US3579258A - Gas blast circuit breaker using a generally axial flow main blast - Google Patents

Abstract

Discloses a gas-blast circuit breaker comprising an upstream electrode, a downstream electrode spaced therefrom, and an orifice having an opening positioned between said electrodes. During interruption, an arc established between the electrodes extends through the orifice opening, and a gas blast is caused to flow through the orifice opening via paths extending along the external surface of the upstream electrode and generally axially of the arc adjacent the upstream electrode. Improved flow conditions adjacent the upstream electrode are produced by providing a series of jets issuing from circumferentially-spaced points about the orifice opening and directed convergently toward the central region of the downstream face of the upstream electrode.

Description

United States Patent [72] Inventor John W. Beatty 3,270,173 8/1966 Barkan.... ZOO/148(2) Newtown Square, Pa. 3,288,969. 11/1966 Reece 200/148 [2]] Appl. No. 761,674 3,435,166 3/1969 Barkan ..200/ 144(APRT) {22] Filed Sept. 23 1968 4s Patented Mayl8, l97l Pmm'y [73] Assi ee General Electric Com an Att0meysJ. Wesley Haubner, William Freedman, Melvm M.

p y Goldenberg, Frank L. Neuhauser and Oscar B. Waddell [54] GAS BLAST CIRCUIT BREAKER USING A M E RALL AXIAL MAIN G NF Y -FLow BLAST ABSTRACT: Discloses a gas-blast circuit breaker comprising 5 Claims, 3 Drawing Figs.

an upstream electrode, a downstream electrode spaced [52] US. Cl th f and an orifice having an opening positioned between said electrodes. During interruption, an are [5 l Int. Cl 01h 33/70 established between the electrodes extends through the ifi ofsml'ch opening and a gas is caused to flow through the orifice I482, 144 opening via paths extending along the external surface of the upstream electrodevand generally axially of the arc adjacent [56] g s gl gs gglams $e upstream electrcade. lmprogledegltaw conditions adjacent UNHE e upstream e ectro e are pro uc y provl mg a senes 0 2,297,818 10/1942 Van Sickle 200/148 jets issuing from circumferentially-spaced points about the 2,494,661 I/I950 Latour 200/148 orifice opening and directed convergently toward the central 3,180,959 4/1965 MacNeill et a1. 200/148 region of the downstream face of the upstream electrode.

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I N4 l 1 x 12 Pate nted May-18,1971 3,579,258

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' ATTORNLY Pat nt Ma -18,1971 3 519,258

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JOHN W. BL'ATTY,

- 8y ATTORNEY GAS BLAST CIRCUIT BREAKER USING .A GENERALLY FLOW MAIN BLAST This invention relates to a gas blast circuit breaker of the type using a generally axial flow main blast and, more particularly, to means for improving the interrupting ability of such a circuit breaker.

The usual gas blast circuit breaker comprises means for establishing an electric arc across a gap between two electrodes and means for directing a high velocity blast of gas into the arcing region. The purpose of the gas blast is to cool the arc and to scavenge the arcing region of arcing products so as to increase the rate at which dielectric strength is built up across the gap when the current zero point is reached. By increasing this rate of dielectric recovery, it is possible to improve the ability of the gap to withstand the usualrecovery voltage transient which builds up as soon as current zero is reached, thus improving the interrupting ability of the circuit breaker.

In an axial blast type of circuit greater, there is typically provided an orifice through which the are between the electrode extends and through which the gas blast flows axially of the arc about-the periphery of the arc. The purpose of the orifice is to guide the blast with respect to the arc and to impart the desired high velocity to the blast. The electrode that is located upstream from the orifice is referred to hereinafter as the upstream electrode, and the electrode that is located downstream from the orifice is referred to hereinafter as the downstream electrode.

In the typical axial blast circuit breaker, there is a stagnation zone on the downstream side of the upstream electrode. The gas blast that flows past the upstream electrode toward the orifice opening separates from the surface of the upstream electrode adjacent its downstream side and creates this stagnation zone radially inwardly of the region at which such separation occurs. Typically, the gas blast forces the upstream terminal of the arc into the stagnation zone and holdsit captive therein. From an interrupting ability viewpoint, this is not an ideal position in which to maintain the upstream arc terminal Both the scavenging process and the arc cooling process are ordinarily relatively inefi'tcient in the stagnation zone, because the gas in this zone tends to move in large scale eddies of relatively low velocity; and this low velocity detracts from both scavenging and arc cooling.

An object of the present invention is to increase the efficiency of both the scavenging and the arc-cooling processes in this zone at the downstream side of the upstream electrode.

Another-object is to force the gas blast to adhere more closely to the downstream side of the upstream electrode,

thereby improving the scavenging in this region, and to do this by means which involves no modification of the simple upstream electrode typically used in this type circuit breaker.

In carrying out my invention in one form, l.provide a gas blast circuit breaker that comprises an upstream electrode, a downstream electrode, and an orifice having an opening positioned between said electrodes. During an interrupting operation, an arc is established between the electrodes that extends through the orifice opening, and a blast of gas is caused to flow through the orifice opening via paths extending along the external surface of the upstream electrode and generally axially of the are adjacent said upstream electrode. The upstream electrode has a downstream surface facing the orifice opening, and the gas blast tends to separate from this downstream surface as it travels toward the orifice opening, leaving a low velocity zone centrally of the downstream surface. For modifying the path of the blast, I produce a series of jets which issue from circumferentially spaced points around the orifice opening and are directed convergently toward the central region of said downstream surface. These jets coact with the gas blast to deflect it toward the center of downstream surface, thus causing it to adhere more closely to the downstream surface, thereby reducing the size and effect of the stagnation zone.

For a better understanding of my invention, reference may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a portion of a predominantly axial blast circuit breaker embodying one form of my invention.

FIG. 2 is a cross sectional view of certain parts of conven, tional axial blast circuit breaker.

FIG. 3 is a diagrammatic plan view of the circuit breaker of FIG. 1 with portions broken away to show internal features.

Referring now to FIG. I, the circuit interrupter shown therein is of the sustained-pressure, gas-blast type described and claimed in my US. Pat. 2,783,338, assigned to the assignee of the present invention. Only those parts of the interrupter that are considered necessary to provide an understanding of the present invention have been shown in FIG. I. In. this respect, only the right-hand portion of the interrupter as been shown in section inasmuch as the interrupter is generally symmetrical with respect to a vertical plane and the left-hand portion is substantially identical to the right-hand portion. As described in detail in my above-mentioned patent, the interrupter comprises a casing 12 which is normally filled with pressurized gas to define an interrupting chamber 11. Located within the interrupting chamber 11 are a pair of relatively movable contacts 14 and 16 which can be separated to draw an arc within the pressurized gas within the chamber 11. The contact 14 is relatively stationary, whereas the other contact 16 is mounted for pivotal motion about a fixed, currentcarrying pivot 18. When the movable contact 16 is driven clockwise about the pivot 18 from its solid-line closed position of FIG. 1, an arc is established in the region where the contacts part. The movable contact 16 is shown by dotted lines in FIG. 1 in a partially open position through which it passes during a circuit-interrupting operation after having established an arc.

The movable contact 16 is supported by means of its current-carrying pivot 18 on a conductive bracket 19 that is preferably fonned integral with a stationary cylinder 32. The cylinder 32 at its lower end is suitably supported from a generally cylindrical casting 33. The casting 33 at its lower end is suitably secured to a flange 35 rigidly carried by the stationary metallic casing 12.

For producing a gas blast to aid in extinguishing the arc, the cylindrical casting 33 contains a normally closed exhaust passage 36 leading from the interrupting chamber 11 to the surrounding atmosphere. The casting 33 at its upper end is provided with a tubular nozzle member 38 having an orifice portion 39 at its outer'end defining an inlet 37 to the exhaust passage 36. This inlet 37 is referred to hereinafter as the orifice opening. The flow of arc-extinguishing gas through the tubular noule 38 and the exhaust passage 36 is controlled by means of a cylindrically shaped reciprocable blast valve member 40 located at the outer, or lower, end of the exhaust passage 36. This blast valve member 40 normally occupies a solid-line, closed position wherein an annular flange 42 formed at its lower end sealingly abuts against a stationary valve seat 34 carried by the exhaust casting 33.

During a circuit interrupting operation, the movable blast valve member 40 is driven upwardly from its solid-line, closed position of FIG. 1 through a partially open intermediate position shown in dotted lines in FIG. 1. Opening of the valve member 40 allows pressurized gas in the chamber 11 to flow at high speed through the orifice opening 37 and nozzle 38 and out the exhaust passageway 36'past the valve member 40 to atmosphere as indicated by the dotted line arrows B of FIG. 1. The manner in which the gas blast acts to extinguish the arc will soon be described in greater detail.

At its upper end, the cylindrical blast valve member 40 surrounds a projecting tubular support 41 upon which the valve member 40 is smoothly slidable. The tubular support 41 is fixed to the casting 33 by suitable means (not shown). A compression spring 44 positioned between the movable valve member 40 and the lower end of support 41 tends to hold the valve member 40 in its closed position against the valve seat 0 protect the support 41 and the upper end of the valve member 40 from the harmful effects of arcing, a protective I metallic tube 43 is positioned about these parts and is suitably secured to the support- 41. Adjacent the outer surface of this tube is a downstream probe or electrode'45, preferably of a refractory metal, which is located in the path of the, gas blast flowing through the passageway 36. This electrode 45 is supported on and electrically connected to casting 33 by a conductive rod 45a. As will soon appear more clearly, the downstream terminal of the arc is transferred to this electrode 45 during an interrupting operation and, after such transfer, occupies a position generally corresponding to that shown at- 46. The downstream terminal of an are reaching the electrode 45 attaches to the electrode and is thus prevented from being driven further downstream by the gas blast.

For controlling the operation .of the movable blast valve Y40 and movable contact 16, a combined operating mechanism 50 is provided. This mechanism 50 is preferably constructed in the manner disclosed and claimed in my aforementioned US. Pat. No. 2,783,338, and its details form no part of the present invention. Generally speaking, this mechanism 50 comprises a blast valve-controlling piston i and a contact-controlling piston 52 mounted within thecylinder-32. The blast valvecontrolling piston 51 is coupled to the movable blast valve member40 through a piston rod 54 suitably clamped to the valve member 40. The contact-controlling piston 52, on the other hand, is connected to the movable contact 16 through a piston rod 58 and a cross head 59 secured to the piston rod. A link 60 pivotally joined to the cross head 59 and 61 and to the movable contact 16 at 62 interconnects the cross head 59 and the movable contact 16. When the blast valve-controlling piston 51 is driven upwardly, it acts to open the blast valve member 40, and, simultaneously, to drive the contact-con trolling piston 52- upwardly to produce opening movement of the movable contact member 16.

Opening movement of the contact member 16 first establishes an are between the ends of the contacts 14 and 16. Shortly thereafter, however, the blast of gas which has been flowing through the orifice opening 37, as indicated by the dotted line arrows B, forces the upstream terminal of the are on to an upstream arcing electrode 70, which is electrically connected to the stationary contact l4 through a conductive support 71. As opening motion of the movable contact 16 continues, the gas blast forces the downstream terminal of the arc to transfer from the movable contact 16 to orifice struc ture 39, which is electrically connected to the movable contact 16. The gas'blast then impels the downstream terminal of the arc through the orifice opening 37 and nozzle 38 on to the upper end of the protective metallic tube 43. From there, the gas blast drives the downstream arc terminal downwardly and onto the electrode 45. The are then occupies the position generally shown in 46. When the arc is in this position, the arc column extends through the orifice opening 37 and is sub- I breaker to prevent the are from reigniting at a current zero depends upon the rate at which dielectric strength is recovered across the arcing region when arcing ceases at current zero. The faster the'dielectric recovery rate, the lower the chances I for reignition and thus the better the chances for successful interruption at this time.

Substantial improvements in the dielectric recovery rate can be made lay-eliminating, or at least reducing the size 'of, the stagnation zone that has existed at the downstream face of the upstream electrode 70 so that this zone is for the most part, characterized by high velocities instead of the low velocities previously present. The high velocities promote rapid cooling of the arc plasma and more efficient scavenging, thus improving the dielectric recove y rate.

The stagnation zone referred to in the immediately preceding paragraph is illustrated in FIG. 2, which shows a conventional upstream electrode E being enveloped by an axial blast streams past the upstream electrode E are designated B. As shown in FIG. 2, these paths B follow the external contour of the electrode E rather closely about the outer periphery of the electrode but eventually separate from the surface of the electrode at points designated S in FlG.'2 near the outer periphery of the downstream face of the electrode E. Radially inwardly of these points S there is a zone 74 in which the gas flows at relatively low velocities in large scale eddies such as depicted at 75. This zone 74 is referred to herein as the stagnation zone.

The upstream tenninal of an are established between the contacts 16 and 14 is transferred from the contact 14 onto the upstream electrode 70 by the gas blast following the paths B. The gas blast then drives the upstream terminal in the direction of the gas blast into the stagnation zone 74. As pointed out hereinabove, this is not an ideal position for' the arc terminal since the gas in this zone is flowing in large scale eddies 75 at relatively low velocities, and these low velocities detract from both scavenging and are cooling.

In one typical circuit breaker, a passageway 77 extending through the upstream electrode 70 is provided primarily to deny the arc terminal a possibly stable footing at the center of the upstream electrode; There is some gas flow through this passage 77, but this gas flow is minor and doesnot affect the basic flow pattern heretofore described as being present in the stagnation zone. I

In accordance with the present invention, 1 very substantially reduce the size of the stagnation zone by producing a series of jets 80 which issue from the orifice 39 at circumferentially spaced points around the orifice opening 37. As will be apparent from FlG.- 1, these jets 80 are directed generally upstream with respect to the main gas blast and convergently toward the central region of the downstream face of the upstream electrode. Their effect is to deflect the main gas blast'toward the center of the downstream surface, thus causing the blast to adhere more closely to the downstream surface. Separation of the blast from the downstream surface is prevented until the blast almost reaches the central passage 77. By sweeping'substantiall y the entire downstream surface with the high velocity main blast in this manner, I substantially improve the scavenging of arcing products in this region and improve the dielectric recovery rate. These improvements are especially notable in the switching of capacitance currents, a type of duty which imposes particularly severe voltage conditions following current zero. a

For providing the jets 80, 1 form the orifice 39 with an annular header passage 82 that extends within the orifice wall completely around the orifice opening. Jet passages 84 communicate with this header passage 82 at circumferentially spaced points along its length. Although FIG. 1 shows only two of these jet passages 84, it is to be understood that many more are actually present at circumferentially spaced points 1 around the orifice opening. The header passage 82 is connected to a source of pressurized gas at a pressure substantially higher than the pressure in the casing 12. This is schematically illustrated in FIG. 3, which shows an auxiliary tank 85 containing gas at a higher pressure than the pressure in tank 12 connected through supply lines 86 and 87 to header passages in the two orifices 39 of the circuit breaker. A normally closed control valve 90 in line 86 normally prevents the high pressure gas from flowing into the main interrupting chamber 11. This valve 90 is opened (by suitable means not shown) at an early stage in a circuit breaker-opening operation, whereupon high pressure gas from auxiliary source 85 flows through lines 86 and 87 into the header passages 82 in the orifice 39, thus creating the previously described jets issuing through the jet passages 84.

In the type of circuit breaker illustrated, it is customary to provide a resistor shunting each set of main contacts l6, 14 of the breaker. This resistor remains connected across the contacts during the circuit interrupting operation for the purpose of reducing the rate of rise of the recovery voltage at current zero. The resulting current through the resistor is interrupted of gas. The primary flow paths followed by the gas blast as it 75 shortly thereafter by opening a resistor switch connected in series with the resistor. A trated at and the resistor are not shown since these can be conventional, as is shown for example in US. Pat. No. 3,133,176 to Schneider, assigned to thesassignee of the present invention.

The illustrated resistor, switch comprises an orifice 102 through which an auxiliary blast 103 flows when the blast valve 42 is opened. When the resistor switch is opened as above described, a relatively low current are is established and immediately transferred to a position between an electrode 105 inside the orifice 102 and an upstream electrode 106 spaced from the orifice and supported on an insulator 108. This are is cooled by the auxiliary blast 103 in substantially the same manner as described withrespect to the main orifice. Once again, however, there is the problem of a stagnation zone developing in front of the downstream face 107 of the upstream electrode 106 and detracting from the cooling and scavenging. To reduce the size and effect of the stagnation zone, I provide orifice 102 with substantially the same jetfomiing means the main orifice 39 is provided with. Accordingly, in orifice 102 there is an annular header passage 110 with jet passages 112 leading off therefrom at circumferentially spaced points about the orifice opening. These jet passages, like jetv passages 84, are directed convergently toward the central region of the upstream electrode and serve to deflect the blast toward the center of the downstream face 107, preventing separation of theblast from the downstream face until the blast has almost reached the center of the downstream face.

Although the current interrupted at the resistor switch is relatively low compared to that interrupted at the main con-. tacts, severe voltage conditions can develop at the resistor switch particularly during capacitance switching operations.

To enable the resistor switch to consistently withstand these voltages without-breakdown, it is important that the gap between the electrodes be scavenged of dielectrically weak arcing products as soon as possible. The improved flow pattern resulting from the jets improves this scavenging and thus improves the ability of the resistor switch to withstand the severe voltages accompanying capacitance-switching operations.

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

lclaim: I

l. A gas blast circuit breaker comprising a chamber containing gas at a first pressure and further comprising:

a. an upstream electrode and a downstream electrode 7 located within said chamber,

b. an orifice having an'opening positioned between said electrodes, c. means for establishing an are between said electrodes that extends through said orifice opening,

d. means operative when said arc is established for causing a gas blast to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said arc adjacent said upstream electrode,

e. said upstream electrode having a downstream surface constituting a portion'of saidexternal surface and facing said orifice opening when an arc is present between said electrodes, and means for producing a series of gas jets issuing from said orifice at circumferentially spaced points about said orifice opening and directed generally upstream with respect to said gas blast and convergently toward the central region of the downstream face of the upstream electrode, thereby forcing said gas blast to adhere more closely to the downstream face of said upstream electrode.

2. The circuit breaker of claim 1 in combination with:

a. circumferentially spaced passageways for said jets extending through said orifice, and

b. a reservoir for supplying gas to said jet passageways, said reservoir containing gas at a higher pressure than said first pressure.

3. The circuit breaker of claim 1 in combination with:

' a. circumferentially spaced passageways for said jets extending through said orifice,

b. a header passage located withing said orifice and extending around said orifice opening, and

c. means for supplying pressurized gas to said header passage to provide high pressure gas for said jets.

4. The circuit breaker of claim 1 in combination with a resistor switch within said chamber for interrupting resistor current following extinction of saidarc, said resistor switch comprising:-

a. an upstream electrode and a downstream electrode located within said chamber,

b. an orifice having an opening positioned between said latter electrodes,

0. means for establishing a resistor-switch are between said resistor-switch electrodes that extends through said latter orifice opening,

d. means operative when 'said resistor-switch arc is established for causing a blast of gas to fiow through said latter orifice opening via paths that extend along the external surface of said resistor-switch upstream electrode and generally axially of said resistor-switch arc adjacent said upstream electrode,

.'sai d latter upstream electrode having a downstream surface constituting a portion of said external surface and facing said latter orifice opening when the resistor switch arc is present between said. electrodes,

f. and means for producing a series of gas jets issuing from said orifice of said resistor switch at circumferentially spaced points about said orifice opening of said resistor switch and directed generally upstream with respect to said resistor switch gas blast and convergently toward the central region of the downstream face of the upstream electrode of said resistor switch.

5. The circuit breaker of claim 4 in which:

a. circumferentially spaced passageways for said jets extend through both of said orifices,

b. connecting means is provided for interconnecting all of said jet passageways,

c. a reservoir is provided for supplying high pressure gas to all of said jet passageways through said connecting means, said reservoir containing gas at a higher pressure than said first pressure.

Claims (5)

1. A gas blast circuit breaker comprising a chamber containing gas at a first pressure and further comprising: a. an upstream electrode and a downstream electrode located within said chamber, b. an orifice having an opening positioned between said electrodes, c. means for establishing an arc between said electrodes that extends through said orifice opening, d. means operative when said arc is established for causing a gas blast to flow through said orifice opening via paths that extend along the external surface of said upstream electrode and generally axially of said arc adjacent said upstream electrode, e. said upstream electrode having a downstream surface constituting a portion of said external surface and facing said orifice opening when an arc is present between said electrodes, f. and means for producing a series of gas jets issuing from said orifice at circumferentially spaced points about said orifice opening and directed generally upstream with respect to said gas blast and convergently toward the central region of the downstream face of the upstream electrode, thereby forcing said gas blast to adhere more closely to the downstream face of said upstream electrode.

2. The circuit breaker of claim 1 in combination with: a. circumferentially spaced passageways for said jets extending through said orifice, and b. a reservoir for supplying gas to said jet passageways, said reservoir containing gas at a higher pressure than said first pressure.

3. The circuit breaker of claim 1 in combination with: a. circumferentially spaced passageways for said jets extending through said orifice, b. a header passage located withing said orifice and extending around said orifice opening, and c. means for supplying pressurized gas to said header passage to provide high pressure gas for said jets.

4. The circuit breaker of claim 1 in combination with a resistor switch within said chamber for interrupting resistor current following extinction of said arc, said resistor switch comprising: a. an upstream electrode and a downstream electrode located within said chamber, b. an orifice having an opening positioned between said latter electrodes, c. means for establishing a resistor-switch arc between said resistor-switch electrodes that extends through said latter orifice opening, d. means operative when said resistor-switch arc is established for causing a blast of gas to flow through said latter orifice opening via paths tHat extend along the external surface of said resistor-switch upstream electrode and generally axially of said resistor-switch arc adjacent said upstream electrode, e. said latter upstream electrode having a downstream surface constituting a portion of said external surface and facing said latter orifice opening when the resistor switch arc is present between said electrodes, f. and means for producing a series of gas jets issuing from said orifice of said resistor switch at circumferentially spaced points about said orifice opening of said resistor switch and directed generally upstream with respect to said resistor switch gas blast and convergently toward the central region of the downstream face of the upstream electrode of said resistor switch.

5. The circuit breaker of claim 4 in which: a. circumferentially spaced passageways for said jets extend through both of said orifices, b. connecting means is provided for interconnecting all of said jet passageways, c. a reservoir is provided for supplying high pressure gas to all of said jet passageways through said connecting means, said reservoir containing gas at a higher pressure than said first pressure.

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