US2794063A

US2794063A - Electric condenser

Info

Publication number: US2794063A
Application number: US347500A
Authority: US
Inventors: James H Nicholas
Original assignee: G&W Electric Specialty Co
Current assignee: G&W Electric Specialty Co
Priority date: 1952-02-01
Filing date: 1953-04-08
Publication date: 1957-05-28
Anticipated expiration: 1974-05-28

Description

May 28, 1957 J. H. NICHOLAS 2,794,053

ELECTRIC CONDENSER Original Filed Feb. 1, 1952 4 Sheets-Sheet l COND UC TION GLAZ E INVENTOR. James H. Tllcho las May 28, 1957 J. H. NlCHOLAS ELECTRIC CONDENSER 4 Sheets-Sheet 2 Original Filed Feb GLAZE CONDUCTION INHENERI mes H. u: 0 06 J. H. NICHOLAS 2,794,063

ELECTRIC CONDENSER 4 sheets-sheet 3 Miy 28, 1957 Original Filed Feb. 1, 1952 VOLTAGE DISTRIBUTION BETWEEN cououcmn 4 EXTERNAL GROUNDED SURFACE OF men 510511555 CONTROL TUBE,

INVENTOR. James H. Nicholas B 1 1/ I 1/ I z; 1 1 l C 1 C w w m WE .U Q C 9C5 UM [4W HmwM D 4 A W N NL% ML 0 06 4 80 C C .4 4C

May 28, 1957 J. H. NICHOLAS ELECTRIC CONDENSER 4 Sheets-Sheet 4 GLAZE v CONDUCTION GLAZE INVENTOR. James H. nwholas Original Filed Feb. 1, 1952 United States Patent ELECTRIC coNDENsER James H, Nicholas, Chicago, Ill., assignor to G & W

Electric Specialty Company, Chicago, Ill., a corporation of Illinois Original application February 1, 1952, Serial No. 269,365,

now Patent No. 2,745,897, dated May 15, 1956. Divided and this application April 8, 1953, Serial No. 347,500

Claims. (Cl. 174-143) This application a division of my co-pending application Serial 269,365, filed February 1, 1952, issued as Patent No. 2,745,897 on May 15, 1956.

This invention relates to electric condensers that are particularly adapted for use in high voltage electrical potheads such as are used for terminating the end of an insulated conductor.

It is one of the objects of the present invention to provide means for controlling the potential gradient in the outer insulator of a pothead or terminator structure to maintain as far as possible a uniform axial potential gradient in the transition from the radial electric field to the axial or longitudinal field.

The use, on extra high voltages, of potential gradient control means such as have heretofore been employed in potheads up to 160 kv. would generally result in an extremely large porcelain tube or tubes, which would be very costly and inefiicient. A considerably greater length and larger bore diameter would generally be required. Therefore, the ability of the porcelain tube to withstand the high internal hydraulic or gas pressures employed on pipe type cable systems would be reduced. The rupture stresses might be so great as to make the design infeasible.

It is one of the objects of the present invention to provide a condenser that is particularly adapted for controlling the external surface potential gradients in such a manner as to keep them at a more uniform value for the entire overall length of the porcelain of the pothead, thus using all of the surface with an equal and therefore high efficiency. In accordance with the principles of the present invention there is employed a ceramic tube of fairly rugged wall section and of material having an extremely high dielectric constant, that is, a specific inductive capacity of 100 to 200. By properly applying a conducting media on the external surface of such a tube or cylinder a very effective radial stress control tube can be ob tained. This is so because the radial voltage division between two coaxial electrodes insulated by two or more dielectric materials is not only a function of the various radii of the electrodes but also of the dielectric constant or specific inductive capacity (S; I. C.), and the thickness of the various dielectric materials. The higher the S. l. C. of one material used compared to the S. I. C. of the other material the less voitage the higher S. I. C. material has developed across it. Therefore, if the ratio of the S. l. C. of the two materials is made quite high, say 50 or 100 to one, then the high S. I. C. material will have a very small potential drop across it.

it is a still further object of the present invention to provide a condenser for controlling the potential gradient in the outer insulator of a high voltage terminator, which condenser is of an annular shape so that it can be slipped over the end of the high voltage conductor in assembling the terminator and wherein the condenser has a body of insulation constituting the dielectric of the condenser, which body surrounds the conductor and extends radially towards the outer insulator. A still further object of the present invention is to provide a simple and economical arrangement for making electrical connections between parts of adjacent gradient controlling capacitor units. This is accomplished, in the preferred construction, by using circumferentially extending garter springs that surround each capacitor unit, each spring being connected to the appropriate adjacent unit by a flexible jumper lead.

While the high voltage condenser of the present invention is primarily intended for use on cable systems which depend upon high internal hydraulic or gas pressures for their statisfactory operation, the principles of the present invention are also applicable to potheads for low pressure systems.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawings forming a part thereof.

In the drawings:

Figures 1 and 2, when placed end to end in axial alignment, are a longitudinal sectional View of a terminator embodying the present invention;

Figure 3 is a half elevational view and a half longitudinal sectional view of a capacitor unit of the present invention;

Figure 4 is a plan view of the capacitor unit;

Figure 5 is an enlarged cross section through the conductor and grading tube and shows the potential gradient therethrough;

Figure 6 is a diagrammatic view showing the approximate distribution of the equipotential lines in a terminator of the present invention; and

Figure 7 is a view similar to Figure 3 but showing an alternate capacitor grading tube.

Reference may now be had more particularly to the drawings wherein like reference numerals designate like parts throughout.

in the high voltage cable terminator of Figures 1 and 2 a cable 1 is mechanically connected to the outer porcelain insulator of a pothead or terminator 2 in the same manner as shown and more fully described in my pending application Serial No. 219,294, filed April 4-, 1951, now Patent No. 2,727,938, to which reference may be had. The means for sealing the end of a cable that enters the pothead may be the same as that shown and described in my application above referred to.

The cable conductor is indicated at 3. It is covered with the conventional wrapped paper insulation and surrounded by a conventional jacket 5 of insulation, of the type known as Polyethylene. in preparing the end of the cable for connection within a cable terminator the jacket end of the cable is removed in the usual manner to terminate at 6, and the cable shielding braid 7 is.removed to a point slightly above the end 6. Thereafter a stress cone insulator 9 is formed around the wrapped paper cable insulation 8. The stress cone insulator may be a preformed wrapping, known in the art. or may be formed in situ, as is also known in the art. In the case of the preformed stress cone it consists of an impregnated wrapped paper tube tightened on the cable during installation. The ground connection of the cable shielding braid 7 is continued by a wrapping of metal braid 10 which continues up to and slightly beyond the point of maximum diameter of the stress cone 9. The metal shielding braid 16 is then covered by a wrapping of cover insulation 11, all as described in the above referred to pending application. The cover insulation 11 is preferably a wrapping that can be compressed considerably without permanently distorting the same. One suitable material is a spongy crepe paper.

A stainless steel conical body 20 having a bottom flange 20a is secured at its lower end to the terminator mounting plate and suitably gasketed to provide a liquid-tight seal, and is grounded. A metal ring 21 is welded within the body 26 for supporting the stress control structure to be presently set forth. The ring 21 has a series of supporting bolts 22 threaded thereinto and secured in place by lock nuts. The supportingbolts 22 are uniformly spaced from one another, there being any suitable number of such bolts, six, eight or more. The supporting bolts 22 are of metal and support at their upper ends a base or seating ring 23 of metal, on which seating ring 23 the capacitor grading equipment, to be presently described, rests. The body has a metal ring 24 welded to the top thereof to facilitate securing the outer porcelain insulator 27 in place, as by six, eight, or more bolts 28 that thread into a one-piece ring 29 that is cemented to the bottom of the insulator for drawing the insulator firmly against a frusto conical sealing gasket 29', all as shown in my application Serial No. 219,294, to which reference may be had.

The capacitor grading equipment of the present invention comprises a radial stress unit 39 that rests on the seating ring 23 and in turn supports a series, in this instance ten, of capacitor potential gradient control units 32. The radial stress unit 30 is a hollow circular tube or sleeve of fairly rugged wall section, having lower and upper surrounding flanges 36-37. The material of which the tube is made is preferably ceramic, and of an extremely high dielectric constant (specific inductive capacity between 100 and 200). One suitable material, by way of example, is titanium dioxide. A conductive glaze or coating 39 is formed on the outer cylindrical portion of the unit 34), covering substantially the entire cylindrical surface of the inner sides of the

peripheral flanges

36 and 37 where the metallic glaze terminates.

The top and bottom of the unit are formed as perfectly fiat surfaces parallel to one another and at right angles to the longitudinal axis of the unit.

The

flanges

36 and 37 merge with the body of the unit along smooth curves, free of sharp edges, so that the metal glaze on the outside of the unit is also free of sharp edges where it extends from the cylindrical portion to the flanged portion of the unit.

Each capacitor potential gradient control unit 32 comprises a cylindrical body 40 of the same material as that of the radial stress unit 30 and also has upper and lower peripheral flanges, indicated at 4l4l, that extend from the cylindrical body 40 along smooth curves free of sharp edges. Midway between the short flanges 41-41 there is a rather wide continuous peripherally extending flange 42 which is an integral part of the rest of the unit 32 and surrounds the cylindrical body 40 thereof, and terminates at its outer edge in a peripheral rim 44 appreciably thicker than the flange 42. The rim 44 joins the flange 42 along smooth curves, free of sharp edges, and the flange 42 likewise joins with the cylindrical body 40 along smooth curves. A conductive glaze or coating 46, of metal or other suitable material, is formed on the outer cylindrical surface of the body 40 below the flange 42. The conductive glaze covers the entire cylindrical portion between the flange 41 and the flange 42 and extends at 4-7 to cover the entire annular surface of the flange 42. This conducting glaze terminates at 48. The rim 44 extends a slight distance beyond the end 48 of the conductive coating. At its lower end the conducting glaze terminates at 49 radially inwardly of the outer end of the flange 41, so that the flange extends beyond the end 49 of the glaze around the entire body 32. The upper half of the unit 32 has a similar metallic glaze 46' formed therein, identical in extent with the glaze 46, so that the upper and lower halves of the unit 32 are identical. The top and bottom surfaces of the unit 32 are flat, parallel planes so that similar units can be placed one upon another with substantially no spaces between them. a

It is apparent from the above description that the two the upper and lower values.

metallic coatings 4646' and the capacitor grading unit 32 constitute plates of a condenser wherein the flange 42 constitutes the dielectric, and that the size and material of the flange determines the capacity of the condenser. In addition, the cylinder surfaces 46-46 are capacity coupled with the cable conductor 3, the dielectric comprising the cylindrical body of the capacitor grading tube 343 or 32 and the mass of insulation between the

unit

39 or 32 and the cable conductor.

In the pothead illustrated in Figures 1 and 2 there are ten capacitor grading units 32 stacked one upon another, the lowermost one resting on the grounded radial stress unit 30. The respective units make a snug fit around the insulation 11 which, due to its compressible character, provides a suitable medium to take care of any radial expansion due to heating of the cable proper. Each axial condenser unit 32 is connected electrically in series with its adjacent units. This is accomplished by providing each grading tube 32 with two separate helically coiled metal garter springs 56 each formed as an end less ring and embracing the metal glaze on the cylindrical portion of the grading .tube, one below and one above the flange 42. Each spring is stretched and therefore tensioned by the cylindrical body of the capacitor grading tube, so that each spring remains in place and in electric contact with the conductive coating on the tube. Connection between adjacent condensers is formed by short braided copper or bronze jumper leads 58 each of which is soldered or otherwise electrically secured at its opposite ends to springs on adjacent capacitor grading tubes, as may be seen from Figures 1 and 2. The lowermost grading tube 32 is connected at its bottom half by a jumper lead 58, to a spring 60, identical with the spring 56, that surrounds and is tensioned around the conducting coating 39 on the lowermost radial stress unit 30, said spring being also connected by a similar jumper lead 62 to one of the grounded bolts 22. The uppermost spring of the series of capacitor grading tubes is connected by a jumper lead 66 to a metal yoke 63 that rests upon the upper flange of the uppermost grading control unit 32, and is electrically connected to the cable conductor. It is thus apparent that the capacitor grading tubes are connected in series between ground potential at their lower ends and the conductor potential at their upper ends. The bight portion 69 of the yoke 68 has a centrally located hole therethrough through which extends a metal connector stud 70 that is mechanically and electrically secured to the end of the cable conductor 3. The yoke 68 is pressed downwardly by a coiled spring 72 that bears at its lower end at the top of the yoke and at the upper end is received in a cap 74 that is held in position by a nut '76 threaded on the stud 70. The spring 72 acting through the yoke 68 presses against the top of the uppermost potential grading tube 32 and maintains all of the grading tubes and the lowermost stress unit St) in engagement on the seat of the seating ring 23 during assembly of the pothead. This stress is taken over by the insulator 27 and the base and cap assembly when the pothead has been assembled.

For mechanical simplicity all of the capacitor grading units '32 may be of identical construction. However, as pointed out previously, there is an electrical advantage 1n making these control units of diiferent capacities rangmg from a maximum capacity of the lowermost unit 32 and a minimum capacity of the uppermost unit 32. The variation in capacity is obtained by making the flanges 42 of the respective units of diiferent thicknesses, the flange 42 of the lowermost unit being of minimum thickness and the corresponding flange of the uppermost unit being of maximum thickness, with the flanges of the intervening units of thicknesses grading between In one preferred construction, which is the one here described, the radial capacity for the unit 30 and for each one of the units 32 was 11.5 micromicrofarads, and the axial capacity between the conductor surfaces 47-47 of the lowermost unit 32 was 2400 micromicrofarads, and the capacity between the conductive glazed surfaces 47-47 of the uppermost or line voltage control unit 32 was 200 micromicrofarads, and the capacities between the surfaces 47-47 of the intervening units graded between those two values.

The upper portion of the pothead is sealed in any conventional manner, for instance, as shown in my pending application Serial No. 219,294 above referred to, to which reference may be had. This seal consists of a cap assembly which includes a metal hood 86 having a closed thin metal tube 88 in which the stud makes a sliding fit, thetube being then compressed on the stud to establish proper electrical and mechanical connections. The upper end of the stud has longitudinal slots therein to permit fluid to flow past the stud within the tube 88, as may be required during formation of the pothead. The hood '86 rests on and is sealed over the upper end of the insulator 27, a suitable frusto conical sealing gasket 89 being interposed to facilitate the sealing action. A unitary ring 90, which is suitably secured to the bottom of the hood, provides means for bolting the hood to a unitary ring 92 that is cemented around the top neck of the insulator 27, all as shown in my aforesaid application. 'The usual metal corona shield 94 is provided. The hood has a tapped boss 95 for receiving fittings used during installation.

. Reference may now be had more particularly to Figure which shows an enlarged cross sectional view through the cable conductor and the grading tube 30 or the lower half of the bottom unit 32, and shows the voltage gradient, in percentage, from the outer surface of the cable conductor, through the cable insulation and through the grading tube to the potential on the glaze 46 of the tube 32, which is ground potential in the case of the lowermost tube 32. If we assume that the insulation between the cable conductor and the grading tube 32 has a specific inductive capacity of 4 and that the specific inductive capacity of the insulation of the tube 32 is 100, then the voltage distribution starting at 100% cable conductor voltage at the periphery of the cable conductor 3, as indicated by the ordinate line 101, is indicated by the curve 100, progressing downwardly along the curve until at the inner periphery of the tube 32 the voltage, indicated at 102, is 0.5% of the total voltage between the cable conductor and the metallic glaze 46 on the outside of the tube 32. From the point 102, which indicates a voltage of 0.5% on the inner surface of the body of insulation 40 of the tube 32, the voltage gradient then follows along the line 104 through the thickness of the insulation 40 to the potential of the conducting glaze 46. It is thus apparent from the curve of Figure 5 that the potential on the inner surface of the respective grading tubes 32 is only 0.5% of the voltage on the outside of the potential grading tube, so that within the pothead insulator 27 the potential on the outer surface of the wrapped insulation around the cable conductor is, at each point of the axial length thereof, at a value substantially equal to that of the adjacent

outer condenser plate

46 or 46. Since the capacitor grading tubes 32 are arranged to provide a uniform stepped voltage stress distribution from the line voltage at the top of the pothead to ground voltage at the bottom theref, it is thus apparent that substantially the same voltage distribution is obtained along the axial length of the cable conductor covering insulation.

Reference may now be had more particularly to Figure 6 which shows the approximate distribution of the equipotential lines in the pothead above described. In this pothead the ten capacitor grading tubes 32 are of identical heights and the ilanges 42 of the respective ones thereof are of different thicknessses to give an axial capacity of 2400 micromicrofarads for the bottommost tube '32 and 200 micromicrofarads for the uppermost tube 32, as set forth above. The total axial capacitance, namely, the equivalent capacity of the group of capacitances 32 in series are such that the capacity current controlling the voltage division is not appreciably affected by external stray capacities and leakage currents. The axial capacity current is made to be of the order of one to five milli-amperes, depending upon surface conditions and voltage rating. The equipotential lines 111 to 120 are lines from 5% to of the line to ground voltage in uniform steps of 10% between successive ones of the lines 111 to 120. These lines show the relative uniform axial distribution of the voltage both in the internal dielectrics as well as in the external dielectric.

In considering the flow of capacity current through the connected condensers of the respective capacitor grading tubes 32 there are a number of factors that must be borne in mind. One is the usual current flow through the condensers that are connected in series from the line potential to the ground potential as determined by what might be called the axial capacity of the respective units. Another is the fact that capacitance exists between each unit capacitor and the insulated cable conductor that passes within it. This may be referred to as the radial capacity as distinguished from the axial capacity. It is apparent that all of the units are required to carry the capacitance current resulting from the axial capacity and that the capacitor units 32 near the grounded end of. the structure would be required to carry more of the radial capacitance current than is required of those units 32 that are nearer the conductor or line potential end, since the radial capacitance current at any point of the cable flows to ground only through those units 32 between. that point and ground. This increased current passing through the lower units would normally tend to produce a greated potential drop across the lower units 32 than the potential drop across the units 32 nearer to the top of the pothead. Therefore, a uniform potential gradient would not be obtained with uniform axial capacity in the respective capacitor grading tubes 32. By having the capacitor units of progressively increasing values between the line end and the grounded end, and properly graded, a uniform voltage division between the respective grading tubes 32 and the flange 42 of each such unit is obtained.

It is desirable that individual capacitor sections 32 be employed because this simplifies manufacturing problems and permits production dielectric testing of the respective units and capacity adjustment in assembling units of different capacities. However, a one-piece construction of two or any other number, up to all, of the units 32, with or without the unit 30, may be provided in which the equivalent condensers formed at the respective flanges 42 of that unit are electrically in series the same as the different units 32. This is illustrated in a fragmentary manner in Figure 7, wherein the unit, indicated at 32a, comprises two or more, up to all, of the units 32 of Figures 1 and 2. The parts of Figure 7 that are the same as corresponding parts of the unit of Figure 3 have been designated by the same reference numerals with the subscript a added to designate this alternate structure.

The high voltage pothead described above is primarily adapted for use on cable systems which are of the high internal hydraulic or gas pressure type. The principles can, however, be applied to potheads for low pressure systems. In the design of such systems there is much greater leeway as to the outer porcelain bore diameters, since these diameters are not limited by the porcelain rupture stresses involved on the high pressure systems.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merely illusavs goss trative of the principles of the invention. What I consider new and desire to secure by Letters Patent is: 1. An electric condenser comprising an open ended sleeve through which a'high voltage conductor may be extended, said sleeve having a thin radially outwardly extending surrounding flange, the sleeve and the flange constituting one integral body of insulation, and separate unconnected metallic conducting areas covering the opposite surfaces of the flange to form two conducting areas constituting opposite plates of a condenser, and at least one of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve.

2. An electric condenser comprising an open ended sleeve through which a high voltage conductor may be extended, said sleeve having a radially outwardly extending surrounding flange intermediate the ends thereof, which flange in turn is surrounded by a rim, the sleeve and the flange and the rim constituting one integral body of insulation, and separate metallic conducting areas covering the opposite surfaces of the flange and each terminating at its outer periphery at said rim so that the two conducting areas constitute opposite plates of a condenser, and each of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve, the opposite ends of the sleeve being flat planar surfaces to permit stacking of similar condenser units one upon another.

3. An electric condenser comprising an open ended sleeve through which a high voltage conductor may be extended, said sleeve having a radially outwardly extending surrounding flange intermediate the ends thereof, which flange in turn is surrounded by a rim, the sleeve and the flange and the rim'constituting one integral body of insulation, and separate metallic conducting areas covering the opposite surfaces of the flange and each terminating at its outer periphery at said rim so that the two conducting areas constitute opposite plates of a condenser, and each of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve, the opposite ends of the sleeve being flat planar surfaces to permit stacking of similar condenser units one upon another, and means for connecting the condenser in a circuit comprising two metal helical springs each coiled to form an endless ring that are tensioned respectively around the conducting areas on the sleeve on opposite sides of the flange.

4. An electric condenser comprising an open ended sleeve through which a high voltage conductor may be extended, said sleeve having a radially outwardly extending surrounding flange intermediate the ends thereof, which flange in turn is surrounded by a rim, the sleeve and the flange and the rim constituting one integral body of insulation, and separate metallic conducting areas covering the opposite surfaces of the flange and each terminating at its outer periphery at said rim so that the two conducting areas constitute opposite plates of a condenser, and each of said conducting areas extending also along the outer surface of the sleeve, and means for establishing electrical connections to said conducting areas comprising metallic helical springs coiled to form separate endless rings, the respective rings being tensioned around the conducting areas of the sleeve.

5. An electric condenser comprising an open ended sleeve through which a high voltage conductor may be extended, said sleeve having a radially outwardly extending surrounding flange intermediate the ends thereof, which flange in turn is surrounded by a rim, the sleeve and the flange and the rim constituting one integral body of insulation, and separate metallic conducting areas covering the opposite surfaces of the flange and each terminating at its outer periphery at said rim so that the two conducting areas constitute opposite plates of a condenser, and each of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve, the opposite ends of the sleeve being flat planar surfaces to permit stacking of similar condenser units one upon another, and means for connecting two such condenser units in series comprising two metal helical springs each coiled to form an endless ring that are tensioned around the respective sleeves.

6. In combination with a current carrying conductor, a condenser element formed by an open ended insulating sleeve surrounding said conductor, said sleeve having a radially outwardly extending. surrounding flange of insulating material formed intermediate its ends and separate conductive areas on the outer surface of said sleeve, the ends of said sleeve each being flat to facilitate coaxial stacking of similar condenser elements, said conductive areas covering the opposite surfaces of said flange to form two spaced conducting members constituting opposite plates of a condenser and said flange of insulating material forming a condenser dielectric, and each of said conducting areas extending also along the outer surface of the sleeve into capacitive coupling relationship with said current carrying conductor, whereby said conductor and said portion of the conductive areas surrounding said sleeve forming respective condensers which in turn are electrically connected with said first-mentioned condenser.

7. A condenser assembly comprising a pair of stacked condenser elements each of which comprises an open ended sleeve of insulating material having a radially outwardly extending surrounding flange intermediate its ends, said sleeves also having respective end flanges at their opposite ends which project a lesser amount from the sleeves than said first-mentioned intermediate flange, and separate conductive areas on the opposite sides of the intermediate flange of each sleeve, said conductive areas extending from the end flanges of each sleeve along the body of the sleeve and along the opposite surfaces of said intermediate flange to form opposite plates of a condenser separated by a dielectric constituted by said intermediate flange, and means for electrically connecting said two stacked condensers comprising two metal helical springs each coiled to form an endless ring which are tensioned respectively around the adjacent conductive portions of said respective sleeves and a jumper lead electrically connecting said helical springs.

8. An electric condenser comprising an open ended sleeve having a cylindrical inner surface forming a bore through which a high voltage conductor may be extended, said sleeve having a thin radially outwardly extending surrounding flange, the sleeve and the flange constituting one integral body of insulation, and separate unconnected metallic conducting areas covering the opposite surfaces of the flange to form two conducting areas constituting opposite plates of a condenser, said sleeve having an outer surface parallel to the inner cylindrical surface for a substantial fractional part of the axial length of the sleeve, and at least one of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve.

9. An electric condenser comprising an open ended sleeve through which a high voltage conductor may be extended, said sleeve having a radially outwardly extending surrounding flange intermediate the ends thereof, which flange in turn is surrounded by a rim, the sleeve and the flange and the rim constituting one integral body of insulation, the sleeve being of uniform thickness for a substantial portion of its length on opposite sides of the flange, and separate metallic conducting areas covering the opposite surfaces of the flange and each terminating at its outer periphery at said rim so that the two conducting areas constitute opposite plates of a condenser, and each of said conducting areas extending also along the outer surface of the sleeve to form a capacity coupling with a high voltage conductor that may be extended axially through the sleeve, the opposite ends of the sleeve being fiat planar surfaces to permit stacking of similar condenser units one upon another.

10. In combination with a current carrying conductor, a condenser element formed by an open ended insulating sleeve surrounding said conductor, said sleeve having a radially outwardly extending surrounding flange of insulating material formed intermediate its ends and separate conductive areas on the outer surface of said sleeve, the ends of said sleeve each being flat to facilitate coaxial stacking of similar condenser elements, said conductive areas covering the opposite surfaces of said flange to form two spaced conducting members constituting opposite plates of a condenser and said flange of insulating material forming a condenser dielectric, said sleeve being of uniform thickness for a substantial portion of its length on opposite sides of the flange, and each of said conducting areas extending also along the outer surface of the sleeve 10 into capacitive coupling relationship with said current carrying conductor, whereby said conductor and said portion of the conductive areas surrounding said sleeve forming respective condensers which in turn are electrically connected with said first-mentioned condenser.

References Cited in the file of this patent UNITED STATES PATENTS 1,868,962 Atkinson July 26, 1932 1,870,141 Regerbis Aug. 2, 1932 1,878,169 Myers Sept. 20, 1932 2,065,921 Gerth Dec. 29, 1936 2,161,326 Webb June 6, 1939 2,251,540 Buschbeck Aug. 5, 1941 2,297,200 Buschbeck Sept. 29, 1942 FOREIGN PATENTS 601,961 Germany Aug. 28, 1934 478,602 Great Britain Ian. 21, 1938 1,000,191 France Oct. 10, 1951 1,010,397 France Mar. 26, 1952