US1661823A - Insulator - Google Patents

Description

March 6, 1928. 1,661,823

K. A. HAWLEY INSULATOR Filed June 4 1921 vao Patented Mar. 6, 1928.

UNITED STATES PATENT OFFICE.

KENT A. HAWLEY, F NEW YORK, N. Y., ASSIGNOR T0 LOCKE INSULATOB CORPORA- TION, 0]' BALTIMORE, MARYLAND, A CORPORATION 0F MARYLAND.

IN SULATOB.

Application Med June 4,

The invention relates to grading means for high tension insulators, and more particularly to insulator units so constructed or formed as to provide means which, when a string is assembled and in use, will act to reduce the electrical stresses imposed upon the units closely adjacent the conductor by distributing these stresses throughout the series of units in the insulator string.

The principal object of my invention, broadly stated, is to rovide a string of insulator units which have combined with the insulating bod portions thereof, conducting elements, t us making the said surfaces slightly conducting, the said surfaces being adapted to act as elements of conden sers when the insulators are in use.

Another object is to provide a grading means for insulator units so as to furnish each unit of a string of suspension insulators with means for minimizing the electrical stresses imposed upon the said insulator units adjacent the conductor, said means being adapted to proportion the said stresses among the insulating units.

The medium surrounding a conductor, such as a wire carrying electricity, has to withstand a certain pressure, potential or voltage. This pressure or voltage carried by the wire always tends to escape to the earth through the medium surrounding the conductor or through a grounded conductor, and it is therefore essential to insulate the conductor from the earth or grounded conductor by means of insulating units. The greater the pressure in the conductor the more eiiicient must be the insulators which prevent the escape of this pressure to the grounded conductor. In other words, there 1s a ressure between the conductor and a metalic structure or grounded conductor 'tending to complete an electric circuit. Each inch of the medium surrounding the conductor has to stand a part of this ressure. Hencefif the conductor is insu ated from the earth through insulators the pressure which each insulator has to bear depends upon its distance from the grounded support or conductor. It is known that the further the conductor which is carrying the electricity is from the grounded conductor the less pressure insulator nearest the groundedconductor has to bear and 1921. Serial No. 475,003.

the greater pressure that the insulator adjacent the conductor or wire must withstand. Consequently in supporting high v oltage conductors by a string of suspenslon insulators, the insulators adjacent the conductor carrying the electric current are subjected to a tremendous pressure tending to cause thebreakdown of the insulator units adjacent the conductor, while the units which are farthest removed from the current carryln conductor have racticall no pressure Imposed thereon. The resu t of thus subjectin the u nit or units adjacent to the con uctor to the tremendous voltage which is now carried by high tension transmission lines has been that the insulators adjacent the conductor are stressed practically to their limit electrically, while the additional units in the string rform hardly any useful function electrical y, their function beingl mechanical as they act as a support for the insulators adjacent the conductor. It is vfor this reason that it is lmpossible, without using some method of gradin the insulators, to carry voltages throug the wires which exceed the electrical resistance of the units adjacent the insulator, that is, the combined electrical resistance of the entire string of units cannot be used as a measure of the insulation obtained by these units. ff

Heretofore attempts have been made to avoid this diiiculty by grading insulators of the suspension type by fastenin to certain insulators metallic elements whic act as elements of condensers, and certain other attempts have been made by using metallic elements connected to the supports or to the conductor, the metallic elements in both instances acting to distort the electrostatic vfield and thus more uniformly distribute the electrical stresses throughout the insulators. All of these efforts have been directed in connection with the application to the insulator units or to the conductors of extraneous metallic members, and as far as I am aware no attempt has been made prior to my invention to grade insulator units without applying thereto these extraneous metallic elements.

In the drawings, Figure 1 shows a String of suspension insulator units and beside the same, coordinates, the horizontal coordinate re resenting voltage and the vertical coor nate re resenting the number of insulators and `igure 2 shows a section through one ofthe units. f

' The support or grounded conductor is vdiagrammatically illustrated by the reference character A, each insulator unit by the reference character B, and the conductor by the reference character C. The curved line l) indicates the voltage drop between the insulators B, and the vertical line E which l crosses the curved line is intended to indicate the theoretically perfect grading between insulators.

It is impossible to so grade the insulator units that the actual voltage dro between units will lie along the theoretica ly perfect line; but by grading the units it is possible to make the volta e drop substantially uniform whereby a i-ne D is obtained which will approach approximately to the average line, and it will of course be apparent to those skilled in this art that the nearer this line approaches the average the nearer perfect is the grading.

In carrying out my invention I ap'ply to the insulator units, either in the formative stage or in the finished form, a high resistance or sli htly conducting ingredient, this ingredient eing intimately associated with the entire surface of the insulator unit and not separable therefrom mechanically.

The slightly conducting ingredient is preferably mixed with and forms an integral part of the glaze which is applied to the insulator unit, and I may use a graphite compound carried in suspension in the glaze. It is to be understood, however, that I do not limit myself to the use of graphite since other equivalent elements may advantage` ously be employed in this connection. It is also possible to coat the entire surface of the insulator units with graphite prior to the application of the glaze, and all of these methods I consider within the scope of my invention.

It will be understood that the insulating bodies of the units may be produced in any desired manner and Athat the special glaze is applied to these units after the same are formed and is then baked or red on the insulating body.

The result of applying this slightlyv conducting ingredient to the entire surface of the insulator unit is to transform the nonconducting surface of the insulator unit into a partially conducting surface or one coated with an attenuated or lm conductor. In other words, each insulating unit has on its entire surface a conducting element of high resistance, which acts as a leakage path between the main conductor C and the support A. As each insulator unit will have approximately the same resistance over its surface as each other insulator in the string,

it follows that there will be a continuous or unbroken ath for Ileakage currents, and the voltage rop will be divided approximately equa'lly between these different umts, approaching the grading indicated by the theoretically perfect line E. It will` be possible to make this resistance so high thatl the electricity escaping through the resistance will not re resent an appreciable power loss, yet it will e suicient to overcome the disturbing effect produced by the unequal volta e drop through the air.

1. Means for insulating and supporting a current carrying conductor from a oun ed conductor, comprising a string of insulator units each having a conducting surface of high resistance which forms a continuous and unbroken path for leakage current between the current conductor and the grounded conductor.

2. Means for supporting and insulating a current conductor from a grounded support, comprising a series of insulator units interposed therebetween and connected therewith, each unit havin al high resistance conducting material em edded in its surface forming a continuous and unbroken path for leakage current between the conductor and the grounded support.

3. Means for supporting and insulating a current conductor from a ounded support, comprisin a series of insulator units interposed there etween and connected therewith, each unit having a high resistance conducting surface forming a continuous and unbrokenpath for leakage current between the conductor and the grounded support, said high resistance surface being present on every exposed portion of each unit.

4. Means for insulating and supportin a current carrying conductor from a groun ed support, comprising a strin of msulator units each having a conducting surface of high resistance which forms a continuous and unbroken path for leakage current between the current conductor and the grounded conductor, said high resistance surface -consisting of slightly conducting material permanently united to and forming an inseparable part of everyexposed portion of the insulator.

5. Means for supporting and insulating a current conductor from a grounded support comprising a series of insulator units each having .a glazed surface embodying a conducting ingredient of high resistance to 'form a continuous and unbroken path for leakage current between the current conductor and the grounded support.

iis l 6. An insulator unit havingbits entire sur face provided with a glaze em resistance conductin 7. An insulatorA odying a high material. or high voltage lines comprising a disc of insulating riiaterialf having a resistance substance forming a reprising a disc of porcelain having a path of sistance path extending from the central resistance material extending over its eX- porton across the upper surface to the peposed surface from the central portion of 10 riphery and then across the under surface the upper surface to the central portion of v 5 and directly under the resistance path upon the lower surface.

the upper surface to the central portion. In testimony whereof I aix 1n signature. 8. An insulator for high voltage lines com- Y KENT A. HWLEY.

Images