US1259383A - Insulator. - Google Patents

Description

GHARLE$ LIE G. FORTESGUE, OF EITTSBURGH,

JEIGUSE ELECTRIC AND MANUFACTURING Mil /KEANE,

YLVAHEA.

Specification oi Letters Patent,

PENNSYLVANIA, ASSIGNOR T0 WESTING- A CQRPO'BATION 0F PENN- INSUIJATOR.

Patented Mar. 1%, 1918.

Application filed May 11, 1914., serial No. 837,?4-2.

To all whom it may concern:

Be it known that 1, CHARLES Ln G. Fonrnsoun, a subject of the King of Great Britain, and a resident of Pittsbur 'h', in the county of Allegheny and State of ennsylvania, have invented a new and useful Improvement in Insulators, of which the following is a specification.

My invention relates to electrical insulating bodies or structures, and particularly to such structures as are employed for supporting high-voltage lines or conductors. I

I have discovered that, if the electrostatic flow lines in fields external to insulating bodies are precluded from concentrating upon their surfaces, the insulating structures are capable of effectively insulating coni highly desirable to obtain equal divisions of sign.

ductors of extremely high potentials. In order to provide insulating structures of the most efiicient design, it is necessary to con sider the application of the insulating materials, and also the production of substantially uniform electrostatic fields in the regions external to the structures. Accordingly, the E maximum insulating strength of structures .may be obtained if the external electrostatic fields are so distributed as to create uniform surface stresses upon the 1nsulat1ng structures.

A desirable form qfa transmission line insulating support comprises a system of con-' densers connected in series relation. It is potential .difierence between the insulating units comprlslng the condensers, but this 1s not the only req'iurement of a successful de- The aforementioned condition may actually be obtained, andyet the system of insulators will break down at a very much lower potential difference than the sum of the breakdown strengths of each insulator. To increase the strength of the system, the external electrostatic field should be so distributed as to secure a substantially uniform surface distribution of the electrostatic stresses imposed thereupon, as above mentioned. The external field will then be substantially uniform and vision of potential between the individual insulators or condensers. The eificiency of the combination is thereby increased in exactly the same way'that the efficiency of a condenser-type bushing of a particular design is increased by the addition of a large dish, namely, because it completes the surface dlsagree with the ditributio-n of the electrostatic field in the region surrounding the bushing. lit is unnecessary, however, to 'so design an lnsulating support as to efiect an equal di- VlSlOIl of the potential difference between the various units comprising the support in order to obtain good results, inasmuch as a substantially uniform distribution of the electrostatic field surrounding the support greatly enhances the insulating value of the support. Of course, when itis preferred to have the most efficient design and to minimize the overall length of the structure, it is desirable, for maximum efficiency, that the external field be substantially unlform and agree with the division of potential between the individual insulators comprising the structure. a v

One object of my invention is to provide an insulating structure for electrical conductors that 'shall be simple in construction,

and that shall substantially preclude the con-.

ing description and the accompanying draw-.

ing in which Figures 1 and 2 are sectional and side elevational views, respectively, of insulating supports equipped wlth devices built in accordance with my invention, and

Figs. 3 and 42 are similar views of suspension type insulators embodying forms of my invention.

Tn Fig. 1, a high-potential conductor 1 is secured, by means of a clamping device 2, to an insulating support 3 which engages a pin 3 The support 3 comprises a series of insulators or condensers 4 superposed upon one another, the upper and lower members 5 and (5 of which are provided with discoidal shaped electrodes or conducting members 7 and 7 that extend laterally beyond the insulators 4:.

Each insulator 4 comprises a metal bell or petticoat 8 into which is molded an insulating compound 9. A recess 10 is provided in order that the adjacent bell may benested therein, substantially as shown. The surface 11 of the dielectric or insulating compound 9 which is intercepted between two adjacent bells, is so molded as to conform to the lines of force of the electric field between the two adjacent bells. For the most economical design, it is desirable to have each insulator 1 take up approximately an equal share of the difference of potential between the conductor 1 and the structure from which the conductor-is to be insulated.

In order to obtain the highest efficiency, the discoidalshaped electrodes 7 and 7" are supplied to ap oximate, the result which would be obtained by bounding the insulating supportS by twoinfinite parallel conducting planes perpendicular to the axis of the insulator. By means of the electrodes or conducting members 7 and 7, the electrosta-tic field external to, and surrounding, the

insulating structure 3, will be substantially uniform. The condition for equal division of otential between the units 4 of the insulating structure is that the flux leaving each electrode or metal hell 8 shall be of the same quantity; this means that the capacity of' each electrode 8 to ground must be inversely as-its potential, and that the capacity between adjacent pairs of electrodes 8 must be equal. This is approximated very closely if the high potential electrode 5 and the Again, if the dimensions of the insulating structure as shown, are doubled, the capacity of the insulating structure to resist .hi h potentials is doubled.

t is apparent, however, that, by the ap- 7 plication of discoidal shaped bOdIQS 7 andto types of insulating supports other than i the one shown in Fig. 1, as, for example,

the'support shown in Fig. 2, the insulatmg.

strength of the support is greatly enhanced.

' The conductor 1 in Fig. 2 is supported by any adequate means upon the insulating structure 12 which comprises a plurality of superposed porcelain insulators 13 of a well known, type. The 'discoidal hhaped bodies .7 and 7 a are supplied to the upper andlower portions of the sup ort"12 in order to efiect a substantially uni orm distribution of the electrostatic field surrounding the. support 12 and to thereby preclude concentration of electrostatic stresses upon the surfaces thereof. v

In Figs 3 and 4, I have shown my invent1on applied to suspension type insulators.

shown.- The lower ends of the rods 17 are proyided with hooks 19 which engage eyelets 20 formed in the top portions of. an ad acent conducting. member 16. To securely hold the rods17 in pl ace, the insulating compound or dielectric 9 is molded around the top portio 18 of the rods, and the exposed surface 11 is preferably molded to conform to the electrostatic flow lines between the adjacent conducting members 16. In order to disengage the hook 19 from a coijperating eyelet 20, it is desirableto provide a recess 21 in'the molded material. v The recess 21 will not affect the insulating properties of the structure.

In this instance, a high potential conductor 22 is suspended from a clamping device 23 disposed on the lower end of a rod 24 secured to a lower conducting member 25. The conducting member or electrode 25, in cooperation with an upper conducting member or electrode 26, is provided with laterally extending portions 27 and 28, respectively. The whole is suspended from a hook 29 attached to any suitable supporting tower, pole, etc. (not shown). The electrodes 25 and 26 serve in this structure for the same purpose that the electrodes 7 and 7'- served' in the structures shown in Fi 1 and 2, and, what is said relative to t e most eflicient design of the structure in 1, may be applied with equal effectiveness to the most eflicient design of a structure to be made in accordance with the device shown in Fig. 3.

In Fi 4, the insulators 14 have been replaced y porcelain suspension type insulators 30.of a well known type of construction. While the device'shown in Fig. 4 is not as efiicient in resisting potential stresses as the device shown in Fig. 3, it has, how- Although I-have shown and described devices of specific structural details, many 1 modifications may be effected therein within the spirit and scope of my invention, and I desire that only such limitations shall be imposed as are indicated in the appended claims.

I claim as my invention:

The combination withan insulator compr sing a plurality of superposed separate umts, of conducting members secured to the upper and lower portions thereof, said members havmg' laterally extending flux-dis- 1 tributing isurfaces that coincide with the -to preclude substantially the concentration of electrostatic stresses upon. the surfaces of lower edges ofthe upper and: lower units of said insulator in order'to produce a substantially uniform surface distribution of.

the electrostatic stresses imposed thereupon.

2. The combination with an insulator comprising a plurality of superposed separate units, of parallelly disposed conducting memberslaterally extending beyond the insulator and secured to the upper and lower portions thereof, the laterally extending surfaces of said conducting members lying in the same planes as the lower edges of the upper and lower units in order to efiect a substantially uniform distribution of the electrostatic field surrounding the insulator.

3. The combination with an insulator com prising a plurality of superposed and separate insulating units, of parallelly disposed and laterally extending discoidal shaped electrodes for the upper and lower portions of the insulator, the flux-distributing surfaces of said discoidal shaped electrodes lying in the same planes as the lower edges of the upperand lower insulating units in order the insulator.

4. The combination with an insulating structure comprising a series of superposed insulating members, of conducting extensions for the upper and lower members that extend laterally beyond said members and lie in the plane's coinciding with therlower edges of said members in order to effect a uniform surface distribution of the electro; static field in the region surrounding the said insulating structure.

5. An insulating support for an electrical conductor comprising a built-up column of insulating members, and laterally-extending electrodes for the upper and lower members thereof, said electrodes being of relatively wide extent in order to produce a substantially uniform distribution of the external electrostatic field wherein it agrees with the division of potential between the insulating members comprising said built-up column.

6. An insulating support comprising. a plurality of separate units arranged one above the other -and constituting a system of condensers connected in series relation, and means to effect a substantially uniform distribution of the external electrostatic field surrounding the superposed units.

7. An insulating support for an electrical conductor. comprising a plurality of separate and similar units arranged above one another and constituting a system of condensers connected in series relation, and means to effect asubstantially uniform distribution of the external electrostatic field surrounding the said superposed units in order to obtain a substantially equal division of the potential differences therebetween.

8. An insulating support for an electrical conductor comprising a plurality of separate unis arranged above one another and constitutmg a system of condensers havlng sub.

stantially equal capacities, and means to effect a substantially uniform distribution of the external electrostatic field surrounding the said condensers in order to obtain a substantially equal division of the potential differences therebetween.

9. An insulating support for an electrical .sulating units, and discoidalshaped electrodes extending laterally from the top of the upper insulating unit and from the bottom of the lowest insulating unit in order to provide an external electrostatic field that agrees with the division of potential between the said insulating units.

11. An insulator comprising a built-up structure of equallyspaced andidentical insulating units, and conducting members extending laterally from the top of the upper insulating unit and from the bottom of the lowest insulating unit, said conducting members severally having fiat parallel surfaces that are opposed to each other in order to provide an external electrostatic field that agrees with the division of potential between the said insulating units.

12. An insulating support comprising a series of superposed insulating units, and fiat conducting members extending laterally from the top of the upper unit and from the bottom of the lowest unit in order to inclose all-of said units in asubstantially- Eniformly distributed external electrostatic eld. 'In testimony whereof, I have hereunto subscribed my name this 29th day of April,

, CHAR-LES LE G. FORTESCUE.

Witnesses:

LENORE FLANAGAN,

B. B. HINES.

- conductor comprising a plurality of separate

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