US1687254A - Multigap lightning arrester - Google Patents

Description

Oct. 9, 1928.v

J. RL MCFARLIN MULTIGAP LIGHTNING ARRESTER Filed Jan. ll, 1922 JTTORNEYS Patented Oct. 9, 192.8.

UNITED STATES' PATENT orsi-ca JOHN ROBERT MCFARLIN; or PHILADELPHIA,PnNNsYLvANIAassiettes 'ro 'rRIcsnIwIon SUPPLIES COMPANY, por PHILADELPHIA, PENNsYLvenIn, A oon- 'PORATION OF FENNSYLVANIA. l

"Y MULTIGAP LIGHTNING ARRESTER,

Application niea-Januaryii, 1922: semi 110.528.491.

f My invention relates to lightning arresters of the so called multi-gap type and my` primary obj ect is to provide improved means of high efficiency, as well as simple, convenient and durable construction, for protecting electrical apparatus from 'lightning andother high voltage disturbances, by discharging such disturbances to ground and effectively preventing a following' flowk of dynamic or line current from continuing through the arrester to ground.

Desiderata attained by my invention are high eciency in protecting electri-cal aparatus from variousclasses of lightning or high voltage disturbances; the capacity for successfully discharging charges Iof light or heavy volume, relatively *lowv or high volt'- age and low or high frequency, and flexi- 1 bility in the assembly and adjustment of its constituent parts with. adaptability toy etlicient operation under varying conditions encountered in service. v v

My invention, prises an insulating on top containing a housing having a sealed plate electrode provided with a lug, into which top thelead from the.

line wire passes to a connection with the lug, `and a bottom provided with an yopeningk through which the lead from. the ground wire enters to a connectionrwith a plate electrode on said bottom, in ,combination with a series of dished conducting discs, a series of insulating and non-inductive .resistance spools disposed between discs spaced thereby to vform spark gaps, varying in size and resistivity, and an .insulating bolt passing ythrough said plate electrodes', conducting discs and resistance spools to clamp them together.

The characteristic features of my invention are fully set forth in the following description vand` the accompanying drawings in illustration thereof. Y i In the drawings, Fig. 1 is an elevation of a lightning arresterembodying ments; FigQ is a centrallongitudina'l sectional view of same, land- Fig. 3 isajbroken section mainly on the line BX-BX'offFig. 2.

In the form of my improvements :illustrated in the drawings, an insulating housing 1, adapted to be supported as on apole, has a cap 2 cemented on its top;v A plate electrode 3, containing a central opening 4, is fixed bythe cap 2 on thepbody 1 and has in its preferred form, comthe resistance spools my improve;

a part 5 projecting- `beyond the lbody into the recess 6 of thecap for connection through the recess with the lead 7 to the line wire.v f

A dished metal disc or ring 8, containing the 'central aperture 9 and having the flat peripheral ridge 1,0, has its plane central or body portion'A disposed in engagement with the lower surface ofzthe plate 5, with the circular` peripheral Vridge extending downwardly.V An insulating spool 11y isplaced in engagement with the' body portion of this disc, within its downwardly projecting. v

ridge.

placed in engagementl with the insulating spool 11 in reverse relation to the first disc, with its circular ridge projecting'upwardly,

Af second similar metal disc 8 is the circular ridges of the two discsbeing so Y disposedas to form terminals with an air gap 12V therebetween. `Further similary discs 8 and spools 13 formed of conductive material having a* relatively high ohmic resistance, as forr example 100,000 ohnis each, are arranged in columnar relation concentric with and similarly tothe arrangement ofthe prei viously described discs 8 withthe spool 11;

the lbodies of the discsy between contiguous s poo'ls' being inhcontact,v their. jecting inl opposite directions, and the air Agaps 14 corresponding to the'spools 13 being less'than the gap y12, as here shown.k

Metalfdiscs 15 like the discs v8, but with deeper ridges, are separated by conducting spools 16k having a. relatively .low ohmic resistance as fork example 50 ohms each, thesev discs andspools being arranged as ypreviously described so that'the plane surfacesof thediscs between contiguous spools are in contact and the discs separated by the respective spools have their ,ridges disposed inY opposite directions so as to provide air gaps 17 between them. f i

A plate electrode 18, supported Within the bottom `of the body 1, is engaged by the plane body portion ofthe lowermost disc 1.5, and the severaldiscs and spools are clamped together by an insulating bolt V19y passing centrally therethrough, nuts Aor4 clamping members 20 vand 21 on the endsfof the bolt being disposed l inv recesses top and bottom of the housing respectively. A lead 24 ltothe ground extends through an opening 25 in the bottom of the housingk to a `connection with the electrode 18. f

'ridges pro-q QQand' 23 of thev This assembly secures accuracy of' relationship between the parts as Well as good electrical connections, While permitting ready assemblage in the desired relationship, ready adjustment of the relationship between the parts, and ready substitutions to vary the character of the resistance and the number or character of the air gaps, as may bel desirable by reason of the service for which the mechanism is to be used. Y

In operation, when the line to which the i arrester is connected is overcharged, the disohargeto ground takes Aplace through the arrester in a manner dependingon the frequency of the discharge, its volume and other characteristics.

l/'Vhen a slight accumulation of static ldischarges to ground, it Will ytake the path through the parts 7 and 3 to the disc 3 in contact with the latter, thence across the air gap 12, thence ythrough the engaging discs y between the contiguous spools 11 and 13, and

thence through the spools 13 and 16 by Way of the `discs vbetvveeii them to the loWermost disc 15, the plate 18. and the lead 24: to ground. This discharge of static, in breaking down the air gap 12, ionizes the air be tvv'een the corresponding discs 8 and thus permits a flow of dynamic or normal current to ground through the path taken by the static discharge. But this 110W of dynamic current Will be very 'small being limited by the combined resistance of all the spools in series, and Will be interrupted bythe action of the air gap 12 at the first half cycle of the generator Wave, or Where-the flow Vreverses and passes through zero value.

.A heavier charge of static or lightning, in discharging through the arrester .to

ground, takes the path through the electri-` being expressed as'the product of theohmic resistance of the spool and the current in amperes flowing through the spool. ylVhen this voltage becomes high enough, it Will break down vthe air gap and as a consequence a large part of the discharge Will take the path of least resistance across the gap rather than `through the spool. VThis discharge of static or lightning, in breaking down the air ygap 12 and one or more ofthe air gaps 14, ionizes the air in ythe respective gaps and so permits a flow of dynamic or normal cur-` rent from line to ground over the same path taken `by the static discharge. This iiow of dynamic current Will be limited by the combined resistance of all the spools 13 and 16 through Which it flows and it will bevextinguished by the actions of the air gaps in its path at the first half cycle of ythe gen- .'erator Wave, or Where the fiowl lreversesand passes through zero value.

A still heavier charge of static or lightning, discharging through the arrester to ground, will take the path across all air gapsl 12 and 11 .around the corresponding insulating spool 11 andfhigh resistance spools 13, and thence, `depending on its volume, may take the path across .one or more of the air gaps 17, thence through the consecutivespool or spools 16, the plate 18 and the lead 21 .to ground. Whether any discharge will take the path across an airV gap corresponding to a spool 16, or through such spoohwi-ll depend on the voltagebuilt up. across the ends of the spool,this voltage whenv high enough breaking down the air gap and the discharge :therefore largely .taking the pathV of least resistance across the gap vrather than through the spool itself. VThis discharge of.

static or lightning, in breakingdownthe air gaps across Which it flows, ionizes vthe air in the respective gaps and so permits a Vflow of dynamic or normal current from lineY to ground over .the :same static discharge.v rent will. be limited by the combined resistance of all the loW resistance :spools through Which it flows and Will be :extinguished by the actions of the air gaps in its path at the first `half cycle of the `generator Wave, or Where theflovv .reverses and zero value.

It Will be evident that a large-part of an extremely heavy discharge lmay flovv through path taken iby the passes through' This flow of dynamic cur-` the arrester over a direct air Agap path, suchl path offering .the Vgreatest freedom of dirscharge and consequently affording the vmost efiicient :protection -t0 electrical apparatus. In such case, the flou7 of dynamic ornorma'l current following the discharge to ground will not *be limited by anyof the resistanceV spools -Within the arrester, Ibut the vfunctioning of the arrester is suoli ythat las the resist# ance spools are progressively 'eliminated from the discharge path, additional air lgaps are automatically interposed in the path to leX- tinguish the fioW of' current. The flovv` being assumed to be extremely large, all ofthe air gaps act toelxtinguish the currentat the first half cycle of the generator Wave, or Where the floW reverses and `passes through Zero value. i

Thev flattened ridges -orterminals of the metal discs providev a substantial areaf'roni Which discharges may occur, avoidingV the burning and pitting that takes place in angular and rounded terminals and thus prolonging the vlives of such discs.

The facesof the conducting spools 13 and 16 are covered with a coating material such as copper to afford good electrical contact between such. spools and the metal discs or spark gap electrodes engaged thereby;

In these spark gapelements, the construction is such that thespark takes place between quite exposed surfaces as distinguishedv matically, to afford the utmost freedom in discharging static or lightning charges from line to ground and the maximum protection to apparatus from charges of widely vary! ing character. v

The mechanism shown and described, by

way of eXeinpliying an embodiment of my invention, may be variously modified, as by increasing or diminishing the number and spaces of the air or spark gaps; the number, resistivity and arrangement of the spools and otherwise within the scope of the claim.

Having described my invention, I claim:-

A lightning arrester comprising a plurality ot pairs of contacting gap electrodes having oppositely projecting peripheral ridges,l

hollow spoolsvwithin said ridges and each spacing an electrode of one pair from an electrode of an adjacent pair, said spools being of different resistivities, and an insulating rod passing through said spoolsl and spaced from the inner lsurfaces thereof, said rod having thereon means for clamping said spools and electrodes together. n

In testimony whereof I have hereunto set my hand, this 9th day of January, 1922.

JOHNv ROBERT MCFARLIN.

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