowne, Pa., assignor to General Electric Company, a corporation of New York Application April 6, 1948, Serial No. 19,257

My invention relates to electric circuit breakers and more particularly to an electric circuit interrupter of the fluid blast typehaving interrupting contacts and isolating contacts serially arranged with respect to the interrupting contacts.

In circuit breakers, as in other types of electrical equipment, it is customary to provide permanent insulating structure capable of resisting several times normal voltage in order to'withstand overvoltages arising from lightning, switching surges and other sources; and in circuit breakers, in addition, a comparable sufficiency of insulation iscommonly interposed between the contacts when they are in the open position.

" Circuit breakers of the gas blast type are often so arranged that the interrupting contacts are separated by action of the gas blast and allowed to 'recl'ose when the gas blast is shut of]? following interruption, the final isolating insulation across the breaker being obtained. by means of an associated series switch usually having a visible open-air break.

During the first few cycles following interruption', overvoltages may arise from the operation of the breaker itself, substantially simultaneous operation of another breaker, as at the Iarend of theline protected by the breaker in 'question for instance, or possible lightning s'urges forming subsequent strokes of a multistrokelightning flash of which an earlier stroke "initiated the fault which caused tripping of the either that the blast must be maintained for several cycles after interruption, wasting thereby perhaps several times as much gas as is used excessive accelerating and decelerating forces throughout the blade and its operating mechanism.

In accordance with my invention, I substitute an isolating switch whose contacts sep'ara-tein "a liquid insulating medium of high dielectric strength, such as oil, in place of the convent onal 'a'iribreak isolator. Because a small gap 011 3 Claims. (Cl. 200-148) in interruption, or that the isolating blade must "be'moved with extreme speed, thereby setting up 2 produces the equivalent dielectric strength of a large gap in air, the employment of a comparatively slow-moving oil isolator is equivalent to the use of a fast-opening'airisolator. Henceffor this reason I am able to reduce the expenditure of extinguishing gas because of the earlier blast cutoif which now is permissible, Moreover, because I seal the isolating contacts in an oil containing chamber, adverse weather conditions, such as cause icing up of exposed contacts'cannot impair their operation.

Accordingly it is an object of my invention to provide a device having interrupting contacts and isolating contacts in series therewith 'which utilizes the known advantages of the gas blast principle to interrupt the circuit and which also "takes advantage of the high'dielectric strength of liquid insulating dielectric as a medium for improving the overall dielectric strength of the strains in the isolating switch or its operating mechanism by utilizing a high dielectric liquid as an isolating medium thereby making high speed acceleration and deceleration of the isolating switch and of its operating mechanism unnecessary.

A further object of my invention is the provision of means for mechanically interlocking one of the interrupting contacts with one of the isolating contacts to insure a coordinated relationship between the interrupting and isolating contacts. I

A still further object of my invention is the provision of means for insuring the opening of the interrupting contacts a predetermined time before the opening of the isolating contacts and '"conversely to insure the closing of the isolating contacts a predetermined time before the closing of the interrupting contacts.

A still further object of my invention is the provision of a circuit breaker having interrupting contacts and isolating contacts wherein the description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing which is a side view partly in section of the mechanism of a circuit breaker embodying my invention.

While the device shown in the drawing is a single pole interrupter, it will be understood that my invention is equally applicable to interrupters having more than one pole.

With reference to the construction shown in the drawing the numeral I represents one terminal of the circuit breaker and the numeral 2 is used to designate the point at which the other terminal which is not shown in the drawing would be mounted. Terminal I is mounted on a metallic capping member 3 which forms the cover for the interrupting chamber generally designated by the numeral 4. The isolating chamber is represented generally by the numeral 5. A fluid motor generally designated by the numeral I5 is the motivating means for the interrupting and isolating contacts. The fluid motor 6 is operated by pressure fiuid supplied from storage reservoir I. The flow of fluid from reservoir I to fluid motor 6 is controlled by the operating valve 8. Arc extinguishing fluid is supplied from reservoir 1 to the interrupting contacts through the blast valve 9.

The interrupting chamber 4 is constructed of a cylindrically-shaped ceramic insulating housing In and a cylindrically-shaped insulating casing II disposed within the ceramic insulator II]. A fixed contact I4 is mounted inside the insulating casing II. Movable contact I5 may cooperate with an opening within the lower surface of the fixed contact I4 in such a way as to prevent communication between the spaces above and below the lower portion of the fixed contact I4 when the contacts I4 and I5 are closed as shown in the drawing.

The fluid motor 6 is of a dual cylinder and piston construction comprising contact opening cylinder It and its associated piston I1 and contact closing cylinder I8 and its associated piston I9. The cylinders I5 and I8 are supported on a metallic plate 29 which also serves as the lower end wall of the cylinders I6 and I8. The fluid motor 6 is supplied with operating fluid from tank I through pipe 21, valve 8, pipes 22, 23, and passageways 24 and 25 formed axially within the ceramic insulators 2B and 21.

Upward opening motion of piston II causes its toothed rod 28 which constitutes a rack to move upwardly which in turn rotates gear 29 clockwise about its fixed pivot 30 which is supported by journal engagement with the walls of the metallic enclosing housing 3I. Clockwise motion of gear 29 imparts downward motion to the toothed contact rod 32 on which is mounted the movable way 24 and pipe 22, I have shown a source of electric potential 33, a manually operable switch 34, coil 35, and armature 36 associated therewith. Closing of switch 34 causes the bridging member 31 to engage the fixed contacts 38 and 39 thereby completing the circuit through the coil 35. Energization of coil 35 causes upward movement of armature 36 and valve member 40 against the bias of spring 4I thereby admitting pressure fluid from reservoir I, pipe 2!, valve 8, pipe 22, passageway 24 to the underside of piston I'I.

Upon separation of contacts I4 and I5, a blast of pressure gas or air is admitted to the inside of insulating casing I I which flows with high. velocity around the movable contact I5 and through the opening in the lower wall of the fixed contact I4 to envelop and extinguish the arc drawn therebetween. Exhaust of this blast and of the products of the arc is accomplished through suitable openings in capping member 3 which openings may be shielded from the weather by any suitable means such as by covers 43 and 44 mounted on capping member 3.

The are extinguishing blast is supplied to the interrupting chamber within the insulating casing I I through a passageway 45 in the enclosing housing 3|, the passageway 46 in the tubular insulator 41, and pipe 48 proceeding from blast valve 9.

Blast valve 9 is operated by the coil 49, energization of which causes the armature 50 to move downwardly against the bias of spring 51 to cause the disk 52 to move out of seating engagement with the pipe 53.

Where it is desired to have the arc extinguishing blast from reservoir I through blast valve 9 and through the associated above-described structure to the interrupting chamber within the insulating casing I I occur at the same time that the contacts I4 and I5 are parted, the energy for coil 49 conveniently may be supplied from source 33 through bridging member 54 and contacts 55 and 56 of switch 34. With the elementary control arrangement shown, it will be understood that the opening of the control switch 34 to demergize coil 35 for cutting off the pressure supply to opening piston [1 toward the end of its stroke will also cause an accompanying cutofi for the blast valve 9 because the simultaneous deenergization of blast valve coil 49 will cause the valve disk 52 to r-eseat under the compression of its spring 5|. In many applications, provision would be made for effecting the earliest appropriate cut-off for the blast so as to bring about the greatest conservation of extinguishing gas made possible by the use of the oil isolator of my invention as already pointed out. For producing such earlier cut-off, known means such as a properly timed electrical relay may be provided in the blast valve coil circuit or, alternatively, the valve may be timed to reclose automatically by pneumatic means such as is disclosed, e. g., in U. S. Patent 1,912,024 to Uebermuth which is assigned to the same assignee as this application.

To close the contacts, the switch 51 is used. When switch 5! is closed, bridging member 58 engages contacts 59 and 6!! thereby completing the circuit through coil BI. Energization of coil 6| causes armature 62 and slidable valve member 40 to move downwardly against the bias of spring 63 uncovering the opening in valve 8 to pipe 23. Pressure fluid will then be supplied through pipe 2|, valve 8, pipe 23, and passageway 25 to the underside of piston I9 which, when the contacts are open, will be in the down position. Pressure '5 underneath piston 19 will cause contact l to move upwardly to engage the'fixed contact I 4.

Instead of the manually operable switches 3 and 51, an automatically operable device such as a relay responsive to various circuit conditionscould be used as will be obvious to those skilled in the art and such as is indicated in the aforesaid patent'to Wyman.

The isolating contacts 64 and 65 are disposed within the isolating chamber 5 and are submerged in an insulating liquid 6 8 of high dielectric strength such as oil or other fluid of vastly greater dielectric strength than that of free air. Contact 64 is a relatively fixed contact which is capable of limited axial movement with respect to the conductor 61 by virtue of being mounted on a conducting sleeve 68. A pin '59 secured to the conductor 61 and diametrically extending therethrough serves to limit the travel of sleeve 68 which is constructed with a pair of longitudinally extending slots through which the projecting ends of the pin 69 extend. A compressible spring is is interposed between the conductor El and the right hand end of the sleeve 68. Electrical contact between sleeve 68 and contact 61 may be made by means of a braid 68a, or by any of a number of other arrangements well known in the art. Conductor 61 extends axially through a porcelain bushing H which is mounted on a metallic plate 12 which in turn is secured to a supporting structure 13. I prefer to ground the structure 13 so that a standard bushing transformer l4 conveniently may be mounted on and supported by the bushing -II. This transformer may be used to control relays which in turn 1 could control the functions described above for switches 34 and 5'! or for any other desired purpose. An oil-tight gasket 15 is disposed at each end of the interrupting chamber 5.

To prevent the leakage of dielectric liquid 66 from the chamber 5 to the inside of the enclosing housing 3! which normally is air filled at atmospheric pressure, I provide a stufling-box 16.

Good series electrical conductivity must be provided between the isolating contact 65 and the interrupting contact 15. Accordingly, to insure agood electrical connection between the movable rod 11 on which the contact 65 is mounted and the metallic housing structure 3 l, I provide a plurality of conducting fingers 18 disposed about the periphery of the rod TI and Within a supporting member '59. A biasing spring ,80 for each conducting vfinger .18 insures .a good electrical connection between the rod 1! and the metallic supporting member 19, which may be integrally formed with the 'metallic end wall-8-l of the housing -3l. To insure a good electrical contact -between the housing 3| and the rod 32, aplurality of conducting fingers 82 are pressed against the outer periphery of rod ,32by means of springs 83.

Alternatively, I might employ a flexible electric connection for directly interconnecting isolating contact rod 11 to interrupting contact rod 32.

.The circuit through :the complete circuit breaker, therefore, comprises the terminal I, fixed contact l4, movable contact 15, the upper portion of rod 32, fingers 82, housing 3|, fingers l3, rod ll, movable contact 65, yieldably mounted contact 64, sleeve 68, braid 68a, conductor 61 and terminal 2, which: latter element is not shown.

The isolating chamber 5 is filled with insulating liquid to a suitable level such as is indicated in the drawing and a suitable vent pipe such as 90 may be provided to accommodate pressure changes within the isolating chamber due to the displacement of fluid 'by the action of rod TI.

The proper sequence of operation of the isolating contacts 64 and 65 and the interrupting contacts Hi and I5 is accomplished in accordance with my invention by means of the connecting rod 84 which is pivotally mounted at 85 on the right hand end of the reciprocating contact rod Tl and by means of the crank at which is secured to the gear '29 and rotatable therewith about the shaft 38. The crank -36 is pivotally secured at its outer end to the right hand end of the connecting rod 84 by a pin Bl. It will thus be seen that rod 84 and crank 86 form a toggle which serves as a mechanical variable speed force-transmitting system between the gear '29 and the movable isolating contact 65 and furthermore serves as a positive coordinating means for properly timing in a predetermined sequence the breaking and making of the interrupting contacts I4 and IE5 and the isolating contacts'M and 65. In other words, the rod 84 and crankBG may be regarded as a mechanical interlock between the interrupting and isolating contacts.

More specifically, when piston ii is caused to move upwardly by the introduction of fluid under the piston, the movable contact! 5 simultaneously moves downwardly due to the rack and gear connection between rods 28 and 32. Duringthis interrupter opening movement, the gear '23 will be rotated clockwise, and because the crank 86 is integrally constructed with respect to the gear 29, both will move simultaneously. This clock wise movement of the crank 86 about its fixed pivot 39 will cause the connecting rod 84 and the crank 85 to pass from the overcenter position upwardly through dead center and beyond. This toggle action will cause the contact 65 to move slightly to the left as the crank 86 approaches dead center thereby displacing the yieldably mounted relatively fixed contact 64 to the left and insuring secure engagement between contacts 65 and 65. As the toggle comprising the rod .84 and the crank 35 passes through dead center during the clockwise movement of crank 86, the contact t5 will begin gradually to move to the right and engagement between contacts 6? and 65 will continue to be maintained during an appreciable angular movement of the crank 88 until the left hand end of the slots in the telescoping sleeve 63 engage the diametrically extending pin 63 mounted on .the conductor 61. Thus it will be seen that the isolating contacts 64 and 65 will remain in engagement for a predetermined time after the separation of the interrupting contacts Hi and 5 for, in a sense, they virtually are provided with a long wipe compared to the interrupting contacts.

In view of the above detailed description of the cooperative relationship of the various parts for producing a predetermined sequential parting of the interrupting contacts I l and i5 and the isolating contacts 64 and t5 respectively, it also follows, and will be understood, that the isolating contacts 64 and 65 will be closed a predetermined time before the closing of the interrupting contacts 14 and I5 whenever a closing operation is achieved by introducing pressure below the piston 19. As explained above such pressure causes upward movement of the toothed rod 32 and counterclockwise motion of the gear 29 and the crank 86 during which operation the connecting rod 84 and the crank 86 will move back through dead center and below as the crank 36 rotates counterclockwise. In this reverse rotative closing movement it will be appreciated that the re-engagement of isolating contacts 64 and 05 occurs appreciably before the re-engagement of the interrupting contacts 14 and I5.

In the above described circuit breaker which I have chosen as the embodiment of my invention, that is, where the circuit is re-established by the closing of the interrupting contacts subsequent to the closure of the isolating contacts, it is often preferable that a closing blast be employed. For this purpose I could employ one of several known blast control methods comparable to those discussed herein in connection with the opening blast. Otherwise, I might employ closing blast control schemes comparable to those disclosed in U. S. Patent 2,389,942 to Thumim or U. S. Patent 2,418,739 to Thumim et al., both of which are assigned to the same assignee as the present application.

Thus it will be seen that by my invention adequate isolation is accomplished primarily by the insulating action of the high dielectric liquid soon after the isolating contacts are separated thereby making unnecessary a prolonged and wasteful blast of gas between the interrupting contacts. Furthermore it will be obvious that because of the high dielectric strength of the liquid insulating material this desirable result may be achieved by opening the isolating switch at relatively low speeds thereby avoiding excessive accelerating and decelerating forces throughout the switch blade and its operating mechanism. Also it will be apparent that my invention affords precise and accurate means for operating the interrupting and isolating contacts in the proper sequence and at the same time protects the isolating contacts against the possibility of becoming inoperative due to icing.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that various 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. In an electric circuit breaker of the fluid blast type, relatively movable interrupting contacts, isolating contacts serially arranged with respect to said interrupting contacts, actuating means for imparting opening movement to said interrupting contacts, means for supplying a blast of gas to said interrupting contacts to extinguish the are drawn therebetween upon separation thereof and to prevent the reestablishment of the are immediately after interruption thereof, means coordinated with said actuating means for imparting controlled opening movement to said isolating contacts during the entire opening movement of said actuating means and operable to separate said isolating contacts after separation of said interrupting contacts and interruption of the are drawn therebetween during a circuit opening operation of said circuit breaker, a substantially fluid tight weatherproof chamber enclosing said isolating contacts, and an isolating medium in said chamber of dielectric strength substantially greater than atmospheric air.

2. In an electric circuit breaker of the fluid blast type, relatively movable interrupting contacts, isolating contacts serially arranged with respect to said interrupting contacts, means for imparting opening movement to said interrupting contacts, a source of gas under pressure, means for supplying a blast of gas from said source to said interrupting contacts to extinguish the are drawn therebetween upon separation thereof and to prevent the reestablishment of the are immediately after interruption thereof, means movable in accordance with movement of said means for imparting opening movement to said interrupting contacts and operable to separate said isolating contacts after separation of said interrupting contacts and interruption of the are drawn therebetween during a circuit opening operation of said circuit breaker, a substantially fluid tight weatherproof chamber enclosing said isolating contacts, and an insulating liquid of dielectric strength substantially greater than atmospheric air in which said isolating contacts are submerged at all times.

3. In an electric circuit breaker of the fluid blast type, relatively movable interrupting contacts, a substantially fluid tight chamber containing fluid of substantially higher dielectric strength than atmospheric air, isolating contacts serially arranged with respect to said interrupting contacts and disposed in said chamber, said isolating contacts being immersed in said fluid at all times, means for imparting opening movement to said interrupting contacts, a source of gas under pressure, means for supplying a blast of gas from said source to said interrupting contacts to extinguish the arc drawn therebetween upon separation thereof and to prevent the reestablishment of the are immediately after interruption thereof, and means movable in accordance with the opening movement of said interrupting contacts and operable to separate said isolating contacts after separation of said interrupting contacts during a circuit opening operation of said circuit breaker.

JOHN W. BEATTY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,697,309 Edsall Jan. 1, 1929 2,089,285 Milliken Aug. 10, 1937 2,249,444 Traver July 15, 1941 2,303,492 Peterson Dec. 1, 1942 2,310,905 Blandford Feb. 9, 1943 2,364,981 Journeaux Dec. 12, 1944 2,477,788 Cumming Aug. 2, 1949

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