Bushing Protective Guard

Abstract

A protective guard for attachment to a bushing of high-voltage electrical apparatus, for enclosing and guarding a connector assembly attached to the bushing. A sleeve of resilient electrically insulating material surrounds the connector assembly and has lips which engage the connector assembly and secure the sleeve thereto. A first knockout provides an aperture toward which a projecting portion of the connector assembly may extend to act as a gap electrode and a second knockout provides an aperture for accommodating a conductor to be laterally connected to the connector assembly. A cap of electrically insulating material has a top and a sidewall which fit respectively over and around the sleeve in engagement therewith. An aperture in the top accommodates a conductor to be vertically connected to the connector assembly and at least one aperture in the sidewall of the cap provides access to one of the knockouts. BACKGROUND OF THE INVENTION This invention relates to a device for protecting a terminal of high-voltage electrical apparatus and more particularly to a protective guard for attachment to a bushing of a transformer or the like and adapted for enclosing and guarding a connector assembly attached to the bushing. Protective guards are frequently desired to protect a connection made at a bushing of high-voltage electrical apparatus, such as a transformer in a power distribution system, so as to prevent personnel, birds, or wildlife from coming into contact with the high voltage connection. In such uses, a need exists for a protective guard which is both inexpensive and universal in application. High-voltage connections to power transformers typically are made by means of a conductor which approaches the connection at the transformer or other device either vertically or horizontally. It is also sometimes required that such high-voltage connections include means for providing a spark gap electrode adjacent the connection, as for lightning arresting purposes. It is desirable that a protective guard be capable of use in each of these various applications. Preferable also, the protective guard should exhibit electrically nontracking qualities, i.e., the guard should be of a material which will not develop paths through which there may be high-voltage leakage or conduction. Previously proposed protective guards typically have either not been fully universal in application or have not met all these requirements, or else have been of relatively complex construction, e.g., in having tightening hand wheels. Such complexity has required that the guard be more expensive than is desired. SUMMARY OF THE INVENTION Among the several objects of the invention may be noted the provision of a protective guard on attachment to a bushing of high-voltage electrical apparatus which accommodates either a horizontally or a vertically approaching cable connected through a connector assembly attached to the bushing; the provision of such a guard providing an aperture therein toward which a projecting portion of a connector assembly attached to the bushing of high-voltage electrical apparatus may extend to act as a gap electrode; the provision of such a guard which is capable of receiving a conductor from two positions 180.degree. apart without changing the mounting of the connector on the bushing; the provision of such a guard which minimizes the exposure of electrically live parts; the provision of such a guard which is of electrically nontracking material; the provision of such a guard which is extremely simple, inexpensively constructed, easily installed and long-lasting in use. Other objects and features will be in part apparent and in part pointed out hereinafter. Briefly, a protective guard of the present invention is adapted for attachment to a circular bushing of high-voltage electrical apparatus and encloses and guards a connector assembly attached to the bushing, the connector assembly being of the type including a projecting portion adapted to serve as a gap electrode, and including means for connecting a conductor. The guard comprises a generally cylindrical sleeve of electrically insulating and nontracking elastomeric material. The sleeve includes lip segments projecting inwardly to resiliently engage the connector assembly for securing the sleeve thereto. The sleeve has three knockouts spaced approximately 120.degree. apart around the sleeve. One of the knockouts provides an aperture aligned with and adjacent the projecting portion so that the latter may be utilized as a gap electrode. Each of the additional knockouts provides a respective aperture for accommodating a conductor to be laterally connected by the connecting means. A generally cylindrical porcelain cap has a sidewall fitting around the sleeve in frictional engagement therewith and has openings registering with each of the knockouts. A top portion of the cap extending across the upper end of the sleeve includes an aperture for accommodating a conductor to be vertically connected by the connecting means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an insulating bushing of high-voltage apparatus including a connector assembly attached to the bushing and showing in vertical section a protective guard of the invention enclosing and guarding the connector assembly;

FIG. 2 is a horizontal section of the guard and the connector assembly taken along line 2--2 of FIG. 1;

FIG. 3 is a plan view of a sleeve of the guard;

FIG. 4 is a vertical section of the sleeve taken along line 4--4 of FIG. 3;

FIG. 5 is a view of one end of portions of an eyebolt conductor clamping arrangement of the connector assembly depicted in FIG. 1; and

FIG. 6 is a fragmental side view of apertures and knockouts of the sleeve and a cap of the guard, respectively.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, indicated generally at 11 is an insulating bushing of a power distribution transformer or similar high-voltage electrical apparatus. A conductor within the bushing 11 is illustrated at 13 and includes a stud 15 on which is threaded a connector assembly indicated generally at 17. Assembly 17 is of a commercially available type having circular flange or disk 19 projecting radially outward from the bottom of assembly 17 and which includes an annular skirt 20 depending from disk 19 and fitting around the circular top of bushing 11. Connector 17, which is of course metallic, is adapted to receive and clamp a conductor 21 (shown in cross section) for electrically connecting the conductor to the conductor 13 of bushing 11. The connector is of the so-called bidirectional type permitting connection of a conductor approaching either horizontally or vertically, as explained herein.

In accordance with the invention, a protective guard indicated generally at 23 is fitted over and around connector 17 for enclosing and guarding the latter to prevent contact therewith by wildlife (such as birds, squirrels, etc.) or to prevent persons such as linemen from inadvertently touching the connector. Guard 23 comprises generally a cylindrical sleeve generally indicated 25 of electrically insulating and nontracking elastomeric material which resiliently engages the skirt 20 of connector assembly 17. A porcelain cap, generally 27, also generally cylindrical in shape, has a sidewall 29 fitting around sleeve 25 in frictional engagement therewith. A generally flat top 31 of cap 27 fits over the open ended sleeve 25. Connector 17 includes a body portion 33 against which the conductor 21 10 clamped by an eyebolt clamp 35. The latter includes a stem 37 on which is threaded a nut 39, there being a spring washer 41 positioned between nut 39 and body 33 of the connector. On the terminal portion of stem 37 of this eyebolt clamp arrangement is threaded a cap nut or so-called acorn nut 43 including a rounded end portion which extends toward and through respective apertures 45 and 47 of sleeve 25 and cap 27. Thus this projecting portion of the connector assembly may serve as a spark gap electrode. Another electrode 49 (which may be the electrode of a lightning arrester, for example) is positioned closely adjacent to but spaced from acorn nut 43 to provide a spark gap between these electrodes.

Sleeve 25, which is shown more clearly in FIGS. 3 and 4, is preferably molded of a hydrocarbon-based elastomer such as a terpolymer of ethylene, propylene and a nonconjugated diene (EPDM) exhibiting high dielectric strength, high corona resistance, and high immunity to ozone. Aperture 45, referred to previously, is provided by punching out a knockout. The sleeve is provided with three such knockouts which are illustrated in FIG. 3 and designated generally 51, 53 and 55. These knockouts are spaced at approximately 120.degree. intervals around the sleeve and are each defined by a concentric pair of circular score lines or lines of weakness at each knockout position thereby to provide an aperture of either a smaller size, such as 1/2 inch in diameter, or a larger size, such as 3/4 inch. Aperture 45 is indicated as being an aperture of the larger size. Score lines for knockout 53 are illustrated in FIGS. 3 and 6 at 57 and 58.

In order to secure sleeve 25 to the periphery of skirt 20, the sleeve is provided with three inwardly extending lip segments 59, 61 and 63 which are spaced at 120.degree. intervals around the sleeve and each of which may extend through an arcuate distance of 60.degree.. Each lip extends inwardly a short distance under the edge of skirt 20 of the connector assembly, as illustrated in FIG. 1. These lips are sloped and have rounded axial edges, as illustrated in FIG. 4, to facilitate installation and removal of the sleeve. Weep opening are provided along the interior wall of sleeve 25 at the intervals between lips 59, 61 and 63 by providing the interior wall with three recessions 65, 67 and 69 such as by simply molding sleeve 25 with thinner wall thicknesses at these locations. The thinner wall thickness of sleeve 25 at these recessed portions 65, 57 and 69 provides weep spaces between the interior wall of sleeve 25 and the periphery of skirt 20, permitting moisture to drain from the guard. At the lower edge of sleeve 25, there are also provided three outwardly extending flanges 71, 73 and 75 which are spaced at 120.degree. intervals around the sleeve and each of which may extend arcuately through an extent identical with the lip segments 59, 61 and 63.

The wall thickness of sleeve 25 is somewhat less at the top than at the bottom to provide a slight taper which is apparent in FIG. 1. This facilitates assembly of the guard.

Cap 27 is provided with three apertures each of which is in registry with each of the knockouts of sleeve 25. These apertures are illustrated most clearly in the cross-sectional view of FIG. 2. Aperture 47 constitutes a first one of these three spaced apertures and two others are designated at 77 and 79. These three apertures are spaced at approximately 120.degree. intervals around cap 27. Unlike aperture 47 which is round, apertures 77 and 79 are constituted by slots in the cap extending axially from the lower edge of the cap to the location of the knockout in the sleeve when the guard is assembled. As FIG. 6 illustrates, the width of these slotlike apertures 77 and 79 is approximately equal to the diameter of each of the larger diameter circular score lines providing knockouts in sleeve 25.

Cap 27 is provided with a further aperture 81 in the top thereof which is positioned eccentrically with respect to the vertical axis of the cap so that it is in axial alignment with a conductor clamped by eyebolt clamp 35 when the guard is assembled, as depicted in FIG. 1. The diameter of aperture 81 is approximately equal to that of aperture 47. The sidewall of cap 27 is somewhat thicker at the top than at the lower edge to provide the interior of the sidewall with a taper coinciding approximately with the tapered side of sleeve 25.

As noted previously, connector 17 is of the bidirectional type. Body 33 thereof is provided with jaws of cruciform shape, as illustrated in FIG. 5, there being a first pair of jaws 83a, 83b having a horizontal groove whose axis is perpendicular to the axis of bushing 11 or that of stud 15, and a second pair of jaws 85a, 85b having a vertical groove whose axis is parallel with the axis of bushing 11 or stud 15. Eyebolt clamp 35 includes a pair of jaws 87a, 87b which are grooved along an axis aligned with the hole in the eyebolt clamp, and the latter may be turned so that the jaws 87a, 87b align with either the set of clamp body jaws 83a, 83b, for clamping a conductor horizontally approaching the clamp, or with the set of clamp body jaws 85a, 85b, for clamping a conductor vertically approaching the clamp.

In installing the guard of this invention, sleeve 25 is provided with apertures of appropriate size at the desired locations by punching out one or more of knockouts 51, 53 and 55, depending upon whether a spark gap is to be provided and whether a horizontally approaching conductor, or conductors, will be connected. Sleeve 25 is pressed onto disk 19 of the connector assembly until lips 59, 61 and 63 are forced past skirt 20 and then resiliently peripherally engage and extend under the lower edge of the skirt to secure the sleeve to bushing 11, as shown in FIG. 1. If a conductor is to be laterally or horizontally connected, the conductor is passed through the appropriate aperture, such as 77 illustrated in FIG. 2, and eyebolt clamp 35 is clamped by tightening nut 35 on stud 37 of eyebolt clamp 35. A sleeve or cover 89 of insulating material on the conductor may be utilized and may extend through the aperture into the sleeve, as shown in FIG. 2.

Cap 27 is next placed over sleeve 25 with the slotted apertures of the cap fitting around any horizontally connected conductors. The cap is pressed down onto the sleeve until the lower edge of the cap is resting on flanges 71, 73 and 75 of the sleeve, as shown in FIG. 1. Frictional engagement between the porcelain cap 27 and the rubber sleeve 25 secures the cap to the sleeve, the relative dimensions of the cap and sleeve being such as to provide a relatively tight frictional fit.

Acorn nut 43 is then inserted through the appropriate aperture, e.g., aperture 47 in FIG. 1, and tightened against nut 39. This use of an acorn nut is advantageous in accurately fixing the position of the gap electrode thus provided. Alternatively, the rounded end of eyebolt stud 37 may itself be satisfactorily used as an electrode, but the distance of the end of the stud from the exterior wall of cap 27 may vary somewhat with the size of the clamped conductor and must be accounted for by adjustment of the external electrode, e.g., electrode 49 shown in FIG. 1.

As to the assembled guard thus provided, it may be observed that the apertures provided by sleeve knockouts 53 and 55 (as well as their associated cap apertures 77 and 79) and aperture 81 in the cap have centers all coplanar to permit conductors to approach either horizontally or vertically, or both. As noted hereinbelow, in-line connections are thus facilitated.

It will be observed that aperture 81 in the top of the cap will permit rain or other moisture to enter the guard, but this is not undesirable and in fact is advantageous in keeping the interior of the guard clean. In any case, moisture will drain through the weep openings provided by recesses 65, 67 and 69.

A guard of the invention is thus seen to be advantageous in several respects. Apertures are available in the guard for accommodating either horizontally or vertically approaching conductors. Also, a gap electrode is easily provided if desired. Thus the guard is universal in application as is desirable to permit its use in different applications. A further advantage is that a conductor may approach the connector assembly horizontally from opposite directions, i.e., 180.degree. apart without changing the mounting of the connector. This is possible since apertures 77 and 79 spaced 120.degree. apart on the guard are aligned with the clamp assembly of the connector, as shown in FIG. 2. This facilitates in-line connections of multiple bushings because a single conductor may enter one of apertures 77 or 79, extend through the eyebolt opening, and then out through the other aperture, without bending. The exterior surface of the guard is of porcelain which is electrically nontracking since it is self-cleaning. Further, the construction of the guard is exceedingly simple and low in cost, involving only molding of relatively inexpensive porcelain and hydrocarbon rubber. These materials have high resistance to adverse environmental conditions, providing a guard which is long-lasting in use.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

What is claimed is;

1. A protective guard for attachment to a bushing of high-voltage electrical apparatus and for enclosing and guarding a connector assembly attached to the bushing, comprising a sleeve of resilient electrically insulating material adapted to surround the connector assembly and including means for engaging the connector assembly and securing the sleeve thereto and having a first knockout to provide an aperture toward which a projecting portion of the connector assembly may extend to act as a gap electrode and a second knockout to provide a further aperture for accommodating a conductor to be laterally connected to the connector assembly, and a cap of electrically insulating material having a top and a sidewall fitting respectively over and around the sleeve in engagement therewith, the cap having an aperture in said top to accommodate a conductor to be vertically connected to the connector assembly and at least one aperture in said sidewall providing access to one of said knockouts.

2. A protective guard as set forth in claim 1 wherein said engaging means is constituted by inwardly projecting lip means for peripherally and resiliently engaging a flange of the connector assembly.

3. A protective guard as set forth in claim 2 wherein said lip means comprises a plurality of lip segments.

4. A protective guard as set forth in claim 3 wherein the sleeve includes at least one recess on the inner surface thereof between a pair of said lip segments to provide a weep opening.

5. A protective guard as set forth in claim 2 wherein said sleeve includes means projecting outwardly therefrom for supporting said cap.

6. A protective guard as set forth in claim 5 wherein said means projecting outwardly comprises a flange supporting the lower edge of said cap.

7. A protective guard for attachment to a bushing of high voltage electrical apparatus and for enclosing and guarding a connector assembly attached to the bushing, the connector assembly including a projecting portion and means for connecting a conductor, said guard comprising a generally cylindrical sleeve of electrically insulating and nontracking elastomeric material, and having means projecting inwardly to resiliently engage the connector assembly for securing the sleeve thereto, the sleeve having three knockouts spaced approximately 120.degree. apart around the sleeve, a first one of the knockouts for providing an aperture aligned with and adjacent said projecting portion whereby said projecting portion may constitute a gap electrode, the second and third knockouts each for providing a respective aperture for accommodating a conductor to be laterally connected by the connecting means, and a generally cylindrical porcelain cap having a sidewall fitting around the sleeve in frictional engagement therewith, said sidewall having opening in registry with each of the knockouts, and a top portion extending across the upper end of the cap, said top portion having an aperture for accommodating a conductor to be vertically connected by the connecting means.

8. A protective guard as set forth in claim 7 in combination with means for connecting a conductor including a bidirectional clamp for receiving a conductor approaching the clamp either horizontally or vertically, said second and third knockouts and the aperture in said top portion being coplanar and aligned with the clamp.

9. A protective guard as set forth in claim 7 wherein the cap openings in registry with said second and third knockouts are each constituted by slots extending upward from the lower edge of the cap.

10. A protective guard as set forth in claim 7 wherein the sleeve and the cap each tapers slightly radially outwardly from top to bottom.

11. A protective guard as set forth in claim 7 wherein the sleeve is of hydrocarbon rubber.