US3646296A

US3646296A - Circuit interrupter grid structure for oil-break circuit interrupter

Info

Publication number: US3646296A
Application number: US703410A
Authority: US
Inventors: Robert L Hess; Gerald D Summers
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1968-02-06
Filing date: 1968-02-06
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28
Also published as: GB1253253A; ES362870A1

Abstract

An oil-type circuit breaker has three poles provided in a unitary tank structure, each pole comprising a pair of serially related grid structures. The grid structures are constructed by nesting a plurality of plate elements, constituting vent passages and oil pockets, within an outer cylindrical glass-filament-wound shell. The stationary contact assembly is so arranged as to have a lengthened finger, which serves as an arcing horn disposed adjacent side lateral vent openings. The vent openings are formed by molded vent elements of particular materials and having a splitter plate interposed therebetween. Additional oil pockets and a lower oil-pocket plug, having an entrance opening, assist in guiding the movable contact rod, and additionally providing considerable turbulence within the oil during the opening operation.

Description

United States Patent Hess et al.

[54] CIRCUIT INTERRUPTER GRID STRUCTURE FOR OIL-BREAK CIRCUIT INTERRUPTER [72] inventors: Robert L. I-less, E. McKeesport; Gerald D.

Summers, Greensburg, both of Pa.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

22] Filed: ',Feb. 6, 1968 21 ,Appl. No.: 703,410

[52] U.S.Cl. ..20l)/l50 R, ZOO/150E [51] Int. Cl. ..H0lh 33/68 [58] Field of Search ..200/l50 F, 150.2, 150

[56] References Cited UNITED STATES PATENTS 2,760,033 8/1956 MacNeil et al. ..200/ 150 3,128,360 4/1964 Rieti 200/150 3,214,550 10/1965 Easley 200/150 X 3,335,245 8/1967 McCloud ..200/150 3,356,811 12/1967 Cushing et al. ..200/150 3,392,248 7/1968 Rietz et a1 ..200/150 1 Feb. 29-, 1972 FOREIGN PATENTS OR APPLICATIONS 1,143,891 2 /1963 Germany 200/15O OTHER PUBLICATIONS lTE Circuit Breaker Company Bulletin No. 2031A; March, 1960;

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorney-A. T. Stratton, C. L. McHale and W, R. Crout 5 71 ABSTRACT An oil-type circuit breaker has three poles provided in a unitary tank structure, each pole comprising a pair of serially related grid structures. The grid structures are constructed by nesting a plurality of plate elements, constituting vent passages and oil pockets, within an outer cylindrical glass-filament-wound shell. The stationary contact assembly is so arranged as to have a lengthened finger, which serves as an arcing horn disposed adjacent side lateral vent openings. The vent openings are formed by molded vent elements of particular materials and having a splitter plate interposed f'therebetween. Additional oil pockets and a lower oil-pocket plug, having an entrance opening, assist in guiding the movable contact rod, and additionally providing considerable turbulence within the oil during the opening operation.

13 Claims, 12 Drawing Figures Patented Feb. 29, 1972 4 Sheets-Sheet l Patented Feb. 29, 1972 3,646,296

4 Sheets-Sheet 2 FIG. IO.

Patented Feb. 29 1972 4 Sheets-Sheet 3 FIG. 3.

FIG. 4.

CIRCUIT INTERRUPTER GRID STRUCTURE FOR OIL- BREAK CIRCUIT INTERRUP'IER BACKGROUND OF THE INVENTION As well known by those skilled in the art, it has been common practice heretofore to provide separate tank structures for circuit interrupters of intermediate voltage rating. This has necessitated a considerable cost expenditure for the separate tank units and, additionally, the necessity of providing linking mechanism for interrelating the movable contact structures within the several tank units. It is, therefore, preferable to provide the three pole-units within a single tank structure, thereby reducing the cost and simplifying the linkage for the operating mechanism. To provide such a construction for the same intermediate voltage levels, it is, of course, necessary to provide a highly efficient arc-interrupting grid structure of relatively small size and highly efficient operation. Moreover, it is'necessary to prevent external flashover on the outer surfaces of the grid units by so directing the exhaust gases as to prevent their combination from the several spaced grid structures.

As typical of prior art constructions, reference may be had to U.S. Pat. application Ser. No. 425,728, filed Jan. I5, 1965, now US. Pat. No. 3,356,811, issued Dec. 5, 1967 to George B. Cushing and Frank L. Reese, and assigned to the assignee of the present invention, which exemplifies a prior art structure. According to the present invention, the dimensions have been reduced and the grid elements have been improved, with improved venting channels of constant cross-sectional area, and with oil pockets of such configuration and location, as to provide highly efficient oil grid units, and to enable the radially spaced disposition of six such units within a single tank, thereby permitting the three pole-units, for a three-phase con struction, to be disposed within a single unitary tank structure.

SUMMARY OF THE INVENTION According to a preferred embodiment of the invention, there are provided six grid structures within a single tank having their individual vents directed radially outwardly to prevent external flashover. Each of the six grid units comprises a nesting of several grid elements within an outer cylindrical glass-filament-wound shell, having an upper insert, which enables its ready assemblage to a threaded contact foot. By the use of venting channels and suitably located oil pockets provided by elements of unique composition, a highly favorable arrangement, including gas evolution and oil turbulence, is achieved to result in a highly efficient grid unit of reduced dimensions. As a result, not only are the three poles provided in a single tank, but, additionally, the dimensions of all the elements are reduced and the structure thereby made more lightweight in construction.

Additionally, there is provided a pair of vent channels having a splitter plate interposed therebetween to encourage arc looping into the vent channels and to prevent its physical ejec tion externally of the grid casing.

A general object of the present invention is, accordingly, to provide an improved oil-break grid structure for a circuit interrupter of highly efficient operation and of reduced dimen- SIOIIS.

Still a further object of the present invention is to provide an improved oil grid structure, in which a few of the several insulating elements are provided, such as by molding, from particular resinous materials.

Still a further object of the present invention is the provision of a low-cost, rapidly assembled grid structure, which is highly efficient in operation and of reduced dimensions.

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

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional view taken through a three-pole oil-type circuit interrupter embodying the principles of the present invention, the contact structure being illustrated in the closed-circuit position;

FIG. 2 is a plan view, the line IIII of FIG. 1;

FIG. 3 is a considerably enlarged vertical sectional view taken through the interior of one of the oil grid units, the contact structure being illustrated in the closed-circuit position;

FIG. 3a is a fragmentary view, somewhat similar to that of FIG. 3, but illustrating the disposition of the several parts, and the arc location, during an intermediate part of the opening operation;

FIG. 4 is an end elevational view of the oil grid structure of FIG. 3;

FIG. 5 is an inverted plan view of the contact housing of FIG. 3, taken in the direction of the arrows V-V of FIG. 3;

FIG. 6 is a top plan view of one ofthe venting elements;

FIG. 7 is an end elevational view of the venting element of FIG. 6;

FIGS. 8 and 9 are vertical sectional views taken through the bottom and top molded venting plates respectively;

FIG. 10 is a vertical sectional view taken through the lower insulating molded plug element of the oil grid; and,

FIG. 11 is a top plan view of the lower plug element of FIG. 10.

in section, taken substantially along DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, and more particularly to FIGS. 1 and 2 thereof, it will be noted that there is provided a threephase oil-type circuit interrupter l adaptable for intermediate voltage ratings, such as 34.5 kv., for example, and say, for example, having a current rating of l,200 amperes. As illustrated in FIG. 2, the three pole-units A, B and C are disposed within a single tank structure 2. Reference may be had to the sectional view of FIG. 2 for an illustration of the manner of disposition and electrical interconnection of the three pole-units A, B and C within the tank 2.

It will be apparent that each of the oil grid units 4 is clamped to, and fixedly secured to, the lower ends 5 of the terminal bushing studs 6 extending through the upper cover 7 of the tank 2. Current transformers 8 may surround the terminal bushings 9 beneath the cover 7 for relaying circuits.

With reference to FIG. 2, it will be observed that, generally, each pole-unit A, B or C comprises a pair of serially related grid structures 4, which are electrically interconnected by conducting crossarms 11A, 11B, or 11C, which are reciprocally vertically moved, in an opening and closing direction, by

lift rods

12A, 128 or 12C. Three

such lift rods

12A, 12B and 12C are provided and are mechanically interconnected to the linkage mechanism disposed at the upper end of the tank structure 2.

FIG. 3 more clearly illustrates the internal construction of the grid structure 4. Generally, it will be noted that there is provided an outer cylindrical insulating shell 14 formed of a suitable insulating material, such as gIass-filament-filled epoxy resin, and having the several grid elements disposed therein, as more fully explained hereinafter.

A split casting 15, serving as a contact foot, is threaded, as

a at 15a, onto each bushing stud 6. Bolted to this contact foot 15 is a cast stationary contact finger housing I7. Between these two

components

15, 17 is inserted a cast bevel ring 19, that seats flat, as at 19a (FIG. 3), against the contact foot 15 and into a bevel seat 17a on the top of the finger housing 17. With this arrangement, lateral and pivotal adjustment is possible during contact and interrupter alignment.

Four finger contacts 21, mounted on a finger block 22, make up the stationary contact cluster 24, that is bolted in the finger box 17. Each finger 21 is a Cupaloy, or copperchromium alloy forging fitted with an arc-resistant tungstensilver alloy tip 21a. One of the fingers 24A is five-sixteenths inch longer than the other three, for example. When the breaker 1 opens, the long finger 24A is the last to separate with the moving contact 26, thus acting as an arc horn for protecting the other contact surfaces from burning. All four fingers 21 are spring loaded, as at 27. to provide the proper contact pressure against the rod-type moving contact 26 and the stationary finger block 22 in the closed position, as shown in FIG. 3. The resulting rocker-type action of the four fingers 21 eliminates shunting of the four fingers 21 to the finger block 22.

Mounted below the stationary contact-finger box 17 is the interrupting portion 4A of the interrupter grid 4. The grid portion 4A is composed of a stack of insulating elements of various compositions housed within a 4-inch inside diameter, for example, glass-filament-wound shell 14 of the voltage rating considered. The grid assembly is threaded onto the finger box 17 by means of an aluminum insert 1411, which is incorporated and interlocked in the shell 14 during the actual glass-filament-winding process. When correct alignment is achieved, a small bolt 28, threaded into a lug 29 on the finger box 17, is tightened against the machinedtop surface 146 of the tube 14 locking it in place.

The projection 30 of the arc-horn finger 24A down into the

apertures

31, 32 in the top two

fiber plates

33, 34 of the grid stack 4 make it necessary to mount these two

plates

33, 34 on the finger box 17 with retaining screws 35. The remainder of the stack elements are inserted directly into the glass-filamentwound shell 14, and mate with the top two

fiber plates

33, 34 when the shell 14 is threaded onto the finger box 17. The third and

fifth plates

36, 37 in the grid are each 0.75-inch thick, for example, and injection molded of glass-reinforced Celcon" or Delrin.

Celcon" and .Delrin" are high molecular weight polyoxymethylene materials. They are both thermoplastic resins. Delrin" is commercially available from E. I. du Pont Company and Celcon" from the Celanese Corporation. For details of preparation of suitable polyoxymethylenes, reference may be had to U.S. Pat. No. 3,027,352 and U.S. Pat. No. 2,768,994.

In combination with the fourth plate 39, a splitter made from one-fourth-inch thick, for example, fiber sheet, the group forms the

vent channels

41, 42 for the grid 4. Snouts or

projections

36a, 37a on these three vent elements extend through a hole 44 bored into the sidewall of the giass-filamentwound tube 14. This arrangement provides a positive alignment of the

vent channels

41, 42 of the stack with the hole 44 in the shell 14. Correct alignment of the

vent plates

36, 37 and splitter plate 39 is further insured by two small bosses, on each of the molded

vent plates

36, 37 that fit into punched holes provided in the splitter plate 39.

By molding the

vent plates

36, 37 a unique, constant cross section channel configuration was made possible that would keep the bored hole 44 in the filament-wound shell 14 to a minimum size, thus sacrificing a minimum in tube strength 14. In each item, the channel is 0.5-inch high by 0.75-inch wide, for example, with a 0.06-inch radius at the comers X at the inside end, providing a desired flow area for gasses formed during arcing. From the arcing end X" to the exhaust end Y (FIG. 9) of the

channels

41, 42, the corners blend from the 0.06-inch radius to a 0.34-inch radius, thereby maintaining the same cross-sectional vent area throughout the

channels

41,42. The channel height at the exhaust end Y" is reduced to 0.34-inch high, for example, allowing for the small exit hole 44 in the filament-wound shell 14.

The

rear portion

36b, 37b of each

vent plate

36, 37 is a large cavity, that forms a separate oil pocket when assembled in the filament-wound shell 14.

The sixth, seventh, ninth and

th plates

46, 47, 49, 50 in the grid 4 are simple 0.25-inch thick punched round fiber plates, for example, with a 1.06-inch diameter clearance hole 53 in their center for the moving contact 26. These plates add strength to the inner construction of the interrupter 4 and form oil pockets 55, 56 with the plates above and below them. Variations in fiber thickness, which ultimately affect the grid stack height, are compensated for by substituting, or adding 0.l88-inch thick fiber plates of the same design for these plates. A dimensional check of the interrupter stack can be made before assembly in the shell 14.

The eighth element 48 is more a spacer than a plate. It is machined from polyvinyl chloride resin pipe to fit snugly within the filament-wound shell 14. Bounded by the

above fiber plates

46, 47, it forms the largest oil pocket 55 in the interrupter 4.

Proper compression of the grid stack plates is accomplished with the 11th, 12th and 13th plates 58-60. They are, in essence, three cork-neoprene washers, that compress between the flat fiber plate 50 and the bottom plug 62 when the interrupter 4 is threaded onto the finger box 17.

The bottom plate 62 in the interrupter 4 is unique in that it is also injection-molded of glass-reinforced Celcon." In its design are incorporated many functions. It serves as a plug for the open-ended filament-wound shell 14, seating on a chamfered shelf 14c, that is integrally wound into the shell 14. The fiat cork-neoprene washers 58-60, that seat on this plug 62, encircle a cylindrical section 62a of it, that acts as a stop for the stack when compressed during assembly. In the center of the plug 62 is a tapered entrance hole 62b for the moving contact 26 that assures its proper entry and alignment. An inner cavity 620 in the .Celcon plug 62 forms the lowermost oil pocket 56 in the grid stack 4. I 1

The assembly of the interrupter grid 4 is somewhat in reverse order, than as described above. All of the plates are assembled in the filament-wound shell 14 from the threaded insert upper end, starting with the molded Celcon" bottom plug 62. The simple design used in the construction of this interrupter 4 provides a unit that is easy to assemble, inspect and maintain.

By way of recapitulation, during the opening operation, the mechanical linkage, disposed adjacent the upper end of the tank 2, causes downward opening movement of the three

liftrods

12A, 12B and 12C. This downward opening motion of the three lift-rods causes corresponding downward opening movement of the three conducting crossbars 11A, 11B and 11C. The several, rod-shaped moving contacts 26 move downwardly away from the stationary contacts 24, and cause the establishment of arcs 25 between the arcing finger contacts 24A and the tip portions 26a of the moving contacts 26. FIG. 3A illustrates more clearly the arc establishment, wherein the arc 25 is carried by the explosive action of the oil and vapor out through the

lateral vent channels

41, 42 causing the are 25 to pass through the aperture 39a provided in the splitter plate 39. This hole 39a in the splitter plate 36 stabilizes the arc position, and permits the two looped portions 25a, 25b of the are 25 to move somewhat laterally out of the

vent channels

41, 42 to receive the full lateral thrust of the oil and gas flow externally of the grid unit 4. The provision of the oil venting pockets 36b, 37b and 55 maintains a plentiful supply of oil 3 adjacent the path of movement of the moving contact 26, and causes the vaporization of the oil within these pockets. If the are 25 has not been interrupted by the time that it passes through the apertures 53 of the

plates

49 and 50, it encounters an additional oil pocket 56 adjacent the lower end of the grid structure 4. This will cause an upward and a downward flow of oil along the path of movement of the moving contact 26 to further intensify the extinction of relatively low-amperage arcs. By the time that the moving contact 26 has cleared the lower opening 62b of the lower venting plug 62, are extinction has definitely occurred, and further downward opening movement provides a plurality of isolating gaps in the circuit, as shown by the chain lines 40 in FIG. 1.

During the closing operation, the operating mechanism linkage causes upward closing travel of the

lift rods

12A, 12B and 12C. This causes corresponding upward movement of the conducting cross-arms 11A, 11B and 11C, thereby causing the several moving contacts 26 to come into closed contacting engagement with the stationary contact structures 24, thus completing the circuit through the interrupting device 1.

From the foregoing description, it will be apparent that there has been provided a novel oil-break grid interrupting structure 4 incorporating configured grid elements of unique shape, and providing a highly efficient extinguishing function. As a result, the dimensions have been reduced, and the three pole-units A, B and C may be disposed within a single tank structure 2, with the venting

channels

41, 42 directed radially outwardly within the tank 4 to prevent comingling of the arc gases thereby preventing interphase flashover.

Although there has been illustrated and described a specific structure, it is to be clearly understood that the same was 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.

We claim as our invention: 1

l. A liquid-break type of circuit interrupter including a tank structure, a grid unit having a relatively stationary contact disposed adjacent its upper end, a terminal bushing extending into said tank structure and supporting said grid unit adjacent its lower end, liquid disposed in said tank structure and submerging said grid unit, plate structure disposed interiorly within said grid structure, a funnel-shaped molded plug member of resinous material located at the lower end of said grid unit and having a reentrant wall portion to define a liquid pocket and a central opening therethrough, and a rod-shaped movable contact movable through said central opening into engagement with said relatively stationary contact during the closing operation.

2. The combination of claim 1, wherein the grid unit comprises a tube having a lower inclined supported shelf portion, and the funnel-shaped molded plug member having a radially outwardly extending beveled portion seating on the aforesaid shelf portion.

3. The combination according to claim 1, wherein the funnel-shaped molded plug member is formed of a thermoplastic resinous material.

4. The combination of claim 3, wherein the thermoplastic resinous material is a high molecular weight polyoxymethylene material.

5. In a liquid-break type of circuit interrupter, in combination, a tank structure having a terminal bushing having a terminal stud passing therethrough and extending into said tank structure, a contact foot secured to the lower end of the terminal stud, a stationary contact housing secured to the lower side of the contact foot, an insulating interrupter shell secured to the stationary contact housing, a plurality of separate insulating elements nested within the insulating interrupter shell, at least one of the elements providing a lateral venting channel extending laterally out an opening in the sidewall of said shell, and the same cross-sectional venting area existing throughout the venting channel.

6. The combination according to claim 5, wherein two molded elements provide venting channels extending out of the insulating shell, a splitter plate extending between said elements, and the same cross-sectional venting area existing throughout the venting channels provided by said venting elements.

7. The combination of claim 1, wherein resilient ringshaped means compresses the plate structure during assembly.

8. The combination of claim 7, wherein the resilient ringshaped means comprises one or more washer plates comprising neoprene material.

9. The combination of claim 1, wherein the plate structure comprises one or more molded members having integrally molded generally U-shaped vent-forming portions which extend out a-hole in an enclosing tube structure.

10. The combination of claim 9, wherein two such members are provided with a splitter plate disposed therebetween.

11. The combination of claim 9 wherein the cross-sectional area of the venting channels is constant.

12. The combination of claim 10, wherein the cross-sectional area of the two venting channels is constant.

13. An oil grid unit comprising an outer tube having an opening through the sidewall thereof, spaced vent-forming molded members of thermoplastic material having generally U-shaped venting portions, an intervening splitter plate disposed between said molded members and extending through said hole, means for establishing an arc within sai grid unit, whereby the oil and gas is ejected out of the two venting channels, and the cross-sectional area of the venting channels being constant.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREC'HON Patent No. 3,6 l6,296 Dated 29 February 1972 Inv entor(s) Robert L. Hess and Gerald D. Simmers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[72] should read "Robert L. Hess, E. McKeesport; Gerald D.

simmers Greensburg, both of Pa."

Signed and sealed this 9th. day of January 1973* (SEAL) Attest:

I EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM powso uscoMM-oc scan-Pee i 11,5. GOVERNMENT PRINTING OFFICE: IOII 0-800-"1 DNl'lED STATES PArENr ormbs QETEFEQATE F @EQTKN Patent No. 3,6 46 ,296 Dated 29 February 1972 Inventor(s) Robert L. Hess and Gerald D. Simmers It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[72] should read "Robert L. Hess, E. McKeesport; Gerald D.

simmers, Greensburg, both of Pa."

Signed and sealed this 9th day of January 1973 (SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM P0-1050 uscoMM-oc 6037u-pe9 U,S. GOVERNMENT PRINTING OFFICE I019 O-JOi-SSl

Claims

1. A liquid-break type of circuit interrupter including a tank structure, a grid unit having a relatively stationary contact disposed adjacent its upper end, a terminal bushing extending into said tank structure and supporting said grid unit adjacent its lower end, liquid disposed in said tank structure and submerging said grid unit, plate structure disposed interiorly within said grid structure, a funnel-shaped molded plug member of resinous material located at the lower end of said grid unit and having a reentrant wall portion to define a liquid pocket and a central opening therethrough, and a rod-shaped movable contact movable through said central opening into engagement with said relatively stationary contact during the closinG operation.

7. The combination of claim 1, wherein resilient ring-shaped means compresses the plate structure during assembly.

8. The combination of claim 7, wherein the resilient ring-shaped means comprises one or more washer plates comprising neoprene material.

9. The combination of claim 1, wherein the plate structure comprises one or more molded members having integrally molded generally U-shaped vent-forming portions which extend out a hole in an enclosing tube structure.

13. An oil grid unit comprising an outer tube having an opening through the sidewall thereof, spaced vent-forming molded members of thermoplastic material having generally U-shaped venting portions, an intervening splitter plate disposed between said molded members and extending through said hole, means for establishing an arc within said grid unit, whereby the oil and gas is ejected out of the two venting channels, and the cross-sectional area of the venting channels being constant.