US3290469A - Compressed-gas circuit interrupter having cavitation means - Google Patents

Description

W. M. LEEDS Dec. 6, 1966 COMPRESSED-GAS CIRCUIT INTERRUPTER HAVING CAVITATION MEANS 5 SheetsSheet 1 Filed Sept. 30, 1964 FIG. 5.

6 G F 2 8 VII A ll 7 9 J ,4 9 V/ 4 7 9 OT! 9 Dec. 6, 1966 W. M. LEEDS COMPRESSED-GAS CIRCUIT INTERRUPTER HAVING CAVITATION MEANS 5 Sheets-Sheet 2 Filed Sept. 30, 1964 INVENTOR Winthrop M. Leeds BY M ATTORNEY W. M. LEEDS Dec. 6, 1966' COMPRESSED-GAS CIRCUIT INTERRUPTER HAVING CAVITATION MEANS 5 Sheets-Sheet 3 Filed Sept. 50, 1964 United States Patent Ofifice 3 290,469 COMPRESSED-GASbIRCUIT INTERRUPTER HAVING CAVITATION MEANS Winthrop M. Leeds, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., 2 corporation of Pennsylvania Filed Sept. 30, 1964, Ser. No. 400,366 11 Claims. (Cl. 200-148) This invention relates generally to compressed-gas circuit interruppters and, more particularly, to improved arc-extinguishing structures therefor.

A general object of the present invention is to provide an improved compressed-gas circuit interrupter which will be highly eflicient, inexpensive, and readily adaptable for use over a wide range of current and voltage applications.

Another object of the present invention is to provide an improved compressed-gas circuit interrupter utilizing two different fluids, one of which has preferably highlyefiiicent arc-extinguishing properties, such, for example, as sulfur-hexafiuoride (SF gas, and the other fluid is perferably a relatively cheap operating fluid, such, for example, as compressed air, which may subsequently be exhausted to the atmosphere.

Still a further object of the present invention is the provision of an improved compressed-gas arc-extinguishing structure in which a movable tubular venting contact is utilized, and in which cavitation, or the attaining of a relatively low pressure downstream of the movable contact, is achieved.

Still a further object of the present invention is the provision of an improved compressed-gas arc-extinguishing structure utilizing a highly etficient, sealed, arc-extinguishing gas, and in which a relatively cheap gas, such as compressed air, is employed to effect contact closure.

Still a further object of the present invention is the provision of an improved compressed-gas circuit interrupter in which the high-pressure cylinder for the operating gas is utilized as the upstanding frame support for the circuit interrupter.

Putter-type SP breaker of conventional design force gas flow by piston action into an are drawn between contacts separated in an insulating nozzle, or flow guide. Eifectiveness of such a design at high voltage is limited by creepage breakdown along the insulating nozzle surfaces, which parallel the highly-stressed contact gap. The present invention is directed toward the solution of such a problem by locating the piston downstream from the arcing contacts, so that the movement of the piston lowers the pressure within the hollow moving contact; and gas flow through the arc is produced without the need of insulating orifices, or flow guides partly or completely bridging the contact gap. Reference may be had to US. Patent 2,866,045, issued December 23, 1958, to Winthrop M. Leeds, and to US. Patent 3,114,815, issued December 17, 1963, to Gilbert J. Easley, James M. Telford and Robert L. Hess, for typical types of puffer-type SP circuit-breaker constructions. It is, accordingly, a further object of the present invention to improve upon the arc-extinguishing structures of the foregoing patents, rendering them less conductive to voltage breakdown during the opening operation, and providing highly-effective flow conditions.

Another object of the present invention is the provision of an improved compressed-gas circuit interrupter in which operating rods, levers, and mechanical linkages are eliminated by the utilization of a suitable operating fluid, such as compressed air.

Still a further object of the present invention is the provision of an improved compressed-gas arc-extinguishing structure which is readily adaptable in construction to 3,290,469 Patented Dec. 6, 1966 provide a single break, double breaks, and resistor applications with a minimum of modification.

Still a further object of the present invention is the provision of an improved compressed-gas circuit interrupter utilizing a simplified-type of operation mechanism incorporating a simple three-way valve.

Further objects and advantages will readily become apparent upon reading the following specification, taken in conjunction with the drawings, in which:

FIGURE 1 is a side elevational view of a compressedgas circuit interrupter embodying the principles of the present invention;

FIG. 2 is a considerably-enlarged, fragmentary, longitudinal sectional view taken through the upper arc-extinguishing structure of the circuit interrupter illustrated in FIG. 1, the contact structure being illustrated in the closed-circuit position;

FIG. 3 is a vertical sectional view taken substantially along the line III-III of FIG. 2;

FIG. 4 illustrates a modification of the arc-extinguishing structure of FIG. 2 utilizing two operating pistons, again the contact structure being illustrated in the closedcircuit position;

FIG. 5 is a fragmentary vertical sectional view taken through a modified-type of arc-extinguishing tructure again the contact structure being illustrated in the closedcircuit position; and

FIG. 6 is a fragmentary sectional view illustrating a resistor application to the arc-extinguishing structure of FIG. 5 for interrupting circiuts with relatively high-ratesof-rise of recovery voltage.

Referring to the drawings, and more particularly to FIG. 1 thereof, the reference numeral 1 generally designates a compressed-gas circuit interrupter having a lower base 2, an upstanding cylindrical compressed-air reservoir cylinder 3, and an arc-extinguishing assemblage, generally designated by the reference numeral 4. The arc-extinguishing assemblage 4 generally comprises a centrally-located, grounded metallic casing 5 and a pair of laterally-spaced current transformers 6, 7. In addition, the central grounded metallic casing member 5 has jutting outwardly therefrom a weatherproof insulating casing 9, at the end of which is a line-terminal structure 10. Also extending in an opposite direction from the other end of the centrally-disposed, grounded metallic casing member 5 is a second insulating weatherproof casing 12 having a lineterminal structure 13 supported at the outer end thereof. A line connection L may be attached to the terminal structure 13, as well understood by those skilled in the art.

Fixedly secured to the line-terminal structure 13, and extending longitudinally axially through the center of the weatherproof insulating casing 12, is a stationary contact rod 15, which has a stationary contact structure secured thereto adjacent the right-hand end thereof (FIG. 2), generally designated by the reference numeral 17. The relatively stationary contact structure 17 comprises a plurality of circumferentially-disposed resilient contact fingers 18 secured by bolts 19 to the side of the stationary contact rod 15. It will be observed that the stationary contact rod 15 has a reduced portion 20, constituting thereby an arcing horn, which extends interiorly of a movable tubular Venting contact 22, secured to a piston 23, and biased to a rightward opening position by an accelerating compression spring 25.

Making resilient sliding contacting engagement with the movable tubular venting contact 22 is a relatively stationary contact structure 28, including a plurality of circumferentially disposed contact fingers 30, biased by compression springs 31, which seat in the base portions 30a of the adjoining contact fingers 30. As shown, the relatively stationary contact fingers 30 are disposed within a generally cylindrically-shaped contact housing 33, which is secured by suitable means, not shown, to a conducting metallic operating cylinder 35 having a radially outwardly-extending mounting flange portion 36 at the righthand end thereof, as viewed in FIG. 2. Fixedly securing the operating cylinder 35 into a proper position is a plurality of mounting bolts 37, which extend into tapped apertures 38 provided in a flanged mounting ring 39, the latter being secured, as by a lead connection, to the righthand extremity 9a of the weatherproof ceramic casing 9.

As more fully brought out hereinafter, the region 40 to the rear of the piston 23 is, at times, at a relativelylow, or atmospheric pressure, and at other times is at a relatively high pressure, as brought about by the entrance of high-pressure gas from a compressed-air reservoir cylinder 3. The region 42 interiorly of the arc-extinguishing assemblage 4 is, however, filled with a suitable sealed arc-extinguishing gas, such as sulfur hexafiuoride (SP gas, which may be at pressure of, say 50 to 75 p.s.i.g. It will, therefore, be apparent that no communication between the regions 40, 42 is desired, and to provide such a resilient seal 43, I preferably employ a Bellofram diaphragm 45. As shown in FIG. 2, it will be noted that the Bellofram diaphragm is folded back upon itself, as is permitted by such a device. The Bellofram diaphragm is a rolling-seal diaphragm, such as described in US. Patent 2,849,026, issued August 26, 1958, to John F. Taplin, and is sold by the Bellofram Corporation located in Burlington, Massachusetts. The Bellofram diaphragm provides a better seal than would be obtained by utilizing O-rings sliding with the piston 23.

It will be noted that rightward opening movement of the piston 23 and movable tubular contact 22 will create a cavitation or a relatively low-pressure region within the space 48 in front of the piston 23. Since the movable tubular contact 22 is provided with communicating apertures 22a, sulfur-hexafluoride (SP gas will be drawn into the moving tubular contact 22 and into the cavitation region 48 during the opening operation.

For the purpose of effecting contact closure, and for charging the opening accelerating compression springs 25, there is provided a pneumatic operating mechanism, including a control valve 50, of the three-way type, which is rotatable within an offset portion 51 secured to the cylinder head 52. Thus, counterclockwise rotation of the control valve 50, as effected by an operating lever 53 and a vertical insulating operating rod 54, as effected by energization of a solenoid 56, will permit the passage of highpressure operating fluid, such as compressed air at a pressure of say 100 p.s.i.g., to flow through an insulating conduit 58, and into the region 40 to the rear side of the operating piston 23. The entrance of high-pressure operating fluid, such as compressed air, will cause the piston 23 to be forced toward the left in a contact-closing direction. As a result, the moving contact 22 will engage the stationary contact structure 17 for circuit completion; and also the opening accelerating springs 25 will be charged for a subsequent opening operation.

When the circuit breaker 1 is completely closed, preferably the-re is provided a latching device 60, including a rotatable latch 61 having a nose portion 62, Which will engage a projection 54a of the vertically-extending insulating operating rod 54. Energizatio-n of a tripping solenoid 64 will effect release of the latch 61, and will permit a compression spring 66 to force the valve-operating rod 54 upwardly to cause clockwise rotation of the threeway valve 50, so as to effect communication between the insulating conduit 58 and an exhaust outlet 68, leading to a low-pressure region, such as atmospheric air.

It will be noted that the operating cylinder 35 and piston 23 movable therein constitute a cavitation device 8 with the cavitation region 48 thereof communicatll'llg solely with the enclosed casing by way of the movable tubular venting contact 22.

In the usual puffer-type SP circuit breaker of conventional design, gas flow is produced by piston action into an are drawn between the separated contacts within an insulating nozzle formed of a suitable insulating material, such as polytetrafluoroethylene, sol-d under the trade name Teflon. Effectiveness of such a conventional puffer type design at high voltage is limited by creepage breadown along the Teflon surfaces, which are parallel to the highly-stressed contact gap. The present invention is particularly concerned with the location of the piston downstream from the arcing contacts, so that the movement of the piston 23 will lower the pressure within the hollow moving contact 22, and gas flow through the established are is produced without the need of an insulating orifice, or flow guide, which partly or completely bridges the contact gap. The higher the initial gas pressure within the casing 5, the better the results. A pressure of 50 to 75 p.s.i.g. for the sulfur-hexafluoride (SP gas is recommended.

While the piston 23 can be operated by any mechanical, pneumatic, or hydraulic means, a preferred arrangement, as shown, uses compressed-air pressure behind the piston 23 sealed off from the SP gas by a Bellofram diaphragm 45. For simplicity, the pole-units of the breaker are supported by the cylindrical reservoir 3 used for pneumatic operation. The breaker contacts are shown held closed by air pressure within the region 40, which must be higher than the SP gas pressure, say 100 p.s.i.g. When the control valve 50 dumps this air to atmosphere through the exhaust opening .68, the combined action of acelerating springs 25 and the SP gas pressure on the piston 23 opens the contacts 17, 22 quickly, drawing SP gas through the hollow moving contact 22 and into the volume 48 behind the piston 23. During the closing operation, when the control valve 50 admits compressed air into the region 40, the piston 23 is forced to the closed position, sulfur-hexafluoride (SP gas circulating, by going back through the hollow moving contact 22, or through uni-directional check valves 70.

FIG. 4 shows a modified-type or arc-extinguishing assemblage, generally designated by the reference numeral 72, and including a second movable tubular venting contact 73 having a piston 74 associated therewith. The operation of the piston 74 is identical to that previously described in connection with the piston 23, there merely being provided an additional piston structure 74 for effecting cavitation within the region 76, to effect thereby a drawing of SE, gas into the interior 78 of the second movable tubular venting contact 73. As a result, during the opening operation of the modified-type of arc-extinguishing structure 72, there occurs oppositely-directed exhaust flow from the region 42 through the two movable con tacts 22, 73, and into the regions 48, 76. As will be obvious, an additional insulating conduit 58 will be provided connected to the unitary control valve 50, the operation of which will simultaneously cause the opening and closing movements of both piston members 23, 74.

FIG. 5 illustrates a modified-type of construction in which two series breaks 81, 82 are provided. To effect this end, a central stationary contact structure is provided, being supported interiorly of the grounded metallic casing 5 by insulating spider members 92. The stationary contact structure 90 has pairs of resilient fingers 95, and two oppositely-directed arcing contacts 96. Preferably, the two movable contacts 97 are of the type previously described in connection with FIG. 4, that is, each having its own operating piston 23, 74 to draw arc-extinguishing fluid therein during the opening operation.

It will, therefore, be apparent that in the modified-type of construction in FIG. 5, there are provided two breaks in series, thereby accommodating the higher voltages.

FIG. 6 illustrates a modified-type of construction very similar to that previously described in connection with FIG. 5, but utilizing a shunting resistor R in electrical parallel between the stationary contact structure 90, and one of the two movable tubular venting contacts 97.

Preferably, the contact overlap associated with the second break 82 is greater than that associated with the series break 81 so that the first contact break 81 will be opened prior to the opening of the second break 82. If this is the case, the residual-current arc will be broken at the second break 82. However, the invention is not restricted to a sequential-break arrangement, as just described, but may, for certain applications, be employed with a simultaneous breaking action in the two breaks 81, 82.

The use of the shunting resistor R of relatively low magnitude will lower the rate-ot-rise of the recoveryvoltage transient, as well understood by those skilled in the art, enabling the power factor to be improved, and the current reduced in the second break 82. Such an arcextinguishing arrangement 99 is particularly effective on high-rates-of-rise circuits.

From the foregoing description it will be apparent that there is provided an improved arc-extinguishing structure utilizing downstream flow through a hollow moving contact produced by piston action for effective interruption of high-voltage arcs in a gas-type circuit interrupter. With the disclosed arrangement, it will be apparent that no insulating orifice is required, across which creepage breakdown might occur under certain high-voltage conditions. Moreover, the SP gas flow is caused to occur by spring action, which is charged during the closing stroke by the use of a relatively cheap operating fluid, such as compressed air.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

I claim as my invention:

1. A compressed-gas circuit interrupter including means defining an enclosed casing containing gas under pressure, a relatively stationary contact and a cooperable movable tubular venting contact disposed within said enclosed casing, and means causing a cavitation elfect downstream of the movable tubular venting contact to cause thereby gas flow through the movable tubular venting contact to cause arc extinction.

2. A compressed-gas circuit interrupter including means defining an enclosed casing containing gas under pressure, a relatively stationary contact and a coopera'ble movable tubular venting contact disposed within said enclosed casing, a piston secured to the movable contact and operable within an operating cylinder, and the opening movement of said piston within the operating cylinder causing a cavitation effect downstream of the movable tubular venting contact to cause thereby gas flow through the movable tubular venting contact to cause arc extinction.

3. In combination, a compressed-gas circuit interrupter including means defining an enclosed casing containing gas under pressure, a relatively stationary contact and a cooperable movable tubular venting contact disposed within said enclosed casing, an operating cylinder and an Operating piston secured to the movable tubular venting contact collectively defining a downstream region which is cavitated during the opening operation, and means including the arc-extinguishing fluid pressure adjacent the separable contact structure acting upon said operating piston to effeet cavitation within said downstream region to draw arcextinguishing gas into and through said movable tubular venting contact.

4. The combination of claim 3, wherein an opening accelerating spring biases the operating piston to the open position.

5. The combination of claim 3, wherein compressed air is used as an operating fluid to act on the operating piston and thereby effect contact closure.

6. A compressed-gas circuit interrupter including means defining an enclosed casing containing gas under pressure, a pair of tubular movable exhaust contacts disposed with in said casing, a piston secured to each tubular movable exhaust contact and movable within an operating cylinder, means for effecting opposite opening movement of the pair of pistons and moving contacts to cavitate regions within the two operating cylinders, whereby gas will be drawn through the interior of the two movable tubular exhaust contacts to assist in arc extinction.

7. The combination of claim 6, wherein an intervening relatively stationary contact structure is employed to thereby establish two serially-related arcs.

8. The combination of claim 7, wherein a shunting resistor electrically shunts one of the breaks.

9. An upstanding generally T-shaped compressed-gas circuit interrupter including support means and generally horizontally-extending arc-extinguishing means surmounted on said support means, said arc-extinguishing means including a central grounded metallic casing and oppositely-extending insulating casings defining an enclosed casing containing gas under pressure, terminal structures on opposite ends of said insulating casings, a relatively stationary contact and a cooperable movable tubular venting contact disposed within said casing, an operating cylinder and an operating piston secured to the movable tubular venting contact collectively defining a downstream region which is cavitated during the opening operation, a means including the arc-extinguishing fluid pressure adjacent the separable contact structure acting upon said operating piston to effect cavitation within said downstream region to draw arc-extinguishing gas into and through said movable tubular venting contact, and compressed-air means for acting upon the opposite side of said operating piston to effect contact closure.

10. The combination according to claim 9, wherein a compressed-air storage cylinder constitutes the support means and solely supports the surmounted arc-extinguishmg means.

11. In combination, a compressed-gas circuit interrupter including means defining an enclosed casing containing gas under pressure, means defining an adjacentlydisposed cavitation device (8), separable contacts disposed within said enclosed casing and including one movable tubular venting contact (22) providing the sole means of gaseous communication between said enclosed casing and said cavitation device, and means causing opening movement of said movable tubular venting contact and operation of said cavitation device (8), whereby an exhausting flow of gas under pressure will flow through said movable tubular venting contact to effect arc extinction.

References Cited by the Examiner UNITED STATES PATENTS 2,246,171 6/1941 Grosse 200l48 3,218,420 11/1965 Frowald 200-148 FOREIGN PATENTS 878,65 8 10/ 1961 Great Britain.

ROBERT K. SCHAEFER, Primary Examiner. ROBERT S. MACON, Examiner. P. E. CRAWFORD, Assistant Examiner.

Claims (1)

1. A COMPRESSED-GAS CIRCUIT INTERRUPTER INCLUDING MEANS DEFINING AN ENCLOSED CASING CONTAINING GAS UNDER PRESSURE, A RELATIVELY STATIONARY CONTACT AND A COOPERABLE MOVABLE TUBULAR VENTING CONTACT DISPOSED WITHIN SAID ENCLOSED CASING, AND MEANS CAUSING A CAVITATION EFFECT DOWNSTREAM OF THE MOVABLE TUBULAR VENTING CONTACT TO CAUSE THEREBY GAS FLOW THROUGH THE MOVABLE TUBULAR VENTING CONTACT TO CAUSE ARC EXTINCTION.

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