US2668255A - Expulsion type arrester - Google Patents

Description

Feb. 1954 H. o. STOELTING ET AL 2,668,255

EXPULSION TYPE ARRESTER Filed Oct. 8, 1951 Patented Feb. 2, 1954 EXPULSI-ON TYPE ARRESTER Herman 0. Stoelting, Milwaukee, and Clifiord W. Petersen, Wauwatosa, Wis assignors to McGraw Electric Company, Milwaukee, Wis., a corporation of Delaware Application October 8, 1951, Serial No. 250,232

4 Claims. 1

This invention relates to electrical discharge devices, and more particularly to lightning arresters of the expulsion type for use on electric power distribution systems.

Effective operation of an expulsion type lightning arrester depends upon the arresters ability to produce copious quantities of arc-extinguishing gases at a pressure sufiicient. for blocking follow current while concurrently providing a relatively cool and tie-ionizing atmosphere for quenching conductive arc-sustaining gases.

It is an object of the present invention to provide an expulsion type lightning arrestcr containing a novel expulsion chamber, wherein spark-over occurs at a relatively confined portion of the chamber and where subsequent arcing produces eiiective quantities of arc-extinguishing gases, which gases will concurrently block follow-current, and limit, cool and deionize arcs produced therein.

It is another object of this invention to pro- 'vide a lightning arrester containing a novel expulsion chamber, in which an insulating plug embodying arc-extinguishing material is positioned, said plug defining a passage which is relatively constricted at one end and tapering towards enlargement as it approaches an opposed electrode where de-ionized cool gases may be discharged to atmosphere.

A further object of this invention is to provide a lightning arrester containing a novel expulsion chamber in which is positioned a plug embodying arc-extinguishing material, said plug conjointly providing with the chamber walls a relatively constricted portion intermediate the ends of the chamber and an enlarged crosssectional area at either or both of its extremities to provide a convenient discharge passage for the cooling, tie-ionized gases created within said chamber.

Referring now to the drawings which accompany this specification;

Fig. 1 is a longitudinal view, partly in section, of the arrester, depicting the preferred embodiment.

Fig. 2 is a longitudinal sectional view, partly in diagram, of another embodiment of the inven tion.

Fig. 3 is a cross-sectional View taken on line 3-3 of Fig. 1.

Fig. 4 is a cross-sectional view taken on line 3-4 of Fig. 1.

Referring particularly to Fig. l, the preferred embodiment constitutes a housing of dielectric material-usually porcelain-having a chamber 2, which is nearly coextensive lengthwise with the housing being open at the lower end and enclosed at the upper end except for an aperture 3, which aperture accommodates a stud 4. The stud is electrically connected to a washer 5 to make contact with an elongated electrode memher 6 clamped to the lower end of the petticoat insulator I. The insulator l is anchored to the upper end of the stud 4, which is firmly embedded therein.

A line terminal 8 is fastened to the upper exremity of he insulator; l. and is adap d t ngage a conductor wire connecting with the power line that is to be protected. An electrode, 9 is secured to the upper end of the insulator making electrical contact with the terminal member 8, concurrently serving to hold this electrode member in operating position. An open sparkgap to is formed by the spacing between the free ends of both of the electrode members 6 and 9. Though an open spark-gap arrangement is preferable, it is. within the province of this invention to provide internal spark-gap electrodes (not shown). The spark-gap does not constitute a part of the present invention, but is necessary for isolating the novel expulsion tube from the line terminal 8, thereby preventing leakage currents from traveling to ground through the ex pulsion tube and associated parts. A gasket H may be provided as a clamping cushion between the insulator 1 and the housing member I to prevent chipping of the porcelain when the parts are drawn together.

The components shown assembled within the chamber 2 include a metal electrode plug 12. The plug 52 is threaded externally to engage with a complementary internally threaded tubular retainer member l 3 made of insulating material, preferably horn fiber. The tubular retainer member [3 is reinforced by a metal sleeve to surrounding that member, the upper end of which is preferably kept level with, or below the plane of the lower extremity of the plug I 2. The fiber tubular retainer member 13 is preferably extended above the plug !2 to provide a chamber 53a, which chamber provides a convenient means for increasing the flashover distance between the plug and the sleeve M, thereby confining the are within the novel expulsion tube hereinafter deiscribed, where it may be properly extinguished.

The lower end of the retainer member I3 is externally threaded to engage a flanged metallic fitting 15, which serves concurrently as a closure for the chamber 2, as a support for the novel arcextinguishing tube hereinafter described, and as a lower terminal member to which a ground wire (not shown) may be connected. A cushioning gasket 15 is provided between the retainer meniber la in the fitting i5.

The metallic fitting I5 is provided with a dis-.- charge passage H for releasing gases to the at! mosphere. A means is provided for connecting the arrester with ground, shown here as. a solders less c nnector in. the form of a bolt 18 enga in acomplementary threaded opening in the fittin 15-. A lower electrode member as CD11". currently serves to support the novel plug here,

inafter described and to provide an electrical contact with the fitting H5. The electrode l9 may be vented as shown by providing annularly spaced venting ports 20.

e The preferred embodiment of a novel expulsion type lightning arrested will be described with reference to Figs. 1, 3 and l. The bore of the novel tubular member 13 provides a convenient annular expulsion chamber 25 intermediate metallic arc contacts. A novel insulating plug 26, preferably of horn fiber, extends between the upper arc contact 21 and the lower arc contact 28. Both are contacts are preferably annular sleeves positioned on each end of the plug 26 making electrical contact with the electrode plug l2 the electrode member i9 respectively. The peripheral surface of the plug 26 preferably provides a press fit between the plug and the bore of the retainer member 53 between the top extremity of the plug and a predetermined point bearing the reference numeral 25a. The plug 28 is preferably tapered, as shown in Fig. 1, between this point and its lower end, defining the chamber 25 which flares towards the vented electrode member l9.

It will be apparent that a substantially equivalent means for providing a fiared expulsion chamber may be accomplished by maintaining a constant transverse cross-section throughout the entire length of the insulating plug 26 shown), and flaring the bore of the retainer member from the portion 26a downwardly (not shown). This structure may not be as favorable as the preferred structure shown in Figs. 1, 3,

and 4, inasmuch as additional mechanical supporting means would be required to withstand the internal gas pressure against the relatively thinner wall of the retainer member, especially at its lower end.

The preferred operates as follows: When a surge occurs on a power line, and is of high enough potential, it will simultaneously spark over the external gap l0 and the internal expulsion gap created between the upper and lower arc contacts 22 and 28 respectively, the lower arc contact 28 being electrically connected to ground through the electrode member i9 and the fitting i5.

It has been found that the initial spark-over tends to favor a tightly constricted path. This confined path is provided conjointly by the insulating plug 25 and a retainer member 13 at the portion defined by the upper extremity of the plug and the point referred to by the numeral 26a. Thus, no matter the magnitude of the arc, there will be created an effective amount of arc-extinguishing gases by subsequent arcing after initial spark over. That is; should the surge be of a relatively low magnitude, there will be created a relatively small amount of arcextinguishing gas. However, this relatively small amount will be sufficient to extinguish that particular arc. Accordingly, arcs of higher magnitude will create a relatively greater proportion of de-ionized gases on contact with the defining wall surfaces of the chamber 25 to effectively extinguish these larger arcs. The relatively distended portion of the annular chamber adjacent the lower arc contact 28 will permit these gases to be immediately cooled and discharged through the ports 28 of the electrode l9 and through the discharge passage ll to atmosphere.

-The relatively constricted portion between the upper extremity of the plug and the point 2a concurrently oifers a convenient means for effectively blocking any follow-current, as well as (not embodiment above described providing a convenient initial spark-over path. Under certain conditions, this follow-current may be initiated by the surge, and it will necessarily need to be extinguished in order that the arrester may be returned to its original operating condition. The power current, which is normally GO-cycle current, produces an are that tends to follow the path taken by the abnormal surge voltage that has sparked over the arrester electrodes, and will tend to be confined to the relatively constricted portion between the upper extremity of the plug 26 and the point 26a where the pressure built up will limit, cool, and rapidly extinguish this follow-current at first current zero. The preferred structure provided by this invention utilizes an expulsion gap that requires no intermediate electrodes, but operates to effectively block power follow-current and extinguish arcs produced by surge voltages of either low or high magnitudes. This is also true of other embodiments of this invention, which will be described hereinbelow.

Another embodiment will be described with reference to Fig. 2, and includes an insulating tubular retainer member 3! The retainer member is preferably internally threaded at both ends to accommodate externally threaded electrode members 3| and 32. As shown diagrammatically in Fig. 2, the upper electrode member 3| is electrically connected to an open sparkgap 33, which in turn is connected with the power line. The upper electrode member may take the form shown, which includes venting portions 36 for discharging gases created within the device. It will be apparent, though not shown, that the electrode member IQ of the pre ferred embodiment may be modified and substituted for the member 3| without departing from the scope of this invention.

The lower electrode member 32 provided with discharge ports 35 is substantially identical to the upper electrode member 3|, and is adapted to be connected with ground as is shown diagrammatically. It will be apparent that electrode member E9 of the preferred embodiment, as modified, may be substituted for electrode member 32 without departing from the scope of this invention (not shown).

An insulating plug 318 is contained within the bore of the tubular retainer member 3t, and preferably extends between the electrode members 3| and 32. Both the plug 36 and/or the tubular member 3% are preferably of horn fiber. Arc contact members 3? and 38, in the form of annular sleeves, are provided at each end of the plug 35. The are contact members are in electrical contact with each of the electrode members 85 and 32 respectively. The insulating plug of this embodiment is preferably tapered at both ends, shown, to provide spaced annular expulsion chambers 3i! and as respectively. The portion of the plug 3%; extending between the points referred to by reference numerals 35a and is in intimate contact with the bore walls of the tubular member 30 to provide a relatively constricted arc path. Both expulsion chambers 39 and connect with the parts 35 and 35 respectively. The tubular retainer member 36 is further reinforced by a metallic sleeve ii surrounding that member, both ends of which are preferably kept level with or between the planes of the inner ends of the opposed electrode members 3! and 32.

In some instances, especially in higher lcva. rating arresters, the amount of insulation between the opposed electrode members 3! and 32 may be excessive to permit initial spark-over between the electrode members. In order to restrict the material proportions, it may be desirable to use an intermediate electrode (not shown). Such electrode may consist of a metallic sleeve similar to either of the arc contact members 37! and 33. The constricted portions preferably would be positioned adjacent the intermediate electrode. The use of intermediate electrodes is well known as a convenient means of reducing spark-over values.

It will be apparent that the entire unit shown in Fig. 2 may be positioned within a modified housing similar to that shown in Fig. 1 (not shown). Such modification would require fittings similar to fitting 55 at both ends, with one fitting being connected with ground. The other fitting would be electrically connected with a spark-gap arrangement similar to that provided by the insulator l and its attached gap electrodes 5 and 9 (not shown). A protective insulating housing (not shown) similar to the housing 1 of Fig. 1 would be provided intermediate the end fittings.

The embodiment shown in Fig. 2 operates in a substantially identical manner as that described in conjunction with the preferred embodiment. That is, surge voltages greater than a predetermined value will simultaneously spark-over the external gap 33 and the internal expulsion gap between the arc contacts 37 and 38, the latter being electrically connected with ground. Arcs of relatively less magnitude create comparatively lesser amounts of arc-extinguishing gases. There:- fore, this invention contemplates the use of the constricted area, as is shown between points tea and b to confine the gases in order that they may efiectively block follow-current and properly extinguish these arcs.

This particular embodiment permits the gase to be discharged to atmosphere through ei her or both of the ports 34 and 35 of electrode members 3| and 32 respectively. Higher potential arcs will be effectively extinguished in the relatively distended portions of either or both expulsion chainbers 39 and it proximate to the electrode members 3| and 32 respectively. It will be apparent that a substantially equivalent means for providing the novel flared expulsion chamber may be accomplished similarly as described in conjunction with the preferred embodiment, by maintaining the same transverse cross section throughout the entire length of the insulating plug 35 (not shown), and flaring the bore of the retainer member between each end and its respective portion 36a or 361) (not shown).

It will b understood that the term annular is used in its broadest sense to define an area transversely relative to the longitudinal dimension of the expulsion chamber wherein the chamber surrounds an element defining the inner Wall of the chamber irrespective of the wall contours.

It will be apparent that the present invention contemplates the use of a novel and effective means for extinguishing arcs created by excessive line voltage without regard to the magnitude of said surges, said means taking the form of a novelly defined expulsion chamber which provides both a constricted arc-extinguishing area as well as a distended area for extinguishing arcs of varying magnitudes.

We claim:

1. A lightning arrester of the expulsion type including spaced electrodes, a retainer member having a bore, a tapered insulating plug member contained within said bore, at least one end of said plug member and the bore surface of said retainer member conjointly providing a tapered annular expulsion chamber having a constricted transverse cross-sectional delineation at a point intermediate the ends of said retainer member, one of said electrodes providing an electrode surface transversely of said bore and in the immediate proximity of said constricted cross-sectional delineation, the cross-section of said chamber being relatively distended at a portion longitudi nally spaced from said point and adjacent the other of said electrodes, at least one defining Wall surface of said chamber embodying arc-extinguishing material.

2. A lightning arrester of the expulsion type including two spaced electrodes, a retainer member having a bore and positioned intermediate said electrodes, a tapered insulating plug member contained within said bore, at least one end of said plug member and the bore surface of said retainer member conjointly providing a tapered annular expulsion chamber having a constricted transverse cross-sectional delineation at a point intermediate the ends of said retainer member, one of said electrodes providing an electrode surface transversely of said bore and in the immediate proximity of said constricted cross-sectional delineation, the cross-section of said chamber further being relatively distended at a portion longitudinally spaced from said point and adjacent the other of said electrodes, at least one defining wall surface of said chamber embodying arc-extinguishing material.

3. A lightning arrester of the expulsion type including, two spaced electrodes, a retainer member having a bore and positioned intermediate said electrodes, an insulating plug member contained within said bore, a portion of said plug member being tapered to conjointly provide with the bore surface of said retainer member an annular expulsion chamber, said chamber having a constricted transverse cross-sectional delineation adjacent one of said electrodes, the cross-section of said chamber further being relatively distended at a portion longitudinally spaced from said constricted cross-sectional delineation and adjacent the other of said electrodes, at least one defining wall surface of said chamber embodying arc-extinguishing material.

4. A lightning arrester of the expulsion type including spaced electrodes, a retainer member having a bore and positioned intermediate said electrodes, an insulating plug member contained within and substantially coextensive with tne bore of said retainer member, each extremity of said plug member and the bore surface of said retainer member conjointly providing a tapered annular expulsion chamber having a relatively distended cross-section proximate to each of said spaced electrodes, said expulsion chamber further defining a relatively constricted transverse cross-sectional delineation at a portion intermediate said electrodes, at least one defining wall surface of said chamber embodying arcextinguishing material.

HERMAN "O. STOELTING. CLIFFORD W. PETERSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,289,389 Stroup July 14, 1942 2,336,420 Pittman Dec. 7, 1943 2,418,791 Pittman Apr. 8, 1947

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