US3749869A - Liquid-prevention device for arc-extinguishing gas compressed-gas circuit breakers - Google Patents

Abstract

The arc-extinguishing gas of a compressed-gas circuit interrupter is prevented from liquefying by effecting the circulation of the high-pressure gas by a forced flow through a nozzle causing the gas to circulate through a heating element. The gas, for example, may comprise sulfur-hexafluoride (SF6) gas, or other suitable arc-extinguishing gases, subject to the hazard of liquefaction.

Description

United States Patent 1 Imataki July 31, 1973 [541 LIQUID-PREVENTION DEVICE FOR ARC-EXTINGUISIIING GAS COMPRESSED-GAS CIRCUIT BREAKERS [75] Inventor:

[73] Assignee: Mitsubishi Denk Kabushiki Kaisha,

Tokyo, Japan May 25, 1971 Mitsumasa Imataki, Osaka, Japan [22] Filed:

211' Appl.No.: 146,744

[52] US. Cl 200/148'B, 200/148 E UNITED STATES PATENTS 2,890,312 6/1959 Forwald 200/148 B 2,955,182 10/1960 Caswell et a1.

3,214,544 10/1965 Leeds 200/148 B FOREIGN PATENTS OR APPLICATIONS 753,376 7/1956 Great Britain 200/148 E Primary ExaminerRobert S. Macon Attorney- A. T. Stratton, Clement L. Mcl-Iale and Willard R, Crout [57] ABSTRACT The arc-extinguishing gas of a compressed-gas circuit interrupter is prevented from liquefying by effecting the circulation of the high-pressure gas by a forced flow through a nozzle causing the gas to circulate through a heating element. The gas, for example, may comprise sulfur-hexafluoride (SP gas, or other suitable arcextinguishing gases, subject to the hazard of liquefaction.

7 Claims, 4 Drawing Figures 7 2'. i 6 a D 4 ,2 5 l2 5 8 20 I3 g D l0 9 8 I I 9 H l2 I C I 1 l9 PRESSURE 1 LOW PRESSURE I PAIENIEU JUL 31 ms SHEET 1 OF 2 EQUIDENSITY LINE LIQUIFYING CURVE VAPOR ZONE LIQUID ZON o iuxox mmDmmmmm FIGQI SF6 GAS-PRESSURE- TEMP. CHARACTERISTICS TEMF. C

r r IIIIIIII,

HIGH PRESSURE LOW PRESSURE INVENTOR- 22 Mlisumoso lmcnoki ATTORNEY LIQUID-PREVENTION DEVICE FOR ARC-EXTINGUISHING GAS COMPRESSED-GAS CIRCUIT BREAKERS CROSS-REFERENCES TO RELATED APPLICATIONS Applicant is not aware of any related applications pertinent to the present invention.

BACKGROUND OF THE INVENTION The present invention relates to a liquefactionprevention device for preventing theliquefaction of such gases, for example, sulfur-hexafluoridetsF gas, which is susceptible of becoming liquefied under a high pressure and relatively low temperature, which gas is utilized as the arc-quenching medium in electric-power interrupting equipment. I

With the increase of demand in electric-power equipment, larger-capacity circuit breakers are demanded by the utilities, and the use of such higher-capacity power circuit breakers becomes more extensive. Thus, the use of a liquefiable gas, such as, for example, sulfurhexafluoride (SP gas, which has an excellent record of arc-extinguishing ability, has increasingly been used at high densities and at high pressures.

The interrupting capacity of a circuit breaker using, for example, sulfur-hexafluoride (SF gas, is generally governed by the density of the gas. Since such highpower circuit breakers are operated at outside ambient temperatures, in the event that the surrounding ambient temperature reaches relatively low temperatures, such, for example, as a C., the. hazard of liquefaction is present at such low temperatures. The liquefacin which a minimum number of conduits are provided between high and low voltages.

Further objects and advantages will readily become apparent upon reading the following specification,

taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS I view taken through a high-power high-voltage compressed-gas circuit interrupter utilizing the principles of tion of the gas, of course, as well known by those skilled in the art, results in a considerable drop in'pressure, rendering the gas inefficient for its intended function of providing'a high-pressure stream of arc-extinguishing gas.

SUMMARY OF THE INVENTION According to the present invention, a circulating device comprising afan, heater-element, and nozzle is provided to effect a circulation of the high-pressure arc-extinguishing gas, and by the high-pressure jet of gas flow through the nozzle, a circulation may readily be provided from the low-potential areas of the circuit breaker to the high-potential elements of the circuit breaker. This is ofa distinct advantage, inasmuch as the circulating elements comprising the nozzle, fan and heater-element may be at a relatively low voltage, close to ground potential, and thereby capable of being readily serviced by operating personnel. On the other hand, by a high-velocity jet of gas issuing from the nozzle at a high velocity, the circulation of the gas may be' readily effected to remote areas.

Accordingly, a general object of the present invention is the provision of an improved compressed-gas circuit interrupter in which liquefaction of the arcextinguishing medium is prevented.

Another object of the present invention is the provision of an improved liquefaction-prevention device comprising a circulating means, for example, a highvelocity jet, or nozzle, which effects circulation of the gas through a heating element and into remote areas of the high-pressure reservoir volume.

Another object of the present invention is the provision of an improved compressed-gas circuit interrupter the present invention;

FIG. 3 is a vertical sectional view taken through an improved compressed-gas circuit interrupter embodying features of the present invention, the contact structure being illustrated in the open-circuit position; and,

FIG. 4 is a considerably enlarged view of the blastvalve operating mechanism.

DESCRIPTION OF Tl-IE PREFERRED EMBODIMENTS The power requirements-for the electrical utility industries are ever increasing, and the demand for higher and-higher power circuit-interrupting equipment continuously increases. This results in every effort being made to supply higher and higher capacity circuit breakers to control such vast amount of power blocks.

As well knownby those skilled in the ar't, however,

when highly-efficient arc-extinguishing gases, for example, sulfur-hexafluoride (SF gas, is utilized,"at high pressure, there results the hazardthat at low ambient te'mperatures,'the gas may'become liquefied, and this necessarily will cause a dropin its operating pressure. Such a drop of operating pressureis', of course, undesired, as the possibility exists that the circuit breaker will be incapable of interrupting its current and voltage ratings.

With the increase of demand in electric-power, larger-capacity, power circuit breakers, the use of such highly-eff cient gases, such as (SF gas, as opposed to air, are very attractive. Nevertheless, it is desirable to prevent liquefaction during the use of such gas, for example, (SF gas, at low ambient temperatures.

The interrupting capacityof a circuit breaker utilizing (SF gas is generally governed by the density of the gas. For instance, sulfur-he xafluoride gas, which is used in a circuit breaker, and which has an equidensity line A at its ratedgas pressure, as set forth in FIG. 1, will be liquefied at 8 C. when the pressure reaches 15 kglcm g. Under nonnal operating conditions, and at its having an equidensity line A," as in thecase ofFlG.

1, will lose its interrupting capacity as the gas will become liquefied at such low tempe'ra tures. Tov prevent prevent the gas, used in compressed gas circuit the gas from liquefying, or'to keep the gas usable, ex

interrupter comprising a line terminal 1 connected to a stationary contact 2. The'stationary contact; cooperates with a movable contact 5, which may be actuated to the open and closed-circuit positions by any suitable device, not shown. Generally, as well known by those skilled in the art, such an operating means for the movable contact may comprise a piston device or a mechanical means, as set forth hereinafter. A second line connection 3 connected to a sliding finger contact 4 may be utilized to transfer the current from the moving contact 5 to the second line terminal 3. Consequently, in the closed-circuit position of the device, as illustrated in FIG. 2, the current path extends from the line terminal 1, stationary contact 2, movable contact 5, finger contact 4 to the second line terminal3.

An insulating interrupting chamber 6, which may, for 1 example, be of porcelain, or other suitable insulating material, having-the requisite strength, provides insula tion between the line terminals 1 and 3 in the opencircuit position of the circuit breaker 30, not shown.

It will be noted that the contact separation area 31 is located within the high-pressure chamber 6, which contains a highly-efficient arc-extinguishing gas, such as, for example, sulfur-hexafluoride (SF gas 32 at a relatively high pressure.

Although not shown in FIG. 2, when the circuit breaker 30' operates, the moving contact 5 moves toward the left,'and by suitable means opens the exhaust valve 8 upwardly, thereby exhausting the high-pressure gas 10 supplied through the gas-duct-type bushing 9 into the low-pressure gas reservoir 12 provided in an exhaust bushing, and the blowing of the gas stream, which is generated at the nozzle 13 effects extinction of the arc established between the moving contact 5 and the stationary contact 2, thereby performing the so-called function of a double-pressure exhausting-type gas circuit breaker 30. 1

[f (SP gas is used in place of the high-pressure gas 10, it may become liquefied, if the temperature is relatively low. To prevent this from happening, the present invention provides means within the gas tank 14 connecting a pneumatic duct-type bushing 9, a blower or fan 16, and an electric heater element 17 with conduits l5 and 16, so as to send the gas in jet form out from the exhaust nozzle 19. The arrow at A in FIG. 2 shows the direction of operation of the blower. The highpressure gas within the arc-quenching chamber 9 is drawn into the blower or fan 16, through the conduit 15, due to the gas stream generated in the direction of the arrow at B on the right-hand side of the guide vane 20. The gas, which is drawn into the fan 16, is heated by an electrical heater 17, and it then passes through the conduit 18, and'goes through the nozzle 19 into the stream in the direction C. The gas then passes along the left-hand side of the guide vane 20 and into the arc-guenching chamber 7, 21. It then flows along following the route D" heating the highpressure gas along the route within the chamber 7, thereby preventing the gas from condensing into a liquid.

The control for the electrical heater 17 and the fan, or blower 16 is not shown in FIG. 2, but, as well known by those skilled in the art, may be provided to automatically start and stop operations at prearranged temperatures.

The height H of the circuit breaker 30 from the ground varies to the extent of the electrical voltage rating of the breaker, and its relations with the shape of the nozzle 19, and the capacity of the blower are set forth in the following equations:

' where h distance between the nozzle (19) and the guide plate (20) A, cross section of the nozzle (19) U, speed of the gas flow at the nozzle (19) U speed of the gas flow at the guide plate (20) The above equations permit us to utilize the means preventing gas from liquefying for varius types of circuit breakers.

It is to be noted that the present invention is charac terized by the simpleness of construction having a forced-gas circulation to prevent the liquefying of gas in the arc-quenching chamber 21 of the circuit breaker 30. In other words, by locating the exhausting nozzle 19 at ground potential, and then adjusting the cross- I,

sectional area of the nozzle 19 and the capacity of the blower 16 to the height H of the breaker 30, the

same effect can be obtained that could be obtained by locating the exhaust nozzle 19 in close proximity to the guide vane, or plane 20, the latter, of course, being included in the high-voltage charged areas of the breaker. As a result, this makes it unnecessary to utilize a porcelain-tube insulator between the electricallycharged section and the ground-potential section.

With reference to FIGS. 3 and 4, it will be observed that there is provided a compressed-gas circuit interrupter, generally designated by the reference numeral 23. As shown, the compressed-gas circuit interrupter comprises a high-pressure arcing chamber 24, a blastvalve operating mechanism 25, a supporting structure 26, and suitable operating mechanism including an operating rod 27 extending to ground potential.

As was the case with FIG. 2, disposed interiorly of the arc-extinguishing structure 6 is provided a relatively stationary contact structure '35 makingcontacting engagement with a tubular movable contact 5, which is biased by a compression spring 36 to an open position. More particulary, the movable tubular vented contact 5' includes a contact extension 37 and a spring seat 38 fixedly secured thereto. The accelerating compression spring 36 seats upon the spring seat 38 at one end, and against a guide cylinder 39 at the other end, and constantly biases the movable tubular contact 5' in a circuit-opening direction.

The relatively stationary and movable contacts 5', 35 are maintained in contacting closed position, by a thrust linkage 40 comprising a bell-crank lever 41 pivotally mounted, as at 42, on a stationary shaft. One arm 41a is pivotally connected, as at 43, to a floating link 44, the right-hand end of which is pivotally connected, as at 45, to the spring support 38.

The other arm 41b is pivotally connected, as at 46,

toa floating link 47, the lower end of which is pivotally connected, as'at 48, to the upstanding insulating operating rod 27. a

' The lower end of .the insulating operatingrod 27 is by the accelerating spring 36 by a latching device, not shown.

- The blast-valve mechanism 25 comprises a thrustlever 49 pivotally mounted upon a stationary shaft 56,

and having a thrust pin 51, which is in alignment with a blast-valve stem 52. The blast-valve stem 52 is directly connected to the blast valve 8, which is biased toward a closed position by a blast-valve compression spring. To effect opening of the blast valve 8, the bellcrank linkage 41 is rotated in a counterclockwise direction about the shaft 42 to thereby move a cam portion 53 into engagement with a roller 54, which is carried by a roller lever 55, itself pivotally supported, as at 56, upon a pivot pin carried by the blast-valve lever 49. Preferably, spring means, such as a compression spring 57, surrounding a spring rod 58 is provided to bias the roller lever 55 in an operative clockwise direction about its pivotal support 56.

It will, therefore, be apparent that during counterclockwise rotative movement of the bell-crank lever 41, the cam portion 53 will cam the blast-valve lever 55 in a clockwise direction about the shaft 56, and effect thereby opening movement of the downstream blast valve 8 against the opposition afforded by the blastvalve closing spring. On the other hand, during aclosing operation, the cam portion 53 of the bell-crank lever 41 will rotate the roller lever 55to an inoperative position about its pivotal support 56, and thereby cause the blast valve 8 to remain closed'during such a closing operation. i

A blast manifold structure 59 guides the gas'fiow through the vented movable contact 5' and, in addition, assists in the reciprocal guiding motion of the movable contact. Y

The opening operation of the improved compressedgas circuit interrupter l of the instant invention will now be described. To effect an opening operation, suitable means, not shown, effect energization of the tripping means. This will cause release of the latch, and thereby permit the compression spring 36v to effect opening movement of the movable contact 5. Simultaneously, or at a desired time relationship therewith, the blast valve 8 will be forced open by the cam action exerted by the cam portion 53, so that high-pressure gas 10, such as sulfur hexafiuoride (SP gas, will pass through openings 60, associated with an orifice structure 61, and pass interiorly within the region 63 of movable contact 5' to carry the arc terminal 70 therein, as shown more clearly in FIG. 3 of the drawings. Because of the opening of the downstream blast-valve 8 the gas flow will pass in the direction indicated by the arrows, and will pass interior 78 of the upstanding supporting column 26.

From the foregoing description, it will be apparent that there has been provided an improved gastum, is blown through the tube 9 again. Thus, most of personnel.

Although there has been illustrated and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the scope of the invention.

I claim: I 1. A compressed-gas circuit-interrupter including means defining an enclosed chamber containing an arcextinguishing gas under relatively high pressure having the undesirable characteristic of liquefying under .low-ambient-temperature conditions, means defining a relatively low-pressure region, separable contacts within said enclosed high-pressure chamber separable toestablish an are, at least one of said separable contacts being hollow, means utilizing gas under pressure from said enclosed high-pressure chamber to blast the arc into said hollow contact to effect the extinction thereof and to-exhaust thearced gas into said lowpressure region, and a liquefying-prevention device disposed in the wall of said high-pressure chamber, said device comprising an outlet passage leading out of the high-pressure chamber, a fan, a heater element,-'and-=an injection nozzle directed into said high-pressur'echamber and not associated with the separable contacts, said device extracting at least at' times high-pressure gas gas by means of said fan through the heater element to pressure chamber will tend to heat the other gas liquefying prevention device associated with a comtherein. I

2. The combination of claim 1, wherein the liquefying-prevention device is at ground potential.

3. The combination of claim 2, wherein the highpressure chamber has at least a portion thereof at high potential. v i

4. The combination of claim 3, wherein the highpressure chamber includes an upstanding insulating column. 7 i

5. The combination of claim 1, wherein a deflector vane is utilized to assist in directing the Iheatedgas within the high-pressure chamber.

6. The combination according to claim 5, wherein the deflector vane is at high'voltage. i

7. The combination of claim 4, wherein the nozzleis pointed upwardly so that the heated gas is circulated

Claims (7)

1. A compressed-gas circuit-interrupter including means defining an enclosed chamber containing an arc-extinguishing gas under relatively high pressure having the undesirable characteristic of liquefying under low-ambient-temperature conditions, means defining a relatively low-pressure region, separable contacts within said enclosed high-pressure chamber separable to establish an arc, at least one of said separable contacts being hollow, means utilizing gas under pressure from said enclosed highpressure chamber to blast the arc into said hollow contact to effect the extinction thereof and to exhaust the arced gas into said low-pressure region, and a liquefying-prevention device disposed in the wall of said high-pressure chamber, said device comprising an outlet passage leading out of the high-pressure chamber, a fan, a heater element, and an injection nozzle directed into said high-pressure chamber and not associated with the separable contacts, said device extracting at least at times high-pressure gas from said high-pressure chamber forcing the withdrawn gas by means of said fan through the heater element to thereby cause the withdrawn gas to become heated, and ejecting the then-heated gas out of said nozzle and back into said highpressure chamber only, whereby the resultant circulation effect within said high-pressure chamber will tend to heat the other gas therein.

2. The combination of claim 1, wherein the liquefying-prevention device is at ground potential.

3. The combination of claim 2, wherein the high-pressure chamber has at least a portion thereof at high potential.

4. The combination of claim 3, wherein the high-pressure chamber includes an upstanding insulating column.

5. The combination of claim 1, wherein a deflector vane is utilized to assist in diRecting the heated gas within the high-pressure chamber.

6. The combination according to claim 5, wherein the deflector vane is at high voltage.

7. The combination of claim 4, wherein the nozzle is pointed upwardly so that the heated gas is circulated about in the high-voltage portion of the high-pressure chamber.

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