US1266516A - High-potential insulator. - Google Patents

Description

S. MOMOTA.

HIGH POTENTIAL INSULATOR.

APPLICATION FILED JUNE 14, I916.

Patented May 14, 1918.

Inventor: I

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' sAnAirI momora, or" TOKYO, JAPAN, nssrenon. roonnnm nrino rnrooomrm, A.

CO IEHEOR.ATION OF NEW YORK.

HIGH-POTENTIAL INSUIATOR.

To all whom it may concern:

Be it known that I, 'SAfiAJr MOMOTA, a subject of the Emperor o fi' llapan, residing at Tokyo, Japan, have invented, certain new and useful Improvements in High-Potential Insulators, of which the following is a-specification. v

-This invention relates to means for preventing creeping or surface discharge by so distributing the electric pressure sustained by an insulator surrounding a high voltage conductor that it will be limited at each-and every point on the surface of the insulating mass to a predetermined value. One ob ect of this invention is to prevent the heretofore unavoidable insulating surfacedestruction by distributing the intensity of the electrostatic field in a desired manner.

The invention may be applied to conductor leads or bushings of the condensing type or of .the 'oil. filled type or any other type suitable for'insulating high potentials,

in order .to increase the surface'insulation thereof.

The invention is illustrated in the ac companying drawing, whichr-Figure 1 is a vertical sectional vlew'of. an insulator or bushing of the condenser type with my in- I vention applied thereto; Fig. 2 is a similar view of insulating tubes which surround the. leads of an oil filled electrical apparatus and embodying 'my invention; Fig. 3 is similar to Fig. 1, wlth the condenser cylinders co'nnected through resistances or a transformer H win'ding;'and Fig.4 shows something of the I natural distribution of the electric .p ressure',

on ordinary insulators which do not employ this invention.

Considering for a -'moment f the electric pressure upon theinsulatin covverin'g of a. high voltage conductor to w ichthis'inven-i tion is not applied, we find a ..'condition some I thing like that indicatedin Fig. 4;, that is,

the portion .at A-sustains the greatest difference ofvelectrical potential per unit length and this difference of potential per uni't length gradually decreases toward the point N; in other words, the potential is somewhat concentrated on the'portion A and;tends to cause the surface insulation'to break down first at that portion, then on to points B, O,

' V and so on in order, until the creeping discharge intime perhaps flashes over the whole insulator. In other-words, because of the nonuniformity in the distribution of the electric pressure, the insulating power of other than they Would naturally assume, and' Specification of Letters Patent; I Patl ltd 14,1918, Application filed J'u'ne14, 1916. Seria1No.103,28. I U

The present invention contemparticularly aims at-obviating the defect of. I non-uniform 'distributionof potential by dis tributing the electric pressure onthe insulating shell according to a predetermined ratio between the differences of potential and the unit lengths of'the insulator; in 1 i other words, it a ms to distribute the electrostatic field in a desired manner instead of leavlngit'free to concentrate potential in a less efliclent manner.

III-Fig.- 1 is shown an insulator of the condenser type for insulating -a conductor 1',- the insulator being provided with concentric ,-metallic tubes 2; something like predeter- 'mined differences-of potential exist .between each two adjacent metallic tubes, as is well 4 The outer surfaces of this con- Y known. denser tube. insulating bushing are covered by shells 5 of some suitable insulating mate rial, asporcelain, andthe spaces. between these shells 5' and thebody portionof the insulator carrying the metallic tubes 2 are filled with oil=orother insulating material -6 i toprevent corona effects, etc; @Rings 3 of conducting ma't'erialare connectedxto the difr "ferent metallic-tubes {2' by the conductors l and thereby-fixed "at something like. predetermined.potentials.' These :rin'gs3are disposed one above another adjacent the bush-. ng'surfac'e andsurrounding the conductor 1 I y as illustrated." The rings are inclosed' bytheinsulating material of the bushingand are spac'ed'such, distances-apart along the l bushinglsurfaces that the total potential on th'e'surface of the insulating shell, as'from thepoint A to the point N' (Fig. 4),is so distributed that each unit of length of the insulator (so far as is desirable-under the conditions of the particular case) is subjected to approximately apredetermined desired difference of potential'between its ends.

' This is accomplished, ofcourse, by impressing on each ring a potential of a' desired value and a different value than the natural potential of the-surface of the bushing adj acent that respective rin'g. For example, if

the tubes'2 are so arranged'that equal dif-f ferences of potential occur between adjacent tubes, and the number of rings 3 at one end of the. bushing is equal to the number of tubes 2, the rin 's. 3 adjacent the surface of thatend of thefimshing maybe spaced sub stantially equal distances apart. The electric pressure will then be more equally distributed along the surface of that end of the bushing than were the rings omitted. Of course, the invention may be applied to either or both ends of any bushing. Obviously the members 3 are'not limited in shape to the ring shapes shown, as will be understood' to those skilled in this art.

The present invention is not limited to deriving the potential for any ring 3 (or other substituted member). from the bushing itself, as in the case of Fig. -1, but this potential may be derived from any other suitable source. Furthermore, the'invention may be applied to other types of bushings than the condenser type, as previously indicated, and the number of members 3 used in any casev will be such a number as may be desirable or necessary for that particular case. Thus in Fig. 2 the invention is shown applied to a form of oil filled bushing. The two rings 3 in each bushing in Fig. 2 derive potentlals through conductors 4, connected at suitable points of different potentials on the member 7, the'member 7 being connected toand tion of potential both within and on the sur-- face of the insulating shell is limited by the carrying current between the conductors 1.

The member 7 may be a resistance connected between the conductors 1 or an electrical winding supplied from or supplying the leads 1'. As before, the distribution of potential on the shell of the bushing may be limited as desired by employing a'sui'table number of rings 3 impressed with suitable potentials.

- In the construction of Fig. 3 the distribu member. 7, a resistance or a winding between the conductors 1. The metallic cylinders 2 1 and their respectively connected rings 3 are r separately connected 'to suitable points on the member 7 by means of the conductors 4.

Altogether the present invention is subj ect to more or less modification.

The present invention, it thus appears, greatly increases the insulating power of the surface of the insulation; at the same time, Where he condenser type of bushing is em.

ployed, the electric potentialon each of the condenser elements 2 and members 3-may be exactly determined in spite of the difierences which are unavoidable in the manufacture of the apparatus and inspite ofdiflerences' in electrostatic capacity, and independently of I J plate being embedded in said bushing and so located with reference to said conductor as the conducting areas.

What I claim as new and desire to secure by Letters Patent of the United States, is .1. The combination with a conductor and an insulating bushing surrounding the same,

of a ring of conducting material adjacent the surface of said bushing and surrounding .said conductor, a source of potential of a difi'erent value than the natural potential of the surfacev of said bushing adjacent said ring, and a conductor connecting said ring and said source of potential.

2. The combination with .a conductor and an insulating bushing surrounding the same,

of a ring of conducting material inclosed by the insulating material of said bushing adjacent the surface thereof and surrounding" said conductor,-a source of potential of a different value than the natural potential of the surface of said bushing adjacent said ring, and a conductor-connecting said ring and said source of potential.

3. The combination with a conductor and aninsulating bushing of the condenser type surrounding the same, said bushing being ductor, and a conductor connecting said ring to a condenser plate of a different potential than the natural potential of said surface adjacent said ring.

4. The combination with a conductor and an insulating bushing surr ounding the same,

of a ring of conducting material adjacent the surface of said bushing and surrounding the conductor, a conducting plate of a greater capacity than said ring, said conducting plate being embedded in saidbushing and so located with reference to said conductor as to have impressed upon it a potential of .a difierent value than thei natural potential of the surface of said bush- 'ing adjacent said ring, and a conductor connectin said ring and said plate.

5. T e combination w th a .conductor and an insulating bushing surrounding the same, I

of a ring of conducting material adjacent the surface of said bushing and surrounding "the conductor, a second conductor connected to and carrying current in connection with thefirst mentioned conductor, and another I conductor connecting saidring to-a point on said second conductor of a different potential than the natural potential of the surface of the bushing adjacent said ring.

. a conducting plate ofgreater capacity than 6. The combination with a conductor and I an'lnsulating bushing surroundmg the/same,-

saidconducting -mate1zial, said conducting of the surface of said bushing adjacent said 1 ent values than the natural potentials of the portions of the surface of said bushing adconducting material, and a conductor connecting sa1d conducting plate and said conducti material. 7. T e" combination Withaconductor and an insulating bushing surrounding the same, of a plurality of rings of conducting material spaced apart along and adjacent the surface of said bushing and surrounding said conductor, a source of potentials of different values than the natural potentials of the portions of the surface of said bushing adjacent said rings, and conductors connecting said rings and said source to impress on each of said rings a potential differing from'the potential of each of the other rings and differing from the natural potential of the surface of the bushing adjacent the respective rin 8% The combination with a conductor and an insulating bushing surroundingthe same, of a plurality of rings of conducting material spaced apart along and inclosedby the insulating material of said bushing adjacent the surface thereof and surrounding said conductor, a source of potentials of differjacent said rings, and conductors connecting said rings and said source to lmpress on each of said rings a potential differing from the potential 0 each of the other rings and differing from the natural potential of the surface of the bushing adjacent the respective ring.

9. The combination with a conductor and an insulating bushing surrounding the same, of a plurality of rings of conducting material spaced apart along and adjacent the surface of said bushing and surrounding, said conductor, a source of potentials of different values than thenatural potentials of the portions of the. surface of said bushing adjacent-said rings, and conductors connecting said rings and said .source to impress on said rings such potentials that the difference of potential between each two rings is approximately proportional to the distance between the same. i

10. The combination with a conductor and an insulating bushing of the condenser type surrounding the same, said bushing being provided with the usual condenser cylinders and being provided with insulating mate-- rial beyond the ends of said cylinders forming an external surface of said bushing, of means for reducing creepage along said surface by limiting the distribution of electric pressure, which means consists of a plurality of rings around and adjacent saidsurface of the bushing and conductors separately connecting said rings to said condenser cylinders.

11. The combination with a conductor and a bushing surrounding the "same, of means for reducing the creepage along the surface an insulating bushing of the condenser type surrounding the same, said bushing being provided with the usual condenser cylinders and being provided with insulating material beyond the ends of said cylinders forming an external surface of said bushing, of means for reducing creepage along said surface by limiting the distribution of electric pressure, which means consists of a plurallty of rings around and adjacent said surface of the bushing, a source of predetermined electric pressures, and conductors separately connecting said rings to said c0ndenser cylinders and said condenser cylinders separately to said source.

13. The combination with a conductor and an insulating bushing of the condenser type surrounding the same, said bushing being provided with the usual condenser cylinders and being provided with insulating material beyond the ends of said cylinders forming an external surface of said bushing, of means for reducing creepa e along said surface by limiting the distri ution of electric pressure, which means consists of a plurality of rings around and adjacent said surface of the bushing, a second conductor connected to and carryin current in connection with the first mentioned conductor, and

other conductors separately connectin said rings and condenser cylinders to di erent points on said second conductor.

In witness whereof, I have hereunto set my hand this 8th day of May, 1916.

SADAJI MOMOTA.

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