US2177744A - Voltage limiting and arc extinguishing device - Google Patents

Description

Oct. 31, 1939. R. R. PITTMAN VOLTAGE LIMITING AND ARC EXTINGUISHING DEVICE Filed Feb. 25. 1939 1 1 I r I M/H/ /Z/ l z 2 v INVENTOR Patented Oct. 31, 1939 v UNITED STATES VOLTAGE LIMITING AND ABC EXTINGUISH- ING DEVICE Ralph E. Pittman, Pine Bluff, Ark.

Application February 23, 1939, Serial No. 257,841

6 Claims.

This invention relates generally to devices commonly referred to as lightning arresters, and particularly to devices for the purpose of. limiting the rise in voltage of a connected conductor by means of arcing gaps adapted to break down at a predetermined voltage, together with means -for quickly extinguishing an are which may attend break down of the gaps.

The present invention relates to improvements M in the arc extinguishing device illustrated in Patent No. 2,065,152, dated Dec. 22, 1936, and granted to the inventor herein, and has for one of its objects the embodiment of means, responsive to ,the occurrence of an arc, for moving and elongating the-arc with respect to itsinitial path andthereby facilitate its extinction.

More specifically, it is an object of the present invention to provide an improved construction in an arc extinguishing device embodying spaced electrodes within a restricted annular arc space between juxtaposed elements of insulating material, in which the electrodes are so related that sparkover occurs over a predetermined arc path around the annular space, and in which the arc 5 which may attend sparkover is lengthened by the gaseous are products which pass across the arc toward a vented opening.

Such an organization makes possible a relatively close spacing of the electrodes of the arc- 30 ing gap, and thus provides a high degree of pro-' tection .150 connected apparatus from overvoltages, without sacrifice of. ability to interrupt an are which may occur between an energized condoctor and ground, and this organization is 'an- 35 other object of the present invention.

In the construction illustrated in the abovementioned patent, sparkover is established over a vertical path longitudinally along the tube which houses the arc space. The principle or 4 idea of the present invention is distinguished by a new and radically diflerent arrangement of electrodes which are so related to each other and the other elements of the device that sparkover occurs over a substantially horizontal path ex- 45 tending around an annular arc space. This latter arrangement is such that the gaseous are products move normally across the are, instead of along or past the are as in the former, thereby accomplishing a reduction in are energy due to 50 quicker extinction and more effective cooling.

The above mentioned patent also illustrates a construction in which sparkover occurs along a vertical line of abutment between two curved elements. This is an efiective arrangement for 65 obtaining low in t al br a dow ut eq res a (Cl. Hi -30) very strong structure to resist the impact accompanying the discharge of a high surge current through the restricted path. The present inven-. tion provides a sparkover path for lightning currents which is relatively open, and makes possible 5 .a more economical construction without sacrifice of surge capacity, which is a further object of the present invention.

These and other objects will be apparent from the following description taken in connection 10 with the accompanying drawing and claims forming a part of this application.

In the drawing: Fig. 1 is a side elevational view of. the structure, in which the are extinguishing device is shown in section; Fig. 2 is another elel5 vational view, shown partly in section, of the arc extinguishing device; Figs. 3 and 4 are sectional views taken along the lines IlIIlI-and IV--IV of Fig. 1, respectively, and Fig. 51s an end view of the structure of Fig. 2, as viewed from below.

As shown" in Figs. 1 and 2, a hollow tube ofv insulating material 2|, preferably of hard fiber, is closed at its upper end by means of the metal cap' I9, the latter being secured to the tubular insulator 2| by means of internal threads in tooperation with external threads on the tube. In a similar manner, the lower metal cap 25 is secured to thelower end of the tubular insulator 2|, the cap 25 being provided with a plurality of vent openings 26 in communication with the in- 30 terior of the hollow tube 2|.

To prevent possible damage from creepage currents to the tube 2|, a leakage gap arrangement is provided at the upper end thereof, which includes the insulator l5, preferably of ceramic ma; terial. The latter is secured, in coaxial relationship with the tube H, to the cap i9 by means of the stud |8 the outwardly and upwardly extend- -ing leakage gap electrode I'I being clamped between the insulator IS and the cap H. A thread- 40 ed stud II is secured to the upper end of the insulator IS in any suitable manner, and the leakage gap electrode I4 is held by means of the nut I3, in spaced relationship with the leakage gap electrode H to provide the leakage gap i6. Another nut l2 engaging the threads of the stud provides a terminal for conductor Ill.

To provide a mounting for the device, a stud 21 threadedly extends upwardly into a centrally positioned opening in the lower cap 25, and a mounting bracket 3|, of any suitable design, is clamped between the cap 25 and the nut 28. A second nut 29' on the stud 21 provides a terminal for the ground conductor 30.

The tube 2| contains the cylindrical element 56 of insulating material 22, which may also be oi! sure, and it is thereby stretched over the relahard fiber, and which'has for a substantial portion of its length, a diameter less than the internal diameter of the tube 2|. As a convenient means for holding the element 22 in coaxial relationship with respect to the hollowoi! the tube 2i, and for another reason to be subsequently mentioned, the upper portion of the element 22 snugly fits into the upper portion of the hollow, and at the lower end of. the element 22, an unthreaded integral portion of the stud 21 extends upwardly into a centrally positioned recess at the lower end of the element 22.

Within the tube 2 I, a first conducting electrode 23, in electrical contact at its upper end with the cap l8, extends vertically downward along the element 22 to the top of that portion of.the element122 which is spaced from the tube 2|, and a second conducting electrode .24, in electrical contact at its lower end with the lower cap 25, extends vertically upward along the diametrically opposite side oi. the element 22, preferably to the elevation of the lower end of the electrode 23. Theelectrical strength of the horizontally positioned path in the annular space around the element 221mm one electrode'to the other is purposely made the weakest electrical or preferred path from the cap I! to the cap 25, so that sparkoveroccurs over this substantially horizontally positioned path rather than over any, other path between the caps.

The series arrangement of the internal and external arcing gaps has an electrical strength which is so coordinated with the insulating elements or the device that the weakat electrical path from the conductor it to the ground conductor Q! is through the series arrangement of these gaps, and electrical breakdown in response to aniex'cessive difference in potential between conductor and ground therefore includes the arcing gap between the electrodes 14 and I1, and the arcins' gap between the lower end of the electrode 22 and the upper end of the electrode 2|. While the shortest distance between the electrodes 23 and 24 is through a diameter oi the element 22, electrical breakdown does not occur over this path for the reason that the flashover value oi the element 22 is substantially less thanv the puncture value.

As mentioned above, the tubular insulator 2i and the element 22 are preferably constructed of some material which will evolve gas in the presence of an are"; as hard fiber, since the device depends for. its arc extinguishing qualities upon movement or the gaseous products of the arc. Assuming that the gaps have broken down in response 'to an overvoltage with respect to ground on a connected conductor, such as might be caused by lightning, "the initial path of the current which may attend or. follow from an energized conductor is through a horizontally positioned are which extends around the element 22 from one side to between the element 22 and. the tube 2|, and

along the lower surface of that portion oi the element 22 which snugly fits theupper portion 01 k the tube 2i. Immediately the gaseous arc prod-' nets; in response to the pressure due to the arc,

Q move downwardly through the annular space to-' ward and out of the vent openings 2l.- In so doing, the arc is subjected to a downwardly directed gas blast over its entire length, the gases moving across the arc in a direction normal to that 01' the arc. Since an arc has little weight, it is easily deflected by laterally'applid gas p e the other, in the annular space h tivelycool element 22 in a downward direction to extingulshment.

It will be observed that the arrangement described herein makes possible the use oi an internal arcing gap in a relatively open arc space without sacrifice of protective or are extinguishing ability, thereby, enabling the structure to withstand much greater lightning discharge current and energy than is possible in a highly restricted structure of the same wall strength.

Although the invention has been'shown in but one form, it will be evident to those skilled in the art that other iorms and modifications may be employed without departing from the spirit of the invention as described above or as set forth in the appended claims.

What is claimed is: 1. An arc extinguishing device comprising a longitudinally extending hollow tubular insulator closed at one end andopen at the other end, a substantially cylindrical element of insulating material having a diameter less than the internal diameter of said insulator within said insulator, means holding said element of insulating material within said tube to provide asingle annular space therebetween, and a ilrst conducting and a second conducting electrode spaced apart to provide a preferential spark path there between within said annular space, said first and second electrodes being normally insulated from each other and extending along said element on opposite sides thereof in spaced parallel relationship from the closed end and from the open insulating material within said tube to maintain a single annular space therebetween, a first-conducting electrode carried by said element and extendingvertlcally downward from the closed end 01'. said tube toward but in spaced relationship with the open end oi" said tube, a second conducting electrode carried by said element and extending vertically upward along said element inthe plane passing through said first electrode and the axis of said element, the electrodes being' normally insulated from each other and sorelated that the weakest electricalpath therebetween is in a substantially horizontal plane passing through the adjacent ends of ,said electrodes which extends circumierentially around the surface of cylindrical element of insulating material. i I

-3.,An arc extinguishing device comprising a tubular insulator closed at the upper end and open at the lower end, a substantially cylindrical element of insulating material within said insulator, means supporting said element oi insulat ing material in coaxial relation with said insulator, a first conducting electrode carried by said element and extending downwardly'along. one side thereof from the closed end 'of said insulator .and a second conducting electrode carried by & element and extending upwardly alongthe other side thereof from the open end of said insulator, said electrodes being normally insulated from each other and so related that the weakest electrical path therebetween is along the line exing electrddes spaced apart to provide a preferentiai sparkover path therebetween within said.

annular space, said electrodes extending longitudinally along diametrically opposite sides of said element and being so arranged that the weakest electrical path therebetween extends peripherally around the surface of said cylindrical element of insulating material.

5. In a voltage limiting and are extinguishing device adapted for connection between a condoctor and ground, a vertically extending hollow tube of gas evolving insulating material having a closed upper end and an open lower end, a substantially cylindrical element of gas evolving insulating material having a diameter less than that of said hallow extending in said tube from the open end toward the closed end, means supporting said element within said tube to provide an annular space therebetween, a first conducting electrode extending downwardly along the outer surface of the other side of said element from the upper end of said tube and in parallel relationship with the axis of said tube and a second I conducting electrode extending upwardly along the outer surface of said element in the vertical plane passing through said first electrode and the axis of said element. said electrodes being normally insulated and so positioned that the weakest electrical path through the device is along a .curved line extending transversely around said element from the lower end of said first electrode to the upper end of said second electrode and within said annular space, the arrangement being such that the gas attending sparkover between said electrodes moves both laterally across said weakest electrical path and longitudinally along said element toward the open end of said tube.

-6. In a voltagev limiting and are extinguishing device adapted for connection between a conductor and ground, a hollow tube of gas-evolving insulating material'having a closed upper and an open lower end, a substantially cylindrical element of gas-evolving insulating material having a diameter less than that of said hollow extending in said tube from the open end toward the closed end, means supporting said element within said tube to provide a single annular space between said tube and said element, and structural means for causing sparkover between conductor and ground to initially occur within said space over a predetermined weakest electrical path which extendstransversely with respect to the axis of said tubular insulator around the curved surfaceof said element, the arrangement being such that the gas attending sparkover moves laterally acrou said weakest electrical path as it moves longitudinally along said element toward the open end of said tube.

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