US3586913A

US3586913A - High voltage lightning arrester having a discharge surge counting device mounted on its top terminal by insulating means

Info

Publication number: US3586913A
Application number: US5752A
Authority: US
Inventors: Arthur A Olsen
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-01-26
Filing date: 1970-01-26
Publication date: 1971-06-22
Anticipated expiration: 1988-06-22

Abstract

A high voltage lightning arrester having a vertical height in excess of 20 feet is provided with a discharge surge counting device mounted adjacent its uppermost terminal by insulating members that are so arranged as to prevent them from being subjected to stresses that could break or damage them when the lightning arrester is subjected to horizontal torque-producing forces by high velocity winds.

Description

United States Patent [72] lnventor Arthur A. Olsen [56] References Cited "g Mm UNITED STATES PATENTS $53 i 26 1970 2,200,233 5/1940 Whitehead 317/6l x 3,l56,866 l [/1964 Anderson etal 324/54 X gz f g g fi' com m 3,443,223 5/1969 Kennon 324/54 x g y 3,469,188 9/1969 Hall 324/102 Primary Examiner.lames D. Trammell [54] HIGH VOLTAGE LIGHTNING ARRESTER Attorneys-Francis X. Doyle, Vale P. Myles, Frank L.

A Neuhauser, and Joseph Forman DEVICE MOUNTED ON "8 TOP TERMINAL BY g gf ggi f ABSTRACT: A high voltage lightning arrester having a vertiw cal height in excess of 20 feet is provided with a discharge [52] U.S.Cl 317/6], surge counting device mounted adjacent its uppermost ter- 317/72, 324/ l 02, 340/248 C minal by insulating members that are so arranged as to prevent [5i] lnt.Cl 02h 9/06 them from being subjected to stresses that could break or [50] Fieldof Search 3l7/72,6l; damage them when the lightning arrester is subjected to l74/2; 324/54, 110, I02; 340/253 A, 253 C, 248 C horizontal torque-producing forces by high velocity winds.

HIGH VOLTAGE LIGHTNING ARRESTER HAVING A DISCHARGE SURGE'COUNTING DEVICE MOUNTED ON ITS TOP TERMINAL BY INSULATING MEANS It is common practice in the lightning arrester field to mount surge counting devices on high voltage arresters to maintain an accurate record of the number of overvoltage surges discharged through the arrester during its lifetime. Present day surge counting devices for performing this function generally are of a type that require the counting device to be mounted in series with the arrester discharge path so that substantially the entire discharge current passes through the counting device. Prior to the present invention, these prior art counting devices were conventionally mounted on, or immediately adjacent, the bottom terminal of the lightning arrester so that their numerical register would be conveniently accessible to oneattempting to read the number of overvoltage surge discharges indicated thereby.

With relatively small lightning arresters, such mounting arrangements for the surge counting devices were acceptable. However, it has been found that with the large lightning arresters presently coming into use on extra high voltage electric power transmission lines a major problem has been encoun' tered in attempting to employ conventional methods for mounting counting devices in the necessary series circuit relationship with the arresters spark gaps. Specifically, it has been found that even when insulating support members that possess high mechanical and compression strength are employed to mount the surge counting devices in suitably insulated relationship with respect to the lightning arrester base terminal, the combination of arrester weight, insulator aging and the abnormal torques applied to the insulating supports by movement of the arresters in response to high velocity winds, may cause these supports to be cracked or crushed directly, or by subsequent tightening of mounting bolts to eliminate slack introduced by shrinkage of the insulating supports. Since such insulating support means conventionally are under the lightning arrester, the arresters must be raised to replace any support insulators that are damaged. Of course, such maintenance operations are expensive and it would be most desirable to avoid them if possible. In addition, it would represent a substantial system cost reduction if some means could be found to eliminate the need for expensive insulating materials,

such as Melamine glass, for such insulating supports. A primary object of my invention is to provide a high voltage lightning arrester having a surge counting device mounted thereon in a manner such that the foregoing problems encountered in prior art mounting arrangements are completely avoided.

Another object of my invention is to provide a high voltage lightning arrester having insulated means for mounting a surge counting register adjacent the top of the arrester thereby to prevent the weight of the arrester from being applied to the insulating means with possibly damaging consequences.

A further object of the invention is to provide a mounting arrangement for a lightning arrester surge counting device that enables the counting device to be mounted on top of the arrester in a manner that enables it to be read by a man equipped with a sighting glass standing back from the base of the arrester.

In accordance with the invention, a tall high voltage arrester having a voltage-grading annular frame positioned adjacent its uppermost conductor terminal is provided with insulated mounting means for supporting a surge counting device in insulated, spaced relation with respect to the conductor terminal on top of the arrester. With the insulated counter device supporting arrangement of my invention, the weight of the lightning arrester housing does not rest on the insulating support means, therefore, these support means can be manufactured from electrical insulating materials that have relatively low mechanical strength.

Further objects and advantages of my invention will become apparent to those skilled in the art from the following description of the invention taken in connection with the drawings in which:

LII

FIG. I is a side elevation view of a conventional lightning arrester housing having a surge voltage discharge counting device mounted in customary manner adjacent its lowermost conductor terminal. I

FIG. 2 is a side elevation view of a portion of a high voltage lightning arrester housing having a surge voltage discharge counting device mounted in operative relationship with its uppermost conductor terminal, on insulated support means, pursuant to my invention.

FIG. 3 is a fragmentary top plan view of the lightning arrester housing and uppermost terminal, including the surge counting device, depicted in FIG. 2.

FIG. 4 is a fragmentary side elevation view, partly in cross section, of the top lightning arrester. terminal, the surge counting device, and the insulated mounting means illustrated in FIG. 3. Y

FIG. 5 is a fragmentary side elevation view, partly in cross section, of the insulated counting device support means of my invention as illustrated in FIGS. 2, 3 and 4.

Referring now to FIG. I of the drawing, there is shown a conventional prior art lightning arrester housing 1 having a top conductor tenninal 2 that is adapted to be electrically connected to a high voltage transmission line or other'system that thearrester is intended to protect from overvoltage surges. Arrester I also has a bottom electrical terminal 3 for connecting the arrester to ground. It will be understood by those skilled in the art that a plurality of series connected spark gaps (not shown) are electrically connected between

terminals

2 and 3 to normally insulate these terminals from one another and to provide a discharge path for high voltage surges that spark the gaps over to form a conducting discharge path from uppermost terminal 2 to terminal 3. Of course, it is necessary to provide an electrical circuit to ground from terminal 3 in order to safely dissipate suchovervoltage circuits. In the arrangement shown in FIG. 1, this circuit includes a discharge surge counting device 4 thatis mounted on insulator 5 by a bracket 6. A suitable electrically conducting cable or strap 7 is clamped to terminal 3 by belts or other suitable connectors and also to a connector 8 on the counting device 4. A second cable 9 is electrically connected to a second terminal (not shown) on the counting device 4 and to a suitably grounded point adjacent the base of arrester 1. It will be noted that in this prior art arrester and surge counting device mounting arrangement, the arrester is supported on a plurality of metal legs, two of which are identified by the numerals l0 and 11. The legs 10 and II are insulated from ground by insulating discs 5, 5a, 5b and 5c, disposed respectively on opposite sides thereof, as shown in FIG. I. It will be understood that with this arrangement the insulating cylinders 5a and 5c (and an additional insulator on a third leg which is not shown) bear substantially the entire weight of the arrester housing 1.

With such mounting arrangements, it is necessary to form the insulators 5a and 5c of high compression strength material, such as Melamine, if arrester housing 1 is tall enough to cause it to apply heavy crushing weight on these insulators. In fact, since lightning arresters are frequently mounted in positions where they are exposed to the atmospheric elements, it has been found that high velocity winds apply substantial torques to the mounting legs 10 and 11 of such relatively tall arresters to further increase the risk of damage to the insulating mountings for theselegs. Thus, for extra high voltage arresters of the type needed to protect present day transmission lines such mounting arrangements occasionally fail due to the insulating supporting means 55c becoming crushed or cracked and broken so that they no longer perform their needed insulating function or so that they loosen and allow the arrester to sway dangerously. If such breakage occurs, it may result in the surge counting device 4 being bypassed by surge voltages so that it fails to correctly register the number of overvoltage surges discharged to ground through the arrester housing I. As a consequence, it is possible that wrong records could be made leading to wrong conclusions that could lead to unwise changes in the system.

With my invention, a preferred form of which is illustrated I in FIG. 2, which is now referred to, the risk of such damage is eliminated. The combined apparatus illustrated in FIG. 2 comprises a lightning arrester 12 having an elongated insulating housing 13 that conventionally is formed by stacking a plurality of hollow, cylindrical units on top of each other to form a hollow, vertical column, as shown. Mounted on the top end of housing 13 is an electric conductor terminal 14 in the form of a triangularly shaped metal plate (see FIG. 3) having an upright metal tab 15 thereon to afford a connecting surface for a cable, such as cable 16 that, in the illustrated arrangements, is electrically connected to a high voltage transmission line 17. At the bottom of arrester housing 13, a second electrical conductor terminal 18 is mounted in sealed relationship with respect to the housing 13 and, as is well known in the art, a plurality of spark gaps (not shown) are mounted in housing 13 and are electrically connected in series relationship between the top terminal 14 and bottom'terminal 18 so that they normally insulate these terminals from each other and also form a current discharge path between

terminal

14 and 18 when the spark gaps are sparked over by a predetermined surge voltage. Bottom terminal 18 is electrically connected to a suitable point of ground potential by cable 19.

Pursuant to my invention, the base of lightning arrester 12 is directly mounted on the integral steel legs 20 and 21 that form a part of bottom terminal 18. As can be seen in FIG. 2, legs 20 and 21 rest approximately 10 feet above ground level, directly on concrete mounting pillar 22, without having any insulating cylinders therebetween as would ordinarily be required if a surge counting device (such as counting device 4, discussed above) were to be functionally connected in the series discharge circuit between the spark gaps in housing 13 and bottom terminal 18 of arrester 12. However, a surge discharge counting function is provided by a suitable counter 24 mounted adjacent the top terminal 14 of the arrester 12. The specific mounting arrangement used in the preferred embodiment of my invention is described in detail with reference to FIGS. 3, 4 and 5 of the drawing. As shown in FIGS. 3 and 4, counting device 24 is supported on a mounting means in the form of U-shaped bracket 25 that is clamped to counting device 24 by clamping means 26, in the form of threaded

bolts

26a and 26b that can be adjusted to position the register face (not shown) of the counting device 24 in a suitable position to afford optimum visual inspection of the register from a point adjacent but below and spaced a suitable distance from the lower most terminal 18 of arrester l2. Bracket 25 is secured to a steel bar 27 bya pair of bolts and nuts 28 positioned in suitable apertures through these two members. The bar 27 is, in turn, secured in relatively fixed position by a locked nut 30 and a threaded bolt 29 that extends through an aperture in arrester terminal leg 31 and terminal plate 14, as well as through a pair of load-bearing

insulating cylinders

32 and 33 and a non-load-bearing cylinder 34 (see FIG. 5) and a pair of

washers

35 and 36. (Part 23 is a portion of a support for a voltage grading ring such as the one shown in FIG. 2.)

As can be seen by the structural details shown in FIG. 5, the insulated mounting means afforded by insulating

cylinders

32, 33 and cylindrical sleeve 34 prevent any electrical conduction between electrically conducting bolt 29 and terminal plate 14. Thus, the electrical discharge path from transmission line 17 to lower terminal 18 of arrester l2 follows the path from terminal 15 across the top terminal plate 14, to flexible conductor 37, (see FIGS. 3 and 4) to a first terminal 38 on the housing of counting device 24, through the operating mechanism of device 24 to a second terminal 39, thence through a conducting cable 40 to electrically conducting bolt 29 to leg 31 that is in electrical contact with the uppermost electrode in the plurality of spark gaps housed in cylindrical housing 13. Thus, it can be seen that the insulating means comprising

loadbearing cylinders

32 and 33 and non-load-bearing cylinder 34 prevent any current carrying circuits from being formed in parallel with the conducting path through counting device 24 from top terminal 14 to the series connected spark gaps in housing 13.

It will be noted that with this preferred embodiment of my invention a surge counting device, such as device 24, is electrically connected in series with the surge discharge path by insulating means that are not subjected to dangerously high compressive forces due either to the dead weight of arrester 12 or due to dynamic loading of the insulating means by periodic swaying of the arrester and line conductors, to which it is connected, under the influence of high velocity winds. In this regard, I have found that my invention is particularly suitable for use with high voltage lightning arresters that are at least 20 feet in height, so that their weight is sufficiently great to endanger heretofore conventional surge counting device mounting means. Also, it has been found that use of my invention is desirable even on shorter arresters where the cross-sectional area of the arrester housing, such as housing 13, taken along a vertical plane on the longitudinal axis of the arrester, is at least 30 square feet in size, so that its resistance to wind could cause substantial swaying of the arrester. A further particular advantage of my invention is that its use makes it possible to use insulating materials for load-bearing

cylinders

32 and 33 that have lower mechanical strength than conventional insulating ceramics and glasses that are commonly used to form such supports, since these cylindersneed only withstand the compression force applied to them by the weight and negligible torque forces of top terminal plate 14 and its associated hardware, in combination with the clamping force of

bolts

29, 29, 29" and

nuts

30,30, 30".-

It will be apparent to those skilled in the art that various modifications and embodiments of my invention can be readily made in view of the teaching of the invention presented herein and it is my intention to encompass all such modifications and embodiments within the spirit and scope of the following claims.

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

1. In combination, a high voltage surge arrester having an elongated insulating housing adapted to be mounted with its longitudinal axis in a substantially vertical plane, an electric conductor terminal mounted on the top end of said housing, another terminal mounted on the bottom end of said housing, a plurality of spark gaps mounted in said housing and electrically connected in series relationship between said top and bottom terminals thereby to normally insulate said terminals from each other and to form a current discharge path between said terminals when said spark gaps are sparked over by a surge voltage, a surge counting device electrically connected in series with said discharge path to form the only current conducting circuit between said top terminal and said spark gaps so that substantially all of the discharge current through the arrester passes through said counting device, insulating means mounted between said top terminal and said spark gaps to prevent conducting paths being formed in parallel with the conducting path through said counting device.

2. The invention as in claim 1 wherein said insulating means comprises a plurality of insulating cylinders mounted between said top terminal and said counting device, said insulating cylinders being formed of a material that has a compressive strength no greater than that of glass, and including an electrical conductor extending through said insulating cylinders to form part of said discharge path.

3. The invention as in claim 2 wherein said plurality of insulating cylinders comprises at least one set of a pair of mechanical load-bearing cylinders and a single non-load-bearing sleeve, said load-bearing cylinders being mounted on opposite sides of said top terminal so their respective apertures are in substantial alignment with an aperture through said terminal, said non-load-bearing sleeve being mounted coaxially within said load-bearing cylinders to insulate the top terminal from said electrical conductor extending through the insulating cylinders.

4. The invention as in claim 3 wherein said plurality of cylinders comprises three sets of two load-bearing cylinders and one non-load-bearing sleeve each.

securing said adjustable mounting means in a predetermined position thereby to retain said counting device in said position for optimum visual inspection.

7. The invention as in claim 6 wherein said housing is at least 20 feet in height.

8. The invention as in claim 5 wherein the cross-sectional area of the arrester at a vertical plane along its longitudinal axis is at least 30 square feet. I

Claims

5. The invention as in claim 2 wherein said counting device comprises an electromechanical register that produces a visible indication of the number of overvoltage surges discharged through the arrester and including manually adjustable mounting means whereby said counting device is mounted in a movable manner to enable positioning of it to assure optimum visual inspection of said register from a predetermined point adjacent and below and away from the bottom of the arrester.

6. The invention as in claim 5 including clamping means for securing said adjustable mounting means in a predetermined position thereby to retain said counting device in said position for optimum visual inspection.

8. The invention as in claim 5 wherein the cross-sectional area of the arrester at a vertical plane along its longitudinal axis is at least 30 square feet.