US1717589A - Lightning arrester - Google Patents

Description

June 18, 1929.

I Wk F. 5. SMITH 1,717,589

LIGHTNING ARRES TER Filed Oct. 10. 1922 ATTORNEY Patented June 18, 1929.

UNITED STATES FRANKLIN S. SMITH, OE PHILADELPHIA, PENNSYLVAIIA.

LIGHTNING ARRESTER.

Application filed October 10, 1922. Serial No. 593,511.

My invention relates to lightning arresters and it has for its general object to provide an improved and, novel construction of lightning arrester which is particularly adapted for the protection of high voltage systems.

It has for one of its objects to provide a novel construction of arrester which is adapted for use when immersed in a gas or gaseous mixture, under pressure,say a pressure on the order'of ten atmospheres.

The desirable features of a lightning arrester are that it shall have a maximum discharge c'apacity; the lowest possible equivalent gap, which gap shall be what is known 4 as a fast gap, and which also shall be constant, that is, for example, of a character not affected by the weather; the said gap shall also be cause noticeable surge on the line and should discharge at a constant predetermined voltage. Hence, a further object of the inventionis to provide a lightning arrester possessing all of these desirable characteristic features and functions.

A still further object of the invention is to provide an arrester across which a discharge will be effected upon relatively small rise of voltage above the normal line voltageyand a still further object is to provide an arrester characterized in that it is capable of controlling the dynamic or follow-up power current without interruption of the service.

Other objects and advantages of the invention will be pointed out in the detailed description thereof which follows or will be apparent from such description.

In order that theinvention may be readily understood and its practical advantages more fully appreciated reference may be had to the accompanying drawing in which an illustrative and preferred mechanical form or embodiment thereof is depicted; but itwill be understood that changes in the details of construction may be made within the scope of the claims without departing from the principle of the invention..

In the drawing Fig. 1 is a view showing portions of the casing or tank of a transformer (insection) which is adapted to hold or contain a gaseous dielectric under pressure and connected with which is a high voltage terminal construction, the said terminal construction a device embodying certain features of my in ven'tion, the said device being shown in secof such character as not totion and the said terminal construction being shown partly in section and partly in elevation;

Fig. 2 is a transverse sectional view taken on the line '22 of Fig. 1; and

Fig. 3 is a top plan view of the metallic housing of the said device which housing constitutes one electrode of the arrester gaps.

Although the device is illustrated in the drawings as being employed in connection with the high voltage line or system of a transformer it is to be understood that'such. application is merely illustrative and that it 1s not limited in its application to such specific use and that it may be applied to and employed with high voltage lines in connection with structures and devices other than transformers, an important feature being that the arrester shall occupy a position within a volume of gas or a mixture of gases, such as nitrogenalone or a mixture such as air, or nitrogen and helium, under pressure preferably greater than atmospheric.

Referring to the drawing: 1 designates a metallic bushing which projects through and is secured in an opening 2 through the casing or tank 3 of a transformer. Although the grounding is not shown in the drawings it will be understood that the transformer casing is grounded.

4.- designates a substantially tubular casing of suitable solid dielectric, such as molded bakelite, which is secured upon a threaded outwardly projecting portion 5 of the bushing 1. The lead proper, which comprises the tubular section 6 and the lead wire 7, extends outwardly through the substantially tubular casing 41 and is secured within a metal plug 26 which in turn is secured within the outer end of said casing. The tubular member 6 is thus held in rigid relation and, being associated with the lead wire 7 and with it in electrical connection with the metal plug 26 will thus be responsiveto the same potential as may be impressed upon the lead wire 7.

The intermediate electrode 8 of the arrester device is of tubular form and has screwjthreaded connection with the base 9 of solid dielectric, such as molded bakelite.

The opposite inner edges. of the said electrode 8 are rounded off as indicated. The lead 6 extends through the electrode 8 and is spaced from the inner surface thereof with which it is concentric. The construction of and employment of the tubular section 6, which, as will be seen from Figure 1, passes through the electrode 8, thus insures the maintenance of the intended and desired concentric relation between itself and the electrode 8. The gap is of the necessar configuration and dimensions to form a fast gap. Strips 10 of mica of nonuniform width are wound spirally and in. counterclockwise direction about the electrode. 8 as indicated in Figs. 1 and 2, although, if desired, the winding may be in the opposite direction. This spiral is continued at the point *indicated by the heavier zwhich depend the feet 17 (see Figs. 2 and shading with fibre ribbon 11 which is of uniform width as indicated. The use of fibre ribbon instead of mica is merely for the purpose of economy.

The completed spiral which comprises the mica strips 10 and the fibre ribbon 11 is surrounded or inclosed by a circular metal band clamping and compressing device 12 which is provided at its opposite ends with outwardly extending projections 12 and 12", the latter (see Fig. 2) being longer than.

the former. These projections are provided with openings through which extends a bolt 13 by meansof which the ends are adapted to be drawn toward each other to tightly clamp the said spiral strips and ribbon.

The metallic housing 14 which supports the base member 9 together withthe intermediate electrode 8 and the spiral mica strips, fibre ribbon and clamp thereon, is supported upon the lower inwardly projecting end of the bushing 1, having screw threaded connection therewith as indicated at 15'. The

intermediate portion of the housing 14 is tubular and somewhat enlarged with respect to the screw threaded portion (which is connected to the lower screw threaded end.

of the bushing 1) andterminates in an outwardly extending flange portion 16 from 3) which terminate in outwardly extending projections 18 having openings therethrough thrbugh which bolts 19 extend. These bolts extend through openings in proximity to the outer edge of the fiat disk shaped base 9 and the latter is held in. position against the under sides of the said projections 18 by means of nuts 20 (Fig. 1) upon the lower ends of the said bolts 19.

The feet-.17 are also provided with weblike portions 21, one at least of which is provided with a hole 22 through which one end of a bolt 23 (Fig. 2) extends, the said I I bolt also extends through the projection 12 and upon tightening the said bolt by means of the nut 24 the mica strips 10 and fibre ribbon 11 are still further tightened and held in thep'osition as indicated and shown in Fig. 2 of the drawing.

It will be observed that the upper edges of several of the outer spirals of the mica- .follow suchimpulsev spark over.

strips and of the spiral ribbon 11 are. in contact with the under side of the flange 16 (see Fig. 1) and also that the mica strips 10, the ribbon 11 and the clamping metal band 12 are housed within the space within the feet 17, the base 9 and the upper portion 'of the housing 14.

If a solid dielectric, such as mica, is placed between electrodes, arcs due to impulse voltages (such as the voltages due tolthe transient energy of lightning charge) generally follow the surface. If the dielectrics are smooth the impulse ratio is nearly unity even when the field is not uniform and the surface relatively long. NVhen the dielectric surface has corrugations or is rough the impulse are still generally follows the sur face, but the impulse ratio is higher; that.

is, greater time is required for impulse surface spark over. As already indicated, my arrester is adapted particularly for use when immersed in a gas or gaseous mixture under pressure greater than atmospheric and when so immersed the dielectric spark lag decreases with increasing gas pressure.

In operation, therefore, an arrester embodying my invention has low dielectric spark lag because the corrugated solid dielectric is situated within a volume of gas or gaseous mixture which is under a pressure greater than atmospheric, say of the order of ten atmospheres, and because of the fast gap. In the operation of the device and in case the line including the said device should become charged with transient energy sufficient to effect spark over such spark over occurs from the member 6 of the transformer lead through the gaseous filled gap 'to the intermediate electrode 8, thence by surface spark over from the intermediate electrode 8 alon the surface formed by the uneven upper e ges of the mica strips 10 to the portion 25 of the housing 14 (which constitutes an electrode) and thence to ground; but the dynamic power current is unable to Furthermore, the discharge due to the transit energy or transient impulse isv along radial paths and, in consequence, the impulse current d6I1S1l3y 1S maximumat the axis or center of the devlce and minimum at the portion 25 of the housing 14; as the distance from the center of the device toward the portion of the housing 14 increases the impulse current density decreases and, in consequence, the

dynamic, or follow.

An arrester embodying my invention as power current is less able to herein disclosed and described has a high discharge rate, causes no noticeable surge on the line, discharges at a constant predetermined voltage, is effective on high voltages, requires no charging current, is cheap, and is not liable to get out of order.

Having thus described my invention what claim and desire to secure by Letters Patent 1s:

1. In a protective device, in combination,

a grounded member; a line conductor; and

means interposed between said line conductor and said grounded member, said means including a spark gap adapted to break down at a predetermined voltage and means formed of solid dielectric material for conveying current due to transient energy in substantially radial paths and shaped to provide a surface, for the passage of said current, of an area'increasing in the direc tion in which said current flows.

2. A protective device of the character described comprising a conductor or line for conveying current, and a disk-like body conbeing adapted, when sisting of strips of solid dielectric spirally arranged in a angles to the line, the said disk-like body in the presence of gas under pressure, to convey current along an exposed surface in approximately radial paths from the said line.

3. In a protective device, the combination of the line for conveying current and a disklike body consisting of strips of solid dielectric spirallyarranged in concentric relation to and in a plane substantially at right angles to the said line and between the line and the ground and being in series with a fast gap intermediate the line and the ground.

4. In a protective device adapted for use in connection with a high voltage apparatus, and a disk-like body consisting of strips of mica spirally andconcentrically arranged with re spect to the axis of said lead, a tank containing gas under pressure and one surface of the said disk-like body being in contact with the gas in said tank and the said arrester-including a fast gap which is in series with the lead, substantially as de- Qscribed.

5. In a protective device for the protection of high voltage systems, the combination of a grounded'tank containing gas under pres- I sure, an intermediate electrode consisting of a tubular member concentrically arranged with respect to a portion of said line, the

inner surfaces ofsaid tubular electrode being plane substantially at right 1 therefrom by a ,body of solid dielectric, one side of which is spaced from the said line to form a fast gap, a disk of solid dielectric provided with an opening concentric with a portion of said line in which the said electrode is secured, a plurality of strips spirally arranged around the said electrode, the said strips being of different widths and one edge of each strip being in contact with the adjacent surface of the said disk, the said edges thereby occupying positions in the same plane whereby an undulating opposite surface is provided, and a housing contacting with the upper edges of one or more complete coilsradjacent the periphery of the .body formed by the said spirally arranged strips, which housing has connection with the said tank and is thereby grounded.

6. In a protective device for high voltage systems, the combination of a line, an electrode consistingof a short tubular member through which a portion of said line extends, which tubular member is in concentric rela-- tion to the portion of said line which passes therethrough, a disk of dielectric material having an opening within which the said electrode is secured, grounded metallic means for supporting the said disk and a plurality of strips of non-uniform width spirally wound around the said electrode with one s n u 0 solid dielectric .having an opening therethrough through which the said lead ex tends, metallic means having connection with the said caslng and wlth means constituting an electrode, an intermediate electrode concentrically arrangedwith respect to the said lead and separated fast gap and a disk-like seated against the said supporting disk and the opposite side of which is exposed, the surface of said opposite side being of undulating conformation and the outer portion of said disk-like body being in contact with the said metallic means for supporting-said first named disk. v

8; In a protective device adapted for the protection of high voltage apparatus, the combination of a casing, a lead extending from the interior of said casing, a disk of solid dielectric having an opening therethrough through which the said lead extends, the said lead and openingbeing in concentric relation with respect to each other, a metallic a disk of the said disk for suporting the latter, the said metallic housing supported within the said easing, means for connecting the said solid dleleetric disk with said housing to support the said disk thereon, the said housing constitutlng an electrode, an intermediate tubular electrode secured within the opening through said disk inconcentric relation'with respect to the said lead and separated therefrom by a fast gap, a plurality of strips of mica spirally wound around the said intermediate electrode to form a body 'of disk-like shape, one edge of each of said strips being in contact "with the inner surface of the first named disk and the said strips being of different widths whereby the inner surface of the said disk-like body formed by the said strips comprises elevated and depressed spiral surface-portions and the edges of one or more of the outer spirals being in contact with the said metallic means for supporting.

the said first named disk substantially as described.

9. Ina protective device, in combination, a grounded member, a line conductor, and means intermediate of said member and said line conductor for conveying current due to transient energy from said line conductor to said member, said means including a plurality of strips of solid dielectric material of different widths and arranged flatwise against each other.

10. In a protective device, in combination; a grounded member, a line conductor, means formed of solid dielectric material interposed between said line conductor and said grounded member for conveying current due to transient energy in substantially radial paths from said line conductor to said grounded member and shaped to provide a surface for the passage of said current of an area increasing as the current approaches said grounded member, a gaseous dielectric under pressure, and means for confining said gaseous dielectric so that said last-mentioned means is subjected thereto.

11. In a protective device, in combination, means adapted to be grounded and including a ring-like conductive member, a line conductor passing through said ring-like memberbut spaced therefrom, and a disk-like member of solid dielectricmaterial intermediate of said line conductor and said ringlike member and provided with an irregular surface for conveying current due to trans ient energy in substantially radial paths from said line conductor tosaid ring-like member.

12. In a protective device, in combination, means adapted to be grounded and including a ring-like conductive member, a line conductor passing through said ring-like member but spaced therefrom, an electrode about and spaced from said line conductor and adapted to form therewith a sparkgap, and dielectric means interposed between said electrode and said ring-like member for conveying current from said electrode to said ring-like member.

13. In a protective device, in combination, means adapted to be grounded and including a ring-like conductive member, a lineconductor passing through said: ring-like member but spaced therefrom, a disk-like member of solid dielectric material intermediate of said line conductor and said ring-likemember and provided with an irregular surface for conveying current due to transient energy in substantially radial paths from said line conductor to said ring-like member, a gaseous dielectric under pressure, and means for confining said gaseous dielectric so that the effective surface of said disk-like member will be subjected thereto.

14. In a protective device, in combination, means adapted to be grounded and including a ring-like conductive member, a line conductor passing through said ring-like member but spaced therefrom, an electrode ,about and spaced from said line conductor and adapted to form therewith a spark gap, dielectric means interposed between said electrode and said ring-like member for conveying current from said electrode to said ring-like member, a gaseous dielectric under pressure, and means for confining the latter so that the gap betweensaid line conductor and said electrode as well as the effective surface of said dielectric means will be subject ed thereto.

15. In a protective device, in. combination, a tank adapted to containvan electrical apparatus and having confined therein a gas eous dielectric under pressure, a line conductor pass ng through a wall of said tank and msulated therefrom, and means intermediate of said tank and said line conductor for conveying curent due to transient energy from said line conductor to said tank, said means including a plurality of strips of solid dielectric material of different widths and arranged fiatwise against each other and subjected to said gaseous dielectric.

16. Ina protective device, in combination,

passing through a wall of said tank and paratus and having confined therein a gaseous dlelecti ie under. pressure, a ring-like electrode within said tank, a line conductor ing said conductor in to formtherewith a spark gap, and dielec- 1 trio means interposed between said bushing and said tank for conveying current due to transient energy from said ring-like electrode to said tank.

18. Ina protectivedevice, in combination, a tank adapted to contain an electrical apparatus and havin confined therein a gaseous dielectric under pressure, a line conductor passing through a wall of said tank and insulated therefrom, an electrode spaced form therewith a spark gap filled with said gaseous dielectric, and dielectric means interposed between said electrode and said tank and subjected to said gaseous dielectric thereby for' conveying current due to transient energy from said electrode to said tank.

19. Ina protective device, in combination,

a tank adapted to contain an electrical appa ratus-and having confined therein a gaseous dielectric under pressure, a line conductor passing through a wall of said tank, and means formed of solid dielectric material interposed between said line conductor and said tank for conveying current due to transient energy in substantially radial paths from said line conductor to said. tank and shaped .to provide a surface for the passage of said current to an area increasing as the current approaches said tank, said" means f d t d d t b ing Subjected to said gaseous dielectric. rom sa1 ne con uc or an a vap 0 In testimony that I claim the foregoing as my invention I have hereunto signed my name this 27th day of September, 1922.

FRANKLIN S. SMITH;

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