US3721748A

US3721748A - Device for upgrading the corona resistance of grounding studs

Info

Publication number: US3721748A
Application number: US00250509A
Authority: US
Inventors: J Seaquist
Original assignee: Anderson Electric Corp
Current assignee: Anderson Electric Corp
Priority date: 1972-05-05
Filing date: 1972-05-05
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20

Abstract

The device is for upgrading the corona resistance of grounding studs used in the distribution of electrical power to and from substations so that, as voltages are upgraded to what are commonly referred to as ''''extra high voltages,'''' the existing grounding studs can be modified to function efficiently at the higher voltages. The device is attached to the free end of the stud and in combination therewith provides an enlarged globular head. It can be installed on the stud in situ by means of tools mounted on ''''hot sticks.

Description

0 "*5! limited States Patent 11 1 1 1 3972197413 Seaquist 51March 20, 973

[ 1 DEVICE FOR UPGRADING THE 3,110,757 11 1963 Rawlins ..l74/l46 x (IORONA RESISTANCE 0F 3,239,600 3/1966 Bethea, .lr.... ..174 127 x (GRQUNDING STUDS 3,458,646 7/1969 Eldridge ..174/73 R [75] Inventor: James J. Seaquist, Birmingham, Ala. FOREIGN PATENTS OR APPLICATIONS [73] Assignee: Anderson Electric Corporation, 724,729 2/1955 Great Britain ..174/146 Leeds, Ala.

Prima ExaminerLaramie E. Askin 22 F1 1 1 1 ed May 1972 Attorney-John H. Leonard et al. [21] Appl. No.: 250,509

[57] ABSTRACT 144 The device is for upgrading the corona resistance of [51] lint. (ll. ..H0lt 19/02 grounding studs used in the distribution of electri al [58] Field of Search ..174/73 R, 127, 140 CR, 144, power to and from substations so that, as voltages are 143 C upgraded to what are commonly referred to as extra high voltages, the existing grounding studs can be [56] References Cited modified to function efficiently at the higher voltages. UNITED STATES PATENTS The dev ce s attachedto the free end of the stud and in combination therewlth provldes an enlarged globu- 1,972,616 9/1934 Austin .174/73RUX lar head. It can be installed on the stud in situ by 1,997,627 35 Casey.-.. 4/ 3 R U means of tools mounted on hot sticks. 2,813,179 11/1957 Rugg..... ..174/144 ux 3,046,327 7/1962 Harmon 1. 174/73 R 11 Claims, 7 Drawing Figures DEVICE FOR UPGRADING THE CORONA RESISTANCE OF GROUNDING STUDS BACKGROUND OF INVENTION 1. Field of Invention Corona shields for grounding studs.

2. Description of Prior Art The ever increasing demand for electric power poses many distribution problems. One solution is the increase of voltages into a range known as extra high voltages. These voltages require either new substations or modifications in the input to, and output from, old substations of the system to handle the greater KVA capacity. These modifications are referred to collectively as upgrading. In anticipation of future demands, many of the newer substations are being constructed with ample allowance for future upgrading. One phenomenon imposing a problem at extra high voltages is the corona effect, and a number of devices have been developed for properly controlling it insofar as concerns the main conductors.

Examples are corona shields used on bus bars and include one such as disclosed in US. Pat. No. 3,239,600, issued Mar. 8, 1966 to M. Bethea, Jr. In this form, hemispherical elements which may be solid metal, shells of solid metal, or shells of screenlike material are provided and have ears extending outwardly from one side of the body for clamping, between the ears, the bus bar so that the shield lies alongside the bar.

Another type adapted to be clamped on to the conductors is disclosed in [1.8. Pat. No. 3,046,327, issued July 24, 1962 to R. W. Harmon. In this form, a spherical shell is formed of detachable portions which are arranged so that a conductor can be passed through the center of the shell and clamped between its portions.

A corona cap which may be connected to a terminal pad of a conductor so as to overlie the bolts connecting the connector of the conductor thereto is disclosed in US. Pat. No. 3,458,646, issued July 29, 1969 to E. I... Eldridge.

A corona shield of the loop ring type is disclosed in U.S. Pat. No. 2,232,665, issued Feb. 18, I94] to George M. lRuoff.

These structures are somewhat typical of the types used on power conductors, but they would not be suitable for the present purposes without modification therein which would render them unsuitable for the purposes for which they were originally intended.

As to the corona effect produced at grounding studs, it appears that there has been no general attack on the problem and no prior commercial device offered on the market for that specific purpose. Instead, each individual substation has solved this particular problem with modifications or accessories devised to function only with the specific combinations of equipment which it itself was currently employing.

In general, for use with welded aluminum buses, alu

minum grounding studs are provided. When the system is upgraded, for example, from 169 KV to 230 KV, the grounding stud originally provided generally develops pronounced coronas due to its configuration and inadequate size. The solution generally is to discard that section of the bus having the grounding stud and to provide in its place another bus section with a different and larger stud properly designed to reduce the corona effect within an acceptable range when combined with the particular installation.

SUMMARY or INVENTION In accordance with the present invention, a device is provided for eliminating the necessity of discarding an existing lower voltage rate stud by modifying the stud so as to eliminate or reduce the corona effect which would otherwise occur at the extra high voltage. The present device is one that can be readily attached to existing studs and is so designed that it can be installed in situ, even while the bus is energized, by the use of conventional tools mounted on hot sticks." The device is also arranged so that it can be installed without any misalignment and will remain securely in place under all operating conditions and provide, in combination with the stud, adequate corona resistance far above that of the stud in its original condition.

For purposes of illustration herein, the device is described as applied specifically to grounding studs, but it may be used for other purposes. It is to be noted that grounding studs generally are in the form of elongated rods each having at one end an enlarged portion which is welded in close face to face juxtaposition to a bus or other conductor, and having at the opposite end an enlarged head at which any corona generally occurs.

Specifically, the present invention is to enlarge and make more nearly spherical, the head on the grounding stud of high voltage busses so as to increase its corona resistance and reduce or eliminate the corona when the voltage level is raised into an extra high voltage range beyond the-normal corona resistance of the stud; for example, from 169 kilovolts upwardly. It has distinct advantages over the ring types, caps, connectors, and the like, for reducing the corona in that it is more compact, more readily installable, imposes no stresses due to overhang from surrounding equipment, is unlikely to interfere with existing nearby equipment, and is of general applicability.

Various specific objects and advantages will become apparent from the following description wherein reference is made to the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a grounding stud of the prior art with the device of the present invention installed;

FIG. 2 is a front elevation of the structure illustrated in FIG. 1;

FIG. 3 is an enlarged top plan view of the device, partly in section, showing it in position to receive the head of the grounding stud, indicated by broken lines;

FIG. 4 is a right end view of the device shown in FIG. 3;

FIG. 5 is an enlarged top plan view of the device in installed position onthe stud;

FIG. 6 is a front elevation of the structure illustrated in FIG. 5, parts thereof being shown in section for clearness in illustration; and I FIG. 7 is a left end elevation of the structure illustrated in FIG. 5.

Referring to the drawings, the present device is shown as installed on a grounding stud l,'comprising an elongated rod-like body 2 having at one end an enlarged head 3 and at the opposite end an enlarged portion 4 adapted to be juxtaposed against a bus, such as a tubular bus 5, and welded thereto permanently. The outer end face of the portion 4 is shaped so that it is generally in face to face juxtaposition with the arcuate side wall of the bus 5. The head 3 is sufficiently large to reduce the corona effects of the limited voltages for which the stud was originally designed and rated. However, the extra high voltages now being used are beyond the corona resistance capability of the head 3.

l-leretofore, in upgrading the practice has been to remove a section of the bus with a stud and to replace them with another section of bus with a larger stud of adequate corona resistance to handle the higher voltages.

in accordance with the present invention, the existing stud which in its original form is adequate to handle the much higher voltages, but is inadequate to handle the corona effect resulting therefrom, is rendered adequate to handle the corona effect by attachment of the present device to the head 3.

The device of the present invention, indicated generally at 6, comprises two

body members

11 and 12 which have inner end faces 13 and 14, respectively, facing toward each other when the

body members

11 and 12 are in proper alignment and rotated position relative to each other. Preferably, for convenience and economy in manufacture, the two

body members

11 and 12 are identical castings, but the bolt receiving passage of one is reamed and the other threaded, as is described hereinafter.

The

body members

11 and 12 have

concavities

15 and 16, respectively, opening through their inner end faces 13 and 14. These concavities are such that when the body members are assembled in operating position the

concavities

15 and 16 define or provide a socket 17 in which the head 3 of the stud l is received and firmly clamped. The

body members

11 and 12 also have at their ends adjacent the concavities l5 and 16, notches l9 and 20, respectively, which, when the body members are in operating position, form an entrance passage 21 leading into the socket 17 and sufficiently restricted to prevent withdrawal of the head 3 from the socket l7 axially of the stud.

The

body members

11 and 12 can be moved relatively toward and away from each other. When moved outwardly away from each other a predetermined distance, the restricted passage 21, formed by the notches l9 and 20, is sufficiently large so that the head 3 can be passed therethrough, endwise of the stud, into the socket 17.

In order that the

body members

11 and 12 can be moved from an open position in which the

members

11 and 12 are spaced far enough apart so that the head 3 can be entered through the passage 21 to a clamping position in which the inner end faces 13 and 14 are very close together, suitable means are provided for moving the body members to and from open and clamping positions and for securing them in clamping position.

In the form illustrated, the moving means comprise primarily a bolt 25 which extends into, and is in threaded engagement with, a coaxial threaded passage 26 in the body member 11, and which is slidably received through a reamed passage 27 in the body member 12. By rotating the bolt 25 in one direction the body members can be drawn toward each other into clamping position. By rotating the bolt in the opposite direction, the body members are freed for moving apart to open position.

To move the body members apart when the bolt is rotated in the direction to permit such movement, a coil compression spring 28 is disposed between the

members

11 and 12, preferably in surrounding relation to the bolt 25 so that it is prevented from displacement from between the

body members

11 and 12 when they are in open position. The spring bears at its opposite ends against suitable internal shoulders, as indicated at 29 and 30, in the

body members

11 and 12, respectively, and is of sufficient force to spread them far enough apart, when permitted by the bolt, so that the head 3 can be received head foremost through the restricted passage 21.

Upon rotation of the bolt in the clamping direction, the

body members

11 and 12 are drawn toward each other against the biasing force of the spring 28 sufficiently to retain the head 3 in the socket 17, and preferably to effect snug clamping relation with the head 3.

In order to assure proper relatively rotated positions of the

body members

11 and 12 about the axis of the bolt so that they are in proper alignment, endwise of the bolt, for movement to clamping position, suitable aligning means are provided. In the form illustrated, these aligning means comprise a finger 31 on member 11 and a similar finger 32 on member 12. The member 11 has a socket 33 spaced from its finger 31 and correspondingly, the member 12 has a socket 34 spaced from its finger 32. The fingers and sockets are so arranged that when the body members are in the proper rotated position about the axis of the bolt 25, the finger of each member can enter the socket of the other member and thus prevent relative rotation of the members about the axis of the bolt.

The

fingers

31 and 32 are of such length that they can enter the sockets while the

members

11 and 12 are spaced by the bolt 25 and spring 28 sufficiently apart so that the head 3 can enter into the socket 17. The

fingers

31 and 32 are of such length that they can seat endwise in their associated sockets before the

members

11 and 12 are in final position. Also, they have clearance with respect to the walls of their associated sockets. As a result they can rock in their sockets transversely of their length. These clearances, the lengths of the fingers.3l and 32 and depths of the associated

sockets

33 and 34 are so chosen that seating occurs after the head 3 is entered into the socket 17 and before the

members

11 and 12 move into clamping relation with respect to the head 3. Accordingly, the fingers and their associated sockets act as guide means and also provide fulcrums about which the

members

11 and 12 can be swung as they move into clamping relation. These fulcrums are on the opposite side of the bolt 25 from the

concavities

15 and 16, or socket 17. Thus the

fingers

31 and 32 restrain the

members

11 and 12 from engaging each other at their adjacent faces at the side of the bolt 25 opposite from the socket 17, forcing the

members

11 and 12 to rock about the resulting fulcrums and concentrate all of the clamping force of the bolt to be brought to bear to clamp the

body portions

11 and 12 into engagement with the head 3 of the stud 1.

As mentioned, the outer surfaces of the

body members

11 and 12 are free from sharp corners and abruptly intersecting edges. Generally all surface portions merge by transition curves. They present a somewhat globular shape when the members are in assembled relation. However, in order to properly retain the bolt 25 in place so that it does not protrude beyond the outer surfaces of

themembers

11 and 12, the members are provided with

surface concavities

36 and 37, respectively, aligned with the

passages

26 and 27. The concavity 37 accommodates the bolt head, together with a lock washer on the bolt adjacent the head, so that it is disposed inwardly from the outer surface, extended, of the body member 12. The other concavity 36 accommodates the opposite end of the bolt so it does not extend outwardly beyond the extended surface of the member 111. This is necessary because if the bolt did so extend it would provide projections which would interfere with the proper functioning of the body A members in reducing or eliminating the corona.

The exact size of the head provided by the

members

11 and 12, except in relation to the voltage, is not important. it should be substantially larger than the head I 3, and generally is made so much larger that it is satisfactory for extra high voltages ranging from a slight amount larger than would be taken care of by the head 3, to extra high voltages which require a head actually many times the size of the head 3.

It is apparent, therefore, that the present device can be applied to a large number of different sizes of heads and the body members 111 and 12 drawn close enough together to provide, in effect, a large outer head which is relatively smooth and generally globular and free from any sharp corners, ears, points and extraneous projections.

Preferably the end of the bolt opposite its head is peened, as indicated at 38, so that the bolt is held captive and, in turn, it holds the parts in position which makes possible the handling and installation of the device with conventional tools arranged on the ends of hot sticks. All that is necessary is to adjust the bolt so the members ill and 12 are moved sufficiently far apart by the spring 28 so that the head 3 can enter the restricted passage 21. In this position the aligning provided by the fingers and associated sockets, and the extending means provided by the spring 28, are important as the installation, adjustment, and clamping can be effected, with assurance that the final position of the device will be proper, by moving the device into position over the head 3 of the stud 1 while it is supported at the end of the hot stick." Furthermore, in this latter position, the bolt can be readily engaged by a tool at the end of a hot stick and operated to drive the members Ill and 12 into final clamping engagement with the head. Here too, the aligning means assure that the members 1111 and H2 retain their proper position about the axis of the bolt 25 during this installation. The fulcrum effect assures that when the bolt 25 is rotated and tightened, the clamping pressure which it provides is ages where the problem is similar and the heads on the structures originally provided for such purpose are irregular or of such a size that they cannot properly resist the corona effect.

Having thus described my invention, I claim:

1. A device for upgrading corona resistance of a grounding stud having a body portion connected at one end to a bus and having a corona resisting head at its other end, and comprising:

a pair of body members having faces, respectively,

adapted, when the members are in a predetermined rotated position about an axis normal to said faces, to lie in facewise spaced, and predeter mined aligned, relative open position;

interengageable aligning means on the body members, respectively, forholding the body members in said predetermined rotated position when said faces of the members are spaced apart facewise from each other in said predetermined open position;

clamping means to move the members toward each other to, and to hold the members in, a clamping position;

said body members, respectively, being shaped so that when they are in said clamping position, they form a body which is generally globular;

each member having a stud head receiving cavity opening through its said face and an access notch leading thereinto and open at said face;

said cavities, in said predetermined aligned open position of the members, providing a socket shaped to receive said head and said notches providing an entry passage into the socket and shaped so that the head can pass therethrough into the socket; and

said cavities and notches being shaped so that in said clamping position, the socket and entry passages are restricted, and the head is secured in the socket and the stud body is accommodated in the entry passage in the restricted condition of the passage.

2. The structure according to claim 1 wherein the clamping means comprise a bolt extending through coaxial passages in said members which passages are generally normal to said faces.

3. The structure according to claim 2 wherein the bolt is slidable axially relative to one of said members and is in threaded engagement with means carried by the other of said members.

4. The structure according to claim 3 wherein means are provided which hold the bolt captive relative to said members.

i 5. The structure according to claim 2 wherein the members, except for the bolt passages, are identical.

6. The structure according to claim 1 wherein a compression spring is disposed between the members and resiliently holds the members in open position sufficiently so that the head of the stud can be passed, axially of the stud, through the entry passage formed by the notches.

7. The structure according to claim it wherein fulcrum means are provided on the body members in laterally offset relation to the lines of force applied by the clamping means, and at opposite sides of said lines of force from the cavities, and are arranged to engage before the members are in final clamping position and act as a fulcrum about which the members swing toward each other as they approach operating position.

8. The structure according to claim 7 wherein the aligning means are a finger and a finger receiving socket on each member, the finger and finger receiving socket being spaced apart from each other laterally of said face of the associated member and positioned so that the finger of each member is received endwise in the finger receiving socket of the other member and seats endwise therein, when the members are properly aligned, prior to the movement of the members into final clamping position, and provide also the fulcrum means.

9. The structure according to claim 8 wherein, in said clamping position, the aligning means are in fulcruming engagement.

10. The structure according to claim 1 wherein a grounding stud having an elongated body with a corona resistance head at one end is disposed with the head in the socket formed by said cavities, and, in said operating position, the cavity walls are in firm clamping relation to the lateral peripheral wall of the head.

11. A device for upgrading corona resistance of a grounding stud having an elongated body member connected at one end to a bus and having a corona resisting head at its other end, and comprising:

a pair of body members, each having a cavity and a notch so arranged that when the members are moved to an operating position relative to each other, the cavities and notches provide an openend socket in which said head can be clamped and constrained from movement outwardly endwise of the stud and a restricted entry passage connected therewith;

said members, when in clamping relation, providing a head ,larger than said cavity and having a generally curvilinear, outwardly convex, outer surface free from sharp angles and corners; and

a bolt extending through the members and operable to draw the members toward each other into clamping position when the bolt is rotated in one direction about its axis, and a spring surrounding the bolt and biasing the members apart and operative, when the bolt is rotated a predetermined number of turns in the opposite direction, to move said members apart to a position such that the head of the stud can be moved through the entry passage formed by the notches and into the socket.

Claims

1. A device for upgrading corona resistance of a grounding stud having a body portion connected at one end to a bus and having a corona resisting head at its other end, and comprising: a pair of body members having faces, respectively, adapted, when the members are in a predetermined rotated position about an axis normal to said faces, to lie in facewise spaced, and predetermined aligned, relative open position; interengageable aligning means on the body members, respectively, for holding the body members in said predetermined rotated position when said faces of the members are spaced apart facewise from each other in said predetermined open position; clamping means to move the members toward each other to, and to hold the members in, a clamping position; said body members, respectively, being shaped so that when they are in said clamping position, they form a body which is generally globular; each member having a stud head receiving cavity opening through its said face and an access notch leading thereinto and open at said face; said cavities, in said predetermined aligned open position of the members, providing a socket shaped to receive said head and said notches providing an entry passage into the socket and shaped so that the head can pass therethrough into the socket; and said cavities and notches being shaped so that in said clamping position, the socket and entry passages are restricted, and the head is secured in the socket and the stud body is accommodated in the entry passage in the restricted condition of the passage.

5. The structure according to claim 2 wherein the members, except for the bolt passages, are identical.

7. The structure according to claim 1 wherein fulcrum means are provided on the body members in laterally offset relation to the lines of force applied by the clamping means, and at opposite sides of said lines of force from the cavities, and are arranged to engage before the members are in final clamping position and act as a fulcrum about which the members swing toward each other as they approach operating position.

11. A device for upgrading corona resistance of a grounding stud having an elongated body member connected at one end to a bus and having a corona resisting head at its other end, and comprising: a pair of body members, each having a cavity and a notch so arranged that when the members are moved to an operating position relative to each other, the cavities and notches provide an open-end socket in which said head can be clamped and constrained from movement outwardly endwise of the stud and a restricted entry passage connected therewith; said members, when in clamping relation, providing a head larger than said cavity and having a generally curvilinear, outwardly convex, outer surface free from sharp angles and corners; and a bolt extending through the members and operable to draw the members toward each other into clamping position when the bolt is rotated in one direction about its axis, and a spring surrounding the bolt and biasing the members apart and operative, when the bolt is rotated a predetermined number of turns in the opposite direction, to move said members apart to a position such that the head of the stud can be moved through the entry passage formed by the notches and into the socket.