US2778974A - Lightning arrester - Google Patents

Description

Jan. 22, 1957 R. PERILLARD 2,773,974

LIGHTNING ARRESTER Filed Dec. 18, 1955 3 Sheets-Sheet 1 5 INVENTOR ATTORN E Y5 3811- 1957 R. PERILLARD LIGHTNING ARRESTER 3 Sheets-Sheet 2 Filed Dec. 18, 1953 IN VENTOR JOE-WK, PAL

5 Sheets-Sheet 5 Filed Dec. 18, 1953 I NVENTOR United States Patent '0 LIGHTNING ARRESTER Rene Prillard, Wettingen, Switzerland, assignor to Alrtiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a joiut stock company Application December 18, 953, Serial No. 398,913 Claims priority, application Switzerland August 22, 1952 8 Claims. (Cl. 315-36) The present invention which is a continuation-impart of my pending application Serial No. 375,425 filed August 20, 1953, now abandoned, relates to excess-voltage protective devices of the type commonly known as lightning arresters and is directed in particular to an improvement in arresters or" the type comprising serially connected resistance and spark gaps arranged in columnar form within a hollow insulator.

in arresters of the type to which the present invention relates, the function of the resistance elements is to permit the flow of heavy discharge-currents Without producing a low voltage are and hence has the property of conducting to ground heavy-current, excess-voltage discharges at a discharge-voltage which is in excess, but only a small multiple, of the normal line-voltage of the line to which the arrester is connected. It is quite common to use special voltage-dependent material for the resistance elements such as, for example, blocks of molded granulated silicon carbide but, as will become evident, the particular kind of resistance material is immaterial to the present invention which is directed to an improved manner for rranging or stacking the resistance and spark gap units within the surrounding, protective insulator casing.

The function of the spark gaps connected in series with the resistance elements is to cut oil the how of the heavy dischar e current through the resistance elements but, as in the case of the resistance elements, the specific construction of the spark gaps is not germane to the petentablc novelty upon which this application is predicated.

As shown in U. 5. Patent No. 2,135,085 issued to L. R. Ludwig et a1. November 1, 1938 the resistance and sparl: gap elements are arranged within the insulator casing in a single column but in applications of the arrester to very high voltage lines, the single-column arrangement results in an extremely high insulator column. Since the diameter of the insulator casing which contains the resistance and spark gap elements is small in relation to the overall height of the insulator column, it follows quite logically that the wall thickness of the insulator must be selected disproportionately thick of reasons of strength, and special carrying and supporting structure must be provided.

in an effort to reduce the overall height of the column in the interest of effecting reduction in costs it has been proposed to arrange the resistance and spark gap elements in side-by-side relation in the insulator casing so as to form a plurality of columns within each insulator casing. However in all known constructions of this type the several columns of resistances and/ or spark gaps stand practically free inside of the casing and are thus subject to undesirable displacement relative to one another. In an eifort to prevent any movement of the columns, considerable endwise pressure has been applied to the columns but this has not proven satisfactory. Moreover Too with such arrangement the mounting of the arrestor is complicated and expensive.

The present invention provides a more practical and inexpensive construction for arranging the resistance and spark gaps in a plurality of columns Within the insulating casing and is characterized by an interlocking layered construction wherein each layer is comprised of two building units of insulating material of like or similar construction, each of which is provided with wall portions defining at least two cup-like depressions or recesses of different depth which open to the same side of the unit. Two corresponding recesses of each pair of units are aligned and confront each other and form a close chamber. Two other corresponding recesses of each pair are non-aligned and face in opposite directions. Each of these recesses align with and confront a corresponding recess in the building unit in the next adjacent unit pair to form other closed chambers. The resistance and spark gap elements are placed in the closed chambers formed by these recesses which thereby prevent any lateral displacement of the elements, and all elements are electrically connected in series circuit relation. Moreover, the units of each pair are secured together so as to prevent lateral displacement between the units. Each pair of building units thus establishes three parallel recesses thus resulting in the building up of three parallel arranged columns of resistance elements and spark gaps encased within closed chambers as the paired units are stacked vertically one upon the other. The overall width of each pair of units is also made substantially equal to the internal diameter of the outer insulator casing so as to prevent any lateral movement of the units within the easing.

The invention and the many advantages appertaining thereto will become more apparent from the detailed description to follow and the accompanying drawings wherein preferred embodiments of arresters incorporating the inventive features defined in the appended claims have been illustrated.

in the drawings, Fig. l is a central vertical section through one. embodiment of the invention wherein the building units of each pair are so arranged that the three columns of resistance and spark gap elements are in'line such that the centers of all coliunns will be contained in a plane passed through a diameter of the outer insulating casing;

Fig. 2 is a transverse section on line 2-2 of Fig. I;

Fig. 3 is a detailed View showing a pair of the cupped or recessed building units in confronting relation prior to installation of the resistance and spark gap elements;

Fig. 4- is a fragmentary view similar to Fig. l but showing a different arrangement for the resistance and spark gaps with the several columns;

Fig. 5 is a view similar to Fl. 2 but showing a slightly modified angular arrangement between the units of each pair so as to establish the centers of the three columns of resistance and spark gap elements at the corner points of a triangle;

Fig. 6 is a top plan view of a modified construction for a building unit wherein the units of each pair are of identical construction, and may be fastened toget Fig. 7 is a top plan view of a pair of the units shown in Fig. 6 when fitted together without installation of the resistance and spark elements;

Fig. 8 is a vertical section taken along the line 8 S of Fig. 7; and

Fig. 9 is a view similar to Fig. 7 but showing the pair of building units within the insulator column and so arranged as to establish the centers of the three columns of resistance and spark gap elements, formed by stacking the pairs vertically, at the corner points of a triangle.

With reference now to the drawings and Figs. 1, 2 and 3 in particular, the outer cylindrical insulating casing for the arrester elements is indicated at 1 and may be provided with the usual skirt's 1a. The lower end of the casing is closed by a plate 2 preferably of electrically conductive material for connection of the arrester to ground which is indicated by the conventional symbol. The upper end of casing l is closed by a plate 3 also of electrically conductive material to facilitate connection of the arrester to the high voltage line to be protected and may include a ring 4 if a suspension type connection is contemplated.

As is most clearly shown in Fig. 3, the two building units which make up each layer of the three columns of resistance and spark gap elements are made of electrically insulating material, such as a ceramic, are substantially alike in structure, and are designated 5 and 6 in the drawings. Unit 5 is provided with two adjacent cuplike, preferably cylindrical depressions or recesses 5a, 5b, the recesses being open to the same side of the unit but of difierent depth. Unit 6 is of similar construction and its recesses are designated 6a, 6b. The wall which forms the shallower of the two recesses, i. e. recess 5b in unit 5 is preferably shouldered internally at 50 so as to make an overlapping i. e. telescoping fit with the externally shouldered wall portion 60 forming the shallower recess 6b in unit 6 as is clear from Fig. 1 thus fastening the two units 5, 6 together in such manner as to prevent any lateral displacement therebetween. It is thus apparent that the aligned recesses 5b, 6b which confront each other form a closed chamber for receiving the arrester elements. The depths of recesses 5a, 6a in the two mating building units are alike and greater than those of like recesses 5b, 6b by an amount such that the tops of recesses 5a, 6a will be flush with the bottoms 5d, 6d of the units when the two are brought together in the assembled position shown in Fig. l with the re sistance and spark gap elements placed in the recesses.

To electrically interconnect the arrester elements in the adjacent recesses of each building unit, each of said units is provided with a connecting strip 7 which passes through an opening in the partition between the recesses at the floor level of the recess.

Each pair of building units 5, 6 when mated together in the relationship shown in Fig. 1 with recesses 5b, 6b in alignment thus form three cylindrical pockets for receiving the resistance and spark gap elements, the centers of the pockets being aligned in a diametral plane through the outer casing 1. It will be noted that each pair of building units 5, 6 when assembled as shown in Fig. 1 have a combined width substantially equal to the internal diameter of the casing 1 thus eliminating the possibility of any lateral movement of the assembly of arrester element columns within the casing.

The manner of assembly of the arrester elements within the building units and the laying up of the latter to form the three columns should be obvious from an inspection of Fig. 1. Each pair of building units 5, 6 is assembled with a stack of the spark gap elements 8a-8e placed in the chamber formed by the mated center recesses 5b, 6b. The construction of these elements per se is of no particular importance and can be of any conventional construction such as that shown in the aforementioned Ludwig et a1. Patent No. 2,135,085. However they are cylindrical and of substantially the same outside diameter as the inside diameter of the recesses thus making a fairly snug sliding fit which prevents any lateral movement of the elements within the recesses.

The construction of the resistance elements 9a-9f per se is likewise of no particular importance and can for example be blocks of granulated silicon carbide as described in the aforementioned Patent No. 2,135,085. As

with the spark gap elements, the resistance blocks are cylindrical and of such diameter as to make a snug,

' ing units.

sliding fit in the outer, deeper recesses 5a, 6a of the build- It will be seen from Fig. 1 that the outer recess 5a of the lowermost unit 5 in the assembly faces downward and that the lower end of resistance block 9a placed therein establishes electrical contact with the lower closure plate 2 of the outer insulating casing while the upper end of this resistance block makes contact with the strip 7 which serves to connect the same with the upper end of the lowermost stack of spark gap elements 8a in the recesses 5b, 6b of the lowermost paired units 5 and s. Conductive strip 7 in building unit 6 serves a similar function in connecting the lower ends of spark gap stack 8a and resistance block 9b placed in the upwardly opening recess on of the lowermost unit 6, it being noted that the height of resistance block 91) is twice that of the starting block 9a so as to also fill the downwardly opening recess 6a of the unit 6 next above it in the assembly, which arrangement is eifected by placing the units 6 with their recesses 6a in confronting relation to form a closed chamber. Resistance block 9b is connected at its upper end via strip 7 to the upper end of the next stack of spark gap elements 8b in the series and the lower end of this stack is connected via strip 7 to the lower end of the next resistance block placed in the pocket formed by the two confronting recesses 50: of the second and third units 5 in the assembly. In other words, the assembly is built up by arranging the units 5, 6 in pairs with the units 5 of adjacent pairs alternating with the units 6 of adjacent pairs in back-to-back relation so as to establish aligned confronting recesses for receiving the resistance blocks formed by confronting recesses 5a of units 5 alternating with confronting recesses 6a of units 6 to form closed chambers. The uppermost arrester element 9 in the assembly is electrically connected to the upper closure plate 3 and the latter is connected to the high voltage line (not shown) that is to be protected.

While the resistance blocks 9a9f in Fig. l have been illustrated as half and whole blocks, the half blocks 9a, 9 being used at the upper and lower terminal ends of the assembly of arrester elements and the whole blocks 9b--9e being used between the confronting recesses 6a alternating with confronting recesses 5a it will be evident that such blocks may be sub-divided into a plurality of cylindrical axial sections laid atop one another if desired.

The finished arrester assembly of Fig. 1 is thus comprised of three columns arranged side by side in which the resistance elements and spark gaps 8 are connected alternately over the columns in series. The series circuit through the entire assembly runs alternately parallel and transverse to the axis of insulator casing It and is illustrated by the dash-dot line It The height of the columns i. e. the number of arrester elements will of course be dependent upon the voltage of the line to be protected.

In Fig. l, the arrangement is such that all of the spark gap elements 8 are placed in one column and all the resistance elements 9 in the other two columns but such is only one of the many stacking arrangements possible with the present construction.

If desired, the Fig. l arrangement could be reversed in which case all of the spark gap elements would be located in the outer columns, i. e. those columns formed by confronting recesses 50, 6a, and all the resistance elements placed in the central column formed by confronting recesses 5b, 6b.

Another possible arrangement is shown in Fig. 4 wherein each closed chamber formed by confronting recesses of the building units 5', 6 contains resistance elements 9 as well as spark gap elements 8 thus distributing the resistance and spark gap elements over all three columns of arrester elements.

In the arrangement according to Figs. 1-3, the units 5, 6 are so stacked that the confronting recesses 5a are spaced 180 from the confronting recesses 6a. Thus the centers or" the three columns of arrester elements lie in a diametral plane through the outer insulator casing 1. in the arrangement according to it will be seen that the units 5"-t" forming each building pair are arranged at an angle such as the 90 angle depicted thus resulting in a construction wherein the centers of the three columns of arrester elements lie at the corner points of a triangle. With this arrangement it becomes possible to utilize an outer insulator casing of smaller diameter for a given diameter of arrester el ment.

In the construction of the building units shown in Fig. 3 it will be noted that the units which form each pair are similar but not identical. That is to say, the wall forming the more shallow recess 5b in unit 5 is provided with an internal shoulder 50 and the wall forming the more shallow recess 6b in unit 6 is provided with an external shoulder he so as to enable the units 5 and 6 to be fastened together by a telescoping of those walls.

in the modified embodiment of Figs. 69 each unit of the several pairs stacked vertically in the insulator column is identical. Made of ceramic material, the units of a pair are designated l5, 16 in these views. Unit 15 is provided with two adjacent cup-like, preferably cylindrical depressions or recesses 15a, 151), the recesses being open to the same side of the unit but of diflferent depth. Unit id is of identical construction and its recesses are designated 16a, 16b. in the embodiment of Fig. 3, the walls forming the more shallow recesses of each pair were telescoped in assembling the pair of units. in the construction according to Figs. 6-9 however the end faces 15c, 160 of the walls forming the more shallow recesses are brought together in abutting concentric relation as shown clearly in Fig. 8. For securing the units of each pair in such assembled relation, the units are provided respectively with through bores 15d, 16d extending parallel with the recesses and between the same and which come into alignment when the pair of units are assembled. A bolt 17 passed through these aligned bores and secured by nut 18 thus holds the units 15, 16 in assembled relation. As with the construction previously described each unit is provided with a connecting strip, not shown, which passes through an opening 152, 16s in the partition between the recesses at the floor level of the recess. Also similarly to the Fig. 5 arrangement, the pairs of units 15, 16 when assembled as shown in Fig. 9 will establish the centers of the three columns of resistance and spark gap elements at the corner points of a triangle.

Finally it is possible to construct lightning arresters in accordance with the present invention having more than three columns by providing each building unit with more than, but a multiple of, two recesses.

Having thus described and illustrated several practical embodiments for my improvement in lightning arrester construction, what I claim is:

1. In a lightning arrester, the combination comprising an outer insulator casing and a lightning arrester assembly disposed within said casing, said assembly comprising a plurality of like pairs of building units of insulating material stacked vertically one upon the other, the building units of each pair being each provided with wall portions defining at least two recesses opening to the same side of the unit, two corresponding recesses of each pair confronting each other and forming a closed chamber and the two other corresponding recesses of each pair being non-aligned and facing in opposite directions, said other non-aligned recesses confronting respectively corresponding recesses of the building units in the unit pairs next above and below in said assembly and forming other closed chambers, lightning arrester elements in said closed chambers, and means connecting said arrester elements in series from one end of the assembly to the other.

2. A lightning arrester as defined in claim 1 wherein the means connecting said arrester elements in series is constituted by conductive strips extending between the recesses of each building unit at the bottoms of said recesses.

3. A lightning arrester as defined in claim 1 wherein the recesses of each building unit are of different depth and the recesses of lesser depth of the units of each pair are aligned, and the upper and lower edges respectively of each pair of units terminate in a common plane.

4. A lightning arrester as defined in claim 3 wherein the aligned recesses of lesser depth are telescoped to provide a connection between the units of each pair.

5. A lightning arrester as defined in claim 1 and which further includes means connecting together the building units of each pair.

6. A lightning arrester as defined in claim 5 wherein the means connecting together the building units or each pair is constituted by aligned bores extending through said units and a bolt extending through said bores.

7. A lightning arrester as defined in claim 1 wherein said lightning arrester assembly is comprised of three parallel columns of closed chambers containing said arrester elements, said columns being aligned and the centers thereof being contained in a diametral plane through said outer insulator casing.

8. A lightning arrester as defined in claim 1 wherein said lightning arrester assembly is comprised of three parallel columns of closed chambers containing said arrester elements, said columns being non-aligned and the centers thereof forming the corner points of a triangle.

References Cited in the file of this patent UNITED STATES PATENTS 2,542,805 Fink Feb. 20, 1951 2,615,145 Rydbeck Oct. 21, 1952 FOREIGN PATENTS 560,306 Great Britain Mar. 29, 1944

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