US3617618A

US3617618A - Multiring hollow high-voltage insulator with external and internal sheds

Info

Publication number: US3617618A
Application number: US9821A
Authority: US
Inventors: Roy H Albright
Original assignee: ITE Imperial Corp
Current assignee: ABB Inc USA
Priority date: 1970-02-09
Filing date: 1970-02-09
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02

Abstract

An insulator for supporting electrical switches, buses and the like in a high-power distribution system is constructed from annular shells or rings having both internal and external sheds with corrugations on the undersides thereof to increase creepage distances and to function as rain shields. The diameters of the rings are selected according to the stability required for the insulator, while the height of the individual assemblies are selected according to dielectric requirements.

Description

United States Patent Inventor Roy H. Albright Greensburg, Pa.

Feb. 9, 1970 Nov. 2, 1971 l-T-E Imperial Corporation Philadelphia, Pa.

Appl. No. Filed Patented Assignee MULTIRING HOLLOW HIGH-VOLTAGE INSULATOR WITH EXTERNAL AND INTERNAL SHEDS 6 Claims, 8 Drawing Figs.

0.8. CI. 174/209, 174/150, 174/178, 174/211, 174/212 Int. Cl. ron), 17150, 1101b 17/60,I-101b17/66 Field 01 Search 174/30, 141,148,149,149B,150,177,l78, 209, 211, 212

[56] References Cited UNITED STATES PATENTS 1,077,711 11/1913 Hewlett 174/150X 1,937,296 11/1933 Sporn eta1.... 174/141 X 1,998,549 4/1935 Lapp et al..... 174/150X 3,081,375 3/1963 Moussou 174/209 X FOREIGN PATENTS 103,850 7/1926 Austria .1 174/30 1,125,372 7/1956 I France 174/209 1,1 13,247 5/1968 Great Britain 174/209 Primary Examiner- Laramie E. Askin Attorney-Ostro1enk, Faber, Gerb & Soffen ABSTRACT: An insulator for supporting electrical switches, buses and the like in a high-power distribution system is constructed from annular shells or rings having both internal and external sheds with corrugations on the undersides thereof to increase creepage distances and to function as rain shields. The diameters of the rings are selected according to the stability required for the insulator, while the height of the individual assemblies are selected according to dielectric requirements.

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I PAIENTEDuuve new 3,617, 618

sum 20F z MULTIRING HOLLOW I-IIGI-I-VOLTAGE INSULATOR WITII EXTERNAL AND INTERNAL SHEDS BACKGROUND OF TI-lE INVENTION This invention relates to electrical power transmission and distribution systems and, more particularly, to a novel arrangement for insulator columns employed therein.

With the growth of the electrical power industry transmission voltages have increased from modest values of 5 to 15 kv. to the present high level of 500 to 750 kv. As further growth in the industry occurs, it is anticipated that transmission voltages will increase to 1,000 to 1,500 kv. The formidable factor in the design of higher voltage systems is the provision for suffrciently high insulation strength.

During the period that the operating voltages have increased to their present level, the design of insulator columns has been changed to improve their mechanical and electrical characteristics. In addition, the height of the insulator stacks has also been increased to meet the increased dielectric requirement necessitated by the higher operating voltages. However, increases in height have increasingly subjected the slender insulating columns to greater deflections at nominal loads. It will be readily apparent that increasing deflections of ever taller insulator columns (as might be expected with the higher l,000-l,$00 kv. voltages) are not without limit; limits may soon be reached if only to maintain the rigidity of the stack arrangement.

The electrical industry is presently transmitting and distributing electrical power at voltages of 765 kv. Three types of insulator arrangements are in use 'at such voltage for the support of electrical switches, buses and the like. One, the pedestal type of insulator, comprises a plurality of porcelain shells cemented together, with a metal cap cementedto the top shell and with a metal pin cemented to the bottom shell. For 765 kv. service, some -12 of these units are bolted together to form an insulator stack approximately feet high. The second, or station post type of insulator, on the other hand, consists of a one-piece porcelain body, some 40 inches to 50 inches long, with metal caps cemented on both ends. Four or five of these units are bolted together in a typical arrangement to form a stack the same 15 feet in height for 765 kv. operation. The third, or multicone type of insulator, comprises a number of nested porcelain shells cemented together, with a metal cap cemented to the top of the shell arrangement and with a metal pin cemented to the bottom of the shell arrangement. Three or four of these units are bolted together in typical arrangements to make an insulator assembly 15 feet in height for the 765 kv. service.

As is known, these three types of insulator columns undergo considerable deflection due to the existence of cantilever loads which are applied at the top: of the columnar assembly. These leads can result from mechanical forces due to fault conditions, as where phase-to-phase faults in a three-phase system establish repelling forces between adjacent apparatus in the affected phase. Wind loading especially in distribution systems geographically located in the northern hemisphere also cause pronounced deflection, even at such relatively small heights of 15 feet. Operating forces, in addition, as are caused by the opening andclosing of blades in a highvoltage switch construction further cause considerable deflections. Although no determination has yet been made as to the height required for insulator stacks in prospective l,000-1,500 kv. arrangements, itis accepted that insulator heights of the order of 22 to 30 feet will be necessary under such conditions. It is also expected that extension to these heights of present insulator designs most probably will result in increased deflection instability in this high-voltage environment.

One suggestion as how the stability of present designs could be improved as columnar heights are increased has been to increase the diameters of the present insulator types. Such suggestion, however, presents additional problems, especially when the insulator material is formed of a porcelain material.

For the most part, increasing the diameter of the individual insulator arrangement compounds the problems of firing" the unit because of its larger size and, consequently, requires a relatively large furnace to handle the larger insulator. Also, increasing the diameter of the porcelain insulator presents some problems in the firing" of the porcelain because increases in the diameter increase the internal stress of the material. Furthermore, since increases in diameter are usually accompanied by corresponding increases in length of the unit, any increase in diameter to improve stability at the same time presents additional problems of instability due to increased length.

It is an object of the present invention, therefore, to provide an insulator column having sufficient mechanical strength and a dielectric characteristic which enhances the usefulness of the column in high power electrical transmission and distribution systems.

It is a further object of the invention to provide such an in sulator column in which the diameter of the insulator portions can be selected in accordance with the stability requirement desired.

It is another object of the invention to provide such an insulator column in which the height of individual assemblies can be varied in accordance with dielectric requirements.

It is yet another object of the invention to provide such an insulator column in which metal attachments are used only at the top and bottom of the assemblies so as to provide exceptionally high leakage distance for a given length of insulator.

As will become clear hereinafter, such an insulator column is constructed from annular shaped shells or rings having both internal and external sheds with corrugations on the underside thereof. These sheds and corrugations serve to increase creepage distances and to function as rain shields. The insulator column is made hollow because of the shell-like construction so that a rotating stack may pass through the ceriter thereof to control, for example, the opening and closing of a supported electrical switch under direction of an operating mechanism located at the base of the column. As will be appreciated, the prior art type of insulator column discussed above either provided no such hollow configuration which would permit insertion of a rotating stack of this nature or, if hollow, was sealed at the ends thereof to prevent rain washoff from wetting the insulator. The insulator of the present invention is unique in that rain shields are provided at the inside of the hollow column as well as external to it, so that no need for such scaling is necessary.

These and other objects of the invention will be more fully understood from a consideration of the following description taken in connection with the drawings in which:

FIG. 1 shows a multiring hollow insulator embodying the present invention for use in a high voltage electrical power transmission and distribution system;

FIG. 2 shows a perspective view of a section of the rings comprising the column of FIG. 1;

FIG. 3 shows an enlarged end view of the perspective configuration of FIG. 2; and

FIGS. 4-9 show various insulator column configurations according to the invention.

DESCRIPTION OF THE INVENTION Referring to the drawings, and particularly to FIGS. l-3 thereof, an insulator column for use in a high-voltage environ ment providing 1,000-1 ,500 kv. voltages is represented by the reference numeral 10. The column is constructed from a plurality of annular shells or rings ll, l2, 13, etc., which may be of porcelain, epoxy or other insulating material. For use in 1,000-l,500 kv. service, the height of column 10 would be of the order of 27 feet, and employing the principles of the invention, the diameter of the column would be between 3 and 5 feet in width. In FIG. 1, the insulator column 10 is constructed to have a tapered configuration, where the diameter of the uppermost ring is approximately 3 feet while the lowermost ring is of the order of 5 feet in diameter. It will be apparent that this increasing diameter as one proceeds from the top a of the column 10 towards the bottom 10b serves to increase the stability of the column by virtue of there being the greater diameter at the base.

As shown more clearly in FIGS. 2 and 3, the annular rings 11, 12, 13 have shed portions 11a, ll 2a, 13a extending inward of the column 10, and second shed portions 11b, 12b, 13b extending outwardly therefrom. Each of these shed arrangements is configured to have corrugations on the underside thereof, and is slanted downward to end in a

lip surface

11c, 12c, 13c and 11d, 12d, 13d. The corrugations of these sheds -25 serve to increase creepage distance in a known manner so that voltage discharge occurs along the corrugation surface to ground rather than through the air. The overhanging, relatively sharp lip surfaces also function as rain shields in evident manner, to control increases in leakage current due to the presence of moisture on the insulator.

The individual rings ll, l2, 13, etc. are cemented together to form the overall column, and, in well-known manner, sand-bands" are blasted onto the porcelain glaze at the areas to which the cement is affixed. Such sand-bands" are indicated in FIGS. 2 and 3 by the

notations

100 and 200.

The insulator column of the present invention permits construction of a stack of appreciable length having considerable rigidity. It will be seen that by constructing the insulator in ring components, the difficulties of firing" a relatively large insulator unit as a station post insulator is not present. By constructing the column from annular rings, the mass of porcelain which is fired is also less than that in any of the aforesaid arrangements, so that increases in internal stress are not a problem. The rings, by being constructed in annular form, facilitate the use of a rotating insulator stack passing therethrough so as to direct control of electrical switches supported at the top 10a of the column 10 under direction of a mechanism located near the bottom 10b of the column 10. Through the use of the internal ring shed 11a, 12a, 130, etc., no need for sealing the ends of the insulator exists as the penetration of moisture is prevented by the internal shed. The corrugations under these rain shield sheds, furthermore, limit the voltage discharge to ground just as do the corrugations in the conventional outer shed. Lastly, the multiring arrangement may be constructed in a wide variety of manners by selecting the diameters desired according to the strength requirement for the system.

Thus, for larger columns, it is but a simple matter to increase the diameter of the rings employed while still providing the ring shield characteristics and the provision for the use of a rotating central stack. At the same time that the diameters of the rings can be controlled, the number of rings in the stack can also be selected so as to satisfy the dielectric requirements for the system. It will also be noted that the metal attachments for connection to the electrical apparatus to be supported and to the reference or ground plane are the only metal attachments employed in the structure, providing yet another improvement over arrangements where metal top and bottom portions are present in each cemented assembly to reduce the leakage distance for the overall unit.

FIGS. 4-8 show various arrangements for the insulator columns constructed from hollow multiring units of the type described, to be used for supporting various types of electrical apparatus. It will be understood that these arrangements can support the apparatus in conventional orientation wherein the apparatus is attached to the upper end of each column while the lower end is attached to the supporting base or reference plane. As described in pending application Ser. No. 864,016 filed Oct. 6, 1969 and assigned to the same assignee as this invention, instances may arise where inverted mounting of electrical apparatus in underhung arrangement would be desirable. For such mounting, the electrical apparatus and supporting base (not shown) may be connected to the ends of the column opposite those described in the previous paragraph. FIGS. 4 and 7 show insulator column arrangements wherein the diameters of the multirings increase in progressing from the upper end to the lower end while FIGS. 5 and 8 show arrangements where the diameters decrease from top to bottom. FIGS. 4 and 5 show configurations in which change in diameter is gradual over the entire length of the column, while FIGS. 7 and 8 show the diameter change as being gradual up to a point, and to remain constant thereafter. FIG. 6, on the other hand, shows a column arrangement in which the diameters of the individual multirings are maintained constant. Although not specifically shown as such, it will be appreciated that each of the ring arrangements shown in FIGS. 4-8 is of the type shown in FIGS. 2-3 as being annular in nature and having internal and external sheds with corrugations on the underside thereof to serve in increasing creepage distance and as rain shields.

FIG. 9 shows (although not necessarily to scale) a modified construction of an insulator column incorporating some of the features disclosed in pending application Ser. No. 9,525, filed concurrently with this application and assigned to the same assignee as is this instant invention. In particular, the aforementioned application Ser. No. 9,525 describes an insulator column arrangement for use in high-power distribution systems as being a two-component arrangement so as to provide desirable electrical and structural characteristics. Namely, a first insulator column is capacitively graded along its length so as to provide a substantially uniform voltage distribution from the energized electrical apparatus along the length of the column, while a second insulator column provides the mechanical support for the electrical apparatus and for the first column. It is therein disclosed how electrical characteristics are best obtained when the first column is tapered so that the end of the column nearer the electrical apparatus is wider than the end of the column remote therefrom. The second column on the other hand, is constructed so that the end remote from the supported first column is of wider base, that is, of greater diameter, than the portion of the column adjacent to the first column supported thereby. This second arrangement serves to provide mechanical support for larger operating voltages and, together with the first column, presents an overall hourglass appearance which simultaneously exhibits the desired electrical and structural characteristics.

In FIG. 9, a column arrangement is shown in which the upper or first column 75 is of the type shown in FIG. 5, while the second column, the lower column is of the type disclosed in application Ser. No. 9,525 to afford the mechanical stability desired. In such arrangement, a rotating insulator stack (schematically shown as can be assembled from a ground point through a connecting link passing through the center of the upper column to provide opening and closing control of supported switch apparatus by means of mechanism due to the multirings being shell-like in nature. As previously described, the inner sheds with their corrugations serve as a rain shield in this environment in a manner previously accomplished by sealing. However, it will be seen that this arrangement is a simpler one than one requiring sealing which, because of the large size of units heretofore employed, required significant detail in its manufacture.

What is claimed is:

I. An insulator column arrangement for supporting electrical switches, buses, and the like apparatus in a power distribution system comprising:

a plurality of hollow annular shells of electrically insulating material each having only one internally projecting shed and only one externally projecting shed, with each of said plurality of shells having a top portion and a bottom portion each located intermediate said internal and external sheds;

means successively securing the bottom portion of one of said annular shells to the top portion of another of said shells to form an insulating columnar arrangement of hollow construction with open ends, whereby said externally projecting sheds function as rain shields to insure the dropping of water beyond the insulator column and whereby said internally projecting sheds function as further rain shields to prevent wetting of apparatus passing through the internal annular spacing established by the construction of said columnar arrangement in said described manner;

individual ones of said internally projecting sheds being provided with relatively sharp outer lip portions to force water off the rain shields provided, rather than to permit water from rolling around to upset the successive securing of said annular shells.

2. The insulator column arrangement of claim 1 wherein the diameters of said annular shells progressively change throughout the length of said insulator column established by the successive securement of said shells, one to another.

3. The insulator column arrangement of claim 1 wherein the diameters of said annular shells remain substantially constant over a first length of said insulator column established by the successive securement of said shells, one to another, and wherein the diameters of said shells progressively change over a second length of said insulator column established by said successive shell securement.

4. The insulator column of claim 1 wherein each internal shed is positioned at a height intennedi ate the height of the external shed of the same shell and the height of the external shed of the next adjacent shell joined thereto. I

5. The insulator column of claim 4 wherein the diameter of each shell is substantially greater than its height.

6. An insulator column arrangement for supporting electrical switches, buses, and like apparatus in a power distribution system comprising:

individual ones of said internally projecting sheds being provided with corrugated portions on the undersides thereof to increase creepage distances and to force water off the rain shields provided, rather than to permit water from rolling around to upset the successive securing of said annular shells.

Claims

1. An insulator column arrangement for supporting electrical switches, buses, and the like apparatus in a power distribution system comprising: a plurality of hollow annular shells of electrically insulating material each having only one internally projecting shed and only one externally projecting shed, with each of said plurality of shells having a top portion and a bottom portion each located intermediate said internal and external sheds; means successively securing the bottom portion of one of said annular shells to the top portion of another of said shells to form an insulating columnar arrangement of hollow construction with open ends, whereby said externally projecting sheds function as rain shields to insure the dropping of water beyond the insulator column and whereby said internally projecting sheds function as further rain shields to prevent wetting of apparatus passing through the internal annular spacing established by the construction of said columnar arrangement in said described manner; individual ones of said internally projecting sheds being provided with relatively sharp outer lip portions to force water off the rain shields provided, rather than to permit water from rolling around to upset the successive securing of said annular shells.

4. The insulator column of claim 1 wherein each internal shed is positioned at a height intermediate the height of the external shed of the same shell and the height of the external shed of the next adjacent shell joined thereto.

6. An insulator column arrangement for supporting electrical switches, buses, and like apparatus in a power distribution system comprising: a plurality of hollow annular shells of electrically insulating material each having only one internally projecting shed and only onE externally projecting shed, with each of said plurality of shells having a top portion and a bottom portion each located intermediate said internal and external sheds; means successively securing the bottom portion of one of said annular shells to the top portion of another of said shells to form an insulating columnar arrangement of hollow construction with open ends, whereby said externally projecting sheds function as rain shields to insure the dropping of water beyond the insulator column and whereby said internally projecting sheds function as further rain shields to prevent wetting of apparatus passing through the internal annular spacing established by the construction of said columnar arrangement in said described manner; individual ones of said internally projecting sheds being provided with corrugated portions on the undersides thereof to increase creepage distances and to force water off the rain shields provided, rather than to permit water from rolling around to upset the successive securing of said annular shells.