US2752522A

US2752522A - Lightning arrester

Info

Publication number: US2752522A
Application number: US358360A
Authority: US
Inventors: Jr William D Kyle
Original assignee: McGraw Electric Co
Current assignee: McGraw Electric Co
Priority date: 1953-05-29
Filing date: 1953-05-29
Publication date: 1956-06-26
Anticipated expiration: 1973-06-26

Description

June 26, W D KYLE JR LIGHTNING ARRESTER Filed May 29, 1953 IN V EN TGR.

United States Patent() LIGHTNING ARRESTER William D. Kyle, Jr., Milwaukee, Wis., assignor to McGraw Electric Company, Milwaukee, Wis., a corporation of Wisconsin Application May 29, 1953, Serial No. 358,360

6 Claims. (Cl. 313-231) This invention relates to a protective device for discharging excessive electrical potentials from electrical circuits or equipment and for suppressing arcs maintained by the follow current.

Equipment on electrical lines is selected to withstand the calculable voltages but when lightning occurs, the surge potential added to the lines is incalculable. Protective devices such as lightning arresters are utilized for discharging to ground these surges in order to protect the insulation of electrical circuits and equipment from the eects of excessive voltage.

The object of this invention is to provide a lightning arrester with a plurality of arc paths, each path having a relatively light electrode at one end.

Another object of this invention is to provide a light ning arrester with a plurality of arc paths and small electrodes in which the follow current through any given path causes the electrode of said path to burn away, thus lengthening the arc path.

Still another object of this invention is to prolong the life of a lightning arrester.

And another object of this invention is to provide a wedge action between two members of the combustion chamber in a lightning arrester that will tend to form a tighter fit as a result of the enormous internal pressures in the expulsion tube, thereby choking ot follow current.

Other objects of this invention will appear from time to time in the course of the specification and claims.

I illustrate an embodiment of this invention in the ac companying drawing in which:

Fig. 1 is a longitudinal sectional view of this expulsion type arrester.

Fig. 2 is a sectional View taken on the line 2 2 of Fig. l.

This lightning arrester is usually mounted on a pole and if space is available, secured to a cross-arm. Or it may be attached directly to a transformer housing and supported thereby. Its upper terminal may be connected directly to one ofthe transformer terminals or alternatively to a line wire, the lower terminal being connected to ground.

Normally, the arrester is not conductive to power current but it stands ready, continuously, as an easy path to ground for any surge of enough magnitude to threaten injury to the transformer or other protected equipment.

While devices of this character are most widely employed for the protection of line transformers, they are also used to protect other equipment such as capacitors and voltage regulators.

Referring to Fig. l, this embodiment of the invention comprises a housing 1 of dielectric material, usually porcelain, having a chamber 2 which is nearly coextensive lengthwise with the housing and is open at the lower end but closed at the upper end except for an aperture 3.

superimposed upon and supported by housing 1 is a petticoat insulator 4, which clamps between it and the housing 1, the lower end of an elongated electrode member 5. Gasket 6 serves as a cushion between electrode 5 and housing 1 to prevent chipping the porcelain when the parts are tightly drawn together.

Attached to the upper extremity of insulator 4 is a solderless connector 7 adapted to receive and grippingly engage a conductor wire through which electrical connection is made to the line. The connector 7 also serves to secure in place an electrode member 8, the free end of which is spaced from the free end of electrode member 5 to form an open spark gap 9. This open spark gap forms no part of the present invention. Its function is to isolate the hereinafter described expulsion tube from the line upper terminal 7 and thereby prevent the flow to ground of leakage currents by way of the expulsion tube and associated parts.

The assembly within the chamber 2 includes a tubular retainer member 10 made of insulating material such as horn fibre. This tubular retainer member 10 has a portion of its interior tapered inwardly at 11 to mate and form a tight lit with a plug assembly 12 hereinafter described. A lower portion 10a of the tubular retainer member 10 extending below this tapered section 11 is threaded internally.

A metal sleeve 13 encompasses circumferentially this tubular retainer 10 and 10a and serves to strengthen the said tubular section against the disruptive pressure generated within the expulsion tube.

The said tubular member 10 is threaded internally at its upper end to receive a complementary threaded metal closure 14. The metal closure 14 has several air vents 15 and is drilled and tapped through its center to engage the threaded stud 16. The stud 16 has its upper end firmly embedded and anchored in the insulator 4. The stud 16 is electrically connected to the electrode 5 through the medium of a metal washer 17 and it serves both as an electrical conductor and as a means for attaching the insulator 4 and electrode 5 to the housing 1.

The lower end 10a of the tubular retainer member 10 is threaded internally to engage a flanged iitting 18 which serves both as a closure for the lower end of the chamber 2 and as a lower terminal member to which the ground wire is connectable. A lug 18a forming an integral part of fitting 18 is apertured to receive a solderless connector 19 by means of which the ground connection can be aiected. Fitting 18 bears against and holds in place a gasket 20 which acts as a cushion to prevent chipping of the housing 1. The fitting 18 has a plurality of vents 21 to provide discharge paths leading from the expulsion chamber to the atmosphere. Axially through the fitting 18 is a bore 22 which is threaded in its upper portion to receive a threaded lower end 23a of a lower electrode 23.

The lower electrode 23 is tapered and on its upper wider edge contacts the plug assembly 12 consisting of a fibre tubular portion 24 and a cylindrical plug 25. The fibre tubular portion 24 tapers inwardly on its exterior edge and is the mating part to the interiorly tapered tubular section 11 of the tubular retainer 10. The plug 25 could be made of plastic or fibre and is pressed fit into the libre tube 24. The fit is suicient to choke off follow current subsequent to a spark over.

Above the plug assembly 12 and fanning out therefrom and downwardly on the sides are a plurality of copper or brass fingers 26 that serve as short conductors from an upper electrode 27. This upper electrode 27 ts above the fibre tube 24 and plug 25 with the copper lingers 26 held therebetween. A bore through the interior of the electrode Z7 is threaded to receive the lower end 16a of the stud 16.

The stud 16 has a wider portion 16b that serves as a spacer between the electrode 27 and the upper metal closure 14 thus allowing an air chamber 28 to exist therebetween and within the libre tubular retainer member 10.

All designs of expulsion arresters drain oft V-the 'surge and tend to prevent the flow of follow cuurrent after a spark over. Follow current flow for a given design of lightning Varrester is dependent upon vthe magnitude and dura-tion of vsurge current, timing ofthe surge on Vthe 60 cycle voltage, and the magnitude and vvpower factor of follow current.

The basic principle of this arrester is ajlarger number of arc paths each path having a relativelylight electrode 26 at one end. 'The flow of follow current through any given path causes its electrode 26 toburn away, thus lengthening the arc path. On the next surge, the arc will he attracted to an unburned 'light .electrode 126 and thus follow a spark over. VThe `arc is in this .manner persuaded to'use several paths and therefore prolong the life of the arrester.

The use and operation of my invention are as follows:

This lightning arrester is suitable vfor .the protection of transformers and .numerous other electrical equipment. I f an electrical surge occurs on the line,..the surge will cross the gap 9 to the electrode 5 and becarrieddown to the conductor 16. The conductor 16 car-ries the surge to the upperelectrode 27 of the two electrodes within the expulsion tubular member 10. Vents l in the top closure 14 provide passageways for gases to escape. A lower electrode 23 draws the surge along arc paths between the insulating plug `12 and the tubular member lll, and the light electrode lingers 26 become the upper kterminals of these arc paths. The surge tends to travel on the shortest `arc path and with the least spark over. When the surge uses ari arc path, it burns ,oli lthe light electrode at `the upper end of that arc path, thus lengthening that path. The next time there is a surge, it will choose an arc path which is shorter. As each successive surge seeks the shortest arc path, it tends to travel a new path through the expulsion tube each time, .th-us prolonging the life of the lightning arrester.

I claim:

1. A lightning arrester comprising .an insulating tubular .retainer member having a bore closed at one end and Open at the other, the bore of said .tubular retainer .having an upper and lower electrode spaced apart by a tight fitting insulating plug, the upper .of said electrodes pro- ,viding a means for lcarrying an yelectrical surgeoli apower line and having a plurality of ylight electrode lingers lextending downwardly over a portion of the `insulating plug and intermediate the outer periphery of said ,plug and .the bore surface of said retainer niemher,sai d light elect-rode Ylingers providing upper termini for arc paths.

2. A lightning arrester comprising an ,insulating :tubular :retainer member having a bore closed at one end 'and open at the other, the bore of said tubular retainer having an upper and lower electrode spaced :apart by a tight fitting insulating plug, the upper ojf said electrodes providing `a means for carrying an electrical -surge o l a power line and having a plurality of circumferentially spaced light electrode lin-gers extending ydownWardly-,over a fp ortion of the insulating iplug ,and intermediate the outer periphery of said plug and the bore ,surface of said retainer member, each said light electrode Ylinger providing an upper terminus'for anarc path.

3. A lightning arrester comprising aniinsulating tubular retainer member having a bore closed at one-,end and open at the other, the bore of said member having an inwardly tapered portion intermediate its ends vand containing therein an upper and lower electrode spaced apart by -a Vvtight litfting tapered insulating plug, the taper of said insulating plug mating with said taper ol:` said bore, the upper of said electrodes providing a means for carrying electrical surges ofi a power line and having a plurality of light electrode lingers extending downwardly over a portion of the said insulating plug and intermediate the outer periphery of said plug and the bore surface of said retainer member, each said light electrode linger providing an Lipper terminus of an arc path for said surges.

4. A lightning arrester of the expulsion type comprising a tubular retainer member of insulating material having a portion of its interior inwardly tapered, a plug secured to and forming a closure for one end of said member, a conductive discharge fitting secured to the other end ci said member, said litting having a discharge passageway extendi g therethrough, a tapered expulsion plug of insulating material within said member vand embraced laterally by said tapered interior portion., said expulsion plug being 'bounded endwise by electrodes, the lower of said electrodes conductively connected to said conductive discharge fitting, the upper of said electrodes conductively connected to a terminal to receive aneleetrical surge, and having a plurality of small electrode lingers extending downwardly on the exterior of the tapered expulsion plug.

5. A lightning arrester of the expulsion type Comprising a tubular retainer member of insulating material having a portion of its interior inwardly tapered, a plug secured to and forming a closure for one end of said member, a conductive discharge fitting secured to the other end ol said member, said litting having a discharge passageway extending therethrough, a tapered expulsion plug of insulating material within said member and embraced 'laterally by said tapered interior portion, said vei;- pulsion plug being bounded endwise by electrodes, the lower of said electrodes couductively connected to said conductive discharge fitting, the upper of said electrodes conductively connected to a terminal to receive an electrical surge, and having a plurality of small electrode lingers extending downwardly on the exterior ol the tapered expulsion plug, each said small electrode -niger providing an upper terminus for an arc path.

6. A lightning arrester of the expulsion type comprising a line terminal and a ground terminal, a tubular retainer member of insulating material and containing a coextensive bore, a ven-ted closure secured to vone end of said retainer member, -a ,conductive discharge fitting Secured to the other end of said-member, said litting having a discharge passageway extending therethrough, an upper and lower electrode within the bore of said retainer member, the bore of said .tubular member-being inwardly tapered intermediate its ends, said upper electrode conductively connected to said line terminal, said lower electrode oo nductively ,connected to the v.said conductive discharge litting, nsaid upper and lower electrodes being spaced apart `and having a tight .lit-ting tapered plug `oi non-,conductive material .theie.between,'the taper .,oat said plug mating with the taper of said bore, a plurality of thin electrode lingers extending downwardly from said upper electrode intermediate said tight fitting `plug and the bore surface `of said retainer member.

References Cited in the file of lthis patent UNITED v,STATES PATENTS