US3821507A - Circuit interrupters utilizing supersonic flow - Google Patents

Circuit interrupters utilizing supersonic flow Download PDF

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Publication number
US3821507A
US3821507A US00306509A US30650972A US3821507A US 3821507 A US3821507 A US 3821507A US 00306509 A US00306509 A US 00306509A US 30650972 A US30650972 A US 30650972A US 3821507 A US3821507 A US 3821507A
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Prior art keywords
arc
supersonic
flow
combination according
supersonic region
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US00306509A
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English (en)
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W Bratkowski
W Fischer
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ABB Inc USA
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Westinghouse Electric Corp
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Assigned to ABB POWER T&D COMPANY, INC., A DE CORP. reassignment ABB POWER T&D COMPANY, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: WESTINGHOUSE ELECTRIC CORPORATION, A CORP. OF PA.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/02—Details
    • H01H33/04—Means for extinguishing or preventing arc between current-carrying parts
    • H01H33/08—Stationary parts for restricting or subdividing the arc, e.g. barrier plate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H33/00—High-tension or heavy-current switches with arc-extinguishing or arc-preventing means
    • H01H33/70—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid
    • H01H33/7015—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid characterised by flow directing elements associated with contacts
    • H01H33/7038—Switches with separate means for directing, obtaining, or increasing flow of arc-extinguishing fluid characterised by flow directing elements associated with contacts characterised by a conducting tubular gas flow enhancing nozzle

Definitions

  • a circuit interrupter uses transonic or supersonic flow 63 y of an interrupting medium, such as air or other gas to g g of 7074* interrupt direct or alternating currents.
  • an interrupting medium such as air or other gas
  • the intera an one v rupter is provided with a supersonic nozzle and an arc chute constructed to take advantage of high speed ZOO/148 hifig flow to remove ionized gases quickly and of directed [58] Fi B 148 C expansion which stretches the arc core and length to e a c interrupt the arc.
  • the nozzle promotes supersonic flow of the interrupting medium into the arc path, and [56] References C'ted the arc chute provides smooth flow and continuous UNITED STATES PATENTS expansion of the arc gases, thereby increasing the in- 2,284,840 6/1942 Paul 200/ 148 C terrupting ability of the breaker.
  • FIGS. 1 A first figure.
  • FIGII VELOCITY (MACH NUMBER) FIGII.
  • FIGB Q 1 l 1 o I 2 3 4 s s VELOCITHMACH NUMBER
  • FIG. I6 is a diagrammatic representation of FIG. I6.
  • This invention relates, generally, to gas blast circuit interrupters, and, more particularly, to improved interrupting structures involving improved flow systems for efficiently directing the gas at and through the arc for effecting the extinction thereof and for removing the ionized gases while promoting deionization and are extinction.
  • the process of interrupting an electrical circuit is essentially'that of introducing insulation at some point in the circuit so that the current will cease to flow. Opening a knife switch or cutting a wire are examples in which the insulation at the break is air. Other insulating materials, such as oil, or sulfur hexafluoride SF gas, can also be used. However, in many instances such a simple circuit breaker is not adequate'The voltage generated may be high enough to maintain an arc across the gap in the circuit. How well the circuit breaker performs its function is dependent upon the efficiency of the interrupter.
  • the present invention is particularly concerned with a circuit interrupter of a new type which uses transonic of supersonic flow of a fluid to interrupt direct or alternating currents.
  • a circuit interrupter of a new type which uses transonic of supersonic flow of a fluid to interrupt direct or alternating currents.
  • the use of such a flow system permits the breaker to interrupt larger voltages and currents than an equivalent-sized circuit breaker of the types currently being produced.
  • the new circuit breaker of the present invention is able to interrupt larger currents and voltages for the same size breaker than heretofore.
  • the interrupting efficiency of the improved circuit breaker of the present invention is better than that of other breakers of prior art construction.
  • circuit breaker of the present invention is smaller in size for a larger rating, the manufacturing cost is less than for equivalent breakers presently being produced.
  • Circuit breakers are used to interrupt both direct and alternating currents.
  • the general method of interrupting a direct current is to raise the voltage required to maintain the are above the normal voltage supplied by the circuit. This is usually accomplished simply by lengthening the are as the contacts are separated. A strong magnetic field is frequently employed to speed up this lengthening, and barriers or are splitters are placed so as to increase the effective length of the arc.
  • alternating current interrupter depends upon two factors, namely the dielectric strength of the medium between the separated contacts and, additionally, the conductance of the arc. These are major factors in circuit interruption.
  • the novel circuit interrupter construction of the present. invention is particularly concerned with the principle of deionizing the arc space in a much shorter time and the more rapid expulsion of ionized gases than is presently being done.
  • One of the most important factors in deionizing an arc space is the flow and stirring or mixing action of the gas. This flow causes intermingling of the hot ionized arc gases and the surrounding cool un-ionized gas. This action speeds up the diffusion process, and rapid recovery of breakdown strength results from this deionization and cooling.
  • circuit interrupters utilize subsonic or sonic flow conditions.
  • the circuit interrupter of the present invention is particularly concerned with transonic or supersonic flow of the fluid into an are between separating circuit breaker contacts. Accordingly, it is a general purpose of the present invention to provide an improved circuit interrupter of the gas-blast type in which the gas velocity attains sonic, transonic and supersonic velocities.
  • a circuit interrupter is provided with a flow system comprising a supersonic nozzle and an arc chute constructed to take advantage of high speed flow to remove ionized gases quickly and of directed expansion which strethces the are core and length to interrupt the arc.
  • the nozzle promotes supersonic flow of the interrupting medium into the arc path, and the arc chute provides smooth flow and continuous expansion of the arc gases, thereby increasing the interrupting ability of the breaker.
  • FIG. I is a side elevational view, partly in vertical section, of a circuit interrupter embodying principles of the present invention, the contact structure being illustrated in the closed-circuit position;
  • FIGS. 2 and 3 illustrate, respectively, a supersonic and a sonic nozzle selectively employed in the interrupter shown in FIG. 1 for test purposes;
  • FIG. 4 is a graph illustrating the improved performance of the circuit interrupter of the invention over that of prior art construction, the ordnance being expressed in psig and the abscissa in power (KVA);
  • FIG. 5 illustrates diagrammatically certain flow conditions
  • FIG. 6 diagrammatically represents a sonic nozzle
  • FIG. 7 illustrates graphically the relationship between the velocity in feet per second and the pressure ratio for sonic flow conditions
  • FIG. 8 represents diagrammatically a supersonic flow nozzle
  • FIG. 9 graphically illustrates the ratio of stagnation to static pressure and density against Mach number for air
  • FIG. 10 graphically represents the ratio of stagnation to static temperature versus Mach number for air
  • FIG. 11 graphically represents the area ratio versus Mach number for a supersonic nozzle using air
  • FIG. 12 graphically represents the variation of velocity with Mach number for air for a given stagnation temperature
  • FIGS. 13 and 13A represent, in two different block forms the basic units of a supersonic circuit breaker
  • FIGS. 14 and 14A graphically represent, in block form a closed flow system and an open flow system, respectively;
  • FIG. '15 represents schematically a supersonic nozzle with coaeting splitters and contacts utilizing a crossblast construction
  • FIG. 16 illustrates diagrammatically a modified type of axial-flow interrupter with the possibility of utilizing an auxiliary nozzle
  • FIG. 17 illustrates a modified type of nozzle utilizing are runners extending thcrethrough
  • FIG. 18 illustrates a modified-type of flow system in which the arc is drawn axially of the nozzle
  • FIG. 19 illustrates a modified-type of contact and nozzle arrangement in which a serially-related arc establishes the requisite pressure for the transonic and supersonic velocity
  • FIG. 20 illustrates a modified-type of construction utilizing a multi-bre'ak arrangement employing a single nozzle
  • FIG. 21 illustrates diagrammatically a modified arrangement utilizing a plurality of serially-related arcs
  • FIG. 22 illustrates diagrammatically another seriall6-related break arrangement utilizing. a cross-blast construction
  • FIG. 23 illustrates diagrammatically a circulating flow system utilizing a cross-blast type of contact arrangement
  • FIG. 24 shows diagrammatically an expansion section after the contacts which will compensate for the sudden introduction of energy into the interrupting medium due to the are and allow it to expand in such a manner as to maximize the deionization rate, and therefore obtain a more efficient circuit interrupter;
  • FIGS. 25-28 illustrate modified-types of arc chute constructions with different cross-sectional configurations
  • FIG. 29 graphically illustrates the kinetic energy versus Mach number for three gases
  • FIG. 30 is a diagrammatic view of a supersonic nozzle and a supersonic are chute
  • FIG. 31 is a diagrammatic view of a diffuser.
  • Cooling Cooling or low temperature promotes deionization by (a) slowing down ionizing processes, (b) speeding up recombination.
  • Thermal ionization is the principal source of ionization in an electric are. It has been defined as the ionizing action of molecular collisions, radiation, and electron collisions occurring in gases at high temperatures. Thermal ionization can be approximately described by equation (1).
  • Dionization may also be speeded up by recombination.
  • Deionization by recombination means the recombining of the negative ions with the positive ions forming neutral atoms or molecules.
  • the rate of recombination is given by equation (2).
  • Diffusion One of the most important ways in which deionization is accomplished is by diffusion. Wherever a concentration gradient of ions exists, there will be a flow of ions from regions of high concentration to regions of lower concentration. Thus, diffusion produces a deionizing effect in highly concentrated regions. The net quantity of particles diffusing into an area per unit of time is described by equation (3).
  • the diffusion coefficient can also be expressed ir 1 terms of mean free path L and average velocity C. From this relationship, the effects of supersonic flow are more easily seen.
  • Velocity Increased velocity of the interrupting medium obviously helps speed up deionization in that the ionized path will be diluted or swept away at a much faster rate.
  • the conditions just before interruption are shown in F IG. 5.
  • the particles of the interrupting medium, entering the arc path at current zero, have a higher velocity and thus a higher kinetic energy. Therefore, collisions with the ionized particles are more severe, sweeping them away at a higher rate. This can be seen from the following:
  • the insertion of a properly constructed nozzle and are chute into the flow system of a cuicuit breaker is beneficial because (1) the increased velocity improves the displacement capabilities of the medium, and (2) the increased velocity decreases the temperature of the medium which, in turn, speeds up the diffusion process and slows down the ionization process.
  • p0/p (l 1/2lM ('Y)/'Y*l (5)
  • p,, reservoir pressure p, static pressure at a point in the flow M Mach number y is the ratio of specific heats for the fluid in question.
  • p,/p,, 0.528 which is the critical pressure ratio for conventional nozzles.
  • FIG. 8 A schematic of a supersonic flow nozzle is shown in FIG. 8. If the pressure ratio is decreased below the critical ratio in this design, the fluid, after passing through the throat at the velocity of sound, will continue to increase in velocity as it expands and will emerge from the nozzle as a supersonic stream.
  • the relation between the pressure, density, and absolute temperature at any point in the nozzle for supersonic flow is given by equa tions (6) and (7), respectively. They are plotted vs Mach number (ratio of velocity to that of the sonic velocity) for air in FIGS. 9 and 10.
  • Mass flow rate m varies directly with 1 the tank pressure, and A, the throat area, and inversely as the square root of tank temperature T Velocity is an important factor in circuit interruption. It can be seen from equations (10) and (l l that the velocity of the gas at the exit does not increase directly with Mach numbers, but approaches very close to an asymptotic limit.
  • FIG. 11 shows a plot of area ratios vs. Mach number for air.
  • the pressure ratio across the nozzle must be equal to or less than that required to give the desired Mach number.
  • FIGS. 13 and 13A show the basic units.
  • the nozzle and interrupter can be one unit, as shown in FIG. 13A, or separate units, as shown in FIG. 13.
  • the pressure ratio can be obtained by increasing P or decreasing P or a combination of both.
  • the pressure P can be obtained by means of a compressor.
  • FIGS. 14 andl4A show schematics of a closed and an open fluid system, respectively, each using a compressor.
  • the pressure P could also be obtained by means of self-generated pressure due to thermal heating by an auxiliary are, or by means of a puffer.
  • a puffer is comprised of a piston and cylinder which is actuated to compress the gas and force it into the arc.
  • the interrupter can take many forms, such as crossblast. axial-flow, axial-flow with cross-blast, etc.
  • An example of a cross-blast interrupter is shown in FIG. 15.
  • the supersonic nozzle N exhausts into an arc chute AC containing splitters S with the contacts C1 and C2 being drawn apart between the nozzle and the splitters.
  • the nozzle can be circular, square, rectangular, or any other suitable cross section.
  • An axial flow nozzle N is shown in FIG. 16. If desired, an auxiliary nozzle AN may be provided to increase the mass flow of the interrupting medium directed through the arc.
  • FIG. 17 shows diagrammatically an arrangement where the contacts Cl and C2 are drawn apart outside the nozzle N and the are runs into the nozzle on conducting runners AR.
  • FIG. 23 Another circuit breaker scheme is shown in FIG. 23. This is a closed system and is suitable for use with an interrupting medium such as SF to conserve the medium.
  • an interrupting medium such as SF
  • FIG. 18 shows an open system which can be used with'air or any other suitable fluid, which is relatively inexpensive.
  • FIG. 19 shows a self-generated pressure arrangement utilizing a double break.
  • the pressure P is produced by the are drawn between contacts C I and C2.
  • the medium flows through nozzle N to interrupt the are between contacts C3 and C4.
  • FIGS. 20 and 21 show schemes in which more than one break is fed by the same nozzle.
  • FIG. 22 shows a structure in which three nozzles NI, N2 and N3 are fed by one blast valve.
  • the process of interrupting an electric circuit is essentially that of introducing insulation at some point in the circuit so that the current will cease to flow.
  • fluid breakers such as those using compressed air or sulfur hexafluoride
  • the fluid as blown around and through the are and the arc is extinguished.
  • Other breakers such as magnetic or oil breakers, also use a flow interrupter of some type.
  • An efficient breaker must remove the ionized gases as quickly and as efficiently as possible, thus restoring the dielectric strength of the gas between the contacts and interrupting the current.
  • a circuit breaker of the cross-blast type shown diagrammatically in FIG. 24 takes advantage of highspeed flow to remove ionized gases quickly, and of directed expansion to interrupt the are.
  • High-speed flow is obtained by providing a supersonic nozzle N as previously descirbed, and directed expansion is obtained by making the are chute AC a continuation of the nozzle N to provide for smooth flow and continuous expansion of the arced gases.
  • the expansion angle of the arc chute is greater than the expansion angle of the nozzle in order to take care of increased expansion caused by are heat.
  • the are chute may be either generally rectangular, square, elliptical or circular in cross section as shown in FIGS. 25, 26, 27 and 28, respectively, with progressively increasing cross sectional areas between the entrance end of the chute adjacent the nozzle and the exit or outer end of the chute.
  • the are chute used in a prototype breaker hereinafter described was constructed as a two-dimensional plane flow nozzle.
  • the computation of flows of a frictionless incompressible fluid around general twodimensional boundaries presents problems of some mathematical difficulty.
  • the additional condition that the density of the fluid may vary will complicate the problem under certain conditions.
  • a fundamental simplification occurs, permitting again the use of the method of characteristics.
  • This simplification applied to a two-dimensional flow field in which the velocity is everywhere supersonic, permits the flow field to be represented approximately by a number of small adjacent quadrilateral flow fields in each of which the velocity and pressure are constant. These quadrilaterals must be separated by lines representing waves in the flow. Changes in velocity and pressure through any wave can be computed. By increasing the number of small areas into which the complete flow field is divided, the accuracy of this approximate solution can be increased. Such an analysis is applied throughout the entire length of the nozzle from entrance to exit resulting in a complete profile of a two-dimensional plane flow nozzle.
  • HO. 1 shows a prototype circuit breaker embodying principles of the present invention.
  • the breaker comprises a reservoir R, a valve V, a plenum chamber PC a supersonic nozzle N1, a contact piece or transitionmember TM, contact members Cl and C2 and an arc chute AC.
  • the valve V may be an electrically operated valve of a type well known in the art.
  • the valve is connected through a pipe to the plenum chamber and through a pipe 11 to the reservoir R containing air, or other suitable interrupting medium, under pressure maintained by a compressor (not shown).
  • the valve V is controlled to open a short time before the contacts are separated during an interruption. Starting the flow in the system before contacts part is standard procedure on most breakers. Although a plenum chamber is used in the present breaker to avoid turbulent conditions in the nozzle, the plenum chamber can be eliminated by providing a blast valve which will give uniform flow into the nozzle.
  • the nozzle N1 is devised to give a Mach number of 1.44. It is shown in more detail in FIG. 2. A similar nozzle N2, devised to give Mach 1.0, is shown in FIG. 3.
  • Each nozzle may be held on the plenum chamber PC by means of a sectionalized clamping ring 12. Thus, the nozzles may be interchanged for test purposes.
  • the orifice l3 ofthe plenum chamber is well blended into the entrance of each nozzle to assure smooth flow into the nozzle.
  • the stationary contact member Cl and the movable contact member C2 extend through the transition member TM which supports the arc chute AC on the nozzle N1.
  • the member TM is screwed onto the nozzle, the upper end ofwhich is threaded as shown in FIG. 2.
  • the member TM is preferably composed of polytetrafluoroethylene which is sold under the trade name Teflon".
  • the arc chute AC is preferably composed of Teflon.
  • the are chute and a support ring 14 are held on the member TMby a holder 15 attached to the member TM by bolts 16 and nuts 17.
  • the arc chute may be interchanged with other are chutes. Since the nozzles are interchangeable, the effects of various nozzle and are chute configurations upon the are interrupting ability of the breaker can bestudied.
  • the are chute is constructed to provide smooth flow and continuous expansion of the arced gases. The expansion angles takes into consideration the fluid dynamic characteristics of the expanding gases and closely approximates the maximum Prandel-Meyer angle for a change in velocity from M l. to M 1.44, as explained in ELEMENTS OF GAS DYNAMICS, by H.W. Liepmann and A. Roshko, John Wiley and Sons, Inc. This was done to keep the arc chute to a minimum length.
  • a supersonic arc chute constructed as the chute AC shown in FIG. 30, would be more efiicient.
  • the expansion is carried out in only one direction, the other being held constant.
  • the chute can be constructed for multiple direction expansion.
  • the transition member has one-dimensional expansion of flow
  • the arc chute has two-dimensional expansion
  • the nozzle has symmetrical three-dimensional expansion
  • one-dimensional flow or motion takes place in a tube of constant area. Expansion only takes place in the .r direction.
  • Two-dimensional flow involves expansion in two directions only (x, y).
  • Three-dimensional flow involves expansion in directions given by three coordinates x, y, z.
  • the movable contact member C2 is slidably disposed in the transition member TM and inside a plunger tube 21 attached to the support ring 14 by a bracket 22.
  • the outer end of the contact C2 is carried by a guide 23 slidably disposed inside the tube 21.
  • An enlarged portion 24 on the contact C2 is engaged by the guide 23.
  • the movable contact is actuated to the closed position by a cocking screw 25 which is screwed into an insert 26 in the outer end of the tube 21 to engage the end portion 24 of the contact C2.
  • the contact C2 is held closed against the force of an accelerating spring 27 by a tripping latch 28 having a projection 29 disposed in a groove 31 in the guide 23.
  • the latch 28 is pivotally mounted on a support 32 attached to the support ring 14 and is biased to the closed position by a spring 33.
  • Contact pressure between contacts Cl and C2 is maintained by a spring 34 disposed between a collar 35 on the contact member C2 and the guide 23.
  • the screw 25 is returned to the position shown after the contacts are closed in order to permit them to be opened when the latch 28 is released.
  • the tripping latch 28 is released by means of a solenoid 36, the energization of which is controlled by a controller contact 37.
  • the contact 27 is so constructed that solenoid 38 is energized slightly before the solenoid 36.
  • the solenoid 38 opens the valve V against the force ofa spring 39. In this manner the interrupting me dium is admitted to the plenum chamber PC a short time before the contacts Cl and C2 are separated to draw an arc.
  • the contacts Cl and C2 are connected to a power source by conductors (not shown). It will be understood that closing and tripping mechanisms of a type well known in the art may be provided in place of those shown.
  • a gaseous-type circuit-interrupter comprising a nozzle structure having an entrance portion, throat portion, supersonic region and a downstream portion,
  • means defining an enclosure is provided about the downstream portion.
  • a gaseous-type circuit-interrupter comprising a nozzle structure having an entrance portion, throat portion, supersonic region and a downstream portion, means for extablishing a plurality of arcs at a location within said supersonic region, said entrance portion of said nozzle receiving a gas under pressure, said throat portion maintaining sonic flow of said gas, and said supersonic region and downstream portion maintaining a supersonic flow of gas during the interruption of said plurality of arcs.

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4502012A (en) * 1980-11-26 1985-02-26 Phillips Petroleum Company Method of discharging an aerosol container to measure charge buildup on the container
EP0157242A3 (en) * 1984-04-04 1987-12-16 Felten & Guilleaume Energietechnik Ag Arc extinguishing means for electrical-load switches
RU2483407C1 (ru) * 2011-10-11 2013-05-27 Открытое Акционерное Общество Холдинговая Компания "Электрозавод" (Оао "Электрозавод") Заземлитель для круэ
US9945993B2 (en) 2013-03-19 2018-04-17 Hitachi High-Technologies Corporation Curved grating, method for manufacturing the same, and optical device

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4502012A (en) * 1980-11-26 1985-02-26 Phillips Petroleum Company Method of discharging an aerosol container to measure charge buildup on the container
EP0157242A3 (en) * 1984-04-04 1987-12-16 Felten & Guilleaume Energietechnik Ag Arc extinguishing means for electrical-load switches
RU2483407C1 (ru) * 2011-10-11 2013-05-27 Открытое Акционерное Общество Холдинговая Компания "Электрозавод" (Оао "Электрозавод") Заземлитель для круэ
US9945993B2 (en) 2013-03-19 2018-04-17 Hitachi High-Technologies Corporation Curved grating, method for manufacturing the same, and optical device

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Publication number Publication date
JPS46375A (enExample) 1971-08-26
CA938965A (en) 1973-12-25
JPS5138424B1 (enExample) 1976-10-21

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Effective date: 19891229