US2965736A - Circuit interrupters - Google Patents

Description

Dec. 20, 1960 T. E. BROWNE, JR., ETAL CIRCUIT INTERRUPTERS 2 Sheets-Sheet 1 Original Filed Dec. 24. 1954 Fig. l.

o e a i Deg. 20, 1960 T. E. BROWNE, JR, ETAL 2,955,736

CIRCUIT INTERRUPTERS Original Filed Dec. 24, 1954 2 Sheets-Sheet 2 Fig.4.

24 n 4 24 26 26 I 5 o d 5 o a I Q Q 0 2s United States Patent CIRCUIT INTERRUPTERS Thomas E. Browne, Jr., and Albert P. Strom, Forest Hills, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvama Original application Dec. 24, 1954, Ser. No. 477,466,

now Patent No. 2,924,690, dated Feb. 9, 1960. Divided and this application Sept. 27, 1957, Ser. No. 686,775

5 Claims. (Cl. 200-148) This invention relates to circuit interrupters in general, and, more particularly to arc-extinguishing structures therefor.

This application is a division of our parent application filed December 24, 1954, Serial No. 477,466, now Patent No. 2,924,690, issued February 9, 1960, and assigned to the assignee of the instant application.

A general object of our invention is to provide an improved and highly effective circuit interrupter, which will interrupt the circuit therethrough more eifectively than have circuit interrupters heretofore.

A more specific object of our invention is to provide an improved circuit interrupter, particularly one of the gasblast type, in which advantage is taken of the grounded metallic tank structure generally employed in the highvoltage, oil-circuit-interrupter art.

Another object of our invention is to take advantage of the unusual and phenomenal dielectric properties, and arc-extinguishing characteristics, of sulfur hexafiuoride or selenium hexafluoride, particularly when these gases are utilized in conjunction with a grounded metallic tank structure.

Another object of the invention is to provide an improved circuit interrupter including a pair of arc-extinguishing units disposed at the interior ends of a pair of terminal bushings extending into a surrounding tank structure, in which each arc-extinguishing unit includes a piston structure carrying a movable contact and biased in the opening direction to force fluid toward the established arc.

Another object of the invention is to provide an improved circuit interrupter of the type set out in the immediately preceding paragraph, in which the conducting cross-bar, electrically interconnecting the arc-extinguishing units, also serves to charge the biasing means during the closing operation.

Another object is to provide a circuit interrupter of the foregoing type in which the conducting cross-bar, in conjunction with other structure, eflects downward opening movement of a piston structure, the latter carrying the movable contact therewith.

Another object is to provide an improved circuit interrupter of the foregoing type in which the conducting crossbar mechanically latches to the two movable contacts, and subsequently separates therefrom in the fully open-circuit position of the interrupter.

An ancillary object of our invention is to adapt sulfur hexafluoride or selenium hexafluoride gas to tanktype, grounded, metallic structures, in which preferably the gas is maintained at atmospheric, or higher pressures, within the tank to take advantage of its dielectric strength.

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

Figure 1 is a side elevational view, partially in vertical section, of a tank-type circuit interrupter embodying the principles of our invention, and shown in the closedcircuit position;

Fig. 2 is a fragmentary, enlarged, vertical sectional view through one of the arc-extinguishing units of the circuit interrupter of Fig. 1, the contact structure being shown in the closed-circuit position;

Fig. 3 is an enlarged, vertical sectional view through a modified type of arc-extinguishing unit, which may be substituted for the units illustrated in Figs. 1 and 2, the contact structure being shown in the closed-circuit position; and,

Fig. 4 is another modified type of arc-extinguishing unit, which may be substituted for the units of Figs. 2 and 3, the contact structure being shown at an intermediate point in the opening operation.

In the United States Patent No. 2,757,261, issued July 31, 1956, to Harry J. Lingal, Thomas E. Browne, Jr. and Albert P. Strom, and assigned to the assignee of the instant application, the remarkable arc-extinguishing characteristics of sulfur hexafluoride gas are described. It is known that this gas has a dielectric strength equal to that of insulating oil at slightly elevated pressure (2.5 to 3 atmospheres absolute) and so it may be directly substituted for oil as an insulating medium in circuit breakers, and the like, if it can be maintained at the elevated pressure. We have discovered the fact, demonstrated in experimental studies, that SP gas at moderate pressures may be employed in fluid-flow type circuit interrupting devices similar to those ordinarily filled with oil with comparable effect. It has been shown particularly that in such devices which cause a definite volume of fluid to flow through a channel surrounding the arcing contacts, effective interrupting performance can be obtained with a total displaced volume of SR, gas no larger than the volumes of oil ordinarily displaced.

The use of SE, gas instead of oil in structures resembling those used with oil offers many advantages:

1) The gas medium is non-infiammable, and hence eliminates the explosion and fire hazard.

(2) Its lower density reduces the forces required to move it, and so can aid in achieving highest possible operating speeds.

(3) compressibility of the gas serves to cushion the pressure shocks produced by the sudden drawing of highcurrent arcs in a confined fluid. The control of these explosive pressures in structures filled with nearly incompressible oil is a critical problem in the development of circuit breakers for the highest powers.

(4) The use of steel tanks fitted with high-voltage bushings, the common practice with oil circuit breakers, offers many practical advantages for a gas-illed breaker also. The use of SP under a few atmospheres pressure, promises to permit the retention of these practical advantages, especially (a) the availability of inexpensive bushing-type current transformers as a part of the breaker, (b) the dead-tank feature increasing safety against electrical hazards, and (c) the mechanical ruggedness and resistance to explosion of steel containers, which also serve as supporting structures.

(5) If desired, the tanks for SP may be made smaller than for oil by using sufficiently elevated gas pressures to achieve dielectric strengths higher than that of oil.

(6) Energy for producing fluid flow, contact motion, or both, can be stored in the contained gas by virtue of its compression, eliminating the necessity for large springs in the breaker mechanism.

(7) Decomposition products caused by arcing do not include carbon and are all good electrical insulators. The chemical activity of the gaseous products, and the inertness of the SP makes possible absorption of these gaseous products simply by providing some inert solid materials (e.g., activated alumina) within the enclosure 3 in contact with the gas. This should make possible longer periods of use of the breaker before the necessity for replacing or reconditioning the interrupting medium, or cleaning internal insulating surfaces.

(8) For the same amount of arcing, erosion of the contact surfaces should be less with a gas than with a liquid filling. This is especially true for capacitor switching, where contact erosion under oil is a serious problem.

To make most effective use of the gaseous medium, certain modifications of interrupting structures generally used under oil are needed. We have found that contact between the arc and organic materials should be avoided, as pointed out in the aforesaid patent. Hence, such are controlling parts as orifices, splitters and the inner walls of arc boxes should be made of inorganic insulating materials like polytetrafiuoroethylene. For conducting parts, aluminum may be preferable to copper or brass. Because of the high mobility or wandering tendency exhibited by arcs in this gas, the arc space may need to be more definitely restricted than is necessary with oil filling.

Figures 1 through 4 illustrate interrupter designs which embody the above principles, and so are particularly suited to use in metal-enclosed circuit breakers, filled with SP or SeF gas at atmospheric, or higher pressures.

A relatively simple form of tank-enclosed SP or SeF flow interrupter is illustrated in Figs. 1 and 2 of the drawings. Referring to these figures, it will be observed that a grounded, metallic tank 1 is filled with sulfur hexafluoride or selenium hexafiuoride gas at atmospheric or higher pressures, and has extending within it a pair of sealed terminal bushings 2, 3 of the type generally used in the oil-circuit-breaker art. Depending from the interior ends of the terminal bushings 2, 3 are a pair of serially connected arc-extinguishing units, generally designated by the reference numeral 4, and electrically interconnected by a conducting crossbar 5. The conducting cross-bar may be vertically actuated, in the opening and closing movements, by an insulating lift rod '7, which may be operated by a suitable mechanism. As shown, the interrupting units 4 are mounted on the lower ends of the bushings 2, 3 projecting into the enclosed tank 1, and the circuit is completed by the conducting cross-bar 5 movable by the insulating lift rod 7 operated by a mechanism, exactly as is commonly done in oil-circuit-breaker practice, except that the tank 1 must be sealed against gas leakage at the bushing and mechanism entry points. The gas sealed withln the tank 1 may be at atmospheric pressure, but preferably it should be compressed to at least two or three atmospheres absolute pressure.

The interrupter, as shown, is of the puffer type, having a movable orifice 8 and piston 9 movable within an insulating operating cylinder 10. A movable contact 11 cooperates with a stationary contact 12 and is preferably moved downwardly, in the opening direction, by a battery of compression springs 13. The compression springs 13 seat at their upper ends against the bottom 14 of the operating cylinder 10, and have their lower seats on a spring base 15, threadedly secured to the movable contact rod 16.

The extremity 17 of the cross-bar 5 strikes the contact or piston rod 16, and moves it upwardly to the closed-circuit position as shown, against the opposition afforded by the battery of compression springs 13. During the opening operation, the lift rod 7 moves downwardly, as caused by the operating mechanism (not shown), and permits the compression springs 13 to extend, driving the contact or piston rod 16 downwardly. The moving piston rod 16 carries with it the movable piston 9 and the orifice 3, compressing the gas within the region 18 below the piston 9 and causing the gas to flow upwardly through the orifice 19.

Vents 20 are provided at the upper end of the extinguishing unit 4 for permitting the heated gas to expand if necessary to the region within the tank 1.

The interrupter 4 has been demonstrated in the laboratory to have remarkable interrupting performance. With an orifice diameter of only inch, it has successfully interrupted low-power-factor currents up to 3100 amperes at 90,000 volts single phase with SP gas at a pressure of 15 p.s.i. gauge. For application to a circuit breaker having larger interrupting ratings, the orifice diameter 19 would be increased, possibly to two inches, and the piston diameter to about 10 inches. It is apparent in Figs. 1 and 2 that the moving contact 11 is held closed by the cross-bar 5, and the compression springs 13 serve to move the contact 11 and piston 9 to the open position when the cross bar is released. Further additional motionof the cross-bar 5 beyond the limit of the piston stroke provides an additional isolating break, as shown by the dotted lines 22 in Fig. 1. i

To effect closing of the interrupter, the interrupter mechanism moves the insulating lift rod 7 upwardly, compressing the springs 13 and effecting contact engagement between the cooperating stationary and movable contacts 12 and 11 respectively. To reduce the shock incurred by the piston 9 at the end of its opening stroke, a cushion 21 may be provided, formed of any suitable resilient material.

Fig. 3 is an enlarged vertical section view taken through a modified type of arc-extinguishing unit 23, which may be substituted for the unit 4 of Figs. 1 and 2. It will be noted that the interrupting unit 23 is not provided with compression springs, as was the case with the unit of Fig. 2. Instead, as shown in Fig. 3, the contact-carrying piston 9 is pulled to the open position by the cross-bar 5 through latches 24, which are released by earns 25 at the end of the piston stroke, permitting the cross-bar 5 to move down farther and so to provide an isolating break.

The earns 25 are provided by means of downwardly extending insulating strips 26, which are fastened by screws 27 to the bottom 14 of the insulating operating cylinder 10. The latches 24 are biased by a compression spring 23 so that the rollers 29 will maintain engagement with the cam surfaces 25.

During the closing operation, the conducting cross-bar 5 moves upwardly, as effected by the operating mechanism. The noses 30 of the latches 24 reengage the notches 31 provided at the lower end of the contact rod 16a, and the crossbar 5 forces the piston and contact assembly 9 upwardly effecting reengagement between the movable and stationary contacts 11, 12, as shown in Fig. 3. Again a cushion 21 may be provided to limit any shock occurring at the extreme end of the piston opening movement.

Fig. 4 shows an arrangement, which is generally similar to that illustrated in Fig. 3, but incorporates a compression spring 32, which serves to retrieve or retract the piston 9 following release of the latches 24 by the cams 25.

Fig. 4 illustrates the position of the several parts when the releasing action has just taken place and prior to the return movement of the piston 9. Thus, the compression spring 32, disposed within the insulating cylinder 10, returns the moving contact rod 16a and piston 9 to the closed position, after release of the latches 24. This increases the isolating break distance for the same crossbar stroke, and causes final closure of the circuit to occur, upon closing the breaker, at the isolating break outside of the interrupting unit, generally designated by the reference numeral 33.

From the foregoing description of several arc extinguishing units, it will be apparent that we have disclosed gas flow interrupting devices especially suitable for effective operation within a container filled with sulfur hexafiuoride or selenium hexafluoride gas at a moderately elevated pressure. In the forms illustrated in Figs. 14 of the drawings, the operation resulted in no loss of the gas, which experience has shown may be used Without replacement for a large number of interruptions.

The circuit interrupters of our invention are particularly adapted to use at least one gas selected from the group consisting of sulfur hexafluoride and selenium hexafluoride, or admixed with at least one of the group consisting of helium, carbon dioxide, air, nitrogen and argon.

The use of selenium hexafluoride as an arc-extinguishing medium is described and claimed in United States Patent 2,733,316, issued January 31, 1956, to Thomas E. Browne, Jr., Albert P. Strom and Harvey E. Spindle, and assigned to the assignee of the instant application.

Although we have described the interrupters as being particularly suitable for use with sulfur hexafluoride gas or selenium hexafluoride gas in a tank structure, it will be noted that certain features of the invention may be applicable to interrupters operating with gases other than sulfur hexafiuoride gas or selenium hexafluoride gas. We do not, therefore, intend to limit our invention solely to the use of sulfur hexafluoride gas or selenium hexafluoride gas or mixtures containing these gases, since other gases may be substituted therefor with advantage, and use may be made of certain features of the invention in connection therewith.

Although we have shown 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.

We claim as our invention:

1. The combination in a circuit interrupter of a gasfilled grounded tank having a pair of terminal bushings extending therein, an arc extinguishing unit disposed adjacent the interior end of each terminal bushing and having a pair of separable contacts associated therewith, means including said separable contacts for establishing an are within each arc-extinguishing unit, an orificed piston carrying one of said separable contacts for at least one of the units for moving gas and for effecting contact separation, a conducting cross-bar for electrically interconnecting the units in the closed circuit position, means providing a releasable connection between the cross-bar and said orificed piston, and a retracting spring for the orificed piston for effecting engagement of said separable contacts in the fully open-circuit position of the interrupter.

2. In combination, a gas-filled tank having a pair of terminal bushings extending therein, an arc-extinguishing unit disposed adjacent the interior end of each terminal bushing, means for establishing an arc within each arcextinguishing unit, an orificed piston structure for at least one of the units carrying a movable contact, a conducting cross-bar for electrically interconnecting the units in the closed circuit position, means providing a releasable connection between the cross-bar and said piston structure, and a retracting spring biasing said movable contact towards its closed-circuit position.

3. The combination in a circuit interrupter of a gasfilled tank having a pair of terminal bushings extending therein, a pair of arc-extinguishing units secured to the interior ends of the terminal bushing, each unit including an operating cylinder, a piston device including a movable contact and orifice member movable within each operating cylinder, at relatively stationary contact cooperable with each movable contact within each unit, each piston device having a piston rod extension extending out of the operating cylinder, a conducting cross-bar electrically interconnecting the units in the closed circuit position and having latching means at each end thereof for latching for a predetermined time onto the piston rod extensions, and means releasing the latching means at a predetermined time in the opening operation.

4. The combination in a circuit interrupter of a gasfilled tank having a pair of terminal bushings extending therein, a pair of arc-extinguishing units secured to the interior ends of the terminal bushings, each unit including an operating cylinder, a piston device including a movable contact and orifice member movable within each operating cylinder, a relatively stationary contact cooperable witheach movable contact within each unit, each piston device having a piston rod extension extending out of the operating cylinder, a conducting cross-bar electrically interconnecting the units in the closed circuit position and having latching means at each end thereof for latching for a predetermined time onto the piston rod extensions, and cam means releasing the latching means at a predetermined time in the opening operation.

5. The combination in a circuit interrupter of a gasfilled tank having a pair of terminal bushings extending therein, a pair of arc-extinguishing units secured to the interior ends of the terminal bushings, each unit including an operating cylinder, a piston device including a movable contact and orifice member movable within each operating cylinder, a relatively stationary contact cooperable with each movable contact within each unit, each piston device having a piston rod extension extending out of the operating cylinder, a conducting cross-bar electrically interconnecting the units in the closed circuit position and having latching means at each end thereof for latching for a predetermined time onto the piston rod extensions, means releasing the latching means at a predetermined time in the opening operation, and a retrieving spring for each unit for effecting reclosure of the contacts following release of the latching means.

References Cited in the file of this patent UNITED STATES PATENTS 1,052,595 Lanphier Feb. 11, 1913 2,111,416 Balachowsky Mar. 15, 1938 2,442,010 Leeds et a1 May 25, 1948 2,459,599 Strom Jan. 18, 1949 2,780,699 Leeds Feb. 5, 1957 FOREIGN PATENTS 500,731 Great Britain Feb. 13, 1939 519,113 Great Britain Mar. 18, 1940 512,921 Belgium Aug. 14, 1952 147,682 Sweden Nov. 16, 1954

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