US1680671A - Apparatus for interrupting electric arcs - Google Patents

Description

APPARATUS FOR INTERRUPTING ELECTRIC ARCS Filed April l, 1922 3 Sheets-Sheet 1 f d c TTORNEY Aug.` 14, 1928. 1,680,671

o. H. EscHHoLz APPARATUS FOR INTERRUPTING ELECTRIC ARCS Filed April l, 1922 3 Sheets-Sheet. 2

T ummm Aug. 14, 192s. 1,680,671

O. H. ESCHHOLZ APPARATUS FOR INTERRUPTING ELECTRIC ARCS Filed April 1, 1922 5 Sheets-Sheet 3 rT// A o s O s F1 Vf o o 1 /37 O 5 E o s:- I- .O 5 E E O I INVENTOR ATTRNEY Patented Aug. 14, 1928.

4maman STATES PATENT'QFHCE.

rro E: nscnnonz, or wILxrNsnUne, PENNSYLVANIA, AssIGNoa To WEs'rrNG- noUsE Annncrarc a MANUFACTURING vANIA.v l

Appiiction med-April 1,

My invention relates to methods of and apparatus for interrupting-electrical circuits and particularly to means for facilitating the rupture of arcs that are formed between 5 spaced electrical conductors that are contained in tanks such as those of transform` ers and circuit breakers of the fluid immersed type. l My invention has for. its object the provision of means -for preventing the development of excessive pressure within the fluidcontaining tanks of electrical apparatus and for maintaining 'sufficientv pressure rtherein tov insure vthe Veffective extinguishment of arcs that are formed in the electrical apparatus.

Another object of my invention i`s thero-V vision of a throttling chamber or mu ing device of such form Vthat liquid and gaseous mixtures that are thrown from the tank, as

va result of forces developed during and.

immediately after the period of arc rupture may be separated and the liquid returned to .the tanks, and the provision of means whereby explosions of mixtures of arc gases and aii` within the throttling chamber are prevented and the gas is thoroughly vented to the atmosphere.

Uponiseparating current carrying contacts immersed in a body of quenching'fluid, such as oil, energy is rapidly liberated in theform of an electric arc. Due to the "high temperature ofthe arc stream', the liquidin its immediate vicinity is cracked, or dis- '35 integrated. `The chief disintegration products when drawing such an arc in oil have been foundV to be hydrogen, methane and carbonaceous material. The gaseous products,

when mixed with the oxygen in the air space, 40 may produce an explosive mixture that is ignitible by hot gases, incandescent metal, etc. It is recognized that the destructive forces developed by igniting mixtures ofy air-space oxygen and leither arc gases, or arc gases and finely divided oil, constitute an lmportant pressure .hazard in this form of apparatus.

To minimize. suchpressure hazard, it is proposed to utilize the movement imparted to the oil head above the arcing Vcontacts by the sudden generation of a large ,quantity of gas at the arc terminals to eject from the breaker tank gases that are' normally present in the air space, before the arcgases have COMPANY., A' CORPORATIN 0F..'PENNSAYL APPARATUS IIOR INTERRUPTING- ELECTRIC ARCS.

1922. serial Nn. 548,792.

had an opportunity to'combine with them and thereby form an explosive mixture.

n In order to permit the exit of 'oxygen from the tank in advance of the hot gener ated gases and oil and to insure the retention of suicient pressure therein, I provide an opening or vent in the tank of a proper rela'- tive dimension, as will be hereinafter described. v

. Upon the rapid generation of a large gaseous volume within the body of liquid in the tank, the oxygen is forced through the opening above referred to and into a muffling chamber that is connected to said opening. This chamber serves Yto separate the liquid from the gas and permits the oxygen and the cooled arc gases to exhaust to the atmosphere and also facilitates a return low of the liquid to the tank. The design of the muffler is Such that a slight resistanceis offered to a return movement of the expelled gases after the explosive force has been spent. However, this resistance vis so'small as to v produce little or no opposition to the escape of the arc gases under relatively highpressure during the duration of the electrical arc.

After the liquid has returned to the tank, the space above the liquid is occupied by the remaining portion of the arc gases generated by the electrical arc. As has been previously stated, these gases are found to be hydrogen, methane and carbonaceos material, which arenearly free from uncombined oxygen.v .Such gases are `obviously inert gases v when mixed with any -subse uent ases which may be generated by the e ectrica are, whereby danger `from the explosive effects of subsequent arc gases'isxeliminated.

the accompanying drawings,

'Figure 1 is a view, partiallv in side elevation and partially in section, of .a circuit l breaker tank embodying my invention,

Fig. 2 is a similar view looking from the 2 J right of Fig. 1,

Fig. 3 is a view, partial inside elevation and partially in section, o the throttling or muiliing chamber, on an enlarged scale, and

Fig. Llisa view taken on the line IV--IV ofFig.- .l Y

rlhe circuit breaker maybe of .any form 105 with which a fluid-containing tank is employed. In the present instance, it-consists/ @i a base 5 upon which an operatinggnechwf nism and a tank 6 are mounted. The breaker comprises a'pair of insulated conductors 7 and 8 that have main stationary contact members 9 and 10, respectively, and auxiliary contact members or arcing tips 111. A lifting rod 12 carries, at its lower en d a bridging member 13 that is provided with a pair of arcing tips 14. The lifting od is raised o1 lowered by mechanism, which will be hereinafter described. to cause movement of the bridging 'member 13 into and out of engagement with the stationary Contact members 9 and 10 and to cause the arcing tips 11l and" 14 to co-operatein the usual manner. n

The lifting rod 12 is supported at its upper end by a pivot pin16 that vis carried by a lever 17 which is pivoted at 18, to a bell crank flever 19. The lever 19 is pivotally supported at 20 from a lug 21 which is A .carried by the cover casting 22.

The bell crank lever, at its other end, is provided with a pin 24 upon which a pair of links 25 vare pivotally supported. The

other ends lof the links 25 are supportedv A upon a pivot pin 26 that is carried by a crank 27 Y The crank 27 is carried upon a squared shaft 28 -that ma be operated from the exterior of the brea er by a crank 29` (Fig. l)

The shaft 28 is rotatable supported by the Walls 30 of the circuitbreaker cover 22. Upon rotation of the shaft 28 in a counterclockwise direction, the upper end of the crank arm 27 Lv(Fig. 2) is moved downwardly lthrough an arc, Carrying with it the upper ends of the links-,25. This causes the .pivotl pin 24 of the bell crank lever 19 to move 1n a kcounter-clockwise direction.

This movement causes the pivot 18 to travel .downwardly, carrying with it the upper end of the lever 17 and the lifting rod 12, thus moving the bridging member and the arcing kunderside thereof engagesthe cushioning bolt and sprlng, and thus avoids excessive shock to theinoving parts.

A vent'36 is provided at the highest point 1n the up er portion of the ,breaker tank `6, and a mu g chamber or throttling device 37 is secured thereto. The rnuming chamber is provided with .a passage 38 through which it communicates vwith the vent 36 and is also provided with a series of concentric partitions 39 that are perforated, as indicated more clearly in Figs. 3 and 4. It

`will be notedfthat the perforations through each succeeding partition are disposed substantially 180 from the perforations in the next ypreceding partition, and that, therefore, the gas will pass through and around at the upper end thereof. But because of *n the tortuous passage between the vent 36 and the opening 41 a resistance is presented to the return, movement of a column of air. n

The structure of the muflling device is such as to readily cool the gases therein.

During the-'rupture of the electrical circuit within the tank, arcs are drawn between. the relatively movable contact members and particularly across the arcing tips 11 and 14, within the body of a liquid such as oil. As heretofore explained, a rapid displacement, of the oil occurs, causing an expulsion of oxygen, oil and arc'gases, in this order, through kthe vent 36 into the muller. The arrangement .of walls and openings provides a tortuous path ofv such character that the liquid, by virtue of its greater density and inertia impingesuipon, and is baiiied by, the partitions of the chamber 37, while oxygen and arc gases continue their travel to the opening 41 and the liquid en f vdrains back, through the lower openings in the partitions 39 and the vent 36, to the tank 6.

The rush of oil and arc'gases from the tank 6 into the chamberv 37 drives before it the oxygen contained in the upper portion of the tank and in the throttling chamber so that, when the hot gases reach the chamber` 37, the oxygen has been largely expelled therefrom and the danger of an explosion through ignition of the oxygen incident to Y the hot arc gas coming into contact therewith is avoided. Furthermore, tlie exten-y sive surfaces presented by the partitionsk 39 causes a cooling of the heated gases so that liability of ignition in the chamber or at the exit'41 isl minimized.

When the ^explosive force of the electric arc has been s ent, the space between vent 36 and the ui level is filled by the remaining portion of the gases produced by the prior electric arc. By reason of the fact that these gases contain little or no uncombined oxygen, they are inert gases when brought into Contact with subsequent arcrupture gases. By this design of a circuitbreaker, I am able to generate inert gases entirel within the device during an initial operation of the \device, which gases are retained in thel circuit-breaker for the purpose of preventingan explosive action between these inert gases and are rupture gases generated upon subsequent Voperations ofthe circuit-breaker. n f 5" lill) lll) In practicing my invention, 1t has been found that with a tank 20" in diameter, a vent therefrom of substantiallyll/Q diameter gives satisfactory results. That is, with a vent that has a diameter substantially T1/2% of the diameter of the'tank, air space gases will be readily expelled, while sufficient back pressure ismaintained within the tank to insure a rapid circulation of liquid across the arc stream, the arcing co1itacts,

4. able back pressure to prevent throwing of oil and to secure oil circulation in the tank,

as well as to space limitations intank structure, such orifices need rarely to exceed in area 5% that of the tank cross section.

If the tank were made of such strength as to permit of safely retainingall the pressure therein, the increasing pressure caused by the accumulation and ignition of the arc gases .would result in an increasing arc voltage gradient and, therefore, in a further increase 'of are energy and volume of disintegration products, tending to prevent free movement of arcgases from arcingicontacts and thereby greatly increasing the difficulties of rupturing the Aarc and clearing the electrical circuit.'

I have found that the orifice 41, to permit the free escape of oxygen, should be of rela- ,tively large dimensions. p The cubical contentsJ of the gas-escaping structure may ordinarily-approximate from one-tenth to full air space volume of the circuit breaker tank. However, a smaller muiiier' will function properly on liberating comparatively small volumes of arc ases. TheQhead of oil above the contacts o course must be taken into consideration, as well as the amount of arc energy it is planned to dissipate, in properly proportioning the gas-escaping structure. The vent should preferably be placedY at the highest point in the tank-and the walls of the tank should preferably be such as to offer very little resistance to the flow of gas to the vent.

'-fI am familiar with the prior -art in which ,it is shown t0 be old to provide a muffler for a circuit interrupter. These prior art devices were defective because they functioned merely as valves to relieve explosive pressures produced within the tank. These means, inasmuch as they still permitted explosions to take place, did not sufficiently relieve pressure hazards. lIn order to obtain satisfactory results it was necessary to deter:

" gases.

mine the cause of explosions in an oil-containing tank and then design the muiiler and vent to preclude the explosion. It was not my intention to design a muffler to reduce the shock of anexplosion as in an automobile muiHer, but to actually preclude the starting of an explosion by forcing the oxygen from the tank before the hot gases couldmix and ignitefthe same and yet avoid the throwing of oil from the tank as well as to upon an initial arc rupture for displacing the oxygen-containing-gases which occupied a portion of the tank before the initial arc rupture.

I wish also to point out that the relief valves of the prior art have all been of such dimensions as to generate a large back pressure which, in addition to facilitating the production of explosive mixtures of arc gases and air in the tank air space, servedto increase the ditliculty of arc rupture by increasing the arc voltage gradient and hence arc energy and volume of liberated The essential results achieved by me are the free venting of oxygen-and gas while maintaining a slight pressure in the tank to insure circulation of the oil across the contacts, `and precluding the throwing of.

oil from the tank through the vent. I have found that, with pressures as low as twenty pounds per square inch, sufficient movement was imparted to the oil and gas to preclude re-ignition of the arc between the contacts and assure the development of but a small are energy.

It will be apparent4 that, as condltlons vary, the dimensions and arrangementbf parts herein set forth may b e also varied without departing from the spirit and scope of the invention as defined in the accompanying claims.

Iclaim as my invention:

1. The Combination with a liquid immersed circuit breaker, of a .venting device therefor comprising means for permitting reduction of the-excessive pressures in the tank and for maintaining sufficient pressure within the tank vto vquench the arcs, comprising a baiing device, for permitting the entrap a portion of the arc gases generated y passage of gas to the atmosphere and for detraining liquid from the vented gases, the

baffling device comprising a central chamto quench the arcs, comprising a/baflling device into which .the vent leads, for permitting the passage of gas to the atmosphere and for detraining liquid from the vented gases, thegbaifling device comprising a chamber free from obstructions and havingla substantially vertical wall provided with vertically extending openings, one or more partitions substantially parallel to said wall having vertically extending openings and disposed to form a labyrinthine passage for the mixture of liquid and gas and to provide passagesfin a lower plane through which detrained liquid may flow back to the tank.

3. In combination with an oil circuit breaker comprising an enclosed tank, a ventingI device therefor comprising an entrance chamber communicating with said tank through apassage and having an apertured wall extending substantially parallel to the axis of said passage, one or more other v spaced partitions having apertured areas extending substantially parallel to said axis and disposed to provide a tortuous path for outflowing gases, and an outlet to the atmosphere from the apertures in the lastpartition.

4. In combination with an oil circuit breaker, comprising an enclosed tank, a venting device therefor comprising an entrance chamber communicating with said tank through an opening in the top thereof, and having a vertical apertured wall, one

"or more vertical spaced partitions having apertured areas and disposed to provide a tortuous path for outowing gases, and an outlet from the apertures in the last partition to the atmosphere.

5. In combination with an oil .circuit breaker, .comprising an enclosed tank, av 'venting device therefor comprising an entrance chamber communicating with said tank through an opening in the top thereof, a vertical apertured wall, one or more annular vertical partitions having apertures therein, and disposed to provide a tortuous path for outflowing gases and an outlet from the apertures'in the last partition to the at,-

mosphere.

6. In combination with an oil circuit breaker, comprising an enclosed tank partly v each having a vertical row of openings, the

rows in successive partitions being displaced by substantially 180.

7. In combination with an AC line and an oil circuit breaker therefor` comprising an enclosed tank, a venting device therefor comprising an entrance chamber com` municating with said tank lthrough a passage and having an apertured wall extending substantially parallel to the laxis of said passage, one or more other spaced-partitions having apertured areas extending substantially parallel to said axis but disposed to provide a tortuous path for outiowing gases, and an outlet to the atmosphere from the apertures in the last partitionVthe size of said passage and said apertures and the number of said partitions being such that when said circuit breaker opens under ,the maximum load which it is rated to rupture, substantially no oil will be ejected to the Aouter air and any air space above the oil will be emptied in less time than one alternating current period.

8. The method of controlling the passage of liquid and gaseous mediums from a container in which an electrical switch is disposed,iwhich comprises impelling substan-A tially the entire portion of said gaseous medium along a path into a chamber under the influence of said liquidmedium as affected by the operation of said switch, and passing said gaseous medium along with OTTO H. ESCHIIOLZ.

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