US2640096A

US2640096A - Lightning arrester and parts therefor

Info

Publication number: US2640096A
Application number: US249910A
Authority: US
Inventors: John W Kalb
Original assignee: Ohio Brass Co
Current assignee: Ohio Brass Co
Priority date: 1951-10-05
Filing date: 1951-10-05
Publication date: 1953-05-26
Anticipated expiration: 1970-05-26

Description

J. W. KALB LIGHTNING ARRESTER AND PARTS THEREFOR Filed 001;. 5, 1951 May 26, 1953 FIG. I

AALVE BLOCKS IMPROVED ARRESTER 46 49 1"; 3| INVENTOR.

\ 20 ,2} JOHN w. KALB n :3 53 BY I 28 Z/A ATTORNEY Patented May 26, 1953 LIGHTNING ARRESTER AND PARTS THEREFOR John W. Kalb, Barberton, Ohio, assignor to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application October 5, 1951, Serial No. 249,910

15 Claims. 1

This invention relates to an improved lightning arrester. It includes an improved pressurerelease construction and an improved arrangement of Spark gap and valve block-s within the arrester housing.

When a lightning arrester is called upon to withstand currents and/or voltages beyond its capabilities the resulting current follow-up arc is prolonged or sustained sufficiently to raise the pressure of the gases within the housing to damage the housing. According to this invention the cover or sealing cap over one end of the housing of the arrester is provided with a thin easily ruptured diaphragm which gives way under the pressure of the generated gases. This frangible diaphragm is preferably of thin, soft metal such as copper and is dished or domed inwardly to prevent the flexing which would occur as the result oi atmospheric changes and cause crystallization of the metal near the edge of the diaphragm were the diaphragm made perfectly flat. The diaphragm is applicable to arresters of this general design and is not limited to use on an arrester with spark gap and valve blocks arranged as in the accompanying drawings.

It is customary to provide an elongated housing of porcelain or other vitreous or insulating material for a lightning arrester and to locate spark gaps and valve resistor blocks longitudinally of the housing. located at one end of the housing and the valve blocks at the other. According to this invention the gap is located at substantially the longitudinal center of the housing with some of the valve resistor blocks at one end of it and others at the opposite end of it.

There is a decided advantage in such an arrangement of the spark gap and valve blocks, and this is independent of the type of lightning arrester and is in no way dependent upon the use of a diaphragm or other pressure-release means.

When the porcelain of the arrester housing is dry its resistance is very high. The voltage drop over the outside surface of the porcelain housing approaches quite exactly the drop of the gap and valve blocks within the housing, because to a large extent the dry housing gets its voltage from the gap. However, when wet and dirty the outer surface of the housing becomes somewhat of a conductor and is reluctant to have its voltage changed by the effect of the spark gap and valve blocks within it. Any large voltage difference between the inside and outside of the arrester results in flow of current through the The gaps are usually capacity of the porcelain wall. Any current which flows inwardly through the wall causes an additional voltage drop across that part of the housing. This is conducted to ground through the impedance of the gap resistor elements and valve resistor blocks. Since the valve resistor blocks are of relatively very low impedance, they remain unaffected by this current flow.

However, with the spark gap at either the upper or the lower end of the housing, when the housing is wet and dirty the gap resistor elements located within the housing conduct more and more current as the distance from the line terminal increases due to their having to conduct the added current which enters through the wall of the housing. Since the resistance per unit length of the gap is uniform the voltage per spark gap unit must necessarily be greater, the greater the distance of the element from the line terminal.

When thegap is located at the longitudinal center of the housing the voltage differences between the gap and the outside of the housing are much less than when the gap is located toward one end of the housing or the other. Furthermore, the voltage differences are symmetrical with respect to the center of the gap, so that whatever the difference in voltage between the inside and outside of the housing, and whatever the flow of current through the housing, the distribution of the voltage and current is substantially symmetrical on the two ends of the gap. By reducing the difference in potential between the outside of the housing and the gap, and by making the current distribution more uniform, the arrester operates more efficiently and consistently than where there is a larger voltage differential between the exterior of the housing and the gap or the current flow is not as uniformly distributed.

A logical extension of this principle is to arrange small valve and gap elements alternately within the housing, thus even further improving voltage distribution. However, this arrangement involves certain disadvantages not involved by the structure of this invention. These disadvantages are:

l. The gap elements are less rigid than the valve blocks, and, a column in. which several valve blocks and several gaps alternate is free to bulge to one side or the other and there is danger of damaging the valve blocks as they strike the inner housing wall during shipping vibration. On the other hand the large surface contact between two touching blocks prevents shifting between the blocks, and all blcclts at each end of the housing are held in axial alignment, uniformly spaced from the inner wall. of the housing, reducing the liability of damage during shipping. Dividing the valve blocks into two groups and upporting these at therespective ends of the housinggives the moststable internal arrangement, less subject to damage than when all the blocks are together or they are divided into more than two groups.

2. subdividing the gap into a plurality of units necessitates additional operations such as pretesting of several instead of one unit.

The invention will be further described inconnection with the accompanying drawings, in Which Fig. l is a section through the lightning arrester;

Fig, 2 is a section on the line 22 of Fig. l; and

Fig. 3 is diagram illustrating.differences in the flow of current through the housing of a conventional lightning arrester and the improved lightning arrest-er ofthis invention.

The. cylindrical porcelain housing I is of conventional. design. Spaced coacting indentations 3 in-the circular plates dform spark. gaps. Ineach plate indentations spaced downwardly alternate with indentations spaced upwardly, there being three of each type of indentation in each plate positioned in-a circle aboutthe longitudinal axis of. the gap pile Thus each plate forms three spark gaps withtheplate above it and three ci gaps with the plate below it. The plates are spaced by the blocks 6 of insulatin or high re sistance material. The rod 1 passes through centralholes 8 in the plates. The construction of. this type. of gap is more fully explained in Pyk U. S. 2,324,108.

The. plates and rodrest on the metal disc if The rod extends upwardly through the top spacer H. The spring I3 with the conductor M presses the electrodes 4: toward one another, and maintains themin-electrical contact with voltage sensitive valveblocks l5 located above and below the gaps. It also maintains these valve blocks in contactwiththe metal discs 16, and these inturn with the end closures of the housing,

The annular rubber gaskets 22 encircle the openingv at each. end of the housing. Tl ese are held inplace by

deformable metal closures

23 and 24 the edges of which are spun into grooves 26 in the. sides of the housing, forming gastight joints between the housing and the metal closures. Metal-end castings 23 are cup shaped. The inner surface 36 of the cup and the outer edges 3! of the

metal closures

23 and 24 are covered with asphalt and the space between them is filledwith a suitable cement 32. The annular rubber washer 33 prevents the cement from entering the space at the end of the housing.

The annular metal spring 35 in each end of the arrester maintains the correct pressure on gasket 20. The arrester is evacuated through the hole 31 in element 24 which is closed with the metal plug 38.

There is-a domed diaphragm 45 of thin copper which is brazed or otherwise fastened in a gasight manner in the opening in the element 23. This opening is located in a depression surrounded by the ridge 4?. The valve resistor elements are supported on this ridge by the angular support 48 which offers a substantially threepoint support. The diaphragmis as thin as practicable. The lower the pressure at which it rup- Lil tures, the better its per rmance. It is preferably no more than s-.veral mils thick. for example five mils.

The hragm is of smaller diameter than the valve resistor blocks and is protected by them from direct contact "with any electric arc which occurs over the surface otthe valve resistor blocks in the event of the arrester failing to quench or arrest the arc. Thus rupture is a function of pres- .ire only, and is predictable and not affected by are temperature In the event of a prolonged arc and subsequent accumulation of gases un high pressure within-the housing the diaphn sin 45 ruptures permitting the pent-up gases to escape. These rush down around the valve resistor blocks, through the. open end of the support 53 and under it. An end opening is provided in casting 28 to permit the escape of these gases after passing through opening 38 in spring To protect diaphragm '15- under normal. operating conditions, the end o ening is pro xled ith a closure membe preferably a snap-on cover 50, held in place by fingers 3!.

Although the arrester has been described in considerable detail, the domed diaphragm 45 with-0r without a closure member such the snap-0n cover 5-9 may be adapted for use in various types of= conventional arresters.

The diagram in Fig. 3-illustrates theadvantage of'locating the spark gap at the center of the arrc ter housing with valve blocks on each side of. it. Although the diagram compares the effect of such angenient with arranging the spark gap at p of an arrester near the line terminal) only, the advantage of this arrangement over other ccnmntic-nal arrangements, such as locating the spark gap at the bottom of an arrester (near the ground) for instance, will be apparent from the discussion which follows,

Tm us 3 illustrates, diagrammatically, a conventional arrangement at the left with the improved arr geinent at the right. The spark gaps are illustrated by straight lines and the valve blocks by oblongs. The scale betweenthe two arrest-er arrangements indicates the gradation of voltage approached on the outside surface of the arresters from one one to the other after the. arresters have become dirty and are wet. The ures. inside each of the arresters show the voltage drop over the gaps under ideal conditions. In wet weather, particularly after the exteriors of the housings have become dirty, there is current flow through the housings as indicated by the arrows. With the improved arrangement, locating the spark gaps at the center of the housing and the valve blocks at the ends, the maximum voltage differential between the outside of the housing and the gap elements is not as great as the maximum with the conventional arrangements, only one or" which is illustrated. Because of the lesser voltage differential, less current flows through the housing in which the spark gaps and valve blocks are arranged in the improved manner. The less the how of current through the housing, the more uniform. the amount of current flowing through the several gap resistors because more and more current enters the arrcster. as illustrated in connection withthe conventional. arrester, the gap resistors at the bottom of the arrester carry a greater amperage than those at the top. Current flow through the housing is generally objectionable because the amperage carried by the several gap resistors is made non-uniform, and the over-all operation of the arrester less emcient. Maximum efficiency is approached by placing the spark gap at the center of the arrester, with the valve blocks at each end of it.

' What I claim is:

1. A lightning arrester which includes a vertical cylindrical porcelain housing closed at the bottom by a metal casting, a snap-on cover in the center of the casting, a gasket around the ends of the opening through the housing and in contact with the respective ends of the housing, and a deformable metal element at each end of the housing which holds the respective gaskets in place, the edges of said respective metal elements being held in gas-tight contact with the housing, said metal element at the bottom of the housing resting on a spring held under compression between it and the casting, the metal element having an opening at its center in line with the axis of the housing with a depression about the opening and a ridge projecting upwardly around the depression, a thin circular copper diaprhagm domed inwardly located in the depression and so thin that it will be punctured by the pressure of gases generated within the housing on prolonged arcing, at about the longitudinal center of the housing a plurality of metal electrodes forming a spark gap pile, valve resistor blocks at each end of the housing larger in diameter than the dia' phragm, an electrically conducting spring member in the housing maintaining the elements of the spark gap pile and the valve resistor blocks in pressure contact with one another, and means on the ridge supporting the bottom valve block and spacing it above the ridge to permit gases to pass downwardly between the bottom valve block and the ridge and thence through the space occupied by the diaphragm when the diaphragm is punctured by pressure of the gases generated in the housing.

2. A lightning arrester which includes a vertical cylindrical porcelain housing closed at the bottom by a metal casting, a snap-on cover in the center of the casting, a resilient gasket around the bottom edge of the opening through the housing below which is a deformable metal element the edge of which is held in gas-tight contact with the housing so that said metal element encloses the bottom of the housing with the gasket pressed between it and the housing, said metal element resting on a spring held under compression between it and the casting, the metal element having an opening at the center in line with the axis of the housing with a depression about the opening and a ridge projecting up: wardly around the depression, a thin copper diaphragm domed inwardly located in the depres sion and so thin that it will be punctured by the pressure of gases within the housing on prolonged arcing, and means supporting resistor elements above the diaphragm within th housing on the ridge which surrounds the depression in the metal element but with a space between the bottom of the resistor elements and the ridge for the passage of gases under the resistor elements and over the ridge into the space occupied by the diaphragm after it is punctured.

3. A lightning arrester which includes a vertical porcelain housing one end of which is closed by a metal element having in a hole in the center thereof a thin copper diaphragm in line with til) the bore of the housing, which diaphragm is arrester by the metal element and spaced out of contact with the diaphragm so that when said gases are generated within the housing they may pass down through the housing and between the bottom resistor element and the support therefor and thence through the punctured diaphragm.

4. A lightning arrester which includes a cylindrical housing and a covering at one end the central portion of which is formed of thin material adapted to be easily ruptured by excessive pressure of gases generated within the housing due to a prolonged arc.

5. A lightning arrester which includes a cylindrical housing and a covering at one end having a thin copper diaphragm at the center adapted to be ruptured by excessive pressure of gases gen erated within the housing as a result of a sustained arc when the pressure has reached a predetermined value.

6. A lightning arrester which includes a cylindrical housing and a metal covering at one end having at the center thereof an inwardly domed center of thin material adapted to be ruptured by excessive pressure of gases generated within the housing due to a prolonged arc.

'7. A lightning arrester which includes a cylindrical housing and a metal coverin at one end having an inwardly domed center of copper no more than several mils thick.

8. A lightning arrester which includes a vertical porcelain housing having resistor elements therein, a rubber-like gasket surrounding the bottom opening of the housing, and a gas-tight metal element directly under th gasket with its edge sealed in gas-tight relation with the exterior of the housing, the metal element including an internally domed copper diaphragm no more than several mils thick.

9. The lightning arrester'of claim 8 in which there is a cover for the bottom of the hosuing, an opening in the cover and an outwardly releasable closure member therein.

10. The lightning arrester of claim 8 in which there is a metal casting over the bottom end of the housing below the domed diaphragm, an opening in the castin substantially concentric with the housing, and a snap-on cover in the opening.

11. A lightning arrester which includes sparkgap and valve-block resistor elements in a cylindrical housing, a closure at one end of the housing having concentric with the housing a diaphragm which is easily ruptured by the pressure of gases generated in the housing due to a sustained arc, and in that end of the housing over the diaphragm and separating it from the spark gap elements one of said valve-block resistor elements which is circular and larger in area than the diaphragm.

12. A lightning arrester which includes a cylindrical housing having an opening in the center of one end thereof, over the opening a substantially gastight diaphragm at least a portion of the part thereof which covers the opening being frangible and adapted to be ruptured by excessive pressure of gases within the housing, and means shielding the inner surface of the diaphragm from hot gases generated with the arrester.

13. A lightning arrester which comprises valveblock resistors and spark-gap elements in a housing of vitreous insulating material, closure means at each end of the housing joined to the housing in a gastight manner, at least one closure means provided with an opening and a separately formed diaphragm of rupturable' material positioned in said opening concentric withat'he housing, the diaphragm formed of a materialdissimilar to that ofthe. closure means: and of less thickness than the associated closure means and rupturable when: a. predetermined: gas pressure'notto exceed the rupturepressure of the'housing. isformed in the housing asthe result'of a sustained arc, the edges of' the diaphragm being joined tothe adjacent edge of the" opening. inithe closure means ina gastight manner; andprotecting means adjacent the said one closure means-of greater area than that-.- of the diaphragm to prevent an arc from impinging upon the diaphragm.

14-. A-lightning arrester asset forthin claim 13 in-Whichthe protecting means comprises a valveblock Wh'ich-i -positioned adjacent to but spaced from the diaphragm and is of greater diameter than that of the diaphragm whereby saidprotecting: meansoverlaps the diaphragm and prevents any are formed inrthe housing impinging upon. the-diaphragm.

15. A lightning arrester \vhichincludes'acylindrical housing with spark-gapand valve-block resistor elements therein, an opening in one end of the housing, a sheet metal cover-over. the open.- ing with a hole therein substantiallyconcentrio with the axisof the housing and a diaphragm closing said hole and an inwardly extending ridge bent in said cover around saidhole whereby the cover is strengthened, said spark-gap and'valveblock resistor elements being supported on said ridge.

JOHN W. KALBi References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,422,978 Olsen June 24, 1947 2,571,814 Beck Oct. 16, 1951 2,593,955 Ackermann Apr. 22', 1952