US2928919A - Dielectric barrier for oil interrupter - Google Patents

Description

March 15, 1960 E. J. FIELD 2,928,919

DIELECTRIC BARRIER FOR OIL INTERRUPTER Filed Feb. 20, 1956 2 Sheets-Sheet 1 wx hzhn,

R. f.T.-"5- .2 mm

March 15, 1960 E. J. FIELD DIELECTRIC BARRIER FOR OIL INTERRUPTER 2 Sheets-Sheet 2 Filed Feb. 20, 1956 INVENTOR.

United States A Pm o 7 DIELECTRIC BARRIER FOR OIL INTERRUPTER Everett J. Field, Jeannette, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application February 20, 1956, Serial No. 566,542

5 Claims. (Cl. 200-150) My invention relates to construction to prevent arc restrike in an oil column interrupter and more particularly to a construction wherein the interrupter unit is so constructed that a dielectric barrier of oil surrounds the stationary contacts immediately foliowing circuit interruption so that the contacts are not exposed to a partially ionized gas atmosphere of low dielectric strength even though there is no stored or auxiliary supply of energy to cause oil flow.

In the construction of oil column interrupters of the type shown in my copending application Serial No. 566,543 filed February 20, 1956 entitled Dielectric Barrier for Oil interrupter and assigned to the assignee of the instant invention there may be occasional delayed restriking of the are between the open separated contacts three to seven cycles after the arc has been interrupted. It appears that following an initial circuit interruption, there is substantially a complete evacuation of oil from the main interrupting chamber caused by the residual gas pressure. Since the oil column interrupter does not require or have stored energy or derive energy from the moving parts to cause oil'flow, the main interrupting chamber has an oil void during the period of time immediately following circuit interruption and instead is filled with a partially ionzed gas atmosphere. This partially ionized gas atmosphere exists between the separated cooperating contacts and its dielectric strength now continuously and rapidly decreases, so that there is always the possibility that the dielectric strength may decay to a value which would permit the arc to restrike between the cooperating contacts.

This undesirable feature can be eliminated in one of two ways. the contacts a suflicient distance from each other within a sufiiciently short time to prevent any possibility of restrike. However, this is economically unsound as it requires too much space and material.

'A second method which could be used to eliminate the possibility of restriking the arc would be to continuously supply a fresh quantity of oil to the space between the cooperating contacts. In many prior art oil interrupters, energy for oil flow is derived by an auxiliary source or stored during the movement of the cooperating contact so that during the period immediately following circuit interruption oil continues to flow into the area adjacent the cooperating contacts. However, as described and claimed in my above noted copending application, the oil column type of interrupter provides an arrangement wherein a tubular moving contact moves olf of a stationary column of oil to thereby progressively expose cool clean oil to the varea of the moving contact on which the arc terminates.

Although this interrupter supplies a fresh supply of oil to the hottest portion of the arc during interruption, it does so without requiring stored energy or subtracting any energy from the moving parts. Hence, immediately following initial arc interruption there is no supply of energy to cause oil flow into the interrupting chamber to displace First, it could be eliminated by separating 1 2,928,919 Patented Mar..15, i)

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the low dielectric strength ionized gas atmosphere, and hence, an arc restrike might occur within a few cycles.

My present invention requires neither additional separation of the cooperatnig contacts, stored energy, nor energy derived from the movement of the cooperating contacts and still provides a dielectric barrier to prevent restrike.

My invention is directed to an arrangement for an oil column interrupter wherein during the period immediately following circuit interruption there will be suflicient oil supplied to the stationary contacts to provide adequate dielectric strength between the cooperating contacts to prevent restrike and also to maintain this dielectric while the residual gas pressure subsides. This is achieved without requiring either stored energy or storing energy derived from the moving parts during interruption, and furthermore, the dielectric oil barrier that promptly covers the stationary contacts is maintained regardless of the magnitude and persistence of the residual gas pressure within the main interrupting chamber.

Basically, my invention provides an arrangement wherein the cooperating contacts are maintained within a first container with the stationary contact positioned at the lower end thereof. The entire assembly comprised of the first container and cooperating contacts is'irnmersed within a second container which is filled with a dielectric fluid such as oil. Means are provided within the first container to trap and store dielectric fluid during circuit interruption. That is, space is provided within the first container above the stationary contact to'hold dielectric fluid which will not be disintegrated or broken down by the arc during circuit interruption. Since the stationary contacts are contained within the closed lower portion of the first container, the entrapped dielectric fluid will fall or drop to the lower portion of the container immediately following the separation to the cooperating contacts. This dielectric fluid will cover the stationary contacts to thereby set up a dielectric barrier between the cooperating contacts to prevent the possibility of an arc restrike. Thus, the inherent design of my novel interrupter permits a flow of dielectric fluid to immediately cover the stationary contact following circuit interruption so as to prevent restrike of the arc. Thus, instead of requiring stored energy or taking energy from the moving parts during arc interruption, the design of my structure permits the desired flow of fluid following circuit interruption to prevent arc restrike.

Accordingly,'a primary object of my invention is to provide an oil column interrupter wherein a first containercontaining cooperating contacts is completely imimersed within a second container containing dielectric fluid and is so constructed that trapped or stored dielectric fluid within the first container will fall or drop toward the lower end of the first container to thereby cover the stationary contact.

Another object of my invention is to provide an oil column interrupter wherein a dielectric strength between the cooperating contacts immediately following contact separation and arc interruption is not permitted to decay .to the detrimental value at which are restrike could occur and this is achieved without requiring the use of a stored energy device or storing energy from the moving contacts during arc interruption.

' Another object of my invention is to provide an oil column interrupter which progressively exposes a portion of the arc to cool stationary dielectric fluid during interruption and thereafter immediately supplies dielectric fluid to cover the stationary contact without requiring a stored energy device or subtracting energy from the cooperating components. 7

Still another object of my invention is to provide an oil column interrupter wherein the stationary contact con.-

tained within a first container is positioned below any venting means and provides an arrangement wherein oil is trapped during circuit interruption so that the trapped oil will create a dielectric barrier between the cooperating contacts immediately following circuit interruption to prevent arc restrike.

Astill further object of my invention is to provide an oil column interrupter wherein the dielectric fluid entrapped within the tubular contact will fall or drop toward the stationary contact immediately following are interruption to thereby prevent the decay of the dielectric strength and prevent arc restrike.

These and other objects of my invention will be apparent from the following description when taken in connection with the drawings in which:

Figure 1 is a partial cross-sectional view of the interrupter unit embodying the principles of my invention.

Figures 2a, 2b, 2c and 2d are schematic diagrams of the interrupter unit of Figure l and illustrate the various conditions existing within the interrupter during the course of operation.

Referring to the figures, the cooperating contacts are containerz within a first container 10, which in turn is immersed within a second container 11 filled with die ectric fluid such as oil. A platform 12 supported from extension bolts llii is provided with a threaded member 34 with which the insulating tube 15 is threadibly engaged. A terminal cap 16 is threadibly engaged with the lower end of the insulating tube 15. The terminal cap 16 efiectively seals off the lower axial end of the insulating tube 15 to prevent any flow of dielectric fluid from the first container to the second container 11. A plurality of insulating discs 17 are positioned on the internal portion of the insulating tube 15, and lateral venting ports 18 and 20 are provided within the insulating discs to cooperate with appropriate openings such as 21 and 23 within the insulating tube 15. Stationary contact 24 is mounted on conducting member 25, which in turn is secured to the contact nut 26, which is threadibly engaged with the terminal cap 16. A stationary arcing ring 27 is connected through the spinner coil 28 to the stationary contact structure comprised of units 24, 25 and 26.- The moving contact is comprised of a hollow cylindrical or tubular conducting member 29 having movable arcing tip 30. The tubular moving contact 29 is threadibly engaged with its conducting extension member 29a. A terminal connection may be made to the tubular extension 29a in any desirable manner. A rod 31 having a piston head 32 is rigidly mounted and positioned on theaxis of the tubular moving contact 29-2912.

The interrupting unit which embodies the basic concept of my invention may be applied to any type of circuit interrupter such as an oil circuit breaker or an automatic recloser. For explanatory purposes only, I have illustrated the interrupting unit of my invention as embodied in an automatic recloser wherein the cooperating contacts are biased to a closed position and have an arma' ture which is energized by an operating coil through which the fault current flows. Thus, an armature 33 is secured to the tubular moving contact 29a in any desirable manner, as for example, the ring 34. The armature 33 is energized by the operating coil 35 through which the fault current will flow. Spring 36 is positioned between the stationary piston head 32 and the -ledge37 so. as to bias the cooperatiugcontacts 2-2 i into engagement.

A plurality of radial or annular recesses'such as 38, 59 and are formed by the insulating discs 17 immedi ately surrounding the tubular moving contact 29. During the normal operation of the unit, when the cooperat ing contacts are in their fully engaged position, the en tire structure illustrated in Figure 1 is completely im' mersed in dielectric fluid so that all of the radial or annular recesses such as 38, 39 and at as well as the entire internal portion of the tubular moving contact 29-29a, the remainingv portion within-the first-container. 10 as well as the second container 11 are filled with dielectric fluid. On the occurrence of a fault, the fault current will flow through operating coil 35 to thereby attract the armature 33 within the confines of the coil 35. Since the armature 33 is secured to the tubular moving contact 2951 by means of the ring 34, the entire tubular moving contact assembly 29-29a and its arc tip 30 will be moved up toward contact disengagement. Thus, there will be relative movement between the tubular moving contact 29-2901 and stationary piston head 32 so that the tubular moving contact 29--29a will move off of a substantially stationary column 41 of dielectric fluid to progressively expose cool clean dielectric fluid to the area adjacent the arc tip 30 of the moving contact on which the resulting arc terminates. This feature is fully described and claimed in my heretofore noted copending application. The movement of the tubuar moving contact from the engaged position toward its disengaged position can be seen by a comparison of Figures 2a and 21'). As the tubular moving contact 29 is moved toward its engaged position, an arc 42 is drawn between the arcing tip 39 of the moving contact and the stationary arcing ring 27, which in turn is electrically connected to the stationary contact 24. When the are 42 is drawn during the separation of the cooperating contacts, some of the dielectric fluid within t e first container 16 will be disintegrated and broken down and considerable gas will be generated. There will be, primarily, a lateral discharge of gases and vapors from within the interrupting chamber through the radial port 18. As the tubular moving contact 29 continues to separate, there wi l be secondary discharge of gases and vapors laterally through the radial ports 19. There is no intentional discharge through the lateral ports 2%, but due to the internal pressure generated there will be some nominal discharge of dielectric fluid through this venting port. That is, some of the generated gases and contaminated oil will flow from the first container it) to the second container 11. However, it will be as heretofore noted, the entire stationary contact structure consisting of the stationary arcing contacts 28 and stationary contacts 24 are contained in the lower axial end of the first container 10 and below any of the venting ports. Thus, there is a well or cavity formed by the lower end of the insulating tube 15, the terminal cap 16 and the contact nut 26 in which there will be a considerable quantity of dielectric fluid which is not disintegrated by the arc due to the'fact that the arc does not have general access to this area. However, the arc does have access tothe area immediately adjacent and above thestationary contact 24 as clearly illustrated in the schematic view of Figure 2b. Hence, a portion of this dielectric fluid will be disintegrated and broken down by the arc and there will be a partially ionized gas atmosphere of decaying dielectric strength existing herein at the time when the contact is fully opened and the are interrupted as illustrated in Figure 20.

As is well known in the circuit interruption art, the critical period of time is immediately following circuit interruption when there is a large quantity of partially ionized gas, which due to its decaying dielectric strength may cause an arc to restrike. However, with my novel invention I have provided a design wherein there will be an immediate supply of dielectric fiuid to cover the stationary contact structure immediately following circuit interruption to thereby set up a dielectric barrier between the cooperating contacts to prevent the possibility of delayed arc restrike that would ordinarily occur. To this end the entrapped dielectric fiuid within the radial or annular recesses such as 38, 39 and 40, of which only a small portion has been disintegrated or decomposed, will fall to the lower end of the first container it) as illustrated in Figure 20 to thereby cover the stationary contact structure 2427, and hence, set up a sufficient dielectric barrier between the cooperating contacts to prevent arcrestrilce. Furthermore, there is a substantial quantity'of dielectric fluid which remains within the con fines of the tubular moving contact 29a which will drop or fall to the bottom of the first container 10, as seen in Figure 2c, immediately following circuit interruption to aid in covering the stationary contact structure 24-27 with dielectric fluid to thereby set up a suflicient dielectric barrier between the cooperating contacts to prevent a delay arc restrike.

Thus, immediately following circuit interruption, dielectric fluid trapped within the radial recesses such as 38, 39 and 40 together with the remaining dielectric fluid from both the oil column 41 and within the tubular moving contact 29, aided by gravity drops to the space around and over the stationary structure 24-27. This prompt formation of a dielectric fluid over stationary contact structure 24-27 made possible by my novel arrangement creates an effective dielectric shield between the stationary contacts so that delayed arc restriking, that would ordi narily occur, is thus prevented. That dielectric barrier will remain as long as residual internal pressure persists since the pressure can do no more than evacuate the chamber down to the level of the lowest venting port 18. Thus, the depth of the dielectric fluid barrier covering the stationary contact structure 24-27 cannot be reduced below the level of the lateral vent 18 since the entire lower portion of the first container'lt) is sealed ofi. This sealing of the entire lower portion of container 10 is a permanent seal since there is a complete bottom whereby venting is prevented under all interrupting conditions. This is to be contrasted to the typical arrangement wherein a valve or venting means is placed at the bottom of the container so that under normal operating conditions, the bottom of the chamber is closed, but under abnormal interrupting conditions, the valve is opened and venting is permitted through the bottom of the chamber. Cooling and contraction of the ionized gases within the first container 10 causes a reduction of the pressure within the container 10 to thereby cause an inrush of fresh dielectric fluid from the container 11 into the container 10 through the lateral ports such as 18, 19 and 2d. Reclosing of the tubular moving contact draws fresh dielectric fluid within the internal portion of the tubular moving contact 29, and hence, the interrupter is ready for subsequent interrupting operation as seen in Figure 2d.

Thus, in the illustrated construction, the lateral ports 18, and 20 serve a dual function of venting internally generated gases during circuit interruption from the first containeror pressure chamber 10 to the second container 11 and also permits the admission of fresh dielectric fluid from the second container 11 to the first container 16 directly after circuit interruption. The dual function of these lateral ports is accomplished by utilizing pressure differentials between the interior and exterior of an interrupting chamber and the time ratio existing between time to establish interruption and time available before contacts re-close and re-establish the circuit.

Thus in summary, I have provided a novel dielectric fluid interrupter whereina first container containing the cooperating contacts is immersed in the dielectric fluid of a second container and is provided with means to trap and store dielectric fluid during circuit interruption so that it will immediately fall to the bottom of the first container to cover the stationary contact structure and thus immediately set up a dielectric barrier between the cooperating contacts to prevent arc restrike. I have achieved the desired results without requiring a stored energy means nor substracting energy from the cooperating components during circuit interruption.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. A dielectric fluid column interrupter being comprised of a stationary contact, a tubular movable contact, a stationary piston and a first and second container; said tubular movable contact mounted concentric to said stationary piston for axial movement with respect thereto; said tubular moving contact and said said stationary contact extending through said second container into said first container; said second container being filled with insulating fluid with said first container immersed therein; said stationary contact being positioned at the lower end of said firstcontainer; said tubular contact being moved off a stationary column of insulating fluid to progressively expose cool clean insulating fluid to the area of said movable contact on which the resulting arc terminates; said first container having lateral vents to said second container; said lateral vents being positioned above said stationary contact; said first container having a closed lower portion below the level of said lateral vents preventing axial flow of insulating fluid from the lower end thereof under all interrupting conditions to said second container during the separation of said contacts and immediately thereafter to thereby prevent insulating fluid to leave the area adjacent the stationary contact; said first container having an internal radial recess to trap insulating fluid during circuit interruption; said trapped insulating fluid dropping to the lower end of said first container following are interruption to thereby cover said stationary contact.

2. A dielectric fluid column interrupter being comprised of a stationary contact, a tubular movable contact, a stationary piston and a first and second container; said tubular movable contact mounted concentric to said stationary piston for axial movement with respect thereto; said tubular moving contact and said stationary contact extending through said second container into said first container; said second container being filled with insulating fluid with said first container immersed therein; said stationary contact being positioned at the lower end of said first container; said tubular contact being moved off a stationary column of insulating fluid to progressively expose cool cleaninsulating fluid to the area of said movable contact on which the resulting arc terminates; said first container having lateral vents to said second container; said lateral vents being positioned above said stationary contact; said first container having a closed lower portion below the level of said lateral vents preventing axial flow of insulating fluid from the lower end thereof to said second container during the separation-oi said contacts and immediately thereafter to thereby prevent insulating fluid to leave the area adjacent the stationary contact; said tubular movable contact having insulating fluid remaining therein during the separation of said contacts which drops to the lower end of said first container following are interruption; said first container having an internal radial recess to trap insulating fluid during circuit interruption; said trapped insulating fluid dropping to the lower end of said first container following are interruption; said insulating fluid from said tubular movable contact and said radial recess covering said stationary contact to provide a dielectric barrier between said contacts regardless of the magnitude and persistence of the residual gas pressure within said first container.

3. A dielectric fluid column interrupter for an electrical circuit being comprised of a tubular moving contact, a stationary contact, a stationary piston and a first and second container; said tubular moving contact mounted concentric to said stationary piston and having axial movement with respect thereto for engagement and disengagement with said stationary contact; said tubular moving contact and said stationary contact extending through said second container into said first container; said second container being filled with insulating fluid and having said first container immersed therein; said stationary contact extending into the lower axial end of said first container; said tubular moving contact being moved on a substantially stationarycolumn of "insulating fluid when moved from said engaged position to said disengaged position to thereby expose cool clean insulating fluid to the area of said tubular moving contact on which the resulting arc terminates; said first container having lateral vents to said second container to vent gases generated by said arc in said first container to said second container; said lateral vents being positioned above said stationary contact; said first container having a closed lower portion below the level of said lateral vents preventing axial flow of insulating fluid from said lower end to said second container under all interrupting conditions to thereby prevent insulating fluid below said stationary contact from being removed from said first container; insulating fluid from within said tubular moving contact following separation dropping toward tne lower end of said second container to thereby cover said stationary contact and provide a dielectric barrier between said contacts to prevent an arc restrike, cooling of said generated gases permitting fresh dielectric fluid to flow from said second container to said first container through said lateral vents.

4. A dielectric fluid column interrupter for an electrical circuit being comprised of a tubular moving contact, a stationary contact, a stationary piston, and a first and second container; said tubular moving contact mounted concentric to said stationary piston and having axial movement with respect thereto for engagement and disengagement with said stationary contact; said tubular moving contact and said stationary contact extending through said second container into said first container; said second container being filled with insulating fluid and having said first container immersed therein; said stationary contact extending into the lower axial end of said first container; said tubular moving contact being moved ofi a substantially stationary column of insulating fluid when moved from said engaged to said disengaged position to thereby expose cool clean insulating fluid to the area of said tubular moving contact on which the resulting arc terminates; said first container having lateral vents to said second container to vent gases generated by said are in said first container to said second container; said lateral vents being positioned above said stationary contact; said first container having a closed lower portion below the level of said lateral vents preventing axial flow of insulating fluid from said lower end to said second container under all interrupting conditions to thereby prevent insulating fluid below said stationary contact. from being removed from said first container; said first container having an internal radial recess to trap insulating fluid during separtion of said contacts; said trapped fluid falling toward said lower end of said second container to thereby cover said stationary contact and provide a dielectric barrier between said contacts to prevent an arc restrike, cooling or" said generated gases permitting fresh dielectric fluid to flow from said second container to said first container through said lateral vents.

5. An oil circuit interrupter; said circuit interrupter comprisin a stationary contact and a contact movable between an engaged and disengaged position with respect to said stationary contact; a first and second container; said first container forming an interrupting chamber and having said stationary contact mounted at the'bottorn thereof; said bottom portion or" said first container mounting said stationary contact being permanently closed to prevent the flow of oil therefrom; said first chamber being positioned at the bottom of said second chamber; vent means in said first chamber f r communicating between said first and second chambers; said vent means being positioned above said stationary contacts; said second chamher being filled with oil; said oil of said second chamber filling sai first chamber by flow through said vent means; an oil storage means positioned above said stationary contact; said oil storage means permitting the flow of oil therefrom to said bottom of said first chamber during interrupting conditions to assure that said stationary contact will be covered by oil trapped in said permanently closed bottom portion of said first chamber.

References Cited in the file of this patent UNITED STATES PATENTS

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