US1988151A

US1988151A - Bushing insulator

Info

Publication number: US1988151A
Application number: US578766A
Authority: US
Inventors: Arthur O Austin
Original assignee: OHLO BRASS Co
Current assignee: OHLO BRASS Co
Priority date: 1931-12-03
Filing date: 1931-12-03
Publication date: 1935-01-15
Anticipated expiration: 1952-01-15

Description

Jan. 15, 1935. A. 0. AUSTIN 1,983,151

BUSHING INSULATOR Filed Dec. 5, 1931 2 Sheets-Shet 1 NVENTOR Arf/u/r 0. 41/4/07 ATTORNEY Jan. 15, 1935. v ug-rm 7 1,988,151

BUSHING INSULATOR Filed D60. 3, 1931 I 2 Sheets-Sheet 2 Arf/zur 0. Awf/n.

BY W4 4% ATTORNEY Patented Jan. 15, 1935 BUSHING INSULATOB Arthur 0. Austin, near Barber-ton, Ohio, assignor,

by mesne assignments, to The Ohio Brass Company, Mansfield, Ohio, a corporation of New Jersey Application December a, 1931, Serial No. 51am Claims. (01. 173-318) This invention relates to bushing insulators and has for one of its objects the provision of an insulator of the class named which will have maximum efllciency for the size of the opening 5 through which the bushing extends.

Another object is to provide a bushing insulator which will be simple and economical to manufacture and easy to install.

A further object is to provide an insulator which will not permit oil or other insulating liquid to leak through the insulator Joints.

A further object is to provide a bushing insulator which shall be of improved construction and operation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is an elevation with parts in section showing one embodiment of the present invention.

Figs. 2, 3, and 4 are views similar to Fig. 1 showing other forms of the invention.

In high voltage bushings, particularly those used for transformers, circuit breakers and other equipment with line voltages below 100 K. V., it is frequently very diiflcult to obtain a bushing of small size which has the necessary dielectric strength and flashover voltage and is economical in cost. In many bushings, also, it is diflicult to maintain a tight joint between the bushing and the flange for attaching the bushing to the case so that the joint-will not leak oil, particularly whei-e changes in temperature are very material and the current is so high that it is necessary to use flanges of non-magnetic material.

In many installations already operation, it

becomes desirable to replace bushings with others the bushing consists essentially of an outer insulating member 10, an inner insulating member 11-, aflange 12, a conductor 13, and a compressing system comprising upper and lower plates 14- and 15 respectively, and springs 16 acting through the conductor 13 to hold the insulating

members

10 and 11 and the flange 12 together. An expansion chamber 17 may be added and the necessary terminals to provide a conducting cable drawn through the bushing or for utilizing the conduction of the tubular member 13. The insulating member 11 furnishes the outside or insulating sleeve on the lower end of the bushing and is cemented to the flange 12 and telescopes into the upper insulating shell 10. This arrangement provides an insulating baflle for the upper portion of the bushing of the diameter of the sleeve 11 at the point of maximum stress where it is joined to the flange 12 and where it passes through the opening 18 of the case of the transformer or circuit breaker.

Since the clamping means exerts a longitudinal pressure on the member 11 through the flange 15 and gasket 19, this pressure in turn may be transmitted through the cement joint 20 to the flange 12. This exerts pressure on the gaskets 21 and 22, insuring a tight joint at all times at the

gaskets

19, 21 and 22. Since the pressure on these gaskets is maintained by the resiliency in the compression springs 16, tightness will be maintained even though the center conductor expands or contracts or the gaskets change in volume due to pressure. Bolts 23 may be used to hold the springs 16 under compression while the bushing is being installed, after which the force of the springs is taken by the plate li'and nut 24. The bolts 23 may then be removed or left to hold the plate 14 from rotation on its axis; the nut 24 being screwed down to position to take the force of the springs 18.

The flange 12 is secured to the transformer or circuit breaker case 25 by clamping the face 26 of the flange 12 against

gaskets

27 and 30 placed betweenthe lower face 26of the flange 12 and the shoulder 28 surrounding the opening through the top wall of the transformer or circuit breaker case 25. The clamping is done by bolts or cap screws 29. With this construction, any leakage through the joint 20 between the body of the flange 12 and the member 11 will not reach the outside of the bushing, which is one of the most serious objectionsto many bushings.

Where a conservator tank is used in connection with the housing 25 in which the surface of. the oil is above that in the bushing or where a drop of the surface level of the oil in the bushing would be likely to have any eifect upon the operation, it is desirable to prevent leakage between the interior of the bushing and the interior of the tank through the joint 20. F 'or this i a and will expand against the insulating member 11, thereby insuring a tight joint due to the clamping pressure.

A similar joint may be provided at the upper end of the flange 12 if desired by using a metal ring 32 bearing on the gasket 21 on top of the flange 12. The pressure between themetal piece 32 and the gasket 21 will force the gasket 21 inward and tend to create a tight joint. The metal layer 32 above the gasket will prevent leakage through the gasket and also extend the pressure area inwardly from the bearing surface oi the member 10. The ring 32 may have an upwardly extending flange 33 acting as a flux control or screen.

In some cases, as shown in Fig. 2, it is possible to bring the bearing surface of the outer dielectric member 35 very close to the inner member 36 so that an additional metal ring is not needed for creating pressure. The bearing surfaces adjacent to the gasket may be beveled, as shown at 37, so as to force the gasket 38 against the member 36, thereby sealing the joint.

It will be seen that the construction is such that a tight housing orshell may be provided so that the insulator parts may be covered with oil or compound so that there will be no tendency to discharge over the upper end of the sleeves or bafllesll and 34 in Fig. 1, and 36 in Fig. 2. 'The construction insures tightness at all times between the outer porcelain shell and the flange used for attaching the bushing, hence, if a tight joint is provided between this flange and the transformer or circuit breaker case, leakage to the outside is prevented. This is particularly important for equipment having oil reservoirs or conservator tanks for raising the oil level above the flange.

Since the upper portion of the bushing may be given a large diameter without interfering with a small bolt circle, it is evident that a distinct electrical advantage is gained as the upper end of this bushing may be provided with the same field conditions as that of oil fllled bushings. A large. diameter to reduce the stress may be used without the necessity of making thick parts. The construction also permits of internal shielding so as to cut down the surface stress.

With the construction used, the entire length of the upper member is utilized for insulation, thereby making it possible .to reduce the length and cost of the bushing for given voltage requirements. The small diameter of the flange 12 makes it possible to use a bolt circle smaller in diameter than the lower end of the upper insu-'

lating shell

10 or 35. This is particularly important where the diameter of.the bushing is limited, owing to the opening in transformer or circuit breaker case. Since a tight construction is insured, the insulating baflles projecting into the upper cone may be covered with oil or compound which will prevent fiashover inside the case or upper shell 10.

The construction has the advantage that the insulating member subjected to most severe dielectric stress may be made of approximately the diameter of the opening in the transformer or circuit breaker case. This insures an insulating member of fairly uniform section and of maximum dielectric strength and reliability and one which may be made by simply extruding the clay or by other convenient methods.

While the diameter of the upper end of the

inner member

11 or 36 may be somewhat larger than that where it passes through the opening in the transformer or circuit breaker case or where it is attached to the metal flange, it need not be large enough to form the weather sheds, as these are formed on the

upper shell

10 or 35. This is a distinct advantage as a tubular member which must have a small opening and have a large diameter so as to form the weather sheds is difficult and costly to form, and the dielectric reliability is inferior to a piece formed practically to size. With the construction shown, a large diameter may be obtained at the upper end without restriction as to the use of a small hole in the inner piece. In addition, the electrical stress on the upper shell is largely in a longitudinal direction under normal operating conditions.

In Fig. 2 a single dielectric tube 36 extends through the opening in the housing 25, the opening through the tube being of a proper size to receive the conductor rod 39 while the tube is cemented directly in the flange 12. The flange 12 is secured to the housing-25 by cap screws 29, as in Fig. 1, the screws 29 being threaded into a ring 40 which engages the outwardly extending shoulder 28 surrounding the opening in the covershoulder 28 formed outwardly over the ring after the ring is in place. The outer member 35 is clamped upon the gasket 38 by the conductor rod 39 and spring 41 in a manner similar to the construction shown in Fig. 1 except that in Fig. 2 a single spring 41 is used in place of the plurality of springs 16, shown in Fig. 1.

Fig. 3 shows a construction somewhat similar to Fig. 2 but in this figure a packing gland is shown at 42 in which the packing is. compressed by a beveled face 43 of the gland member 44. An additional gasket 45 may be inserted between the lower face of the member 44 and the upper face of the shoulder 28 on the housing member 25. The inner dielectric member 46 may be provided with a flange 4'! forming a recess 48, the inner surface of which is metallized in any suitable way to provide an electrostatic flux control. The outer dielectric member 49 rests upon the flange 50 and is provided with a gasket 51 to form a tight joint. The flange 50 may be provided with a filling opening 52 closed by a plug 53. The flange 50 is cemented to the inner dielectric member 46 and the two dielectric members are held together by the conductor rod 54 provided with a spring 55 which compresses the gasket 51 and also the

gaskets

56 and 57 so that the inside of the bushing is completely closed and the joints at 51, 58 and,57 are held tight by the spring 55. The bolts 29 hold the bushlngin place on the housing 25 and, at the same time, compress the packing 42 and 45 to prevent leakage through the cement joint 58. A closed turn conductor 59 may be interlinked with the spring 55 to prevent heat losses in the spring 55, as explained in my prior application Serial Number 565,047. The conductor from the electrical apparatus in the housing is connected to a terminal member 102 having a spring socket for receiving the terminal member 103 threaded on the end of the conductor tube 54. The terminal 102 has a flexible cable 104 secured thereto which is drawn upwardly through the tube 54 when the bushing is installed to pull the terminal 102 into place. The flexible draw cable 104 may be secured in place by lock nuts 105 at its upper end which rest on the upper end of the tube 54.

In the modification shown in Fig. 4, the inner tubular dielectric member is formed of two separate sleeves, the inner sleeve 60 having a shoulder 61 upon which the lower end of the outer sleeve 62 bears. The sleeve 62 is secured to the flange 63 by cement 64. A ring 65 is provided with a seat 66 upon which the lower end of the upper dielectric member 87 rests; a gasket 68 being provided to insure a tight joint. The upper edge of the fiange 63 is beveled to provide a gland for receiving a packing 69 and the inner face of the flange 63 fits closely to the outer face the tubular member 62 so that the packing 69 may form a tight joint at this point. The flange 63 also fits closely against the outer surface of the dielectric sleeve 62 adjacent the lower end of the flange at '10, and a gasket '11 is placed between an offset portion of the fiange 63 and the housing '12. A metalring 73 may be provided to bear against the gasket '11 and a thin gasket '14 may be placed between the ring '13 and the housing '12 or this surface may be covered with a coat of paint, varnish or other material which will prevent leakage at this point.

I claim:

1. The combination with a housing having an opening through the upper wall thereoi, a' conductor extending through said opening, a tubular dielectric member surrounding said conductor and fitting closely within said opening, a flange cemented to the outer suriace of said tubular dielectric member and bolted -to said wall, said flange having an upwardly extending portion provided with a beveled upper edge forming a gland, packing for said gland, a ring surrounding said tubular dielectric member and bearing upon said packing, an outer tubular dielectric member telescoping with the upper end of said first-named tubular dielectric member and having its lower end bearing upon said ring, and resilient means for connecting said outer tubular dielectric member with said conductor for exerting yielding pressure on said ring to compress the packing in said gland and to hold said outer tubular dielectric member in position.

2. The combinaticn with a cover plate having an opening therethrough, of a conductor extending through said opening, a dielectric sleeve surrounding said conductor, a metallic fitting cemented to the outer periphery of said sleeve, a gasket bridging the cement joint between said sleeve and fitting and bearing upon said cover plate, threaded members for holding said fitting to said cover plate and for compressing said gasket to form a tight joint between said sleeve and cover plate, said fitting having a radially projecting shoulder thereon, a dielectric shell disposed over one end 01' said sleeve and having its open end bearing upon said shoulder, holding members attached to said conductor and bearing against the sleeve and shell respectively, and resilient means cooperating with said conductor and said holding members for pressing said shell against said shoulder to form a tight joint.

3. The combination with a wall plate having an opening therethrough, of a conductor extending through said opening, a dielectric sleeve surrounding said conductor, a metallic band surrounding said sleeve and cemented thereto and having a radially extending flange thereon, a gasket disposed between said flange and said wall plate and bridging the joint between said sleeve and band, threaded members for securing said flange to said wall plate and for compressing said gasket, packing engaging the edge of said band opposite said flange and bearing against the face of said sleeve, a metallic ring having a shoulder engaging said packing and having a radially extending flange, a dielectric shell disposed over the endof said sleeve and bearing upon the last named flange, holding members secured to said conductor and engaging said sleeve and shell respectively, and a spring cooperating with said conductor and said holding members for pressing said shell against said last named flange.

4. An insulator comprising a dielectric member, a metal fitting for said dielectric member, cement connecting said dielectric member and fitting, said dielectric member having a shoulder thereon adjacent the joint formed by said cement, a gasket engaging said metal fitting and said shoulder and bridging the joint formed by said cement and overlapping said metal fitting and shoulder at each side of said joint, and means also overlapping said metal fitting and shoulder.

and engaging the side of said gasket opposite said fitting and shoulder for compressing said gasket to press the same against said fitting and shoulder to prevent leakage through the joint formed by said cement.

5. A bushing insulator comprising a dielectric member, a flange cemented to the outer surface of said dielectric member, a shoulder on said dielectric member registering with one iace of said flange, a gasket bridging the joint between said flange and said dielectric member and overlapping said shoulder and the registering face of said flange, and means also overlapping said shoulder and flange and engaging the side of said gasket opposite said shoulder and flange and pressing said gasket in the direction of the axis of said bushing insulator to hold said gasket against said shoulder and said flange.

ARTHUR o. AUSTIN.