US2401586A - Excess voltage protective device - Google Patents

Description

June 4, 1946. s, H, JR 2,401,586

EXCESS VOLTAGE PROTECTIVE DEVICE Filed April 18, 1942 Inventor":

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Patented June 4, 1946 assist j v EXCESS VOLTAGE PROTECTIVE DEVICE Sidney R. Smith, Jr., Pittsfield, Mass, asslgnor to General Electric Company, a corporation of New York Appllcationdpril 18, 1942, Serial No. 439,507

My invention relates generally to excess volt age protective devices and particularly to means for preventing foreign objects from interferin 2 Claims. (Cl. 200-115) may be suitably supported from a, pole carrying I th transmission line or the like, not shown, as

with the correct operation of such protective'devices.

Protective devices for protecting against high- H voltage surges, such as the well-known expulsion protector tube or other forms of lightning or surge arresters are often used in connection with the protection of transformers, a, circuit-interrupting device, such as a fuse cutout or the like, being connectedin series with the line side of the transformer and the surg arrester being connected with one terminal of the fuse cutout to provide a path to ground for voltage surges. Since the support for the surge 'arrester provides a space for foreign objects, such as birds, to alight, service outages frequently result from arc-overs which have been initiated by the foreign objects establishing a low-resistance path from one of the fuse terminals to ground. For example, birds which alight on the supporting means for the surge arrester are attracted by the adjacent bright metal terminal parts and initiate an arcover by pecking atthese parts.

. It would be desirable to provide means for guarding against this danger. Accordingly it is an object of my invention to provide a new and improved surge arrester and support therefor which is substantially birdproof.

It is another object of my invention to provide an expulsion protective type surge arrester which may be readily removed by a service man without danger to life or property.

Further objects and advantages of my invention will become' apparent as the following dcscrlption proceeds and the features of novelty which characterize my invention will b pointed out with particularity in th claims annexed to and forming a part of this specification.

For a better understanding of my invention,

by a supporting strap or hanger construction, generally indicated at i2, which is adapted to surround a central portion of reduced diameter is of the insulator It. The details of the hanger construction l2 formno part of the present invention but. are disclosed and claimed in my concurrently fied copending application Serial No. 439.506 filed joint y with Ralph S. Bennett, and assigned to the same assignee as the present application. Insulator or supporting structure ll supports in spaced relationship upper terminal assembly l4 and lower terminal assembly I! which are preferably of the type disclosed and claimed in the above-mentioned copending application and these terminalassemblies l4 and i5 are preferably connected to suitable line terminals.

Th e ectrical circuit between terminal assemblies I4 and I5 is completed through upper fuse link supportin arm It, a fuse link generally indicated at H, lower fuse-link supporting arm I8,

and conducting member I! which pivotally supports lower fuse-link supporting arm l8 and electrically interconnects it with lower terminalassembly IS. A suitable spring 20 is provided for biasing pivotally mounted lower fuse-link supporting arm 18 in a counterclockwise direction as viewed from Fig. 2, thereby providing tension on fuse link IT to cause rapid separation of the fuselink terminals upon rupture of th fusible element. Although I have disclosed upper and lower be understood that these supporting arms might reference may be had to the accompanying drawing in which Fig. 1 is an elevational view of a fuse cutout and associated birdproof surge protector embodying my invention, Fig. 2 is a view partly in section taken on lin !---I' of Fig. 1, Fig. -3 is n exploded view of a portion of the r e P tector and support therefor, and Figs; 4, 5, and 6 are modifications of blrdproof surge protectors embodying my invention.

Referring now to Figs. 1 to 3 of the drawing, I have illustrated the birdproof surge protector embodying my invention as associated with a spe-- ciflc type of fuse cutout. It should be understood, however, that the specific typeof fuse cutout illustrated is merely for the purpose of illustration since my invention is applicable to any circuit-" be constructed of inherently resilient material in which case it would beunnecessary to provide additional'spring means. such as 20.

Fuse link I! preferably comprises a fusible element and, if necessary, a parallel strain wire, not

-sl'iown, enclosed within an insulating tube 2 I. The

ends of the fusible element which may be paralled by a strain wire are connected to the ends of flexible cable portions 22. one of which is connected to upper fuse-link terminal 23 and the other to lower fuse-link terminal 24. These fuselink terminals are preferabl'y'provided with a loop or other means for inserting a switch stickto permit ready re-fusing of the cutout in a manner which will be obvious from Figs. 1 and 2. Upper and lower fuse-link supporting arms l6 and is are provided with spring-biased clamping or jaw members 25 and 26. respectively; The fuse link If may have the u per and lower ends thereof inserted in these clamping members which are constructed to facilitate ready. insertion and removal of the fuse links I I. The fuse cutout described heretofore forms no part of the present invention Since the hanger construction i2, as shown in ing application which is particularly adaptable v for use with a hanger construction, such as 12. Conducting support or member 21, preferably extends at right angles from insulator I I with reference to upper and lower fuse-link supporting arms I3 and It. Any suitable surge arrester may be supported by member 21 and. accordingly, I have illustrated a surge arrester oi the expulsion protector tube type disclosed and claimed in United States Letters Patent 2,050,397. Such an expulsion protector tube type of surge arrester comprises a pair of spaced electrodes. one of which is connected to the line to be protected and the other to a suitable ground. To insure early extinguishment oi the are drawn between the'electrodes due to a voltage surge, a dielectric struc ture is provided surrounding the gap between the electrodes, thereby confining the arc space to maintain a high are voltage. This dielectric structure is furthermore composed of a material capable of evolving large quantities of substantially non-ionized gas when in close proximity to an arc discharge. Such an expulsion protector tube type surge arrester is shown in Fig. l in which the dielectric structure comprises a tube 29 having a conducting terminal 29 at one end thereof and a conducting terminal 30 at the other end (see Fig. 3). These terminals 29 and so are preferably threadedly mounted on the dielectric structure comprising tube 28. In order rapidly to extinguish any are drawn between the electrodes, not shown. contained within the tube 29, the bore of the tube and, consequently, the electrode within this tube bore is very small. It terminal 29 were connected directly to the high-voltage line to be protected, difliculties due to corona discharge from this small electrode would occur and, to prevent this, conducting terminal 29 of the expulsion protector tube type 01 surge arrester is not connected directly to terminal I4 but instead has a gap 3| interposed between terminal 29 and an electrode 32, which, in turn, is connected to terminal assembly l4. Electrode 32 preferably comprises a bent rod, whereby the setting of gap 3| may be adjusted by merely sliding the rod in terminal assembly l4. With this arrangement, terminal 29 and the electrode associated therewith contained within tube 23 are normally maintained at a low potential relative to the potential of the electrode 32. The terminal 33 of the expulsion protector tube type of surge arrester illustrated in Figs. 1

to 3 is electrically connected to conducting support 21, which, in turn, is connected to ground through hanger construction l2.

In order to permit ready removal and replacement of tube 23 and the associated terminals 29 and 3., terminal 33 is preferably provided with two parallel contact faces 33 and diametrically opposed trunnions 34. Conducting support or member 21 on the other hand is provided with cooperating contact portions 35 for engaging with parallel contact faces 33. Also, cooperating contact portions 33 include trunnion receiving 4 notches 39 which open in a downwardly direction so that the trunnions 34 may be inserted therein by an upward movement. The contact faces 33 or terminal 30 are preferably provided with indentations 31 into which embossed portions 38 of coopcrating contact members 35 may be inserted to latch terminal 3|! into firm conducting engagement with cooperating contact portions 35 supported by conducting member 21. To insure good contact between these members, cooperating contact portions 35 are preferably somewhat resil lent to grasp closely contact faces 33. A suitable hook or switch stick receiving portion 39 may be associated with upper terminal 29 to' facilitate ready removal of the expulsion protector tube surge arrester comprising tube 28 and terminals 29 and 30. By merely pulling outwardly on hook 39, tube 28 will be rotated with trunnions 34 as a pivot so as to force embossed portions 38 out of indentations 31 whereupon tube 28 and associated terminals 29 and 30 are released and may be completely removed from conducting support 21. To insert the expulsion protector type surge arrester in position on conducting support 21, a lineman would simply move tube 28 and its associated terminals, supported on a switch stick by hook 39, in an upward direction until trunnions 34 engage notches 35 after which the tube would be rotated about trunnions 34 until latched by 1 means of embossed portions 33 and indentations 31. It should be understood that operation of the expulsion protector tube type of surge arrester illustrated entails an upward force on support 21 due to the rapid expulsion of arc gases iromtube 23. The removable mounting arrangement for tube 28 limits the upward movement of the tube inasmuch as trunnions 34 are restrained from moving upward by notches 29. with my new and improved arrangement. the setting of gap 3| remains constant at a fixed distance and it is, consequently, possible to remove asurge arrester, such as illustrated, from service and replace it with a new one 01' the same standard dimensions, maintaining the setting of gap 3| without additional adjustment being required. Furthermore, this replacement may be accomplished while the associated transmission line is still energized.

With the arrangement described thus far, it will be obvious from Fig. 1 that, without additional means, foreign objects. such as birds might alight on conducting support 21 and peck at electrode 32, thereby initiating an arcover with a resultant service outage. To prevent this, I provide in accordance with my invention a bird guard 21" which might be molded from a plastic material. such as aceto butyrate or the like, and which is so shaped that it could readily be snapped over the edges of arm 21. With this arrangement foreign objects, such as birds, can no longer alight on conducting support 21, thereby eliminating any difliculty in this regard.

Although in Figs. 1 to 3, I have illustrated a surge arrester associated with a fuse cutout. such a surge arrester might be supported adjacent the high-voltage terminal of a transformer, for example. and, in Fig. 4 I have chosen to illustrate a modification of my invention applied to the highvoltage bushing 40 of a transformer, not shown. A suitable conducting support 4| of relatively short length is welded or otherwise iastened to the grounded transformer tank, only a small conductor portion 42 being shown in Fig. 4. A suitable expulsion protector tube type of surge arrester comprising tube 43 and terminals 44 and 45, respectively, has the lower terminal 45 thereof electrically connected to conducting support 4| as by means of hollow bolt 46 passing through a slotted opening 4'! in conducting support 4|. The opening in bolt 45, not shown, permits gases to escape from tube 43 during operation thereof. With this arrangement, the expulsion protector tube type of surge arrester is mounted in a substantially vertical position to form a gap 48 between upper tube terminal 44 and an electrode 49, electrically connected to the transformer terminal associated with bushing 40. Adjustment of the gap 48 may be accomplished by moving tube 43 horizontally on conducting support 4|, which may be accomplished by virtue of the slot 41. Also because of the relatively short arm 4| and the vertical position of the expulsion protector tube type surge arrester, the arrangement of Fig. 4 is substantially birdproof since there is insufiicient space for a bird to alight on arm 4|. Further to insure such birdproofing, it may be desirable to use a bushing terminal guard 50 which may be substantially identical to that disclosed and claimed in United States Letters Patent 2,263,319, granted November 18, 1941, upon an application of E. D. Treanor, and assigned to the same assignee as the present application. I have discovered that, by using the short conducting support 4| of Fig. 4, the surge arrester may be mounted on the transformer bushing and the entire unit including the transformer shipped in a standard crate, which is not possible when a longer conducting support 4| is utilized.

To prevent insects from entering the lower open end of tube 43 thru the opening in hollow bolt 45 it may be desirable to provide an insect guard such as 5| comprising a flexible metal plate which is supported by bolt 45 and bent over to close the opening at the bottom of the expulsion protector tube. This will prevent insects from building their nests within the bore of the tube prior to the first tube operation, and since flexible insect guard 5| will be blown downwardly by the expelled gases when the tube operates, it will also serve as an indicator with respect to whether or not the surge arrester has operated. Such a guard might also serve the additional purpose of a name plate for the device.

In Fig. 5, I have shown a modification of the arrangement disclosed in Fig. 4 with the corresponding parts thereof designated by the same reference numerals. Instead of using the short supporting arm 4| as shown in Fig. 4, a longer supporting arm 4| is used, in which case, tube 43 is mounted at an inclined position somewhat similar to that disclosed in Fig. 1 rather than the more nearly vertical position indicated in Fig. 4. To permit adjustment of gap 48, electrode 49' comprises a bent rod similar to rod 32 of Fig. 1. To prevent birds from roosting or alighting on conductor support 4|, I provide a suitable insulating guard 52 which substantially fills the space between bushing 40 and tube 43 and which is suitably fastened as at 53 to conducting support 4|. 7

It might be desirable to provide such a surge arrester in connection with the conventional enclosed type of fuse cutout such as is disclosed in United States Letters Patent 2,081,813, granted May 25, 1937, upon an application of B. R. Hermann, and assigned to the same assignee as the present application. Accordingly,

supported from a crossarm or the likeby means of a hanger 55 cemented to the rear wall of the cut-out housing. An expulsion protector tube.

type of surge arrester comprising tube 43 and terminals 44 and 45 may be supported from I hanger 55 by means of a strap 56 electrically connected to lower terminal 45. A suitable gap 51 may be provided between terminal 44 and an electrode 58, which may consist of a straight rod bent at one end, the rod extending into the enclosed housing of the cutout through opening 59 and being electrically connected to a line terminal within the housing. The setting of gap 51 can then be adjusted by merely twisting the rod sulating jacket, it will be impossible for a, bird to initiate an arcover by alighting thereon and engaging electrode 58.

While I have shown and described several embodiments of my invention, I desire to have it understood that the specific forms shown are merely illustrative and I 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 combination, an insulating support, a supporting arm of conducting material extending outwardly with respect to said insulating support, said supporting arm including contact portions having trunnion-receiving notches therein, a surge arrester of the expulsion type including a terminal having trunions extending therefrom adapted to be received by said trunnion-receiving notches, latching means for latching said surge arrester in a predetermined position on said support so that said terminal of said surge arrester is electrically engaged by the contact portions of said supporting arm, and

, a guard of insulating material mounted on said in Fig. 6, I have disclosed such an enclosed type of cutout generally indicated at 54 which may be supporting arm between said insulator and said surge arrester for preventing foreign objects such as birds from standing on said supporting arm and short circuiting said surge arrester.

2. The combination with an electric switching device having an insulating support and a pair of spaced terminal contacts, means for supporting an electric switching element from said support and electrically connected between said contacts, a supporting arm of conducting material extending outwardly with respect to said insulating support, said supporting arm including contact portions having downwardly opening trunnion-receiving notches therein, a surge arrester of the expulsion type including a terminal having an opening therein from which gases may be expelled. upon operation of said surge arrester and including trunnions extending therefrom adapted to be received by said trunnion-receiving notches, and means including embossed portions for latching said surge arrester in a predetermined position on said support by rotating said surge arrester about said trunnions in said trunnion-receiving notches.

SIDNEY R. SMITH, JR.

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