US3028465A - Fluid blast circuit interrupter - Google Patents

Description

April 1962 H. N. SCHNEIDER 3,028,465

FLUID BLAST CIRCUIT INTERRUPTER Filed Oct. 6, 1953 Fig.2.

WVllllllllfllllllllllllll"I"IllIIIIIIIIIIIIIIIIHIHII W!IlllMIIIIHIIIIIIIIIW' LENGTH llIllllllllIIllllllllllllllllllllllllfi Inventor:

Harold N. Schneider,

His Attorney United States Patent O 3,028,465 FLUID BLAST CIRCUIT INTERRUPTER Harold N. Schneider, Springfield, Pa., assignor to General Electric Company, a corporation of New York Filed Oct. 6, 1958, Ser. No. 765,663 4 Claims. (0. 200-150) This invention relates to an electric circuit interrupter and, more particularly, to an interrupter of the fluidblast type in which a circuit-interrupting arc is established within a body liquid contained with-inan arc-extinguishing unit.

When an arc is established within a body of liquid, the arc reacts with the liquid to generate gases having a volume varying directly with the magnitude of the current interrupted. If the liquid is located internally of an on closed arc-extinguishing unit and the current interrupted is of great magnitude, large quantities of the gases generated must be rapidly vented from the unit in order to prevent excessive pressures from developing within the enclosure. For venting such gases, it is customary to provide the unit with exhaust ports leading from the arcing region to the exterior of the unit. The area available for these ports is limited by considerations such as the need for avoiding excessive venting during the interruption of lower currents and the mechanical strength of the walls of the enclosure. Hence, it is important that efficient use be made of the overall exhaust port area that is available. Prior exhaust port arrangements of which I am aware have not been as efficient as might be desired in allowing for venting of these gases.

Accordingly, an object of'the present invention is to provide an improved exhaust port arrangement which is exceptionally efiicient in venting the relatively large volume of gases generated during heavy current interruptions.

To facilitate the interruption of high-current arcs, it is important, as a general rule, that the are be cooled as rapidly as possible. This cooling is accomplished in a fluid blast interrupter by driving pressurized fluid through the arcing region. By utilizing this fluid flow to'best advantage, lower pressures may be relied upon within the arc-extinguishing unit for interrupting currents of a given value. From a mechanical strength viewpoint, a lessening of internal pressures is, of course, desirable.

Accordingly, another object of my invention is to provide an exhaust port arrangement which lends itself to obtaining a near-maximum in arc cooling effect from -a given amount of flow through the exhaust ports.

In carrying out my invention in one form, I arrange the exhaust ports in such a manner that the venting areas provided along the length of a typical heavy current are, in efi'iect, match the gas-generation characteristics of the are. More particularly, in the region where the arc is hottest, i.e., centrally of its length, its gas-generating ability is the greatest, and it is in this central region that the largest venting area is provided. At the arc terminals the arc is relatively cool as compared to centrally thereof, and, accordingly, in these regions, venting areas of lesser size than in the central region are provided.

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

FIG. 1 is a side elevation-a1 view partially in section of a fluid-blast interrupter embodying my invention.

FIG. 2 is an enlarged view taken along the line 2-2 of FIG. 1.

HS. 3 is a graphic representation of certain temperature characteristics of a high current are.

FIG. 4 is a cross sectional view of a portion of a modified interrupter embodying my invention.

FIG. 5 is a cross sectional view taken along the line 5-5 of FIG. 4.

Referring now to FIG. 1, the interrupter shown therein is of the general type disclosed and claimed in Patent No. 2,749,412, McBride et a1., assigned to the assignee of the present invention. This interrupter 1 is mounted along with another similar interrupter (not shown) inside a relatively large oil-filled enclosing tank. The two interrupters are electrically connected by a reciprocable blade contact 2 of conventional form, such as shown, for example, in U.S. Patent No. l.,548,799I-Iilliard, assigned to the assignee of the present invention.

7 The interrupter 1 is supported from the tank by means of insulating bushing structure 3. The bushing structure The-interrupter 1 comprises an insulating casing 5 enclosing a pair of separable interrupting contacts which are electrically connected in the power circuit extending from the adapter 4 through the interrupter. ,One of the contacts of the pair is a relatively fixed contact assembly 1% and the other is a relatively movable rod-type contact 11. The fixed contact assembly 10 is preferably of the conventional cluste -type comprising aplurality of fingers 12 circumferentially spaced about a conductive rod 14 integral with the adapter 4. The fingers 12 are pivoted adjacent their upper ends on the conductor 14 and arebiased radially inward by suitable resilient means (not shown). When the interrupter is in its closed position, the movable rod-type contact 11 is in its position of FIG. 1, where it is shown embraced by the radially-inwardly biased fingers 12 of the stationary contact assembly 10.

The movable rod-type contact 11 is supported on asuitable conductive cross-head 16 having an external contact button 17 projecting downwardly therefrom. This contact button 17 cooperates with an isolating contact 18 secured to the movable switch blade 2 to form a pair of isolating contacts.

A contact-opening operation is performed by driving the switch blade 2 rapidly downward. This allows a suitable compression spring 19 to force the crosshead 16 together with movable rod contact 11 rapidly downward to draw a circuit-interrupting arc in the region where the rod contact 11 parts from the stationary contact assembly 10. After a predetermined downward movement, the crosshead 16 is blocked by suitable stop means (not shown) from following the switch blade 2. The switch blade 2, however, continues moving downwardly and, as a result, establishes an isolating break between the contacts 17 and 18 in a well-known manner.

The above-described circuit-interrupting arc reacts with the surrounding oil inside the interrupter Ito create a blast of fluid through the arcing region, and this blast aids in extinguishing the are, as will soon be described in greater detail.

For directing the fluid blast into the arcing region, an arc-extinguishing unit in the form of a ba'ille stack 20 is provided immediately beneath the stationarycontact 10. This baffle stack 20 is formed of a plurality of superposed bafi'le plates 23 of insulating material, preferably of a circular configuration in planview. These baflle plates 23 are clamped together and have registering apertures provided internally thereof so as to form a verticallyextending arcing passageway 24 for receiving the vertically movable rod contact 11. Most of the battle plates 23 are also slotted so as to provide flow passages radiating from the arcing passage 24. The flow passages 25 located to the right of the arcing passage 24 direct the fluid blast into the arcing region, whereas those passages 26 to the left of the arcing passage 24 constitute exhaust passages for venting the arcing products and the fluid blast from will be noted that certain of the intermediately-located bafile plates 23 are not provided with slots. Those edges of these plates which surround the arcing passage 24 serve as barriers for restraining the are within the arcing passage 24 so that it is not driven through the exhaust passages 26 into the region outside the interrupter by the fluid blast.

The present invention is particularly concerned with the configuration of the exhaust passages 26, especially at the months, or outer ends, thereof. These outer ends are hereinafter referred to as exhaust ports and are designated 27a, 27b and 270. The slots forming the flow passages 26 preferably have their minimum width at the exhaust ports, and, thus, the flow passages 26 are less restricted upstream from the exhaust ports than they are at the exhaust ports. It will be noted that the casing S is provided with an opening 28 that aligns with these exhaust ports to allow for escape of the arcing products into the surrounding oil. The configuration of the exhaust ports 27a, 27b, and 270 is best illustrated in FIG. 2, which is an enlarged view taken from outside the interrupter looking in the direction of exhaust ports. It will be noted from FIG. 2 that the central exhaust port 27a hasa considerably larger area than the exhaust ports 27b and 270 located at vertically opposite sides thereof. This exhaust port configuration provides for highly etficient venting of the arcing products for reasons which will now be explained.

For the purposes of explanation it will be assumed that an are such as shown at 30 in FIG. 3 is established between a pair of contacts corresponding to the contacts and 11 of the interrupter of FIG. 1. The temperature of the arc taken at points along its length has a character istic curve of the configuration shown immediately beneath the arc. As indicated by the curve, the arc temperature is the highest centrally of the arc length and is of a considerably lesser value adjacent each contact or electrode. This is the case because vaporized electrode material, which is relatively cool compared to the temperature, of the arc plasma, cools the ends of the arc. Since the amount of gas generated when the arc reacts with the surrounding oii'varies directly with temperature, it will be apparent that more gas will be generated in the central region of the arc than at its ends. In other words, if the volume of gas generated at particular points along the arc length were to be plotted against arc length, then the resulting cunve would have generally the same character'i'stic shape as the temperature curve plotted in 7 FIG. 3.

To exhaust these generated gases in the most efiicient manner with a given overall exhaust port area, I have concluded that the exhaust port area configuration should substantially match the gas-generating characteristics of the are. In other words, where the gas-generating capacity is the greatest, the greatest exhaust area should be provided, and where the gasgenerating capacity is the smallest, the smallest exhaust port area should be provided. This end is achieved in the interrupter of the present invention by proportioning the exhaust ports so that the greatest venting area is located centrally of the arc length and venting areas of lesser size are located adjacent the ends of the arc. The arc length may, of course, vary for currents of difierent magnitude, but the arc length that Should be used as a reference base for positioning of the ports is the arc length at which maximum gas-generation will take place when interrupting currents near the maximum interrupting rating of the interrupter. This condition results at or slightly past the point of peak current preceding interruption.

It is recognized that for other arc lengths, e.g., the.

longer are lengths that would beencountered with lower currents, the arcing products would not be exhausted with the same high degree of efficiency, but for such conditions,

the quantity of gases generated is relatively low, and, thus, 1

the same high degree of: eificiency is not necessary. 7

One might inquire as to whether it would be disadvantageous to make all three of the exhaust ports of the same size as the centrally located exhaust port 27a. With regard to this inquiry, there are a number of disadvantages which would result from such an approach. First of all,

it the overall exhaust port area is increased appreciably 7 I Increasing the size of opening 28 is disadvantageous because it tends to mechanically weaken the casing 5 and to thus impair the ability of the casing 5 to withstand the high pressures encountered during extreme high current V interruptions.

Another advantage thatthe disclosed exhaust port configuration has over one which utilizes exhaust ports of equal area and shape is that the disclosed configuration provides for a more efiicient cooling of the arc. In this regard, in the particular region where the arc temperature.

is the highest, i.e., centrally of its length, the greatest amount of flow is provided, and in the regions where the arc temperature is the least, i.e., at its ends, the least amount of flow is provided. Since the cooling that takes place at any region along the arc length is dependent upon the flow across that particular region, it will be apparent that distributing the flow in accordance with the arc temperature provides for flow commensurate with cooling requirements. Accordingly, there is no appreciable amount of flow wastefully dissipated adjacent the ends of the arc, and thus efiicient utilization is made of the flow that is present. v

The fact that the cross-section of the arc is of a lesser size near its ends than centrally thereof is another factor which renders the disclosed exhaust port arrangement highly efiicient from a cooling viewpoint. In this regard, the restricted nature of the end exhaust ports causes the transverse flow adjacent the arc ends to be directed closely adjacent the arc periphery rather than along some path relatively remote from the are where the .cooling efiect would be much less pronounced. The ability toefiiciently utilize the available flow enables a lesser amount 7 of flow to be relied upon to perform the same amount of cooling. If lesser flow is required, the pressures within the interrupter which produce this flow may be of alesser value, Hence, by efficiently utilizing the flow, my exhaust port arrangement enables lesser pressures to be utilized for interrupting currents of a given value than would be required with less efiicient flow patterns. .Lessening of internal pressures is, of course, desirable from a mechanical strength viewpoint.

To facilitate low currentinterruptions in, the interrupter of FIG. 1, a conventional impulse pump 40 is provided at the right hand side of the interrupter casing 5. This pump comprises a piston 41 mounted for vertical movement inside a. cylinder 42 and biased by means of a com-' pression spring 44 tomove downwardly in response to opening of the interrupter. While the interrupter is closed,

the piston 41 is maintained in its elevated position of FIG. 1 by means of a plunger 45 secured to the switch blade 2 and abutting against the lower end of the piston rod. However, when the switch blade 2 is driven downwardly to open the interrupter, the restraint of the plunger is removed and the spring 44 is free to begin driving the piston 41 downwardly against the opposition of the oil therebeneath.

When the piston moves downwardly, it tends to force liquid into the flow passages 25 via a conventional check valve 43 interposed between the pump at} and the flow passages 25. The check valve43 comprises a slidably mounted valve element 43a which allows flow to take place only from the pump into the casing 5 and not in a reverse direction. Low current arcs generate within the interrupter relatively low pressures which are incapable of holding the check valve 43 closed, and, hence, the pump is capable of directing a flow through the passages under such conditions. This flow aids in extinguishing low current arcs. Under high current interrupting conditions, however, the pressure generated within the interrupter is higher than the pump pressure and forces the check valve 43 to remain closed until after the interruption is over. Upon completion of the interruption, the pressure within the interrupter quickly diminishes, and the pump then becomes operative to scavenge the interrupter of arcing products. Impulse pumps such as are well-known, and reference may be had to the aforementioned McBride et al. patent for a more complete description of pump of this character.

A modified interrupter wherein the exhaust port configuration of the present invention has been found particularly advantageous is illustrated in FIG. 4. Here the arcing products, instead of being vented from the exhaust ports 27a, 27b, 27c directly into the surrounding oil, are

vented through a pressure-responsive exhaust valve before entering the surrounding oil. An exhaust valve of this character is shown and claimed in my application SN. 717,892, filed February 27, 1958, now Patent No. 2,927,181, issued March 1, 1960, and assigned to the assignee of the present invention.

For the purposes of the present application, the following brief description of exhaust valve 50 is believed to be suificient. Referring to FIG. 4, it will be noted that the exhaust valve 50 comprises a tubular valve body 51 suitably secured within an opening formed in the casing 5. The securing means may be of any conventional form, but preferably comprises a nut 57 and a shoulder 58 between which the wall of the casing 5 is clamped. Within the tubular valve body 51 is a flow-controlling vane 52 coupled to a pivotally mounted shaft 53. A tension spring 54 disposed about the outer periphery of the valve body 51 acts through suitable cranks 55 coupled to the shaft 53 normally to bias the vane 52 into its closed position of FIG. 4. During low current interruptions, the pressure developed within the interrupter is relatively low, and under such conditions the spring 54 holds the vane 52 closed, thereby assuring that suflicient pressure will be built up inside the interrupter to enable low current arcs to be efficiently extinguished. Under high current interruptions, large quantities of gas are generated within the interrupter, and accordingly relatively high pressures are built up therewithin. In response to such pressures, the vane 52 is forced open against spring 54 to allow the arcing products to be vented from the interrupter, thereby preventing excessive pressure rises within the interrupter.

To avoid impairing the mechanical strength of interrupter casing 5, it is desirable that the valve body 5'1 be as small as possible. the valve body 51 must be large enough to allow for a sufiicient flow of arcing products during extreme high current interruptions to prevent excessive pressures from being developed within the interrupter 1. The exhaust port arrangement of the present invention enables the valve body to be of a near-minimum size because the .thus enabling these products to be rapidly exhausted before excessive pressures can be developed.

The exhaust ports in FIG. 5, like those in FIGS. 1 and 2, are positioned along a length of the interrupter which is generally coextensive with the arc length at which maximum gas-generation will take place when interrupting currents near the maximum rating of the interrupter. Along a diameter of the .bore of valve body 51 extending lengthwise of the interrupter, the central exhaust port 27a provides a larger venting area than the exhaust ports 27!) and 270 near the terminal of the arc.

While I have shown and described particular embodiments 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.

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

1. -In an electric circuit interrupter for interrupting currents up to a predetermined rated value, an enclosure containing a body of insulating liquid and an arc-extinguishing unit immersed within said liquid, means for establishing within said unit circuit-interrupting arcs that are adapted to react with said insulating liqiud to gencrate a volume of gas dependent upon the current being As a limiting consideration, however,

sages having a region of maximum restriction defining an 1 exhaust port of fixed cross-sectional area in said exhaust passage, said ports being disposed along a length of said unit generally coextensive with said predetermined general length and providing centrally of said general length a substantially larger venting area than at either end of said general length, those arcs that have a low current.

value in comparison to said rated value extending over said predetermined general length plus an, additional length of said arc-extinguishing unit. 7

2. The interrupter of claim 1 in which said arc-extinguishing unit is constructed of a plurality of superposed baflle plates stacked lengthwise of said unit, said bafile plates including slots extending transversely of the length of said arc-extinguishing unit to define said exhaust passages, each of said exhaust pasages having its region of maximum restriction at its outer end to define one of said exhaust ports, those slots located centrally of said general length being substantially wider at said exhaust parts than those slots located at either end of said general length.

3. In an electric circuit interrupter, an enclosure containing insulating liquid and an arc-extinguishing unit immersed therein. said arc-extinguishing unit having an arcing passage extending longitudinally of said unit and longitudinally of said enclosure, means for establishing within said arcing passage an are adapted to react with said insulating liquid to generate gases said arcing passage having a predetermined general length over which those arcs having a current valuue near the maximum rated current value of said interrupter extend at the instant of maximum gas generation, means for venting said gases from said unit in a direction transverse to the length of said enclosure comprising a plurality of exhaust passages in said arc-extinguishing unit extending transversely from said arcing passage to the exterior of said unit for venting arc-generated gases therefrom, each of said exhaust pasages having a region of maximum restriction definingan exhaust port of fixed cross-sectional area in said exhaust passage, said exhaust ports providing a substantially larger venting area centrally of said predetermined general length of said arcing passage than at either end of said predetermined general length of said arcing passage, those arcs that have a low current value in comparison to said rated value extending over said predetermined general length plus an additional length of arcing passage.

4. In an electric circuit interrupter for interrupting currents up to a predetermined rated value, an enclosure containing a body of insulating liquid and an arc-extinguishing unit immersed within said liquid and containing an arcing passage, means for establishing within said arcing passage arcs that are adapted to react With said insulating liquid to generate a volume of gases dependent upon the current being interrupted, those arcs that have a current value near said predetermined rated value extending over a predetermined general length of said arcing passage at the instant of maximum gas generation, means for venting said gases from said unit comprising a plurality of exhaust passages extending transversely from said arcing passage to the exterior of said unit forventing aregenerated gases therefrom, each of said exhaust passages having a region of maximum restriction defining an exhaust port of fixed cross-sectional area in said exhaust passage, said exhaust ports being located along said pre determined general length of said arcing passage in communication with said arcing passage, a valve body having a generally circular flow passage extending therethrough, means for supporting said valve body adjacent said arc extinguishing unit in a position wherein said flow passage aligns with said plurality of ports and provides an outlet for fluid flowing through said ports, said ports beinglo-.

cated along a diameter of said flow passage extending generally parallel to said arcing passage, said ports providing centrally of said diameter a substantially larger venting area than at the opposite ends'of said diameter,

and pressure-responsive means for controlling flow through said flow passage in accordance with the pressures developed within said unit as a result of an interrupting operation, those arcs that have a low current value in comparison to said rated value extending over said predetermined general length plus an additional length of said arcing passage.

References Cited in the file of this patent UNITED STATES PATENTS

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