US3604872A

US3604872A - Pressurized gas interrupter structure

Info

Publication number: US3604872A
Application number: US29401A
Authority: US
Inventors: George A Wilson
Original assignee: ITE Imperial Corp
Current assignee: ABB Inc USA
Priority date: 1970-04-19
Filing date: 1970-04-19
Publication date: 1971-09-14
Anticipated expiration: 1988-09-14

Abstract

A pressurized SF6 gas interrupter structure is used with a conventional mechanical circuit breaker operating mechanism. The operating mechanism is not opposed by high gas pressure, used for arc interruption, while the high gas pressure is used for high initial contact parting speeds. Maximum gas flow is obtained during contact opening for arc extinction purposes, while gas flow is restricted during closing to conserve the supply of pressurized gas.

Description

United States Patent 3,226,513 12/1965 Frowein et a1. 200/148 R 3,268,697 8/1966 Morioka 200/148 R 3,350,528 10/1967 McKeough 200/148 R FOREIGN PATENTS 660,394 5/1938 Germany ZOO/148 BV 16.414 1968 Japan 200/148 BV Primary Examiner-Robert S. Macon .Attorney0strolenk, Faber, Gerb & Soffen ABSTRACT: A pressurized SF gas interrupter structure is used with a conventional mechanical circuit breaker operating mechanism. The operating mechanism is not opposed by high gas pressure, used for are interruption, while the high gas pressureis used for high initial contact parting speeds. Maximum gas flow is obtained during contact opening for arc extinction purposes, while gas flow is restricted during closing to conserve the supply of pressurized gas.

PRESSURIZED GAS INTERRUPTER STRUCTURE 7 RELATED APPLICATIONS SUMMARY OF INVENTION This invention relates to circuit interrupters and, more particularly, relates to a circuit interrupter using a pressurized high dielectric gas for interrupting arcs and for supplying a high dielectric medium between the open interrupter contacts. A conventional mechanical operating mechanism, of the type employed in a magnetic-air breaker, is then used to operate the contacts through a suitable bellows seal which prevents escape of the high dielectric gas such as SF which is used to fill the interrupter chamber which carries the contacts.

Where a multipole breaker is provided, the poles of the breaker may then be conventionally mechanically coupled to insure simultaneous making and breaking of the contacts. Moreover, conventional safety interlocking and operational features of well known and reliable operating mechanism can be used.

The gas-handling arrangement of the interrupter is next designed so that these pressures do not oppose the closing mechanism while the gas pressure is used to obtain high initial contact parting speeds. Moreover, the gas system is so arranged that there is maximum gasflow through the contacts from a high-pressure region to a low-pressure region when the contacts separate, while there is only a restricted flow during contact closing. This, then conserves the supply of pressurized gas.

As a further feature of the invention, the contacts are arranged with a minimum number of current transfer points in the circuit. This minimizes contact heating at high currents.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF PREFERRED EM BODIMENT Referring to FIGS. 1 to 4, it will be recognized that the interrupter structure of the invention is shown schematically to facilitate understanding of the essential structures. One skilled in the art will immediately recognize that components shown as a single piece would, in practice, best be made of a number of smaller pieces which are fastened together. The interrupter is schematically shown within a housing 10, which may, in practice, be a multisection cylinder of conductive material. A

. first circuit breaker terminal 11 (shown only in FIG. 1) is connected to'housing 10. The housing is completed by a housing section 12 (shown only in FIG. I) which is a gastight housing which is continuous with housing 10. A terminal 13 (shown only in FIG. l) exte nds from a stationary contact structure 14 which is suitably supported within housing section 12 by an appropriate support (not shown) which insulates contact 14 (and its terminal 13) from housing section 12 and housing 10. I

A compressor 20 is then provided having its suction end connected, as shown by the dotted line, to the low-pressure region 21 within chamber 10 and its high-pressure end connected, as shown by the dotted line, the high-pressure rcgion 22 within chamber portion I3. Suitable filters, dryers and control valves will be provided for compressor 20. If desired, the compressor 20 can also cooperate with a reservoir of high pressure gas, such as SF which fills

chambers

22 and 21 at pressures, for example, of 240 p.s.i.g. and 20 p.s.i.g., respectively. This pressure difference is-maintained by appropriate operation of compressor 20.

The movable contact structure for the interrupter consists of sliding main movable contacts 30 which are carried on tubular arcing contact section 31. Tubular arcing contact section 31 is carried on movable body member 32 from which an arcing tip 33 projects. Body member 32 is then secured to axially extending shaft 34 which is continuous with operating shaft portion 35 which has one end extending through opening 36 in chamber 10. A flexible bellows 37 forms a seal between the shaft 35 and housing 10, but permits longitudinal motion of shaft 35. An operating mechanism 38 (FIG. I) of any conventional type, well known for use in air-magnetic-type circuit breakers, is connected to operate shaft 35, and will be provided with conventional operating circuits and mechanisms, safety interlocks, and the like. Moreover, the entire interrupter can be conventionally mounted and providedwith conventional terminals so that it can be mounted and operated in conventional switchgear cubicles.

The outside diameter 40 of main movable contact 30 makes sliding contact with the interior surface 41 of housing 10. Note that an appropriate sliding contact material could be mounted relative to housing 10 to receive this sliding contact engagement. Preferably, main movable contact 30 will be segmented, as shown in FIG. 5. The interior surface 45 of contact 30 engages the outer contact surface 46 of stationary contact 14. If desired, the portion of contact 14 carrying surface 46 can be segmented, and the segments biased outwardly into engagement with surface 45 of main movable contact 30. Thus, main movable contact 30 is movable to a connection between the stationary contact 14 and housing 10, thereby to close the connection between terminals 11 and 13.

Stationary contact 14 is provided with a reduced diameter arcing contact surface 50 which cooperates with the interior contact surface 51 of tubular arcing contact section 31. If desired, one or both of contact 31 or the section 50 of stationary contact 14 could be segmented to insure appropriate contact pressure and engagement between the two. When the contact 30 is not segmented, it is provided with slots, such as slots 60 and 61, which permit easy gasflow from chamber 22 to chamber 21 when such flow is permitted.

A sliding valveplate 70 is then slidably mounted on shaft portion 34. Valveplate 70 contains a first sealing gasket 71 in its left-hand surface and a-second sealing gasket 72 in its righthand surface. Note that gasket 71 could be carried on body member 32. Plate 70 in its left-handmost position is enclosed by rim 73 of body member 32 and a pedestal 74 of body member 32 compresses and seals against gasket 71, having a disk-shaped channel 76 between sealed plate and body member 32. i

A reduced diameter section 80 of housing 10 (which obviously need not be unitary with housing 10) then carries an an,- nular bead 81 on its left-hand side which can seal with gasket 72 on plate 70. Section 80 also carries a sealing gasket 82 on its right side. Gasket 82 can then receive the annular sealing bead 83 which terminates the outwardly flared section of shaft 38. A central cavity 85 in shaft section 35 then receives a biasing spring 86 which biases plate 70 to the left and away from surface 87 of shaft section 35. A sleeve 88 projecting from plate 70 aids in guiding spring 86.

The operation of the interrupter is as follows:

With the breaker in the open position of FIG. 1,

contacts

30 and 31 are drawn to the right by operating mechanism 38. The high-pressure gas of chamber 22 extends to region 76 and presses plate 70 and its gasket 72 against sealing bead 81, thereby isolating low-pressure chamber 21 from the high-pressure gas. The sealing pressure on plate 70 is opposed by the force of biasing spring 86. Note also that the open contacts including

movable contacts

30 and 31 and stationary contact 14 are immersed in high dielectric SF, gas and can withstand high voltage across the open gap. The

force holding contacts

30 and 31 in the open position is the relatively small differential force on member 32 where the small internal region of plate 70 within gasket 71 is at the low-pressure of chamber 21.

In order to close the breaker, shaft 35 is driven to the left, overcoming only the relatively small differential pressure on member 32 and the contact friction forces. In the arrangement of FIG. 2, contact surface 51 engages surface 50, and, thereafter, main contact 30 engages surface 46. Thus, any closing arcs are applied to arcing contact 51 and not to main contact 30.

In the embodiment shown herein, there is no gas blast during closing. Thus, when the contacts close in FIG. 2, a second high-pressure seal is made between

chambers

22 and 21 by head 83 on shaft 35. Thereafter, and due to intentional leakage along the connection between plate 70 and shaft 34, the chamber between surface 87 and plate 70 increases in pressure until the force of spring 86 is high enough to move plate 70 to the left. The interrupter is now fully closed and in the position of FlG. 3 with current flowing from housing 10, through contact 30, and into stationary contact 14. The highpressure gas in chamber 22 surrounds the closed contacts and is isolated from chamber 21 by the seal at components 82 and 83.

in a typical embodiment of the invention, for example, for a 34.5 kv., 3000-ampere interrupter, the frictional drag on the main and arcing contacts could be about 300 pounds. A closing force of about 460 pounds, obtained from closing mechanism 38 and applied to shaft 35 provided a suitable relatively slow closing speed without gasflow for the interrupter. The novel interrupter, however, is conditioned for a high speed, full gas blast opening operation.

in order to open the interrupter, a mechanical force of about 1,600 pounds is applied to the operating shaft 35. This opening force is aided by the high-pressure on surface 87 of shaft 35. FIG. 4 shows the movable contact assembly, half way in its travel to the fully open position. The valve between gasket 82 and bead 83 is opened, thereby permitting a strong gas flow between the separating contacts and from high-pressure chamber 22 to low-pressure chamber 21. Main contact 30 first separates from stationary contact surface 46, and current then transfers through arcing contact 31 and surface 50. Note that the current must follow a reentrant path so that, when contact 31 separates from surface 50, the arc is subject to magnetic forces tending to drive the arc toward arcing tip 33. This movement of the arc is assisted by the blast of SP gas through the arc and the arc subsequently transfers from arcing contact 51 to tip 33. Thus, the arc current takes the path of housing 10, contact surface 40, longitudinally along contact 31 to body 32 and from arcing tip 33 to a corresponding arcing tip at the end of stationary contact 50. This arc is then fully extinguished by the SF gas deionizing action, and the gas blast is extinguished with the closing of gasket 72 and sealing head 81. The breaker is then in the open position of FIG. 1.

If it is desired to have a gas blast during closing as well as during opening, the plate 70 can be fixed to member 32, of, if desired, can be eliminated with gasket 72 being formed in the right-hand surface of body 32. With this arrangement, when body 32 moves to the left to close the interrupter contacts, there will be a gas blast until bead 83 engages gasket 82.

After one or more interruption operations, compressor will operate to restore the desired pressure difference and to move arcing products from the gas.

Although this invention has been described with respect to particular embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and, therefore, the scope of this invention is limited not by the specific disclosure herein, but only by the appended claims. 8 i

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows;

1. A circuit interrupter comprising, in combination:

a. a stationary contact;

b. a movable contact longitudinally movable into and out of engagement with said stationary contact;

c. an operating shaft mechanically connected to said movable contact for moving said contact longitudinally between engagement and disengagement with said stationary contact;

d. an operating mechanism connected to said operating shaft;

e. a housing for housing said circuit interrupter and containing a high-pressure chamber and a relatively low-pressure chamber; at least said high-pressure chamber being filled with gas;

. said movable and stationary contacts being supported within said high-pressure chamber;

g. said operating shaft extending through a wall of said housing in gas-sealed relation with respect thereto, and extending through said low-pressure chamber;

h. a sealing means fixed to the interior of said housing and defining the boundary between said high-pressure and low-pressure chambers;

. a first sealing member operatively connected to said movable contact and movable therewith at least when said movable contact moves to a disengaged position relative to said stationary contact; said first sealing member engaging said sealing means when said movable contact is in its disengaged position, thereby to seal said high-pressure chamber from said low-pressure chamber;

. said operating shaft having a radial shoulder thereon; and a second sealing member extending around the outer face of said radial shoulder; said second sealing member engaging said sealing means when said movable contact is in engagement with said stationary contact;

k. said movable contact being moved to said disengaged position under the combined influence of the mechanical force of said operating mechanism and the high pressure of said high-pressure chamber acting on said shoulder.

2. The interrupter of claim 1 wherein said first sealing member comprises a first sealing ring disposed on the downstream side of said movable contact and out of the path of the fiow of high-pressure gas while said movable contact is in transit from the engaged to the disengaged position; and wherein said sealing means secured to said housing includes a second sealing ring facing toward said shoulder and receiving said second sealing member when said movable contact engages said stationary contact.

3. The interrupter of claim 1 wherein said gas is sulfur hexafiuoride; and wherein the gas pressure in said high-pressure chamber is about l0 times the pressure in said low-pressure chamber.

4. The interrupter of claim I wherein said movable contact comprises a main contact surface and a laterally displaced arcing contact surface; said main movable contact surface making continuous sliding contact engagement with said housing and being slidably engageable with said stationary contact; said arcing contact surface being disposed downstream of said main contact surface and disposed for disengaging said stationary contact after said main movable contact surface disengages said stationary contact; the current path from said housing, through said main contact surface, said arcing contact surface and said stationary contact having a reentrant shape whereby magnetic forces on an arc drawn from said arcing contact surface to said stationary contact force said are downstream.

5. The interrupter of claim 1 which includes an axially movable valveplate mounted on said shaft and disposed between said movable contact and said shoulder of said shaft; said movable valveplate having a seal-ring means on the surface thereof facing said movable contact for engaging said movable contact over a relatively small area; said first sealing member mounted on the opposite surface of said valve plate, whereby said valveplate maintains a seal across said sealing means when said movable contact moves to its engaged position, and until said second sealing member engages said sealing means whereby high-pressure gas in said high-pressure chamber is not consumed during contact closing.

6. The interrupter of claim 4 which includes an axially movable valve-plate mounted on said shaft and disposed between said movable contact and said shoulder of said shaft; said movable valve-plate having a seal-ring means on the surface thereof facing said movable contact for engaging said movable contact over a relatively small area; said first sealing member mounted on the opposite surface of said valveplate, whereby said valve-plate maintains a seal across said position, and until said second sealing member engages said sealing means whereby high-pressure gas in said high-pressure 8. The interrupter of claim 7 wherein said gas is sulfur hex afluoride; and wherein the gas pressure in said high-pressure chamber is about l0 times the pressure in said low-pressure chamber.

9. The interrupter of claim 4 wherein said stationary contact has a first and relatively large diameter contact surface for slidably receiving said main movable contact surface. and a second and relatively small diameter contact surface for slidably receiving said movable contact arcing contact surface.

Claims

2. The interrupter of claim 1 wherein said first sealing member comprises a first sealing ring disposed on the downstream side of said movable contact and out of the path of the flow of high-pressure gas while said movable contact is in transit from the engaged to the disengaged position; and wherein said sealing means secured to said housing includes a second sealing ring facing toward said shoulder and receiving said second sealing member when said movable contact engages said stationary contact.
3. The interrupter of Claim 1 wherein said gas is sulfur hexafluoride; and wherein the gas pressure in said high-pressure chamber is about 10 times the pressure in said low-pressure chamber.
4. The interrupter of claim 1 wherein said movable contact comprises a main contact surface and a laterally displaced arcing contact surface; said main movable contact surface making continuous sliding contact engagement with said housing and being slidably engageable with said stationary contact; said arcing contact surface being disposed downstream of said main contact surface and disposed for disengaging said stationary contact after said main movable contact surface disengages said stationary contact; the current path from said housing, through said main contact surface, said arcing contact surface and said stationary contact having a reentrant shape whereby magnetic forces on an arc drawn from said arcing contact surface to said stationary contact force said arc downstream.
5. The interrupter of claim 1 which includes an axially movable valveplate mounted on said shaft and disposed between said movable contact and said shoulder of said shaft; said movable valveplate having a seal-ring means on the surface thereof facing said movable contact for engaging said movable contact over a relatively small area; said first sealing member mounted on the opposite surface of said valve plate, whereby said valveplate maintains a seal across said sealing means when said movable contact moves to its engaged position, and until said second sealing member engages said sealing means whereby high-pressure gas in said high-pressure chamber is not consumed during contact closing.
6. The interrupter of claim 4 which includes an axially movable valve-plate mounted on said shaft and disposed between said movable contact and said shoulder of said shaft; said movable valve-plate having a seal-ring means on the surface thereof facing said movable contact for engaging said movable contact over a relatively small area; said first sealing member mounted on the opposite surface of said valveplate, whereby said valve-plate maintains a seal across said position, and until said second sealing member engages said sealing means whereby high-pressure gas in said high-pressure chamber is not consumed during contact closing. 7 The interrupter of claim 4 wherein said first sealing member comprises a first sealing ring disposed on the downstream side of said movable contact and out of the path of the flow of high-pressure gas while said movable contact is in transit from the engaged to the disengaged position; and wherein said sealing means secured to said housing includes a second sealing ring facing toward said shoulder and receiving said second sealing member when said movable contact engages said stationary contact.
8. The interrupter of claim 7 wherein said gas is sulfur hexafluoride; and wherein the gas pressure in said high-pressure chamber is about 10 times the pressure in said low-pressure chamber.
9. The interrupter of claim 4 wherein said stationary contact has a first and relatively large diameter contact surface for slidably receiving said main movable contact surface, and a second and relatively small diameter contact surface for slidably receiving said movable contact arcing contact surface.