US3662082A

US3662082A - High voltage cable terminating assembly

Info

Publication number: US3662082A
Application number: US69334A
Authority: US
Inventors: Donald R Heppner
Original assignee: G&W Electric Specialty Co
Current assignee: G&W Electric Specialty Co
Priority date: 1970-09-03
Filing date: 1970-09-03
Publication date: 1972-05-09
Anticipated expiration: 1989-05-09
Also published as: CA944829A

Abstract

There is disclosed a factory assembled slip-on type of cable terminator in combination with electrical equipment comprising a cylindrical shell of insulating material, a dielectric media contained within the electric equipment and surrounding the insulating material of the cylindrical shell and a selfenergizing resilient contact spring member within the cylindrical shell for improving the mechanical and electrical connections for current transfer. In addition, the self-energizing resilient contact spring member, together with other elements of the assembly, permits easy insertion of the cable connector although preventing accidental cable pull-out or cable blow-out under fault current conditions.

Description

United States Patent Heppner 1451 May 9,1972

[ HIGH VOLTAGE CABLE TERMINATING ASSEMBLY [72] Inventor; Donald R. l-leppner, Chicago, Ill.

[73] Assignees G & W Electric Specialty Company, Blue lsland,1ll.

[22] Filed: Sept. 3, 1970 [21] Appl. No.: 69,334

Related US. Application Data [63] Continuation-impart of Ser. No. 887,820, Dec. 24,

1969, abandoned. I I

[52] US. Cl. ..l74/l8, 174/19, 174/73 R, 174/75 D, 339/256 S [51] int. Cl ..H02g 15/22, l-lOlb 17/30 [58] FieldofSearch ..174/12BH,18,19,31R, 73 R, 174/75 R, 75 D, 78, 80; 339/255 RT, 256 R, 256

RT, 256 S [56] References Cited UNITED STATES PATENTS Edmonds ..l74/75 D X Lusk 3,439,110 4/1969 ...l74/73 R 3,445,580 5/1969 Lusk ....l74/l2 BH 3,474,393 10/1969 Woods ..174/18 UX FOREIGN PATENTS OR APPLICATIONS 105,795 11/1938 Australia ..339/256 RT 227,696 4/1960 Australia 510,189 8/1920 France ..339/256 S 948,159 l/1964 Great Britain ..174/31 R 1,145,629 3/1969 Great Britain 1 74/12 Bl-l Primary Examiner-Laramie E. Askin A!!orne v--Fitch, Even, Tabin & Luedeku l 57] ABSTRACT There is disclosed a factory assembled slip-on type of cable terminator in combination with electrical equipment comprising a cylindrical shell of insulating material, a dielectric media contained within the electric equipment and surrounding the insulating material of the cylindrical shell and a self-energizing resilient contact spring member within the cylindrical shell for improving the mechanical and electrical connections for current transfer. In addition, the self-energizing resilient contact spring member, together with other elements of the assembly, permits easy insertion of the cable connector although preventing accidental cable pull-out or cable blow-out under fault current conditions.

10 Claims, 9 Drawing Figures PATENTEBMAY 9|972 .562082 SHEEI 3 BF 3 HIGH VOLTAGE CABLE TERMINATING ASSEMBLY CROSS-REFERENCES TO RELATED APPLICATIONS Mechanical-Electrical Connection For Electrical Equipment Terminations.

BACKGROUND OF THE INVENTION The invention relates to cable termination systems and has reference in particular to cable terminators for insulated cables, that is, plastic, paper, rubber, varnished cambric, etc., wherein all the necessary components are factory assembled and so designed that the cable terminator can be installed on location at the site without the need of special skills or special equipment.

Overhead electrical power distribution systems are aesthetically displeasing and thus, they detract from the appearance of a residential area. In an attempt to improve the external appearance of distribution systems, the electrical utility companies have installed direct burial cables with the termination sectionalizing equipment and the like being located within metallic housings which are supported on concrete pads at or below ground levels. Completely underground power distribution systems with concrete vaults are also used in built-up commercial areas and also in the more congested portions of cities and towns. Although the underground system improves the appearance of the neighborhood and minimizes the problem of wind, ice, and lightning damage, the high cost of an underground system in comparison to overhead systems has discouraged the more widespread adoption of the underground distribution systems.

When the electricpower cables above a certain voltage rating are to be terminated at transformers and at oil switches, fuse cut-outboxes and the like, it becomes necessary to build up the cable insulation to a diameter sufficient to form a cone for controlling the electrical stresses prevailing between the cable conductor as one electrode and the ground as the other electrode of zero potential. It is well known that buried and semi-buried power distribution systems are difficult and costly to install since the primary cable terminations at the equipment site require either a pouring of the potting compound in the field or a manual taping to construct-the stress cones.

SUMMARY OF THE INVENTION The general purpose of this invention is to provide an electro-mechanical terminator which allows a power cable to be installed at the location of electrical equipment, e.g., a transformer or a switch, without requiring access to the inside of the equipment itself. To attain this, the present invention contemplates a unique terminator in combination with electrical equipment comprising; a cylindrical shell of insulating material having a metal end portion fixedly secured to the base end of the cylindrical shell and to the electrical equipment, a dielectric media contained within the electrical equipment and surrounding the insulating material of the cylindrical shell, a clamping plate member secured to the base end portion of the cylindrical shell having a central opening for accommodating the end of a power cable adapted to be inserted through the base end portion and within the cylindrical shell, a diaphragm having location and which is confined between the base end portion and the clamping plate member so as to form a seal with the parts, the diaphragm having an opening in axial alignment with the opening in the clamping plate member, a plastic film located between the diaphragm and the base end portion and which is confined in the same manner as the diaphragm, the plastic film sealing the opening in the diaphragm and thus, sealing the entrance end of the terminator device, a metalhood portion in fixed sealed relation with the top end of the cylindrical shell and having a recess therein in axial alignment with both the opening in the diaphragm and the opening in the clamping plate member, and a contact spring arrangement located in the recess of thehood portion and adapted to have resilient contact and'telescoping relation with the terminal end of the power cable following insertion of the same within the cylindrical shelhwhereby to improve the mechanical and the electrical connection between the power cable and the said hood portion.

It is, therefore, an object of the present invention to provide an equipment cable entrance that allows the cable to be installed in the field without gaining access to the unit inside the equipment, that can be installed in a relatively easy manner and which will provide greater flexibility and greater overall economy than is now possible with the constructions presently available on the market.

Another object of the invention is to simplify and improve the mechanical and also the electrical connections for better current transfer with respect to electrical equipment of the type utilizing high power transmission cables.

A further object is to provide a cable terminator of the slipon type similar to that disclosed in the Lusk U.S. Pat. No. 3,322,883, granted May-3, 1967, but wherein the mechanical and electrical connections for current transferare materially improved by a self-energizing female type of resilient contact spring member and wherein the terminator is in combination with electrical equipment containing a dielectric media.

Another and more specific object of the invention resides in providing a slip-on type of cable connector as described which will incorporate a self-energizing resilient contact arrangement permitting easy insertion of the male connector with adequate contact force for good current transfer, but which will prevent accidental cable pull-out or cable blow-out under fault current conditions.

With these and various other objects in view, the invention may consist of certain novel features of construction and operation as will be more fully described and particularly pointed out in the specification, drawings and claims appended thereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view showing a power cable termination device which embodies the improvements of the present invention;

FIG. 2 is a sectional view of the cable receiving portion of the terminating device as shown in FIG. 1, the same illustrating certain structural details comingwithin the invention;

FIG. 3 is an elevational view, parts being shown in section, of the prepared end of a power cable ready for insertion and for location within the cable receiving end of the present terminator device;

FIG. 4 is a sectional view showing the prepared end of the power cable of FIG. 3 in inserted relation with the present terminator device;

FIG. 5 is an elevational view showing the resilient contact spring as contemplated by the invention for obtaining a better mechanical and electrical connection for improved current transfer;

FIG. 6 is a top plan view showing a modified form of the resilient contact spring;

FIG. 7 is a sectional view of the hood portion of the present terminator device showing the recess within which the resilient contact spring is located;

FIG. 8 is a perspective view with portions removed of a three-phase terminator which embodies the improvements of the present invention; and

FIG. 9 is a top view of the terminator in combination with electrical equipment.

I DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGS. 1 through 9 a terminator assembly for a plastic dielectric insulated cable. The terminator assembly 100 comprises a terminator portion connected to an electrical equipment housing 20. The terminator portion 10 connected to the electrical equipment housing 20 enables the insulated power cable to be installed at the electrical equipment location without needing access to the unit inside. In the preferred embodiment, the terminator assembly 100 is adapted for three-phase operation (FIGS. 8 and 9); however, it will be recognized by one skilled in the art that single-phase operation may also be employed without departing from the spirit and scope of the invention.

Referring now to FIGS. 1 through 4, it can be seen that the terminator assembly 100 comprises terminator portion 10 formed of any suitable insulating material such as a ceramic and having the outwardly projecting skirts 11 and the cylindrical base portion 12. The metal end portion 13 is fixedly secured as by cementing at 14 to the cylindrical base portion 12 and to a wall 21 of said electrical equipment housing 20. Said metal base portion depends below to provide an interior space for the metal stress control shield indicated in its entirety by the numeral 15. An elastomeric sponge element 16 is also located within the space provided by metal base portion in surrounding relation with the stress control shield and the base portion additionally provides the outlet portion 17 to which is secured the plug 18 (FIG. 2) or the plastic container 19 (FIG. 4). v

The electrical equipment housing 20 may comprise the housing for any electrical equipment such as a transformer or a switch. Contained within the housing 20 is a dielectric media 22. One such dielectric media 22 may be transformer type oil. The dielectric media 22 completely surrounds the ceramic terminator 10 and is required for the proper operation of the terminator assembly 100. It will be noted that the length of the ceramic insulator portion 10 is relatively short when compared with a terminator such as that shown in U.S. Pat. No. 3,439,110, granted Apr. 15, 1969, to George Lusk and assigned to the G & W Electric Company. Because of this relatively short length, the dielectric media 22 is required to provide necessary insulation for the terminator assembly 100. In the preferred embodiment, the wall 21 of the housing 20 is interposed between a resilient gasket 22 as shown in FIG. 2, thereby securing the terminator portion 10 to the electrical equipment housing 20.

Again referring to FIGS. 1 and 2, it can be seen that the stress control shield is formed of metal and the same is generally annular so as to have surrounding relation with the solid dielectric insulation 23 of the cable. The metal shield is suitably supported by the legs 24 and said shield provides a plurality of inwardly bent fingers 25 for good pressure contact .with the power cable overshield. The shield may be formed of beryllium copper although other conductive and springy metals may be employed. The specially formed contour of the fingers 25 facilitates insertion of the prepared end of the cable within the terminator portion 10 and also provides electrical grounding contact between the shield and the cable overshield when the cable has been fully inserted.

The closure structure for the factory assembled cable terminator is best shown in FIG. 2. The clamping ring 26 is suitably secured to the metal end portion 13 by securing screws, not shown, but which are similar to the. securing screws shown in the Lusk U.S. Pat. No. 3,439,110, granted Apr. 15, 1969. An elastomeric diaphragm 27 and the plastic film 28 in superposed relation are located between the base of the end portion 13 and the clamping plate and the said elements are clamped in place. The diaphragm 27 is formed with a central opening 30 for receiving the prepared end of the cable and said film closes said opening and retains an insulating compound within the factory assembled terminator. The opening 30 which may be punched or molded centrally of the diaphragm 27 is smaller than the diameter of the cable portion to be eventually associated therewith following insertion of the cable. Thus, when the parts have been completely assembled as in FIG. 4, the diaphragm has a strong sealing contact with the cable and the diaphragm opening is in tension.

lator by the peened ring member 34 and the bore 33 gradually decreases in size at the top end of the hood to form the threaded opening 35, FIG. 7, which is normally closed by the plug 36. The bore 33 at the base end of the hood 32 is somewhat enlarged in diameter for receiving a contact spring arrangement indicated in its entirety by the numeral 37. The spring arrangement is retained in place within the base end of the hood by the metal retaining ring 38 which may be peened or otherwise fixedly secured to the base end of the hood. The contact spring arrangement is adapted to receive the male connector 40 which as shown in FIG. 3 is applied to the terminal end of the metal conductor 41 after said terminal end is exposed by removal of the insulation 23. It can be seen that the hood portion 32 is disposed within the electrical equipment housing 20. The hood portion 32 is electrically connected by any suitable means (not shown) to the electrical equipment itself. For example, hood portion 32 could be connected to a switch contact contained within the electrical equipment housing 20.

The self-energizing female type of contact spring arrangement indicated by numeral 37 may take the form of a continuous spiral spring of predetermined diameter and length to fit within the enlarged cavity 33 in the base end of the hood. The spiral convolutions of such a continuous springelement will be in substantial contact when in inserted relation within the hood. Also the continuous spring element may have a formation in plan of any multi-sided regular plane figure such as a square, a pentagon or a hexagon. It may be more particularly stated that the contact spring element will be polygonal in shape with the pentagon shape of FIG. 6 being preferredsince best results in connector insertion have been achieved by this shape. In the place of the continuous spring element, a

satisfactory modification may be formed of a plurality of shorter continuous spring segments such as indicated by numeral 42 in FIG. 5. Each spring segment may consist of several convolutions of spring wire each having a polygonal shape such as a pentagon and wherein the size of the spring segments and also that of the continuous spring arrangement is predetermined by the diameter of the male connector 40 to be inserted within the hood portion of the terminator device. A plurality of spring segments 42 can be located within the cavity in the hood portion and the same will function as a good mechanical and electrical connecting means in the same efficient manner as the continuous spring element 37.

Another modification of mechanical and electrical contact spring arrangement is shown in FIG. 6. In this modification the arrangement consists of a plurality of single convolutions such as 43 which are substantially plano and which preferably have the shape of a pentagon. The single convolutions are formed from a length of wire that has been bent to leave a gap or a split opening 44 in one corner. The continuous spring arrangement and also the single convolution arrangement when in place within the hood portion will allow easy insertion of the male connector 40 and will also materially improve the current transfer between the metal conductor 41 of the cable and the hood portion 32 of the terminator device.

The present cable terminating assembly is preferably equipped with improved cable entrance means such as shown in the Lusk U.S. Pat. No. 3,445,580, granted May 20, 1969. The entrance plate ring 45, which is generally formed of metal, is suitably secured by screws, not shown, to the clamping ring 26 and the two elements clamp the entrance plate gasket 46 therebetween. An elastomeric boot 47 is associated with this entrance end of the cable and the said boot has a special formation at its top end and also at its bottom. The top end of the boot is formed to provide the circular flange 48 which seats in a cavity formed in the under surface of the entrance plate ring 45. The lip 50 at the bottom end of the elastomeric boot is designed to have tight circular contact with the cable. The elastomeric boot is enclosed by the metal cup 51.

The terminator assembly 100 as described is assembled at the factory so. that after the cable end has been prepared, the same can be inserted within the terminator assembly with a resulting good electrical and mechanical connection being achieved without needing access to the inside of the electrical equipment Before the plug 36 is threaded in place the space within the terminator is filled with an insulating compound which will have a dielectric constant or specific inductive capacitance approximately equal to that of the plastic materials used in the manufacture of the cable insulation. This provides a dielectrically compatible system of isotropic nature. The compound'should also possess a high tack value to both the cable insulation, the inside bore of the terminator and the stress control shield 15.It is also desirable that the compound have the ability to retain its flexibility at temperatures as low as 20 Fahrenheit.

To prepare the end of the power cable requires that the cable jacket be removed for a specified distance as determined by the voltage size of the specific terminator device and then the insulation 23 is removed for a distance to expose the copper or aluminum conductor 41. The male connector 40 is fitted on the exposed terminal end of the metal conductor and a tight fit between the conductor and the male connector is desirable. The molded plastic plug 18 is now removed and the plastic tube 19 is screwed in its place. The cable grip 52, metal cup 51, the elastomeric boot 47, the entrance plate ring 45,

gasket 46 and the grounding strap 53 are placed on the power cable in sequence as shown in FIG. 3 and the power cable is ready for insertion within the terminator assembly. Using a constant force, the male connector 40 causes the puncture of the plastic film 28 and the connector will thus enter by way of the opening 30 in the elastomeric diaphragm. As the cable enters the terminator an equal amount of compound will be displaced and discharged to the plastic tube 19. The compound under pressure and being tacky in nature will cling to the cable insulation surface, thus leaving no voids or trapped air bubbles. The cable is inserted until the male connector passes through the contact spring arrangement 37 and into contact with the hood portion 32. The resiliency of the contact spring arrangement is such as to permit an easy insertion of the male connector 40, it being understood that the size of the opening of the spring arrangement and the diameter of the male con nector have been correlated to this end.

With the cable connector fully inserted within the terminator device, the grounding strap 53 is attached to the clamping ring 26 by the screw 54 and then the entrance assembly and cable grip are slid in place and fastened to the terminator. The cable grip 52 is formed of spring wire and the said grip is held at the termination end 55 by being fastened to the entrance plate ring 45. Layers of plastic tape can then be applied over the cable grip and for some distance along the cable jacket. With the removal of the plastic tube 19 and replacing of the same with the plug 18, the termination of the power cable is complete.

The cable grip holds the inserted cable securely in place and meets requirements for accidental cable pull-out or blow-out under fault current conditions.

Referring now to FIGS. 8 and 9, there is shown a terminator assembly 100 adapted for three-phase operation. The terminator assembly 100 comprises three terminator portions disposed within the electrical equipment housing 20 in a manner identical with that described above with regard to the single phase operation shown in FIG. 1. The terminator portions are again completely immersed in a dielectric media 22 and are adapted to allow a power cable to be installed at the electrical equipment location without needing access to the unit inside. Each of the termination portions 10 may be identical to those terminator portions 10 shown in FIGS. 1 through 7 and when a cable is inserted, the cable grip of the terminator will hold the cable securely in place.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A terminator assembly for use with a power cable having a prepared end exposing a portion of the solid dielectric insulation of the cable and the metal conductor at the terminal end thereof and having a male connector in fixed relation on said exposed metal conductor, said assembly comprising a tubular shell of insulating material having a metal end portion fixedly secured to the base end of said tubular shell, a clamping plate member secured to said metal end portion and having a central opening for accommodating the prepared end of the power cable, an elastomeric diaphragm having a central opening aligned with the opening in said clamping plate member, said diaphragm being clamped between said end portion and said clamping plate member, a plastic film located between the diaphragm and said end portion for sealing the opening in the diaphragm, a metal hood portion in fixed sealed relation with the top end of said tubular shell and having a recess therein in axial alignment ,with both the sealed opening in the diaphragm and the opening in the clamping plate member, a contact spring arrangement located in said recess and comprising a plurality of convolutions of resilient metal, a cable grip comprising a conductive wire sheath for surrounding and gripping the insulation of the cable and attached to a conductive termination member having a central opening for passing the cable end therethrough, and an entrance plate member having a central opening concentric with the other of said openings and adapted to clamp said termination member between said entrance plate member and said clamping plate member after the prepared end of the cable is inserted into the terminator assembly, whereby the plastic film sealing the opening in the diaphragm is ruptured and said male connector engages said contact spring arrangement in telescoping relation therethrough, said diaphragm forming a seal about the cable at the entrance of said terminator assembly, and said grip supporting said cable to maintain the connector engagement.

2. A terminator assembly according to claim 1 further comprising a stress control shield having a location within the metal end portion of said assembly.

3. A terminator assembly according to claim 1 wherein said plurality of convolutions of resilient metal have a polygonal shape in plan.

4. A terminator assembly according to claim 3 wherein said polygonal shape is a pentagon.

5. An electrical equipment housing including a terminator assembly for use with a power cable having a prepared end exposing a portion of the solid dielectric insulation of the cable and the metal conductor at the terminal end thereof and having a male connector in fixed relation on said exposed metal conductor, said assembly comprising a tubular shell of insulating material having a portion thereof within said housing and having a metal end portion fixedly secured to the base end of said tubular shell, a clamping plate member secured to said end portion and having a central opening for accommodating the prepared end of the power cable, an elastomeric diaphragm having a central opening aligned with the opening in said clamping plate member, said diaphragm being clamped between said end portion and said clamping plate member, a plastic film located adjacent said diaphragm for sealing the opening in the diaphragm, a metal hood portion in fixed sealed relation with the top end of said tubular shell portion within said housing and having a recess within said hood portion in axial alignment with both the sealed opening in the diaphragm and the opening in the clamping plate member, a contact spring arrangement located in said recess and comprising a plurality of convolutions of resilient metal, a cable grip comprising a conductive wire sheath for surrounding and gripping the insulation of the cable and attached to a conductive termination member having a central opening for passing the cable end therethrough, and an entrance plate member having a central opening concentric with the other of said openings and adapted to clamp said termination member between said entrance plate member and said clamping plate member after the prepared end of the cable is inserted into the terminator assembly, said equipment housing further comprising means for maintaining said terminator assembly in fixed sealed relation to said housing with the central opening of said diaphragm accessible from the exterior of said housing, and a dielectric medium contained within said housing and surrounding the portion of said terminator assembly therewithin, whereby the power cable may be installed at the location of the electrical equipment housing by insertion of the prepared end of the cable through the sealed opening in the diaphragm, causing the rupturing of the plastic film and the engagement of the male connector with said contact spring arrangement in telescoping relation therethrough, said diaphragm forming a seal about the cable at the entrance of said terminator assembly, and said grip supporting said cable to maintain the connector engagement.

6. An electrical equipment housing according to claim further comprising a stress control shield having a location within said metal end portion of the terminator assembly.

7. An electrical equipment housing according to claim 6 wherein said metal end portion is located exteriorly of said housing.

8. An electrical equipment housing according to claim-5 wherein said convolutions of resilient metal of said terminator assembly have a polygonal shape in plan.

9. An electrical equipment housing according to claim 8 wherein said polygonal shape is a pentagon.

10. An electrical equipment housing according to claim 5 comprising a plurality of terminator assemblies like said terminator assembly first mentioned, means for maintaining each terminator assembly in fixed sealed relation to said housing with the central openings of the respective diaphragms accessible from the exterior of said housing, and the dielectric medium surrounding the portion of each terminator assembly therewithin.

Claims

1. A terminator assembly for use with a power cable having a prepared end exposing a portion of the solid dielectric insulation of the cable and the metal conductor at the terminal end thereof and having a male connector in fixed relation on said exposed metal conductor, said assembly comprising a tubular shell of insulating material having a metal end portion fixedly secured to the base end of said tubular shell, a clamping plate member secured to said metal end portion and having a central opening for accommodating the prepared end of the power cable, an elastomeric diaphragm having a central opening aligned with the opening in said clamping plate member, said diaphragm being clamped between said end portion and said clamping plate member, a plastic film located between the diaphragm and said end portion for sealing the opening in the diaphragm, a metal hood portion in fixed sealed relation with the top end of said tubular shell and having a recess therein in axial alignment with both the sealed opening in the diaphragm and the opening in the clamping plate member, a contact spring arrangement located in said recess and comprising a plurality of convolutions of resilient metal, a cable grip comprising a conductive wire sheath for surrounding and gripping the insulation of the cable and attached to a conductive termination member having a central opening for passing the cable end therethrough, and an entrance plate member having a central opening concentric with the other of said openings and adapted to claMp said termination member between said entrance plate member and said clamping plate member after the prepared end of the cable is inserted into the terminator assembly, whereby the plastic film sealing the opening in the diaphragm is ruptured and said male connector engages said contact spring arrangement in telescoping relation therethrough, said diaphragm forming a seal about the cable at the entrance of said terminator assembly, and said grip supporting said cable to maintain the connector engagement.

6. An electrical equipment housing according to claim 5 further comprising a stress control shield having a location within said metal end portion of the terminator assembly.

8. An electrical equipment housing according to claim 5 wherein said convolutions of resilient metal of said terminator assembly have a polygonal shape in plan.