US2835769A

US2835769A - Electric circuit breaker

Info

Publication number: US2835769A
Application number: US438786A
Authority: US
Inventors: James M Milne; Harold N Schneider
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1954-06-23
Filing date: 1954-06-23
Publication date: 1958-05-20
Anticipated expiration: 1975-05-20

Description

y 20, 1958 J. M. MILN E ETAL 2,835,769

ELECTRIC CIRCUIT BREAKER Filed June 2 3, 1954 7 Fig.2.

Inventors: James M. Milne,

Harol N. Schn ider, b

Theirttorneg.

United States Patent 2,835,769 ELECTRIC CIRCUIT BREAKER James M. Milne, Swarthmore, and Harold N. Schneider, Springfield, Pa., assignors to General Electric Company, a corporation of New York Application June 23, 1954, Serial No. 43am;

9 Claims. (Cl. 200-150) This invention relates to an electric circuit breaker and, more particularly, to a circuit breaker of the type which has separable contacts immersed within an insulating liquid.

For housing such an insulating liquid, which in the usual case is oil, it has been conventional for many years to employ a tank of cylindrical configuration. In recent years, it has become apparent that such tanks require an excessive volume of oil, a major portion of which serves no useful purpose from the standpoint of insulation or aiding in the circuit interrupting process. A considerable reduction in the volume of oil required may be achieved by constructing the tank so that it has a lenticular, or ellipsoidal configuration, or more particularly, a generally elliptical cross-section in one plane and a generally circular cross-section in a plane normal to the one plane. It is with such lenticular tanks that our invention is primarily concerned.

This lenticular configuration not only permits more efficient use of the oil but also is ideal for resisting the heavy shocks and strains which frequently accompany circuit interruption. More particularly, the ellipsoidallyconfigured dished sides of the lenticular tank are capable of yielding slightly thereby to cushion the impact due to the pressure wave emanating from the are at the contacts, whereas the circular peripheral portion forms a strong unyielding area which is, from the standpoint of structural strength, an ideal location for a welded seam for uniting the dished sides.

Another distinct advantage of the lenticular configuration is that its circular peripheral area is capable of equally distributing and thereby neutralizing the areproduced impacts which occur during circuit interruption, as a result of which, these impacts are incapable of producing appreciable forces external to the tank. Holding such external forces to a minimum makes it possible to minimize destructive straining and loosening of the tank supporting structure.

The more nearly this lenticular tank configuration can be preserved in a practical circuit breaker, the more ideal will be its shock-resisting characteristics. In a practical tank-type circuit breaker, however, the tank must be provided with suitable bushings for electrically connecting the breaker contacts to a circuit exterior to the tank, and must also be provided with a suitable operating mechanism for controlling the relatively movable contacts. In combining these components with a generally lenticular tank structure, prior arrangements have modified the lenticular configuration of the tank to such an extent that the shock-resisting advantages of the lenticular configuration have been largely, if not wholly, lost.

Accordingly, a primary object of our invention is to provide a circuit breaker which utilizes to the fullest extent the shock-resistant advantages of the lenticular tank configuration.

A further object of our invention is to construct and arrange the bushing and operating mechanism structure Patented May 20, 1958 2 of the circuit breaker in such a manner that combining this structure with a lenticular tank requires no material alterations in the lenticular configuration of the tank.

In accordance with one form of our invention, the lenticular tank, which is formed from a pair of domes joined together along a peripheral seam, is provided with a pair of tubular housings for receiving the usual high voltage bushings. Because the tubular housings are c on-. structed as distinct, spaced-apart components which pro-' ject :from the periphery of the tank, it is possible to pre-' serve the generally lenticular tank configuration even in the tank area adjacent the bushing housings. The level of the oil within the tank is always maintained within the housings and above the upper periphery of the lenticu lar portion of the tank, as a result of which, only liquid is interposed between the lenticular walls of the tank and the point at which the circuit-interrupting arc is initiated. This latter feature permits the lenticular configuration to be most effectively used for suppressing the transmission of shocks to the tank supporting structure.

For a better understanding of our invention, reference may be had to the accompanying sheet of drawing, wherein Fig. 1 is a front elevational view partly in section of an oil circuit breaker having a tank constructed in accordance with my invention, and Fig. 2 is a side elevational view partly in section of the circuit breaker of Fig. 1.

Referring more specifically to the drawing, there is shown a high-voltage circuit breaker 8 comprising a metallic tank 9 which contains an insulating liquid 10, which preferably, though not necessarily, is oil. The tank 9 is formed by welding together the generally circular rims of a pair of semi-ellipsoidal domes 11 along a generally circular circumferential seam 12. The tank resulting from so uniting the domes is of a generally ellipsoidal or lenticular configuration, or more particularly, it has a generally circular cross section in the plane of Fig. l and a generally elliptical cross section in a plane normal thereto,

respective housings are a pair of conventional high-

volt age bushings

15 and 16. These bushings terminate at their respective inner ends in

circuit interrupters

17 and 18. Each of these interrupters contains suitable separable contacts (not shown) which are electrically interconnected in series circuit relation when the beraker is in closed-circuit position by means of a conductive cross bar 19. Since the details of the interrupters form no part of the present invention, they may assume any suitable form, such as is disclosed for example, in U. S. Patent 2,522,994, issued to T. R. Coggeshall and assigned to the assignee of the present invention. The contacts within the interrupters are connected to the

power lines

20a and 20b by the usual conductive studs extending through the center of the bushings.

Control of the multibreak circuit through the breaker is efiected by lowering and raising the cross bar 19 by means of an operating rod 7 connected to a suitable operating mechanism 21 mounted within an enclosure 22. Actuation of the mechanism 21 is effected by a movable link 6 extending into enclosure 22 through an opening sealed by suitable means (not shown); In accordance with my invention, the mechanism enclosure 22 is spaced from the upper periphery of the tank 9 by means of a vertically-extending pipe 23, which closely surrounds the operating rod 7. The pipe 23 is suitably joined at its opposite ends, as by welding, to the enclosure 22 and the tank 9, respectively.

At all times when the breaker is to be operated, the oil Within the tank is maintained at a level which is disposed above the uppermost portion 24 of the periphery of the tank 9. As a result, only liquid is disposed between the

interrupters

17, 18 and the walls of the lenticular tank 9. There is no intervening air or gas space between these parts as in the usual oil-type breaker. The importance of this feature will soon appear more clearly.

When the circuit breaker is tripped open from the closed position of Fig. 1, the cross bar 19 moves rapidly downward and causes each pair of the contacts within the interrupters to separate and establish an arc. This arc immediately reacts with the surrounding oil to create a rapidly expanding gaseous bubble. This reaction produces a pressure wave which is transmitted radially outward in all directions from the bubble, through the surrounding liquid, to the walls of the tank. Because the gaseous bubble is initiated at a point near the center of the tank and because only liquid is interposed between the bubble and the walls of the tank, the impact created by the pressure wave acts substantially simultaneously about the entire circular periphery of the tank, as a result of which the impact forces in the plane of the periphery are substantially neutralized and produce no appreciable resultant force external to the tank. Since the sides of the tank defined by the domes are generally symmetrical with respect to the central vertical plane, along which they are joined those impact forces acting thereagainst are also substantially neutralized. The internal pressures created by the arcing are relieved thereafter by venting the pressurized arcing gases to the space above the liquid through the comparatively restricted annular passage ways around the bushing and the operating rod. Dissipating the arcproduced impacts in the described manner produces important advantages which will become more apparent when compared to the practice of the prior art.

The conventional practice of the prior art is to provide an air space between the top of the tank and the liquid level. In such arrangements the air space cushions the top of the tank against the upwardly acting component of the pressure wave, but the downwardly acting component, which is transmitted to the tank bottom directly through the liquid, imparts an abrupt downwardly-acting impact to the tank bottom. In the meantime, the gaseous bubble created by initiation of the arc begins to expand rapidly with the result that a large mass of oil is impelled through the upper air space and into contact with the top of the tank, with a resulting upwardly-acting impact. This upwardly-acting impact closely follows the downwardly-acting impact with the net result being that alternate downward and upward forces are imparted to the tank supporting structure. After repeated circuit interruptions, especially of large currents, these alternate forces will have seriously strained and loosened the supporting structure of the breaker.

In accordance with my invention, however, the impact forces from the pressure wave are substantially neutralized about the periphery of the tank, and as a result, create no appreciable resultant force external to the tank. Additionally since the pressurized gases are vented relatively slowly through the comparatively restricted annular passages surrounding the bushings and the operating rod, no heavy mass of oil is thrown against the top of the tank, as a result of which, the upwardly acting impact of the prior art is minimized.

An important factor which contributes to the improved shock-resisting performance of my tank is that the lenticular or ellipsoidal configuration of the tank is preserved to the fullest practical extent, as a result of which, the forces acting against the tank periphery may effectively neutralize themselves. Only the minimum-surface areas required for the entry of the bushing-housings l3 and M and the entry of the operating rod 7 have been removed from the tank periphery.

Also, by preserving the lenticular configuration of the tank 9, we are able to fully utilize the yieldability which is inherent in the semi-ellipsoidal side walls. Because of this inherent characteristic, the side walls are capable of. yielding to absorb the violent circuit interrupting forces and thereby to minimize the external effects of such forces. Since the major welding'operation is confined to the substantially non-yielding circular periphery of the lenticular tank, the weld'is ideally located from the standpoint of structural strength.

To further decrease the ground shock which accompanies circuit interruption, the spaced supporting.

legs

25 and 26 of the tank are of a semi-resilient construction. More particularly, each of the legs comprises a pair of relatively yieldable segments, a first one of which 27 extends gcnerally vertically and a second one of which 28 extends generally radially with respect of the tank. This yieldable construction further decreases the possibility that the tank mounting bolts 30 will be loosened by the circuit-interrupting impacts.

For venting the space above the liquid level so as to permit the gaseous arcing products to pass to atmosphere, we utilize a single vent 32 which is mounted to extend through a cover 31 provided for the mechanism enclosure 22. Only this single vent is required because the equalizing conduits 33 and 34 are provided for interconnecting the gas space within the mechanism enclosure 22' and the gas space within each of the bushing housings. These conduits not only serve to afford communication between all of these gas spaces but also serveto rigidly brace the mechanism enclosure, this latter function being quite important because of the limited supporting area provided by mounting pipe 23. it also is to be noted that by utilizing conduits such as described, We are able to provide between the gas spaces a form of communication which does not impair the lenticular configuration of the body of tank 9.

Another advantage of our tank construction is that a simplified vent may be utilized without the hazard of oil being impelled therethrough by the arc-produced forces which accompany circuit interruption. To this end, all of the flow passages leading to the vent 32 from the oil are either of a circuitous or an effectively restricted nature. For example, the flow passage which extends to the vent through the oil in each of the bushing housings follows a circuitous path through the diverging bushing 13 or 14, through the cross conduit 33 or 34 and thence through the mechanism housing 22 to the vent 32, whereas the flow passage which extends about the operating rod 7 is quite small and, thus, effectively restricted.

While we have shown a particular embodiment of our invention, it will be obvious to those skilled in the art that various modifications may be made without departing from the invention in its broader aspects and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States:

1. In a circuit breaker, a lenticular tank comprising a pair of domes of ellipsoidal configuration having generally circular rims joined together along a generally circular peripheral seam, a pair of tubular, spaced-apart housings mounted at opposite sides of the uppermost portion of the generally circular periphery of said tank and arranged to communicate with the interior of the tank, and a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost peripheral portion.

2. In a circuit breaker, a lenticular tank comprising a pair of domes welded together along a generally circular peripheral seam, a pair of tubular, spaced-apart housings mounted adjacent the uppermost portion of said circular periphery and arranged to communicate with the interior of the tank, and a supply of insulating liquid Within said tank having its minimum level during circuit breaker operation disposed in said tubular housings and above said uppermost periphe al portion.

3. In a circuit breaker, a lenticular tank comprising a pair of domes joined together along a generally circular peripheral seam, relatively movable contacts mounted in a centrally disposed location within said tank, a pair of tubular, spaced-apart housings mounted adjacent the uppermost peripheral portion of said tank and arranged to communicate with the interior of the tank, a bushing mounted within each of said housings and having a conductive portion electrically connected to at least one of said contacts, and a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost peripheral portion.

4. In a circuit breaker, a lenticular tank comprising a pair of domes joined together along a generally circular peripheral seam, relatively movable contacts mounted in a centrally disposed location within said tank, a pair of tubular spaced-apart housings mounted adjacent the uppermost peripheral portion of said tank and arranged to communicate with the interior of the tank, a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost peripheral portion, a bushing mounted within each of said housings and having a conductor electrically connected to at least one of said contacts, and means for operating said contacts comprising an elongated rod operatively coupled to one of said contacts and extending in closely-surrounded relationship through an opening in the circular peripheral portion of said tank.

5. In a circuit breaker, a lenticular tank comprising a pair of domes joined together along a generally circular peripheral seam, relatively movable contacts mounted within said tank, a pair of tubular, spaced-apart housings mounted at opposite sides of the uppermost circular portion of the periphery of said tank and arranged to communicate with the interior of the tank, a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost circular peripheral portion, an elongated rod operatively coupled to one of said contacts and extending outwardly through the periphery of said tank between said tubular housings, a contact-controlling mechanism coupled to said rod, a pipe closely surrounding said rod and projecting radially outward from said tank periphery, a casing mounted on said pipe and enclosing said mechanism.

6. In a circuit breaker, a lenticular tank comprising a pair of domes joined together along a generally circular peripheral seam, separable contacts mounted within said tank, a pair of tubular spaced-apart housings mounted adjacent the uppermost peripheral portion of said tank and arranged to communicate with the tank interior, a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost peripheral portion, an elongated operating rod operatively coupled to one of said contacts and extending outwardly through the periphery of said tank between said tubular housings, a contact-controlling mechanism coupled to said rod, a casing mounted on said tank and enclosing said mechanism, a pair of conduits each of which is secured in bracing-relationship between said mechanism casing and one of said bushing housings, said conduits being disposed above the maximum level of said liquid whereby to afford communication between the spaces at the top of said casing and each of said housings, and means forming a venting passageway extending from said casing to atmosphere.

7. In a circuit breaker, a lenticular tank comprising a pair of ellipsoidally-configured domes joined together along a generally circular peripheral seam, a pair of tubular, spaced-apart housings mounted at opposite sides of the uppermost portion of the circular periphery of said tank and arranged to communicate with the interior of the tank, a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above u 'rpermost peripheral portion, and a pair of spacedapart tan '-supporting legs secured to said tank, each of said legs comprising a pair of angularly-disposed relaiively-yieldable segments, one of which extends generally radially from said tank and the other of which extends generaily vertically.

8. In a circuit breaker, a lenticular tank comprising a pair of ellipsoidally-configured domes joined together along a generally circular peripheral seam, a pair of tubular, spaced-apart housings mounted at opposite sides of the uppermost portion of the circular periphery of said tank and arranged to communicate with the interior of the tank, a supply of insulating liquid within said tank having its minimum level during circuit breaker operation disposed within said tubular housings and above said uppermost peripheral portion, and a pair of spacedapart, tank-supporting legs secured to said tank, each of said legs comprising a pair of angularly-disposed, relatively-yieldable segments.

9. In a circuit breaker, a metallic tank containing a supply of insulating liquid, separable contacts mounted within said tank beneath the level of said liquid, a pair of tubular, spaced-apart housings mounted atop said tank and projecting from the tank periphery, the minimum level of said liquid supply during circuit breaker operation being disposed within said tubular housings and above the uppermost portion of the tank periphery, a bushing mounted within each of said housings and having a conductive portion electrically connected to at least one of said contacts, an elongated operating rod coupled to one of said contacts and extending in closelysurrounded relationship through an opening in upper portion of said tank, a contact-controlling mechanism coupled to said rod, a casing mounted on said tank and enclosing said mechanism, a pair of conduits each of which is secured in bracing relationship between said casing and one of said housings, said conduits being disposed above the maximum level of said liquid, and means forming a venting passageway extending from said casing to atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,655,464 Huber Ian. 10, 1928 1,737,636 Burnham Dec. 3, 1929 1,782,594 Allan Nov. 25, 1930 2,581,571 Baker et a1. Jan. 8, 1952 2,693,519 Baker et a1. Nov. 2, 1954 FOREIGN PATENTS 626,198 Great Britain July 11, 1949