US2440995A - Electric circuit breaker - Google Patents

Description

EEK-140,995

May 4, 1948. T. w. wlLcoX ELECTRIC CIRCUIT BREAlEl Filed Juhe 10, 1944 Patented May 4, 1948 ELECTRIC CIRCUIT BREAKER Thomas W. Wilcox, Kenton, England, assignor to General Electric Company, a. corporation of R New York Application June 10, 1944, Serial No. 539,738 In Great Britain August 9,1943

(Cl. zoo-14s) 2 Claims. l

My invention relates to high voltage electric circuit breakers, and more particularly to circuit breakers of the fluid or gas blast type having separable contacts between which a blast or gas or fluid is directed for extinguishing arcs. Specifically, my invention is an improvement on Rankin Patent 2,306,186, granted December 22, 1942, and assigned to the same assignee as the present application.

The interruption of a high voltage power circuit such as for example, a 13B kv. circuit by means oi a gas blast involves a. number of difncult problems due to the limited dielectric strength of gases (such as air) most commonly used. A few years ago oil circuit breakers were almost exclusively used for such interrupting duty since the dielectric strength of oil is many times that of air. Accordingly, when the arc is extinguished at current zero by the oil circuit breaker the intervening oll dielectric is much bet ter able to withstand the returning recovery voltage than air. Pte-establishment of the arc, therefore, does not occur and the circuit remains open. Air, on the other hand, may be so stressed by the recovery voltage across the interrupting gap that breakdown occurs. The power arc is thereby reignlted and failure of the breaker resuits.

lt is known that the dielectric strength ci a gas increases according to pressure increase. It is also known with, respect to gases flowing through an oriilce, that `the velocity of ilcw tl'lrough the orifice occurs at c, soscallsd critical velocity" sclon4 the basis pressure at the orifice is not more than 53% of the source pressure. In the above mentioned Rankin pcfcnt eiective use was made of these phenomena in that a back pressure excess of 50% of the applied pressure is utilized with no appreciable decrease in the velocity ol the gas through the nozzle. Consequently, the contacts are main.- tained within a. reasonably high pressure atmosphere of gas furnishing a good dielectric to prevent the recovery voltage from causing restriking of the arc..

It is an object of my invention to utilize the' advantages mentioned above and in addition proa vide a prolonged blast without requiring unduly large quantities of gas under pressure.

it is another object ci my invention to provide a gas blast electric circuit breaker for high voltage alternating current circuit having a, high operating efficiency based upon conservation of compressed Sas and at the same time providing 2 better interrupting characteristics at high voltages.

Further objects and advantages o! my invention will become apparent as the following deof relatively movable contacts between the arcing surfaces of which a gas blast is :forced during separation oi the contacts, the gas exhausting into a chamber which is eiliciently closed for the arc interrupting period and is thereafter effectively open to atmosphere, the chamber being of such volume having regard to the pressure of the gas and the area oi the opening into the chamber, that gas flows into the chamber at its critical velocity for a time period at least sulficient to secure arc extinction. By critical velocity l mean the maximum velocity at which gas will how through an orice across which exists a pressure diierence, this velocity stantially that o! sound in air.

A gas blast circuit breaker according to the present invention may comprise :relatively movable contacts each ci which is provider; with a central orifice for the passage oi a gas' blast dur ing circuit interruption. whereby the products ci ionization or" the arc drawn are swept away 'the intereengagirig arising suriaces, the orlil one of the contacts ireelg to atmosphc whine that in other contact les i tc a ci or nearly closed chenilles in which pressure c f to the blast im built up during initial col @ELS il opening movement angl is subsequently relieved by regurgitation when the gas supply is inter rupind.

For a better understanding of my invention reference may be had to the accompanying' drawing in which Fig. l is an elevational view, partly in section, of a high voltage electric circuit breaker embodying the present invention with the arcing contacts thereof shown in closed position, and Fig. 2 is an enlarged sectional view ol a portion of the circuit breaker shown in Fig. l. with the arclng contacts shown in a position asn sumen during a circuit interrupting operation.

Although my invention may be applied to a circuit intermpter having a single set of arc extinguishing contacts, I have chosen to illustrate my invention as applied to a circuit interrupter comprising two sets of arcing contacts arranged in series so as toy form two breaks in ries.

being sub-l Referring now to the drawing, the high voltage circuit breaker comprises essentially two sets of relatively separable arcing contacts III-II and I2-I3, respectively. These ,sets of contacts |-I Iv and I2`I3 are each suitably enclosed in an arcing chamber, the former in a chamber I4 and the latter in a chamber I5. Arcing chamber I4 is partially denned by a cylindrical wall of insulating material Ilwhile arcing chamber I is partially deiined by a similar cylindrical wall of insulating material I5', lCylindrical walls or members It' and I5' are preferably enclosed in an outer insulating cylinderor housing I6, of weather-proof construction such as porcelain or the like. The contacts I0 and I2 are illustrated as identical in construction and furthermore areA preferably stationary contacts suitably supported within their respective arcing chambers It and I5.

In accordance with my invention I provide a fluid storage or regurgitation chamber Il in the form of a cylindrical housing suitably supported within housing I6, between members I4' and IE'. Chamber I'I defines the boundary between the two arcing chambers I4 and I5 containing the arcing contacts IIl--II and I2-I3, respectively.

Preferably regurgitation chamber I'i supports each stationary arcing contact lo and I2 within its respective arcing chamber, and furthermore provides the means by which these arcing contacts are electrically connected in series. In accordance with my invention communication between chamber I'I and each of the arcing chambers I4 and I5 is provided in the form of fluid passageways I8, one through each stationary arcing contact I0 and I2 which are illustrated as being arranged on the axis of housing I5.

The arcing contacts II and It which are substantially videntical with each other, are illus trated as movable contacts of the retractable type. l It should be understood, however, that stationary'contacts III and I2 might also be movable contacts, and movable contacts II and I3 might be stationary contacts. The arrangement disclosed in the drawing is believed to be prefer= able since it does not necessitate movement of regurgitation chamber Il. Each of the movable contacts II and I3 is reciprocally movable alone the axis of housing I5 and is provided with an oriiice I9 symmetrical about this axis. As illustrated movable contact Il is supported for reciprocal movement within a housing or enclosure 2@ suitably supported from the lower end of insulating casing It, as by a lower conducting support 2l. Similarly, contact I3 is supported for movement in a housing 22 suitably supported from the upper end of housing It by upper conducting support 23. Within each enclosure or housing 2li and 22 there is provided a tubular member 2d coaxially arranged with respect to orifices I5 in arcing contacts II and I3, respectively. Arcing contacts II and I3 are guided for reciprocal movement as is clearly shown in Fig, 2 of the drawings, by tubular members 2Q within enclosures 2li and 22, respectively.

A suitable spring 25 is provided within each of the enclosures 2li and 22 to bias arcing contacts II and I3 to the closed position indicated in Fig. 1. Preferably, the contact engaging portions of arcing contacts III-II and I--It are so arranged that the orifices therethrough are blocked by the interengaging faces of the contacts when in the closed position as indicated in Fig. 1. Arcing contact I3 is electrically connected by means of enclosure 22 and support 23 4 with an upper terminal 26 which maybe suitably connected toan associated electric circuit. Arcing contact II on the other hand is electrically connected through'its associated enclosure 20 and support 2| with a lower terminal 21. In view of the fact that the arcing contacts are normally biased toward the closed position by means'of springs 25, it is desirable to provide a suitable isolating contact in series with these arcing contacts, In accordance with the disclosure of the above mentioned Rankin patent, the lower terminal 2l of my circuit breaker may conveniently form the stationary contact of a set of relatively movable isolating contacts.l Since the construction of `the isolating contacts form no part of my invention they have been omitted from the drawing, and in this regard reference may be had to the above mentioned Rankin around regurgitation chamber I'I. This gas under away from fixed contacts IIJ and I2, whereupon two arcs in series are drawn one between contacts I0 and II and the other between contacts I2 and I3. Upon relative separation of the arcing contacts the orifices or openings I8 and I9 within these contacts are exposed and a blast of uld under pressure is caused to flow through each of these orifices so as to subject the arc drawn to a strong arc-quenching iniiuence. The blast of gas or iiuid flowing through the orifices I9 in movable contacts II and I3 passes through tubular members 2li to atmosphere, Tubular member 2d associated with arcing contact II extends into a conduit 29 leading directly to at- Tubular member 2li associated with Y mosphere. arcing contact I3 also opens directly to atmosphere. A suitable weather-proof cowl 3o. (Fig. 1) prevents the interior of the upper portion of casing I6 from being exposed to the weather without interfering with the free venting to atmosphere of the gas blast flowing through orifice I9 in contact I3.

The blasts of gas to which the two arcs in series are subjected during a circuit opening operation might cause the two aros to combine into a single long arc which may attach itself to extremity electrodes such as SI, one provided adjacent one end of each tubular member 2li. Preferably extremity electrodes 3l may be provided with means for causing movement of the aro roots on the extremity electrode, which is illustrated as' of the type disclosed and claimed in U. S. Patent 2,391,759, granted on an application filed by me and assigned to the same assignee as the present application. The provision of orifices in both fixed and movable contacts ensures minimum burning of the current carrying contact surfaces, for both arc roots of each series arc are instantly blasted well away from their points of origin at the line of contact and are driven effectively through the orifices I8 and I9, Because the arc roots are permitted no dwell on the metal constituting the interrupting nozzles, and due to the total absence of vaporable insulating ma terials in the immediate vicinity. a minimum o! products of `vaporization is generated which might impede the rapid passage of arc extinguishing gas through the nozzles.

When gas under pressure is supplied to the arcing chambers I4 and I i, as mentioned above, causing relative separation of the serially arranged arcing contacts, the openings or passageways I8 in stationary arclng contacts I II and I2 are uncovered and a portion of the blast oftluid ilows through each of the passages I8 into regurgitation chamber I1. The volume of regurgitation member I1, the areas of the fluid passageways I8,and the pressure of the gas supplied to the arcing chambers Il and I5 are so related that during the relatively short period of time required for the main blast of pressure uid to extinguish the arc, and which maybe of the order of three cycles o! thel alternating current producing the arc, exhaustpressure is not built up in the chamber I1 to cause the ow o1' pressure fluid through thel orifices I8 to de-4 crease below its critical value which, as previously mentioned, is the same as the velocity of sound. As is well known in the art, pressure on the exhaust side of an orifice or nozzle does not become back pressure effective to reduce the critical velocity flow through the orifice until it rises above a value approximating 53% of the entrance pressure. Therefore, by maintaining the velocity of the :fluid flowing into the chamber I1 during the entire arclng period at the maximum value at which fluid can be delivered from the chambers I4 and I5 throughthe orifices I8, the process of storing the pressure fluid in the closed chamber I1 does not in any way impede the flow of without isolating is required it may be desirable to provide means for dumping the fluid under pressure stored within regurgitation chamber I1 immediately after the circuit interrupting operation has been completed. Accordingly in Fig. 2 I have illustrated by dotted lines. a dumping valve 8l which may be connected by a conduit 8l with an opening il in regurgitation chamber l1. Suitable control means may be provided for valve 84 to cause it to open to atmosphere after the circuit has been interrupted.

Although I have disclosed my invention in connection with a circuit breaker employing a refluid from the chambers I4 and I5 during the f arcing period because the iiow of fluid therefrom is exactly the same as though the orifices I8 connected these chambers directly to atmosphere. As soon as the circuit is interrupted and the supply of gas passing through-supply conduit 28 is shut off, the gas under pressure stored in regurgitation chamber I'I is regurgitated through passageways I8 so as to produce a iiow of gas in the reverse direction through passageways I8 which regurgltated gas blast flows through orifices I8 to atmosphere.

It now will be apparent that these regurgitated blasts of fluid surround the contacts with a high pressure dielectric to decrease the possibility of restriking of the arc and furthermore provide a prolonged blast which maintains the contacts open by using stored fluid which otherwise would be lost and which already has usefully contributed to the interrupting process. Since the orifices I8 are relatively large, the gas jets flowing from regurgitation chamber Il may exhaust to atmosphere with no excessive back pressure so that retracting contacts I I and I3 may vigorously and decisively reclose.

Regurgitation chamber Il may be provided with suitable cooling fins 32 on the outside thereof te aid in cooling the gases which may be forced therein.

Preferably my improved circuit breaker is arQ ranged to be vertically mounted as shown in Fig. l on a suitable insulator 33 through which supply conduit 28 may extend. It should be understood, however, that the housing I6 might equally well be mounted horizontally if it is so desired, or in some other suitable position.

In certain cases, as for example when instantaneous reclosingv of the interrupting contacts tractable arcing contact of the type disclosed in Blerrnanns Patent 2,084,885, it should be understood that it is also applicable to gas blast circuit breakers oi the type disclosed and claimed in U. 8. Letters Patent 2,284,842, Prince et al., assigned to the same assignee as the present application.

In view of the detailed description included above, the operation of the circuit breaker embodying my invention will be obvious to those skilled in the art. During the circuit interrupting operation a portion ot the fluid blast is stored within regurgitation chamber II. As soon as the circuit is interrupted and the supply of pressure gas stopped, regurgitation of the gas stored in chamber Il takes place to provide a prolonged fluid blast adjacent the contacts without requiring any additional fliid from the source of gas under pressure.

It will be apparent to those skilled in the art that my invention is not limitedto the particular construction shown, but that changes and modications may be made without departing from the spirit and scope of my invention, and I aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a circuit interrupter, means defining a pair of substantially enclosed arcing chambers with a closed chamber interposed between said pair of arcing chambers, said closed chamber having a common wall between it and each of said pair of arcing chambers, -a pair of relatively movable cooperating contacts in each arcing chamber comprising a movable contact having an opening therein extending between the interior and the'exterior of the arcing chamber and a cooperating iixed contact mounted on the associated common wall and having an opening therein extending between the arcing chamber and said closed chamber, all of said openings being in alignment, means normally biasing each movable contact into engagement with its associated fixed contact to cover the openings therein so as to shut ofi communication between said .openings and the interior of the associated arcing chamber, means for supplying a blast of arc extinguishing fluid into each arcing chamber, and means in each arcing chamber responsive to fluid pressure therein for moving the associated movable contact out of engagement with its cooperating fixed contact to establish an arc therebetween and to establish communication between the associated openings and the arcing chamber.

2. In a circuit interrupter, means defining a pair of substantially enclosed arcing chambers with a closed chamber interposed between said pair of arcing chambers, said closed chamber having a common wall between it and each of said pair of arcing chambers, a pair of relatively movable cooperating contacts in each eroine chamber connected in series circuit relatip with said closed chamber, said pair of contacte comprising a movable contact having en opening therein extending between the interior andthe exterior of the arcing chamber and a cooperating fixed contact mounted on the associated common wall ami having an opening therein extending netween the arcing chamber and said closed chamber, all of said openings being in alint, means normally biasing each movable Contact into ene gagement with its associated iixed contact to close the series circuit through-said interrnpter and to cover the openings in said iixed contacts so as to shut ofi" communication between seid openings and the interior of the associated nrcing chamber, means for supplying a blast of are extinguishing iuid into each arcing chamber, and meam in each arcing chamber responsive to Enid pressure therein for moving the associated mov able contact out oi engagement with its cooper ating fixed contact to establish en 'arc therebetween and to establish communication between the associated openingsand the arcing chamber.

THoMAs w. winnen. 25

are of record in the 'ie folio r `ie oi' this patent:

" Bmw STATES PATENTS Number Name Date 1,947,224 Pani Feb. 13, 1934 1,981,404 itneyet al Nov. 20, 1934 2,994,995 ermenns June 22,1937 2,125,525 Thoen Aug. 2. 1938 '2,144,372 t Halier et al Jan. 17, 1939 2,169,673 Prince May 30, 1939 2,393,925 Cox Dec. 1, 1942 2391529 er Dec. 8, 192 2,306,16 nm:- n Dec. 22, 1942 2,396,242 Bertiett Dec. 22, 1942 2,313,159 Ludwig-et el Mar. 9, 193

` FORMGN PA:.-.'

Number Country Date 489,495 Great Britain Feb. 22, 1938

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