US2179356A - Bushing - Google Patents

Description

Nov. 7, 1939.` A. A. sKvoRTzor-F BUSHING Filed May 2l, 1936 Patented Nov. 7, 1939 UNITED STATES IBUSIIING Alexander A. Skvortzoi, Sharon, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Httsburgh, Pa., a corporation of Pennsylvania.

Application May 21,

3 Claims.

The invention relates generally to bushings and more particularly to transformer bushings.

The object of the invention, generally stated. is the provision of a bushing that shall be simple in construction and which may be readily and economically manufactured.

A more specic object of-the invention is to protect electrical apparatus from 4surges which may occur in electrical systems by dissipating a part or all of the accumulated energy before it reaches the apparatus.

Another object of the invention is to provide for dlssipating charges of electrical energy through a bushing.

Other vobjects of the invention will in part be obvious and in part appear hereinafter.

For a fuller understanding of the objects of the invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawing, in which Figure 1 is a view partly in section and partly in side elevation of a bushing constructed in accordance with this invention,

Fig. 2 is a view in cross-section of a bushing taken along the line II-II of Fig. 1 showing details of a modified arc chute,

Fig. 3 is a view partly in section and partly in side elevation of a modification of the invention in a form that is known as a pocket type bushing.

Referring now to Fig. 1 of the drawing, a conductor I0 capable of carying heavy currents is provided. The common practice is to make the conductor I0 from a copper bar. The conductor in addition to its function as a conductor, is utilized as a support in assembling the bushing.

A central insulator II is disposed on the conductor support I0. The insulator shown in Fig. l is shaped to simulate a hollow cylinder being provided with a shoulder I2 and a flange I3. On the flange I3 a metal ring I4 is provided to iacilitate the mounting of the bushing in any suitable casing provided for the eletrical apparatus to be protected. The usual practice is to electrically connect the metal ring I4 to the transformer or other case thus grounding it. In this particular modification, the ring I4 is utilized for mounting the bushing on a transformer tank. This is common practice and will not be described in detail.

In order to provide a tight joint when mounting the bushing,l it is good practice to provide gaskets I5 .on both sides of the flange I3. As illustrated in Fig. 1, the lower gasket I5 is disposed between the lower face of the flange I3 and a boss provided on the transformer cover. In present day construction, it is usual` practice to weld such bosses to the cover.

If desired, the ring I4 may be extended inwardly and its inner edge shaped to conform to the conical portion of the insulator II adjacent 1936, Serial No. 81,040

it. When the ring is shaped in this manner and is drawn downwardly against the gasket I5 by tightening the mounting bolts, it engages the insulator. A cemented joint may be made between the inner face of the ring I4 and the insulator.

An electrode I6 of any suitable metal, for example, cold roll steel, is loosely disposed on the conductor I0 above the central insulator II. In the modification illustrated in Fig. l, a gasket I`I is disposed between the electrode I6 and the central insulator II. In the assembling of the bushing, the electrode is drawn into tight engagement with the gasket I'I.

'I'he electrode I6 is provided with two out- Wardly extending iianges I8 and I9 which perform functions that will be referred to hereinafter. As shown, the flanges I8 and I9 define a circumferential chamber or depression in the electrode which cooperates in arc quenching processes.

An outside insulator or weather casing of the usual construction is carried by the flange I8 of the electrode I6. In order to provide a tight joint, a gasket 2l is disposed between the members I8 and 20. The Weather casing 20 is made with an overall Wet breakdown voltage capacity of about 115% of the voltage to be imposed on the conductor III. As shown, the outer insulator 20 is spaced from the central insulator I I.

An arc chute comprising two be'r cylinders 22 and 23 is disposed between the insulators II and 20. 'The fiber employed is of the well known kind commonly utilized in circuit breakers and has the characteristics that when exposed to an arc, it generates gases, a function that it is desired to utilize in this invention. Since this characteristic of certain kinds of fiber is well known in tle art, it will not be described in detail here.

The inner ber cylinder 23 is disposed between the iange I9 provided on the electrode I6 and the shoulder I2 of the central insulator II. In the present modification, the ber cylinder 23 is cemented to the central insulator II. Any suitable plastic cement well known in the art may be employed for this purpose.

The cement serves two purposes. It helps retain the fiber cylinder in a predetermined position and serves as a cushion to protect the central insulator II from high mechanical stresses.

The upper end of the fiber cylinder is beveled on one side to give a wedge shaped member which engages in a complementary groove` provided in the electrode I6. The construction of the electrode I6 with flanges I8 and I9 facilitates the centering of the ber cylinders 22 and 23.

A ring 2t is mounted on the lower end of the cylinder 23 to protect it during arcing. The ring 24 may be cemented to the cylinder 23.

The outer fiber cylinder 22 which is spaced a sufficient distance from the inner cylinder 23 to provide an arc chute is supported between the upper flange I8 of the electrode I6 and a metal member 35 carried by the insulator 20. In this manner, an arc chute is provided which extends from the circumferential depression provided in the electrode I6 to a point below the outer insulator 20.

As shown, a space is provided between the outer fiber cylinder 22 and the weather casing 20. This space communicates with the outside atmosphere and isprovided to prevent the imposing of high mechanical stresses on the outside insulator during arcing.

In order to tie all the elements of the bushing together, a metallic cap 26 is provided to engage the threaded upper end of the conductor I0. These members I0 and 26 are preferably swetted to one another. A gasket 2'I is disposed between the outer insulator 20 and the cap 26 while a spring 28 is utilized between the cap and electrode I6. The upper end of the cap 26 is threaded to receive a nut 29 provided for retaining a conductor 30 in electrical connection with the cap.

As shown in the modiflcation of Fig. 2, the fiber cylinders 22 and 23 may be centered relative to one another by means of fiber spacers 33. If desired, the spacers 33 may be made integral with one of the cylinders thus forming longitudinal ribs. It has been found that While an accurate centering of the ber cylinders 22 and 23 is usual practice, it is not essential for good functioning of the apparatus. It has been found in the manufacture of this bushing that even if the cylinders are not accurately centered it functions with great efficiency.

Referring now to the modification shown in Fig. 3, which is generally known as a pocket type bushing, the central insulator II is shaped somewhat differently but still simulates a hollow cylinder. In this instance, the insulator will be made from some suitable fiber. It is disposed on a conductor I0 which extends through it. Instead of retaining the elements of the bushing together by means of a cap such as 26 in Fig. 1, the inner upper end of the central insulator II is threaded and receives the lower threaded end of the electrode I6.

As shown, the outer member 22 which cooperates with the insulator II to form an arc chute is preferably made from fiber. The conductor I0 is connected to a power line through the electrode I6 and conductor 30. As shown, the conductor 30 is swaged to the electrode I6. The outside insulator corresponding to 20 of the modification shown in Fig. l is shaped somewhat differently, the upper end conforming to the shape of a hollow cylinder adapting it for insertion into an opening provided in the case -of the electrical apparatus with which it is to be utilized. The skirt portion is also cylindrical on the outside.

As illustrated, openings 3I are provided in the outer cylindrical fiber member 22 to permit gases to escape. Further it will be noted that the metallic member 32 is provided on the lower end of the fiber member 22 to prevent burning when anarc occurs and to cooperate in directing the travel of the arc. As shown, this protective member 32 is threadedonto the threaded lower end of the fiber member 22.

' The fundamental features of the two bushings are quite similar and they function in much the same manner. When a surge occurs on a line connected to the bushing and builds up a voltage of a great enough magnitude to arc across the two gaps in series, that is, in Fig. 1, from the electrode flange I9 to the ring 24 and from the ring 24 tc the ring I 4 or, in Fig. 3 from the member I6 to the ring 32 and from the member 32 to the tank wall, a discharge occurs. Immediately upon the occurrence of an arc gases are generated through the action of the arc on the fiber tubes 22 and 23 of the structure shown in Fig. 1 and from the members II and 22 in the structure shown in Fig. 3. These gases and the air conned in the chamber between the flanges of the electrode I6 will build up a pressure which causes the gases to flow downwardly through the arc chutes. The gases owing through the chutes function to blow arcs.

The foregoing is a description of the manner in which a bushing dissipates electrical energy that results from a surge. It protects apparatus such as transformers, regulators and the like by dissipating the accumulated energy caused by surges through arcs which are grounded outside of the apparatus casing.

In conclusion, it is pointed out that while the illustrated examples constitute practical embodiments of the invention, I do not limit myself to the exact details shown, since modifications of the same may be considerably varied without departing from the spirit of the invention, as defined in the appended claims.

I claim as my invention:

l. In a bushing, in combination, a central insulator, a flanged electrode carried by the central insulator, the upper flange of the electrode extending beyond the lower flange, an outside insulator carried by the electrode, the outside insulator being disposed substantially concentric with the central insulator and spaced therefrom, a plurality of liber members disposed between the insulator in spaced relation providing an arc chute, the inside fiber member being mounted between the central insulator and the lower flange of the electrode, a supporting member carried by the outer insulator, the outside fiber member being disposed between the electrode and said supporting member carried by the outside insulator, and means for retaining all of said members in predetermined positions relative to one another.

2. In a bushing, in combination, a central insulator, a flanged electrode carried by the central insulator, an outside insulator disposed substantially concentrically with the central insulator and spaced therefrom carried by the electrode, a plurality of fiber members disposed between the insulators in spaced relation in an arc chute, the outside fiber member and the flanged electrode forming a gasl chamber in which gases collect in the operation of the device, and means for retaining the members in predetermined positions relative to one another.

3. In a bushing, in combination, a rigid conductor adapted to be utilized as a support, a central insulator carried by the conductor, a flanged electrode carried by the central insulator, an outside insulator disposed substantially concentrically with the central insulator and spaced therefrom, carried by the electrode, fiber members spaced from one another to form an arc chute disposed between the insulators, the outside fiber member and the flanged electrode cooperating to provide a gas chamber, the outer fiber member being spaced from the outside insulator to protect it from stresses that are caused by the operation of the device, and means cooperative with.

the conductor support for retaining the members of the bushing in predetermined positions relative to one another.

ALEXANDER A. SKVORTZOFF.

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