US3021409A - Circuit interrupter - Google Patents

Description

Feb. 13, 1962 J. D. COBINE ETAL 3,021,409

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United States Patent 3,021,409 CIRCUIT INTERRUPTER James D. Cobine, Rexford, and Newcll C. Cook, Schenectady, N.Y., assignors to General Electric Company, a corporation of New York Filed Sept. 24, 1959, Ser. No. 842,011

Claims. (Cl. 200-149) Our invention relates to an improved circuit interrupter.v While not limited thereto, the present invention relates particularly to surge voltage protectors for alternating current distribution systems and gas type circuit breakers or interrupters for such systems.

In surge voltage protectors for alternating current sysor interrupter poses a similar operational problem. Here the average circuit opening operation involves separation of the electrode contact faces while current is flowing, and hence, the creation of an arc. The are is frequently maintained for a very considerable portion of the alternating current half-cycle. It is usually not possible-and indeed it is frequently undesirableto interrupt the arc prior to the next occurring current zero. However, when the instantaneous current does reach a zero (whether the first following electrode separation or some subsequent zero), it is important to assure positively that the are is not restruck when the voltage recovers.

In accord with the present invention, the unusual volt age recovery properties of silicon. tetrafluoride and the characteristics of metal silica-fluoride double salts are utilized to provide highly effective surge voltage protector and gas circuit breaker or interrupter operation. The silicon tetrafluoride gas is characterized by a very rapid recovery of dielectric strength following arcing. While the arc exists, the gas provides conduction carriers for the electric current. However, when the arc. current flow goes to zero, this gas very abruptly loses its conducting capabilities and very quickly forms a medium of relatively high dielectric strength. In an actual surge voltage protector or circuit breaker constructed in accord with the present invention, the effective length of the are through the silicon tetrafluoride gas is madeof sufficient length to define a rate of electric strength recovery exceeding the rate of recovery of system voltage. This assures that the arc is not restruck. I

Further in accord with the present invention, the silicon tetrafluoride gas is formed by the action of the arc itself upon a non-conducting metal silico-fiuoride located within the zone of thermal influence of the arc. The required silicon tetrafluoride gas is thus formed by the play of the are upon the metal silica-fluoride, this action serving to decompose the metal silico-fluoride into the silicon tetrafluoride. The particular metal silico-fluoride may be any one of a variety of metals. For commercial and other reasons cuprous silico-fluoride (CuSiF is preferred. The silico-fluoride may be located on or be a part of the arcing surfaces of the electrodes, it may be a separate body within the zone of influence of the are, it may be a component of the glaze used on an insulator over which the arc plays, or it may be otherwise located to respond to the arc by the production of silicon tetrafluoride.

3,021,409 Patented Feb. 13, 1962 In accord witha specific embodiment of the present invention, the interrupter is defined by electrodes located within a substantially enclosed chamber. If desired, the chamber can be completely enclosed and filled with a gas providing a particularly high normal dielectric strength. Alternatively, the enclosure may be incomplete and air may be used as the initial gas. In either event, the silicon tetrafluoride formed by the arc remains generally in they chamber after arc extinction. Over a subsequent period of time it recombines with the residual metal fluoride formed when the silicon tetratluoride is generated. In substantial measure the metal silico-fluoride is thereby regenerated and the unit conditioned for further operations. In one embodiment of this form of the structure, the electrodes themselves are a repository of metal silicofluorides so that the reformed metal silico-fluoride is on the electrodes .and is necessarily physically located so as to be subject to the influence of the arc, and hence become the source of silicon tetrafluoride for further interruptions. I It is, therefore, an object of the present invention to provide an improved circuit interrupter utilizing the usual properties of silicon tetrafluoride.

A further object of the present invention is to provide a circuit interrupter using silicon tetrafluoride and in which the current interrupted generates the required silicon tetrafluoride gas.

Another object of the present inventionis to provide a circuit interrupter using silicon tetrafluoride gas in which it is unnecessary to surround the arc-electrodes with silicon tetrafluoride gas ina gas-tight chamber.

Still another object of the presentinvention is to provide an improved circuit interrupter in which a metal vide a circuit interrupter especially suitable for use as a surge voltage protector where, ceramic insulating surfaces such as insulator. strings are subjected to the thermal influence of thearc.

Yet another object of the present invention is to provide a circuit interrupter especially suitable for use with I an air or other gas circuit breaker in which the arc initially formed between separating contacts is propelled against arc-quenching surfaces.

, The novel features which we believe to be characteristic of our invention are set forth with particularity in the appended claims. Our invention itself, however, both i understood by reference to the following description taken in connection with theaccompanying drawings, in which: FIG. 1 is a diagrammatic view of a circuit interrupter ofthe expulsion type constructed in accordance with the present invention;

FIG. 2 is an alternative embodiment of the circuit interrupter of FIG. 1; I I

FIG. 3 is a view of an insulator string with arcing 'rings defining a surge voltage protector in accordance with the present invention; and I I FIG. 4 is a cross-sectional view of an enclosed surge voltage protector constructed in accordance with the present invention.

Referring now to FIG. 1, there is shown in a. somewhat diagrammatic view a circuit interrupter of the gas type. In the form shown, the interrupter is of the airbreak expulsion type. In this type of interrupter, the

,arc is drawn into a narrow channel or "tube composed and is connected by lug 4 to one conductor 5 of the connected electric system. The other electrode 2 is in the form of a finger. it is also of a suitable conducting material such as copper. Electrode 2 at its end 2a is rounded to be received in the mating cup-like recess in of the upper electrode 1 to form an effective current conducting path.

The electrode 2 is movably supported by suitable means (not shown). it is connected to a conductor 6 of the connected electrode system by the connector 7, which may be of any suitable form not interfering with the up and down movement of the electrode 2. In a typical application of an interrupter of this form, the conductors 5 and 6, together with the electrodes 1 and 2, may be in series with an electric system load. In such application, the actuating mechanism (which may include a fusible element) pulls the conductor 2 from the contactmaking to the contact-breaking position of FIG. 1 in response to excessive load current.

As shown in HS. 1, the sleeve 3 is embedded in and protrudes from the upper electrode 1. This sleeve has a longitudinal bore 8 which receives the movable electrode 2 with a small annular clearance space. Normally, this sleeve is made of a material that generates copious quantities of gas under the influence of an are drawn as the electrode 2 is brought down out of contact with the electrode 1. This gas tends to serve as a coolant and to aid in quenching the arc.

in accordance with the form of the present-invention shown in PEG. 1, the sleeve 3 has at least its inside surface including a silico-fluoride material. That is, a material that contains a metallic silico-fiuoride. Such material may, for example, be incorporated in the mate rial from which the entire sleeve 3 is made. Alternatively, it may be incorporated in a resin paint or coating that is applied to the inside surface of the sleeve and subsequently hat-dens. In still another construction, the sleeve 3 may be of ceramic material and the inner bore 8 coated with a glaze containing silico-fiuon'de material.

Many metal silico-fiuoride double salts may be used as the silicofiuoride material. Cuprous silico-fiuoride (CuSiF is especially useful because it has a favorable ionizing potential and is commercially available at a reasonable price. Other suitable materials include calcium silico-fluoride (CaSiF barium silico-fluoride (BaSiF sodium silico-fluoride (Na SiF ammonium silico-lluoride ((NHQ SiF and lead silico-fluoride (PbSiF These and other metal silico-fiuoride double salts have the characteristic of decomposing under the influence of the electric arc. The decomposition products include silicon tetrafluoride (Silk), a gas under the conditions of the arc.

Like all the other gases in the are, the silicon tetrailuoride ionizes and thus provides conduction carriers for the current. However, this gas has the unusual characteristic of providing a very rapid dielectric recovery voltage upon arc inten'uption. In an exceedingly short time after arc quench, a space containing a substantial quantity of silicon tetrafluoride deionizes and defines a space of substantial dielectric strength. An apparatus such as that of FIG. 1 thereby is capable of withstanding a very rapidly increasing applied voltage following are extinction and may be applied to an electric system with a rapid voltage recovery following a current interruption.

'FIG. 2 shows an alternative form of the structure of FIG. 1. In this form the upper electrode 1 is impregnated with a silico-fluoride material. Since the arc plays upon the electrode surface, this material decomposes to generate silicon tetrafluoride in the same fashion above described with reference to sleeve 3. If desired, the movable electrode 2 could be so impregnated in lieu of or in addition to electrode 1. It is preferred that at least electrade 1 be so impregnated so that the silicon tetrafluoride gas evolved will tend to sweep over the space of the are before discharging into the atmosphere.

FIG. 3 shows a transmission line conductor 9 carried by support arm 10 through the insulator string and surge voltage protector 11. The insulator string is made up of a group of connected insulators of the conventional porcelain type capable of sustaining the weight of the conductor 9. These are glazed with a material containing a silico-fluoride double salt, such as cuprous silicofiuoride. The arcing rings 13 are provided to form points of comparatively high electric field gradient between which the arc is initially struck in the event of an overvoltage on the line conductor 9.

In the event of an are between the arcing rings 13, FIG. 3, the are quickly envelops the insulators 12 and plays upon them. Silicon tetrafluoride evolves from the glaze on the insulators 12 under this action of the arc. The arcing space is thus occupied by silicon tetrafiuoride gas and rapidly recovers its dielectric strength when the surge voltage disappears and the current zero takes place.

FIG. 4 shows still another embodiment of the present invention as applied to a surge voltage protector. In this instance, a pair of electrodes 15 are located in spaced relationship in the envelope l4 and have hook portions 16 outside the envelope for attachment to the circuit terminals to be protected. The envelope 14 is of any suitable insulating material defining a closed space. Either the electrodes 15 or some other portion of the unit subjected to the influence of the arc is impregnated or coated with a metal silico-fiuoride double salt, such as cuprous silico-fiuoride. In the event or" a voltage surge, arcing takes place between electrodes 15, the metal silico-fluoride decomposes to form silicon tetrafiuoride, and when the current is ultimately interrupted the silicon tetrafiuoride defines a space of rapid dielectric strength recovery to withstand the system recovery voltage applied between the electrodes.

The closed device of FIG. 4 is essentially completely self-regenerating When the arc is interrupted, the silicon tetrafiuoride in the container envelope begins a process of reuniting with whatever metal it contacts. In a structure similar to FIG. 4, where essentially all of the exposed metal is also subjected to the are, essentially all the resulting metal silieo-fiuoride double salt becomes available to generate silicon fluoride upon the next arc interruption. This regenerative feature is provided to a substantial degree in structures like those of FIGS. 1 and 2, where a substantial quantity of the silicon tetratluoride recombines with exposed residual electrode materials. It is most effectively obtained, however, in a completely closed system such as that of FIG. 4.

While silicon tetrafiuoride provides a rapid dielectric strength recovery, the ultimate dielectric strength of this gas is of the same order of magnitude as air. In a closed device such as that of FIG. 4, the ultimate dielectric strength of this gas is of the same order of magnitude as air. In a closed device such as that of FIG. 4, the ultimate dielectric strength can be somewhat increased by incorporating a gas of greater dielectric strength. One such gas is sulfur hexafluoride (SP With a gas of the type in the envelope 14, the normal breakdown strength of the protector is determined by the dielectric strength of this gas and the rate of dielectric strength recovery following are interruption is determined largely by the action of the silicon tetrafluoride.

If desired, the envelope 14 of FIG. 4 may be provided with a vent to prevent excessive pressure buildup. Some silicon tetrafiuoride will tend to escape through such vent, but to a considerable degree the self-regenerating feature of the structure of FIG. 4 is retained.

in any of the devices made in accordance with the present invention it is necessary that the quantity of silicon tetrafiuoride evolved to be suflicient in relation to the arcing space to provide the necessary dielectric strength. That is, when the arc is interrupted, the silicon It will be noted that in each of the devices here shown and described a pair of spaced electrode faces are provided between which an arc extends prior to interruption. The metal silico-fiuoride is located on someportion of the mechanism exposed to the action of the arc. As shown by the respective embodiments, the location of the silicofluoride material maybe varied as desired so long as it is acted upon by the are.

While we have shown and described particular er'nbodi-i ments of the present invention it will, of course, be understood that various modifications and alternative constructions may be made without departing from its true spirit and scope. The invention may, for example, be applied to fuses for high voltage interruption, air circuit breakers where the arc is magnetically or otherwise driven onto deionizing means such as arc-chutes and the like (which may include a non-conducting metallic silico-fiuoride double salt to generate silicon tetrafiuoride) and in other similar applications. We therefore intend by the appended claims to cover all such modifications and alternative constructions as fall within their true spirit and scope. a

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

4. A surge voltage protector comprising in combination: a pair of spaced electrodes with arcing faces defining an arc-space to be spanned by an arc prior to inter-.

ruption; and means locatedwithin' the zone of thermal influence of the arc and including a metal siltco-fiuoride material which when exposed to arc current fiow generates silicon tetrailuoride gas that momentarily occupies the arc-space to provide a mediumof rapid dielectric strength 7 recovery upon arc extinction, I V 5. A surge voltage protector comprising in combination: a pair of spaced electrodes defining an arc-space between which an arc is'struck upon application of predetermined surge voitage; and means located within the zone of thermal influence of the arc and including a metal silico-fiuoride material which when exposed to are current flow generates silicon tetrafluoride gas that momentarily occupies the arc-space to provide a medium of determined surge voltage; and insulating means sustain- 1. A circuit interrupter comprising'in combination: means defining a substantially enclosed chamber; a pair of spaced electrodes within the chamber defining an arcthat momentarily occupies said arc-space to provide a medium of rapid dielectric strength recovery upon arc extinction, the gas further recombining with residual material within the chamber over a period of time to regenerate metal silico-fluoride and to condition the interrupter for future interruptions.

2. A circuit interrupter comprising in combination: means defining a substantially enclosed chamber; and a pair of spaced electrodes within the chamber defining an arc-space to be spanned by an arc prior to interruption, at least one of the electrodes defining an arcing surface and containing a metal silico-fiuoride which upon heating by said arc generates silicon tetrafiuoride gas that momentarily occupies the arc-space to provide a medium of rapid dielectric strength recovery upon arc extinction, the gas further recombining with the residual electrode material over a period of time to regenerate metal silicofluoride and to condition theinterrupter for future interruptions. 3. A circuit interrupter comprising in combination:

ing the electrodes in spaced relation and located within the Zone of thermal influence of the arc, said insulating means including surfaces having a metal silico-fiuoride material which when heated by arc current flow generates recovery upon arc extinction. I

- 7. A current interrupter comprising in combination: a pair ofspaced electrodeswith.arcingfaces defining an arc-space to be spanned by an arc prior to interruption,

at least one of the arcing faces including a metal silicofluoride material which when heated by arc current flow generates silicontetrafiuoride gas that momentarily occupies the arc-space to provide a medium of rapid dielectric strength recovery upon arc extinction.

8. A circuit interrupter comprisingin combination: a

first means defining an electrode face; a second means defining an electrode face;-and third means supporting tion, at least one of said means having portions exposed means defining a substantially enclosed chamber; means including a pair of spaced electrodes with arcing faces defining an arc-space to be occupied by anarc prior to 1 interruption, said means defining substantially the only exposed metal in the chamber and having at least a region adjacent one face comprising a metal silico-fluoride material which upon heating by said are generates silicon to regenerate metal silico-fluoride and to condition the interrupter for future interruption.

to the action of the arc andincluding a metal silicofluoride. V 9. A circuit interrupter comprising in combination: a firstmeans defining an electrode faceya second means defining an electrode face; and third means supporting said first and second means in spaced relationto define an arc-space to be occupied by an arc prior to interrup- 'tion, at least one of said meansdefining portions containing cuprous silico-fiuoride and exposed to the action of the are.

10. A circuit interrupter comprising in combination: a

first means defining an electrode face; a second means defining an electrode face; and third means supporting said first and second meansin spaced relation to define an arc-space to be occupied by an arc prior to interrup tion, at least one of said means including portions glazed with a material including a metal silico-fluoride' andexposed to the action of the arc.

References Cited in the tile of this patent UNITED STATES PATENTS 2,279,040 Grosse Apr. 7, 1942 2,352,984 Walle July 4, 1944 2,596,967 Frost May 20, 1952 2,832,669 Allen Apr. 29, 1958

Claims (1)

1. A CIRCUIT INTERUPTER COMPRISING IN COMBINATION: MEANS DEFINING A SUBSTANTIALLY ENCLOSED CHAMBER; A PAIR OF SPACED ELECTRODES WITHIN THE CHAMBER DEFINING AN ARCSPACE TO BE SPANNED BY AN ARC PRIOR TO INTERUPTION; AND

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