US2422978A

US2422978A - Lightning arrester

Info

Publication number: US2422978A
Application number: US581082A
Authority: US
Inventors: Arthur A Olsen
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-03-05
Filing date: 1945-03-05
Publication date: 1947-06-24
Anticipated expiration: 1964-06-24

Description

June 24, 1947. A. A. OLSEN LIGHTNING ARRESTER File@ March 5, 1945 Inventor Arthur'` A.Olsen Attorney a safe values for connected apparatus.

Ptented June 24, 1947' I LIGHTNING ARRE STER Arthur A. Olsen, Pittsfleld, Masa', assignor to General Electric Company, a corporation of New York Application March 5, 1945, Serial No. 581,()82

Claims.- (CI. 175-30) My invention relates to lightning arresters such as are used for the protection of electric power transmission lines and associated apparatus from the effects of excessive voltages due to lightning, switching Operations or other causes.

Lightning arresters generally consist of a gap structure connected in series with a current limitingelement. The current limiting element should have the property of decreasing and increasing its resistance as the discharge .current increases and decreases to such a degree. that the voltage across the arrester during discharge is held to The gap structure performs the function of a circuit breaker by 'interrupting the power follow current permitted to flow through the arrester by the current limiting element.

For high voltage distribution lightning arrester applications, the gap and current limiting elements are usually mounted in a heavy insulating tube with suitable end fittings and are thus completely sealed against the entrance of moisture.

i Where such lightning arresters are subjected to service conditions over and above that for which the arresters are designed, the gap or current limitlng elements cannot cope with these condi- .tions and arc-over occursi A high pressure is thus built up within the heavy sealed insulating housing which may cause the arresters to fail with such violence that they shatter like bombs, thereby not only endangering personnel but at the same time damaging surrounding equipment.

It is an object of my invention to provide a, new and improved lightning arrester in which shattering of the lightning arrester "casing with damage to surrounding equipment or adjacent Operating personnel will not occur.

It is another object of my invention to provide a pressure release diaphragm for a high voltage lightning arrester whereby blowing apart of the porcelain insulator housing the lightning arrester with resultant damage to adjacent equipment is prevented. r

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the cl'aims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had'to the accompanying drawing in which Fig. 1 is an elevational View, partly in section, of a lightning ari-ester embodying my inventlon; Fig. 2 is a view taken on line 2-2 of sulating material, such as porcelain. The insulat i similarly closed by a heavy metalend cap 8 held Fig. 1, and Fig. 3 is an elevational view of another lightning arrester embodying my invention.

Reterring now to the drawing I have illustrated a lightning arrester generally indicated at'l in Fig. 1, which includes a casing having a cylindrical wall portion 2 formed of weatherproof ining casing 2 is closed at its upper end by means of an end plate 3 arranged in sealing engagement with the upper end of cylnder 2 by virtue of a gasket 4. A heavy metal end cap 5 fastened to the upper end of casing 2 by means of suitable cement 6 completely seals the upper end of the lightning arrester housing. A plurality of suitable clamping means 1 suitably welded to metal cap 5 provide means whereby end fittings or other arrester units may be fastened thereto.

The lower end of the insulating casing 2 is in scaling engagement at the lower end of cylinder 2 by means 'of cement 9. End cap 8 is also provided with clamping means n' to which may be fastened a suitable base membei (not shown) or another 'similar lightning arrester unit as will become apparent by an examination of Fig. 3.

It will be obvious that the gap structure and current limiting element of the lightning arrester of my invention may take any suitable form, such for example as is disclosed in McEachron Patent 2,151,559, granted March 21, 1939, and assigned to the same assignee as the present application. As illustrated in the drawing, I provide a plurality of current limiting elements ll alternately and serially arranged with a plurality of gap units 12. The current limiting elements ll are all iden tical, the upper 'one in Fig. 1 being shown in section 'as'comprising a disk |3 of a resistance material of the type having a high inverse voltage resistance characteristic. A suitable resistance material for this purpose is disclosed in United States Patent 1,822,742, McEachron, granted September 8, 1931, and assigned to the same assignee as the present application. The disk of resistance material |3 of each current limiting element is preferably provided with a ceramic insulating collar !4 pressed and fired as an inherent part of the disk [3, thereby assuring the maximum discharge capabilities of the disk. y

i Each series gap element !2, as may be observed from the uppermost gap unit in Fig. l, consists of two electrodes l5 and 16, respectively, which are separated by insulating means 'generally indicated in Fig. 1 as a cylindrical spacer Il formed of porcelain or the like. In order to control the voltage distribution across the gap element deshoe-shaped member s of resistance material preferably of the same material as the disks I3. The open ends of the horseshoe-shaped member !8 are respectively connected to the electrodes and IS by means of conductors I 9 and 20. Asymmetrical field distribution is provided by virtue of the fact that the horseshoe-shaped resistor ll surrounds the gap structure including electrodes !5 and IS.

As illustrated in the drawing, eight currentlimiting elements H and eight gap elements !2 are arranged in series relationship with a gap structure interposed between two current limiting elements. This column dened by alternate elements Il and |2, is supported by a suitable spacer member 2| in the form of a conducting cylinder, and the uppe'r end of the lightning arrester column is held in conducting engagement with the end cap 5 by mean of a compression spring 22, which furthermore maintains the lightning arrester column in position.

When the lightning arrester fails an' arc strikes between end caps 5 and 8 within insulating cyl inder 2. This are causes hot gases and vapors tobuild up rapidly which may cause the insulating cylinder 2 to blow apart with tremendous violence. In accordance with my invention, I provide a pressure relief diaphragm 23 between lower end cap 8 and gasket 24 enga'ging the lower end of cylinder 2. This pressure relief diaphragm 23 is preferably formed of lead and provided with an annular ridge 25 so as to define an annula passageway 26 between diaphragm 23 and lower end plate 8. The metal end cap 8 is provided with a plurality of pressure relief openings 21 cornmunicating with the annular passageway 26. In order to prevent the spacer 2| from cutting into the lead pressure relief diaphragm 23 I preferably provide a supporting member 28 which spreads the weight of the current limiting and gap elements over a, larger 'area of diaphragm 23. It will be observed that the spacer 2| spaces the gap structure sufiiciently from diaphragm 23 so that heat from arcing across the gap structure short of failure of the arrester will not adversely affect diaphragm 23.

The pressure relief diaphragm 23 provides the desired moisture seal while the perforated end cap 8 provides mechanical protection for the dia phragm and a rugged means for supporting the arrester and connecting it to adjacent units if desired. When an are strikes between the end caps 5 and 8, it immediately burns throughthe diaphragm 23 and connects passageway 26 with the interior of cylinder 2 so that any appreciable pressure build-up is avoided by permitting the generated gases to escape through annular passageway 26 and pressure relief openings 21. Instead of the insulating cylinder 2 blowing apart with great violence the porcelain container 2 4 merely breaks apa't for thermal reasons due to the great heat produced by the arc, with the pieces oi the container harmlessly dropping to the ground.

My invention is particularly useful when a. plurality of units such as l are mounted in end to end relationship such as shown in Fig. 3, as is often the case for higher voltage installations.

In View of the detailed description included above, the operation of the lightning arrester embodying my invention described above will be ob vious to those skilled in the art and no further discussion will be included herein.

While I have shown and described a particular embodiment oi my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

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

1. In a lightning arrester comprising an insulating casing, a gap structure in said casing, means including a conducting member for sealing one end of said casing, a diaphragm for sealing the other end of said casing, said gap structure being suiciently displaced from said diaphragm that heat from said gap structure will not adversely afi'ect said diaphragm, ciosure means including a conducting member for said other end of said casing for protecting said diaphragm, said diaphragm acting as a pressure relief device upon failure of said arrester by being burned through by the arc striking between said conductin members within said casing and which might otherwise cause said casing to shatter with great violence, and means comprising openings in said ciosure means for permittin gases p ssin through the hole burned in said diaphragm by the arc upon failure of said arrester to escape to atmosphere.

2. In a lightning arrester comprising an insulating casing, a gap structure in said casing, means including a conducting member for sealing one en'd of said casing, a lead diaphragm for sealing the other end of said casing, said gap structure being sufiiciently displaced from said lead diaphragm so that heat from said gap struc-` ture will not adversely aiiect said diaphragm, ciosure means including a conducting member for said other end of said casing for protecting said diaphragm, said diaphragm acting as a pressure reli'ef device upon failure of said arrester by being burned through by the arc striking between said conducting members within said casing and which might otherwise cause said casing to shatter with great violence, and means comprising openings in said ciosure means for permitting gases passing through the hole burned in said diaphragm by the are upon failure of said arrester to escape to atmosphere 3. In a lightning arrester comprising an insulating casing, a gap structure in said casing, means for sealing one end of said casing, a, diag phragm for sealing the other end of said casing,

said gap structure being sufficiently displaced from said diaphragm so that heat from said gap structure will not adversely affect said diaphragm, a ciosure member for said other end of said casing for protecting said diaphragm, said diaphragm acting as a, pressure relief device upon failure oi said arrester by being burned through by the arc within said casing which might otherwise cause said casing to shatter with great violence, said diaph'agm having an annular ridge so as to define with said closure member an annular passageway, and means comprising openings in said ciosure member leading to said passageway for permitting gases passing through the hole burned by the arc in said diaphragm upon iailure of said arrester to escape to atmosphere.

4. In an electrical device comprising an insulating casing, means including a conducting member for sealing one end of said casing, a

ing said diaphragm, said diaphragm acting as a.

pressure relief device upon Iailure of said elec-` trical device with consequent'arcing in said cas n between said conducting members by being burned through by the arc within said casing which might otherwise cause high pressure to be developed in said casing causing said casing to shatter with great violence, and means comprising openings in said closure means for permitting gases passing through the hole bu'ned in said diaphragm by the arc upon failure ofsaid electricai device to escape to atmosphere.

5. In a lightning arrester comprising an insulating caslng, a gap structure in said casing, means for sealing one end of said casing, a. diaphragm for sealing the other end of said casing; means for positioning said gap structure a 'sufficient distance !rom said-diaphi'agm so that heat !rom said gap structure will not adversely afiect said diaphragm, a closure member for said other end of said casing for protecting 'said diaphragm, said diaphragm acting as a pressure relief device 20 Number upon faflure .ot. said. arrester bybeing burned through by the are within said casing 'which 'might otherwise cause said casing toshatter with great violence, said diaphragm having an an- 'nular ridge arranged between said casing wall REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PA'I'ENTS Name Date 1,642,239 Golladay Sept. 13, 1927