US2188417A - Bushing insulator - Google Patents

Description

Jan. 30, 1940. H, L, RQRDEN 2,188,417

' BUSHING INSULATOR Filed Feb. 4, 1938 2 Sheets-Sheet 1 w INVENTOR 56 v Hare/0 L. fora m7 BYWJ- ATTORNEY Jan. 30, 1940. H. RORDEN BUSHING INSULATOR 2 Sheets-Sheet 2 Filed Feb. 4, 1938 INVENTOR //4/0/0 L. fin)? /fi ATTORNEY Patented Jan. 30, 1940 UNITED STATES PATENT OFFICE BUSHING INSULATOR Harold L. Borden, Barberton, Ohio, assignor to I The Ohio Brass Company, Mansfield, Ohio, a corporation of New. Jersey Application February 4, 1938, Serial No. 188,691

7 Claims.

. mum.

A further object of the invention is to provide a bushing insulator in. which the danger of overstressing the insulating liquid is also reduced to a minimum.

A further object of the invention is to provide a bushing insulator having a plurality of baffles with means for improving the voltage gradient in the insulation.

A further object of the invention is to provide a device of the class named 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 in the appended claims.

In the drawings:

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

Figs. 2 and 3 are fragmentary sections showing modifications of the invention.

Fig. 4 is a view similar to Fig. 1 showing another form of the invention.

Figs. 5, 6, 7 and 8 are fragmentary sections of bushing insulators showing their modified features of the invention.

In the form of the invention shown in Fig. 1 the number I!) designates a hollow conductor extending through a flange arranged to be connected to an opening in a housing for electrical apparatus such as a switch housing or a housing for a transformer. At the lower end of the conductor H! is a fitting l2 secured to the conductor and supporting the lower dome |3 of the bushing insulator. The dome |3 is preferably made of porcelain but may be made of other suitable insulating material. A shoulder |4 extends outwardly from the upper portion of the dome I 3 and supports the flange I. The cone l5 rests on the flange H and carries an expansion chamber I6. Within the expansion chamber I6 is a compression spring H which supports a ring l8 which engages a collar l9 secured to the upper space within the bushing. Sufiicient slippage is end of the conductor Il The spring exerts a tension on the conductor I0 and a compression on the dome l3, cone l5 and flange I I, thus holding the parts of the insulator together. Secured to the lower end of the conductor I0 is a fitting 5 2|] which carries a porcelain baffle tube 2| surrounding the conductor II]. A second porcelain baflle 22 is secured to the baflle 2| by cement joints 23 and 24. The dome l3 is provided with an extension 25 which projects through the flange 10.

|| so as to increase the insulation between the conductor I0 and the flange. The space within the bushing not otherwise occupied is preferably filled with insulating oil or other dielectric liquid and the inner space 26 immediately surrounding 15- the conductor I0 is preferably separated from the remainder of the space within the bushing by the battle 2| and a metal tube 21 which is secured to the upper end of the bafile 2| by a liquid tight joint at 28. The inner face of the tube 2| is preferably coated with conducting material 29. This coating may be made of copper or other suitable metal sprayed upon the inner surface of the tube. There are several well known methods for coating porcelain with metal any one of which may be used for this purpose. A passage 3|] extends through the fitting an to connect the space 26 with the remainder of the space within the bushing. The gasket 3| is interposed between the expansion chamber l6 and the cone |5 to 30 form a liquid tight joint at this point and the inner edge of the gasket bears against the tube 21 with suflicient force to prevent circulation of the oil from the expansion chamber to the outer permitted, however, to prevent stress due to differential expansion of the bushing parts. When the bushing and the expansion chamber are filled with oil, the oil will expand and contract due to temperature changes, producing a breathing action through the upper portion of the expansion chamber. This will permit the oil in the expansion chamber to contact with the air which is breathed into the chamber and some of the moisture or other contamination in the air may be absorbed by the oil in the expansion chamber. This oil, however, is not in direct contact with the main body of the oil in the bushing, but is separated from the main body by the tube 21 and the baffle 2!. The space immediately surrounding the conductor I0 is of sufiicient volume that the contaminated oil in the expansion chamber will never be drawn through the passage 30 into the space outside the bafile 2|. Deterioration of the oil in the space 26 is of no serious consequence because this space is preferably shunted by a jumper 32 so that even if the oil in the space 26 is not a perfect dielectric, there will be no breakdown of the oil in this region because it is not subjected to electric voltage. It has been found advantageous to provide a shunt across this space to prevent overstress of the. oil even when the oil is not contaminated, because, where the space 26 is not shunted, it is subject to a very high voltage due to the fact that electrostatic lines of force are concentrated in this zone adjacent the conductor; and also due to the fact that oil has -a lower specific inductive capacity than porcelain and consequently, there is a greater drop of potential through the oil than there would be through a like thickness of porcelain. The coating 29 and jumper 32, therefore, perform a double function of short-circuiting the zone of highest electrical. stress and the zone most apt to contain oil which has been affected by contact with the outer atmosphere.

By extending the dome |3 through the flange 1, additional insulation is provided between the conductor and the flange to compensate for the shunted space 26 about the conductor. This insulation is more advantageously placed than the oil in the space 25 because of the greater area at the greater distance from the axis of the conductor. By this arrangement the voltage stress is allocated in the portion of the insulator farther removed from the axis and in a zone where the lines of force are less concentrated so that the dielectric is more effective in withstanding the voltage.

In order to reduce the danger of corona or arcing from the flange toward the expansion chamber, ap'ocket 33 is provided in the lower portion of the cone l5 and the inner surface of the pocket is metallized and connected with the flange so that the electrostatic lines of force will emanate from the lining of the pocket directly into the porcelain and not into the atmosphere.

The form of the invention shown in Fig. 2 is similar to that in Fig. 1 except that the baffles 2| and 22 are both metallized on both their inner and outer faces, there being suflicient space at the ends of the battles which is not coated to prevent discharge aboutthe ends of the b'aflles'. The adjacent coatings are connected by jumpers 35 and 35. thusshunting the oil space between the baiiles and placing the entire voltage stress upon the porcelain. The conductor plates thus provided between the porcelain baffles forms 'a condenser arrangement whichassists in producing a better voltage gradient between the conductor Hi and the flange H.

In the form of the invention shown in Fig. 3 the upper portion of the outer surface of the dome i3 is metallized as shown at 36, the lower edge of the metal coating terminating in a pocket 3'! forming a flux control for preventing electrostatic discharge at the lower edge of the coating 318. The flux control 31 is preferably located far enough down on the dome I3 so that it will be always submerged in the insulating fluid in the housing for the electrical apparatus served by the bushing. This prevents any danger of discharge downwardly from the flange II.

In the form of invention shown in Fig. i the dome l3 terminates at the flange H and an additional keg 33 is carried by the flange within the outer shell of the bushing to help withstand the voltage between the conductor and the flange. In this form of the invention, instead of utilizing air out through the tube 4|.

the inner porcelain baffle 2| to divide the oil space within the bushing, a special metal tube 39 surrounds the conductor ID and is flared outwardly at its upper end to form a flange 40 which is caught between the upper end of the cone I5 and the expansion chamber I6 forming a tight joint at this point. A small tube 4| extends through the wall of the tube 39 and projects upwardly inside of the conductor !0 to a point where it communicates with the outer atmosphere. This permits escape of air from the space within the bushing surrounding the tube 39 as oil is filled into. the bushing. The oil will flow down in the space 26 between the conductor and the tube 3 9 and enter the outer portion of the bushing through the passage 39 forcing the The space 26 between the conductor Hi and the tube 39 is sufficient to accommodate the ebb and flow of the oil due to any breathing action so that contamination due to contact with the outer atmosphere will not affect the oil outside of the tube 39.

Fig. 5 shows a difierent arrangement for permitting escape of air from the outer portion of the bushing when the bushing is being filled with oil. In place of the. tube 4| a valve 42 permits escape of air from the outer portion of the bushing'but prevents entrance of oil into the bushing directly from the expansion chamber.

In the form of invention shown in Fig. 6 a metal tube 43 is soldered to the metal coating 29 on the bafiie 2| and has its upper end turned outwardly and caught beneath the expansion chamber I6 as shown at 44. A tube 45 similar to the tube 4| in Fig. 4 connects the space outside of the battle 2 with the outer atmosphere to permit escape of air when the bushing is filled with oil. i g

In the form of invention shown in Fig. 7 a tube 56 is soldered to the battle 2| and extends past a gasket 3| asin Fig. 1. In this case the space within the expansion chamber communicates with the upper end of the tube 46 through a passage 41 which is elevated somewhat above the bottom of the expansion chamber providing a sump. 48 for the accumulation of moisture which may be entrapped by the oil in the expansion chamber. v

A similar trap 49 may be formed at the lower end of the tube 39 as shown in Fig. 8 by closing the lower end of the tube by means of packing 50 and providing an opening 5| for the escape of oil into the outer portion of the bushing at a point somewhat above the lower end of the tube 39.

I claim:

1. The combination with an electrode having an opening therethrough and a conductorextending through said opening, of a bushing insulator separating said conductor from said electrode, said bushing insulator comprising a housing having space therein closed at its bottom, electric insulation within said space including an insulating liquid, said space being divided into inner and outer compartments, the dominant insulation in said space between said electrode and conductor being disposed in said outer compartment, the liquid in said inner compartment having its surface exposed to atmospheric pressure, said compartments being sealed against communication with each other at their upper ends but connected at their lower ends and being constructed and arranged so that the dominant portion of all liquidentering said outer compartment t0 compensate-rfor, contraction of the liquid in said outer compartment will be supplied from the inner compartment, said inner compartment having suilicient capacity between the surface of the liquid therein and the point of communication between said compartments to accommodate the ebb and flow of the insulating liquid due to expansion and contraction of the liquid in said outer compartment without passage from said inner to said outer compartment of liquid which has been contaminated by contact with the atmosphere.

2. In combination. a bushing insulator comprising a housing, an expansion chamber communicating with the outer atmosphere and con nected with said housing, a conductor extending through said housing and having liquid tight connection with said housing at the lower end of said housing and a baffle tube surrounding said conductor and communicating at its upper end With said expansion chamber and at its lower end with the interior of said housing outside of said baflie tube and dividing the interior of said housing into inner and outer compartments, said bafiie tube at its upper end forming a liquid tight partition between the upper portions of said compartments and preventing direct passage of said insulating liquid from said expansion chamber to said outer compartment, the inner and outer walls of said outer compartment being insulated from each other so that insulating liquid in said outer compartment forms an effective portion of the bushing insulation.

3. In a bushing insulator, a dielectric housing, a conductor extending through said housing, the space within said housing being closed against escape of liquid through the bottom of said housing, an expansion chamber at one end of said housing, and a tube surrounding said conductor and communicating at one end with said expansion chamber and at the other end with the space within said housing outside of said tube for preventing direct passage oi insulating liquid from said expansion chamber to the space within said housing outside of said tube, said space having outer and inner walls insulated from each other.

4. In a bushing insulator, a dielectric housing, a conductor extending through said housing, the space within said housing being closed against escape of liquid through the bottom of said housing, an expansion chamber at one end of said housing and communicating with the outer atmosphere, a tube surrounding said conductor and communicating with said expansion chamber and separating the space immediately adjacent said conductor from the space outside of said tube and means separating said outside space from said expansion chamber to prevent oil from passing directly from said expansion chamber to said outside space, said tube communicating with said outside space at the end thereof opposite said expansion chamber, the inner surface of said tube being conducting and being electrically connected with said conductor to shunt the space between said tube and conductor, said outside space having inner and outer walls insulated from each other.

5. In a bushing insulator a dielectric housing, a conductor extending through said housing, the space within said housing being closed against escape of liquid through the bottom of said housing, a dielectric bafiie tube surrounding said conductor, a conductive coating on the inner surface of said bafile tube, an expansion chamber on said housing and communicating with the interior of said baiiie tube, means for preventing direct communication between said expansion chamber and the space Within said housing outside of said balile tube, said expansion chamber communicating with said outside space through the space between said conductor and the wall of said baffie tube and means for electrically connecting said conductor with the conductor coating on the interior of said baffle tube to shunt the space between said conductor and the wall of said bafile tube, said outside space having inner and outer walls insulated from each other.

6. In combination a bushing insulator comprising an insulator housing, a conductor extending through said housing, the space within said housing being closed against escape of liquid through the bottom of said housing, an expansion chamber disposed on top of said housing, a bafile tube surrounding said conductor and communicating at its upper end with said expansion chamber and at its lower end with the space within said housing outside of said tube, said baflle tube providing communication between said expansion chamber and the space within said insulator outside of said tube, said space being otherwise completely sealed against passage of liquid to and from said expansion chamber, insulating liquid filling said insulator and extending into said expansion chamber, the space within said insulator outside of said tube having inner and outer walls which are insulated from each other so that the insulating liquid within said space forms an eifective part of the bushing insulation.

'7. In combination a bushing insulator housing, a conductor extending through said housing, an expansion chamber at the upper end of said housing, a battle tube surrounding said conductor and communicating at its upper end with said expansion chamber and at its lower end with the space within said housing outside of said tube, the space within said housing being closed against escape of liquid through the bottom of said housing, the point of communication between the upper end of said tube and said expansion chamber being located above the bottom of said expansion chamber and the wall of said tube having liquid tight connection with the bottom of said expansion chamber and forming a liquid tight seal between said expansion chamber and the upper end of the space within said housing outside of said tube to provide a water trap in the bottom portion of said expan sion chamber separated fromsaid outside space.

HAROLD L. RORDEN.

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