US3458676A - Circuit interrupter of the gaseous puffer-type having series high-current explosion chamber with series-connected activated carbon therein - Google Patents

Description

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United States Patent O U.S. Cl. 200-148 7 Claims ABSTRACT F THE DISCLOSURE A circuit interrupter is provided having two sets of serially-related interrupting contacts. One set of contacts is separated within a confined explosion chamber having activated carbon therein to adsorb and desorb an arcextinguishing gas, such as sulfur-hexafluoride (SFS) gas. The other set of contacts has a mechanically-driven pulfer interrupter associated therewith to mechanically force a blast of the same gas by puffer action against the arc drawn at the second set of contacts. This is particularly suitable for low-current interruption, when the series-related activated carbon interrupter is relatively inactive.

The aforesaid circuit interrupter is particularly suitable for use with a load-break disconnecting switch in which both sets of contacts are shorted out in the closedcircuit position by a swinging disconnecting switch blade.

This invention relates, generally, to circuit interrupters and, more particularly, to an interrupter suitable for use as the interrupting device of a load-break disconnecting switch.

An object of the invention, generally stated, is to improve the reliability and increase the interrupting rating of a circuit interrupter.

A more specific object of the invention is to provide a double-break interrupting device for a load-break switch.

As described in a copending application Ser. No. 501,180, filed Oct. 22, 1965 by Daniel Berg and Thomas W. Dakin, activated carbon has the ability to adsorb sulfur hexafiuoride (SFS) gas when cool and expel the gas under pressure when the carbon is heated. In addition,

VU.S. Patent 3,356,808, issued Dec. 5, 1967, Dakin et al.,

describes an interrupting device involving a pressure-responsive movable contact with an electrically series-arranged conducting mass of material having the characteristics of -desorbing an arc-extinguishing gas upon the fiow of excess current therethrough. The mass, such as activated carbon, adsorbs the arc-extinguishing gas upon cooling. Small pressure-equalizing holes are provided between the pressure chamber about the separable contacts and the ballast chamber to prevent contact separation upon an increase in ambient temperature.. Also, a copending patent application filed Oct. l2.2, 1965, Ser. No. 501,137, by Earl F. Beach describes a circuit interrupter provided with an explosion chamber having a restricted orifice outlet. A moving contact rod, movable through the restricted outlet, confines generated gas therein evolved from an activated carbon material, which is conductive and conducts the line current during a portion of the opening operation. The Beach structure is applied specifically to a load-break disconnecting switch. Accordingly, another object of the invention is to provide for utilizing activated carbon and SFS gas in an interrupting unit.

A further object of the invention is to provide an interrupter having an activated carbon portion for interrupting relatively high currents and a pulfer portion for interrupting relatively low currents.

ICE

Other objects of the invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, activated carbon is connected in series-circuit relation with intermediate contacts and putter contacts in an interrupting device for a load-break disconnect switch. The device is filled with SP6 gas. When the main switch blade is separated from the main contact members, the load current flows through the activated carbon in the interrupting device and the carbon is heated to expel SP6 gas under pressure. The intermediate contacts are opened first bythe activating mechanism of the interrupter and the arc is extinguished at the intermediate contacts if the current is high enough to expel sufficient gas from the carbon to extinguish the arc. If the current is relatively low, the arc is extinguished at the puffer contacts which are opened after the intermediate contacts.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIGURE l is a view, in side elevation, of a load-break disconnect switch embodying the principal features of the invention;

FIG. 2 is a diagrammatic view of vice for the switch shown in FIG. l;

FIG. 3 is an enlarged detailed view of the activated carbon chamber, the intermediate contacts and arc chamber, the putter contacts, and the puffer chamber of the interrupting device; and,

FIG. 4 is a detailed view of a modification of the activated carbon chamber shown in FIG. 3.

Referring to the drawings, and particularly to FIG. 1, the structure shown therein comprises a portion of a disconnecting switch assembly 10 and an interrupting de- Vice 11. The disconnecting switch assembly 10 may be of the type described in Patent No. 2,363,360, issued Nov. 21, 1944 to H. L. Rawlins. The switch structure comprises three spaced insulator stacks, only two of which are shown in the present drawing. The insulator stacks are mounted upon a base which is not shown in the present drawing.

One of the insulator stacks 12 is fixed on the base, and the other insulator stack 13 is rotatably mounted on the base. The third insulator stack is fixed on the base, and the top of the stack is connected to the switch structure by means of a supporting and bracing member 14. A housing 15 is pivotally mounted on the member 14 by means of pivot pins 16. As described in the aforesaid patent, a disconnecting switch blade 17 may be actuated into and out of engagement with spaced contact jaws 18 by rotating the insulator 13 by means of a suitable driving mechamsm.

The operating mechanism for the disconnecting switch is so constructed that the switch blade 17 is first rotated about its axis to release contact pressure between the end of the switch blade and the spaced contact jaws 18, and is then pivotally actuated from the horizontal position to a substantially vertical position as shown by the broken lines in FIG. l. Thus, a power conductor (not shown) which may be connected to a terminal plate 19 mounted on the insulator 12, is disconnected from a conductor (not shown) which may be connected to a terminal plate mounted on the third insulator stack and connected to the member 14.

When the lblade 17 is disconnected from the contact jaws 18, the current is compelled to flow through the interrupting device 11 which will be fully described hereinafter. As the blade 17 is raised, a tip end 21 on the blade 17 strikes a laterally extending projection 22 disposed at the end of a crank arm 23 to effect rotation of a drive shaft 24, thereby causing operation of an overcenter toggle the interrupting despring mechanism disposed inside a housing 26 mounted on the upper end of the interrupting device 11.

The operation of the toggle mechanism causes separation of contact members disposed inside and insulating housing 25 of the interrupting device, thereby interrupting the circuit which previously extended from the terminal plate 19 through the contact members in the interrupting device, the housing 26, and an auxiliary or isolating switch blade 28 to the supporting member 14 to which the blade 28 is pivotally connected. The auxiliary blade 28 is biased by a spring assembly 29 toward the main disconnecting switch blade 17. Since the arc is interrupted inside the interrupting device 11, no arc is drawn between the auxiliary contact member 27 and the auxiliary blade 28 during opening of the circuit.

As previously explained, the tip 21 on the blade 17 engages the projection 22 on the crank arm 23 to actuate the crank arm to the position shown Iby the broken lines in PIG. 1. Subsequently, an arm 30, which is attached to the blade 17 and is rotated to extend in a lateral direction, engages the auxiliary blade 28 and moves the latter to the position shown by the broken lines as the main blade 17 is raised to its open position.

During the closing operation, the main switch blade 17, together with the auxiliary blade 28, swing in a counterclockwise direction about the pivot pin 16. As the blades are being closed, the end of the auxiliary blade 28 first engages the auxiliary contact member 27 mounted on the housing 26 ofthe circuit interrupting device 11. However, the circuit through the interrupter 11 is not closed at this time because of the separated condition of the contact members inside the housing 25. As the 4blade 17 continues to travel in a counterclockwise direction, the tip 21 engages a projection 32 on the crank arm 23, thereby actuating the crank arm to the opsition shown by the full lines and causing the oepration of the toggle mechanism in the housing 26 to close the contact members of the interrupting device. This completes the circuit through the nterrupting device and continued travel of the main switch blade 17 causes it to move between the spaced jaws 18.

The rotation of the blade 17 at the end of its closing movement causes an increase in the contact pressure between the blade 17 and the contact jaws 18. Thus, a low resistance path is provided through the main switch members, thereby causing current to flow through the low resistance high pressure contact path rather than the relatively high resistance path through the interrupting device and the auxiliary switch members.

As shown most clearly in FIG. 2, the interrupting device 11 comprises an activated carbon chamber 35, an arc chamber 36, a biasing spring 37, intermediate contacts 38, orifice means 39 and a puffer 40' disposed within the insulating casing 25. The casing 25 is preferably composed of porcelain, or a similar material, and it contains an arcextinguishing gas, such as sulfur hexauoride (SP6) gas. The casing 25 is mounted on a portion of the terminal plate 19 which is supported by the insulator 12.

Por currents of relatively low values, for example under 500 amperes, particularly magnetizing and line dropping currents, interruption is accomplished by means of the puffer contact members. The puffer contact assembly can be made very efficient at low currents since highcurrent interruption does not depend upon the performance of the puffer assembly. For higher currents, a forced iiow of the SP6 gas is generated by the activated carbon as will be described more fully hereinafter.

The activated carbon chamber 35 is shown most 'clearly in the lower portion of PIG. 3. A conducting plate 41 is threaded into an insulating tube 42 which is disposed within the casing 25. The tube 42 s preferably composed of polytetrafiuoroethylene, |which is sold under the trade name Teflon This material has the characteristics of resisting action from the sulfurhexafiuoride gas. The activated carbon may be either in the form of blocks 43 as shown in PIG. 3, or it may be in the form of powder 44 as shown in PIG. 4. If powder is used, the current path is through the plate 41 and posts 45 which are attached to the plate 41. Similar posts 45 are also attached to a conducting plate 47 which is threaded into the upper end of the tube 42. A screen 45 may be provided on the bottom side of the plate 47 to prevent the powder from passing through openings 47 in the path 47. If blocks 43 are used, a washer 46 of the Belleville or spring type, composed of bronze or other suitable conducting material, is disposed between the lower block 43 and the plate 41, and a similar washer 46 is disposed between the upper block 43 and the plate 47. In order to obtain a large area of carbon in contact with the SP6 gas, the blocks 43 are made in two different sizes as shown in PIG. 3. The carbon should have a resistance of approximately 1 ohm. When the main disconnect blade is separated from the main contact members, a small voltage will appear across the gap. This voltage is caused by the fiow of current through the carbon and should be kept as low as practicable.

The present structure is suitable for the utilization of activated carbon since the carbon is shunted by the main disconnect blade when closed, and a disconnect gap 1s present when the switch is open. When the current is transferred to the carbon and through the auxiliary switch blade when the main blade is opened, the carbon is heated and the adsorbed SP6 gas is expelled under pressure. For currents over 500 amperes, a considerable fiow of gas takes place through the holes 47 in the plate 47 into the interrupting or arc chamber 36. A stationary contact member 49 is disposed in the arc chamber 36. The contact member 49 is attached to or formed integrally with the plate 47.

The interrupting or arc chamber 36 is shown most clearly in an intermediate portion of PIG. 3. The charnber is enclosed by an insulating tube 51, preferably composed of Teflon The intermediate contact assembly comprises the fixed contact member 49 and a movable contact member 50 which telescopes over the fixed member 49 when in the `closed position. Since the inside of the movable contact member 50 carries no current when disconnect blade 17 is in fully closed position, it fits loosely over the contact member 49.

The contact member 50 is biased upwardly to the open position by the spring 37, which is disposed between a plate 52, attached to the shaft of the contact member 50, and a spring seat 54 mounted on top of the tube 51. Upward movement of the contact member 50 is halted by its abutting engagement with a stop portion 53 attached to the upper end of a cylindrical portion of the spring seat 54, which has slots 54 to permit the flow of gas during an operation. An O ring 55 functions as a guide for the movable contact member 50.

Shortly after the starting of the upward movement of the contact member 50, the opening at the upper end of the tube 51 is substantially closed by the contact member 50. Thus, pressure builds up in the interrupting chamber 36. When the movable contact member 50 is separated from the fixed contact member 49, gas is forced through the hollow center of the contact 50, through openings 48 in the movable contact member 50 and then is discharged laterally through the slots 54 in the spring retainer 54. The are is extinguished by the axial flow of gas.

The orifice means 39 and the lower portion of the puffer assembly `40 are shown most clearly in an intermediate portion of PIG. 3. The orifice 39 is preferably composed of Teiion. As shown, the upper end of the movable contact member 50 is engaged 'by the lower end of a movable contact rod 57 at the upper end of the orifice 39. The movable contact rod 57 is raised by the operating mechanism of the interrupter in the manner hereinbefore described. A movable puffer cylinder 58, which is composed of suitable insulating material, is attached to a movable plug 59 which is threaded onto the upper end of the moving orifice 39. The moving plug 59 is attached to the moving contact rod 57.' Thus, the cylinder 58 and the orifice 39 are ralsed with the moving contact rod 57.

The upper end of the Puffer assembly 40 is shown most clearly in the upper portion of FIG. 3. A stationary piston 61 is attached to the lower end of a stationary tube 62, the upper end of which is supported by the housing 26 of the interrupter mechanism. A piston ring `63 lls the space between the stationary piston 61 and the movable puffer cylinder wall 58. Thus, when the cylinder 58 is moved upwardly with the moving contact rod 57, gas is compressed in the puier chamber 56. When the moving contact rod 57 separates from the intermedlate contact member 38, the gas is forced through the moving orifice 39 to extinguish the arc.

As previously explained, the pffer break is utilized only if the carbon break at the intermediate contacts 49, 50 is not effective because of low current. The intermediate contacts 49, 50 are separated by the spring 37 prior to the separation of the puffer contacts S0, 57. Therefore, if the arc is interrupted by the intermediate contacts which are in series-circuit relation with the putter contacts no interrupting takes place at the pufer contacts. However, if the current is of such a low value that the activated carbon is not heated enough to expel sufficient gas to cause interruption to take place at the intermediate contacts, the interruption then takes place at the puffer contacts.

In order to permit gas to enter the top of the pufr'er chamber 56 through the stationary piston 61, a check valve 64 is provided in the piston assembly. The valve 64 is normally biased to the open position by a spring `65. When pressure starts to build up in the pufer chamber 56, the valve 64 is closed by the unbalance in pressure. The valve is opened by the spring 65 when the puffer contact members have reached the full open position and the gas pressure has equalized.

From the foregoing description, it is apparent that the invention provides a circuit interrupter which is partticularly suitable for use with a load-break disconnect switch. The interrupter makes efficient use of activated carbon and an are extinguishing gas, such as SP6, to interrupt relatively high values of current. The interrupter also utilizes a puffer assembly and the arc extinguishing gas to interrupt relatively low values of current. Thus, the interrupter is efficient over the entire range of currents to which a load-break switch may be subjected. The interrupter is simple in construction and it may lbe manufactured and installed at a relatively low cost.

Since the high gas pressure is produced by the heating action of the current through the activated carbon, low mechanical energy is required to obtain a relatively high interrupting effort, much greater than that available if a puffer type device alone is used.

Since numerous changes may be made in the abovedescribed construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawings, shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit-interrupting device including, in combination:

(a) casing means (25) for confining an electronegative-arc-extinguishing gas;

(b) means defining an arcing chamber (36) disposed insideI said casing means (25) having a restricted outlet; l

(c) contact means including a movable contact rod (50) movable out of said restricted outlet for establishing an arc interiorly of said arcing chamber (36);

(d) a body of activated carbon (43) disposed within said arcing chamber for adsorbing a quantity of the electronegative-arc-extinguishing gas;

(e) means preventing current ow through said body of activated carbon in the closed or non-interrupting state of said circuit-interrupting device;

(f) means including a movable contact (17 for defning a main current path through the device in the closed position thereof;

(g) means for transferring a sufficient amount of the series current through the device from said main current path through the body of activated carbon during the opening operation of the device, whereby to evolve gas therefrom due to the heating thereof;

(h) means including said restricted outlet for directing the evolved gas emitted from said body (43) into the established arc drawn through the outlet to effect the extinction thereof;

(i) the body of activated carbon (43) not coming into contact with the direct arcing; and,

(j) mechanically-actuated puffer means including a pair of serially-connected puffer contacts for interrupting the low-value currents in case they are not extinguished by the flow of evolved gas through the outlet.

2. The circuit interrupting device of claim 1, wherein the pufter contacts separate after the separation of the movable contact.

3. The circuit-interrupting device of claim 1, wherein the puffer means includes a stationary piston and a movable orifice and operating cylinder movable with one of `the movable puffer contacts.

4. The circuitinterrupting device of claim 1, wherein spring means (37) biases the movable contact rod (S0) in an opening direction and toward the pufer contacts.

5. The circuit-interrupting device of claim 1, wherein the electronegative ar-cextinguishing gas is sulfurhexafluoride (SFS) gas.

6. In an electrical switch, in combination:

(a) a main switch blade;

(b) a main contact member engaged by the main switch blade;

(c) operating means for disengaging the main switch blade from the main contact member;

(d) an auxiliary switch blade actuated by the main switch blade;

(e) an auxiliary contact member engaged by the auxilary blade;

(f) an interrupting device connected to the main contact member;

(g) said interrupting device including:

(i) casing means (25) for confining an electronegative arc-extinguishing gas;

(ii) means defining an arcing chamber (36) disposed insilde said casing means (25) having a restricted out et;

(iii) contact means including a movable contact rod (50) movable out of said restricted outlet for establishing an arc interiorly of said arcing chamber;

(iv) a body of activated carbon (43) disposed within said arcing chamber for adsorbing a quantity of the electronegative arc-extinguishing gas;

(v) means preventing current flow through said body of activated carbon in the closed or non-interrupting state of said electrical switch;

(vi) means including the movable switch blade (17) for defining a main current path through theI switch in the closed position thereof;

(vii) means for transferring a suflicient amount of the series current through the switch from said main current path through the body of activated carbon during the opening operation of the switch, whereby to evolve gas therefrom due to the heating thereof;

(viii) means including said restricted outlet for directing the evolved gas emitted from said body (43) into the established arc drawn through the outlet to effect the extinction thereof;

(ix) the body of activated carbon (43) not coming into contact with the direct arcing;

(i) said auxiliary contact member being attached to the interrupting device;

(j) an actuating mechanism operated by the main switch blade' (17) for separating the contact means within the interrupting device to draw an arc within theinterrupting device after the main switch blade has been disengaged from the main contact member; and

(k) a mechanically-actuated puifer means including a serially-related pair of pufer contacts actuated by said actuating mechanism for interrupting low-value 1 currents.

7. The combination of claim 6, wherein theI electronegative arc-extinguishing gas is sulfur-hexauoride (SFS) gas.

8 References Cited UNITED sTATEs PATENTS 2,330,820 10/1943 AEerrrier 20o-148.1

2,445,529 7/14948 `Leeds, 20o-148.1 5 2,757,261 7/1-956 Lirrgai et ai. 2 20o- 148.2

3,077,526 2/1963 owerrs 20o-149 XR 3,122,728 2/1964 Lindberg.

3,356,808 12/1967 ,Dairirr et ai. 20o-140 10 FOREIGN PATENTS 525,244 8/1940 .Great Britain. 1,154,548 9/1963 Germany.

U.S. Cl. X.R.

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