CA2059826A1 - Method of making a cable terminator - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method of making a cable termination assembly for terminating a high voltage current-carrying conductor. The assembly includes an outer porcelain housing and an inner polymeric liner of low durometer, cast in the housing before insertion of the cable. The liner is bonded to the housing wall to prevent air voids.
A metal base member may be employed and may include an upstanding shielding collar extending part way into the housing and being joined thereto by the cast liner.

Description

~lET~OD OF MARING A CABLE: TBRMINA~OR

BACRGRO~lND OF THB INVE1!JTION:
1. ~iel~ of ~he Invention-The present invention pertains to electric cable terminations, and in particular, to terminations for 5 electric cables used for electric power distribution.

2~ De~cription of the Rel~te~ Art.
Electric cables having concentric neutral conductors and embedded wire conductors are becoming 10 increasingly popular. For example, such cables are used in direct burial, Underground Residential Distribution (URD) applications. These cables are typically operated at thousands o~ volts, and hence, care must be taken in managing or controlling the electrical stress at points 15 where the cable is terminated for coupling to electrical components such as switchgear units, for example.
Such cables typically include electrical shielding surrvunding the central current-carrying conductor. For example, cables can include a concentric 20semi-conducting jacket, concentric metallic foil wrapping, or concentrically wrapped, discrete drain wires. The various arrangements of semi-conducting and conducting layers surrounding the central current-carrying conductor control the electric stress 25and induced electrical fields surrounding the central conductor, features which are important for direct burial and the like applications.
Cable terminations typically require removal of the various dielectric, semi-conducting and conductive 30shield layers surrounding the central current-carrying conductor with the various semi-conducting and conducting surrounding layers being appropriately connected to the electrical equipment involved. For example, a porcelain -2- ~ 3 ~

termination kit is available from the Minnesota Mining and Nanufacturing Company as SCOTCHCAST 5903. The kit, which is field-installed, provides termination for concentric neutral URD cable having a semi-conducting jacket surrounding the cable insulation, disposed within a helical wrap of much smaller gauge concentric wires, commonly referred to as drain wires. The various layers of the concentric neutral cable are removed in the field following closely dimensions laid out in the installation instructions accompanying each kit.
For example, the drain wires are pulled back to expose a predetermined length of the cable semi-conductive jacXet. A bottom end cap is inserted over the semi-conductive jacket and forms a lower seal therewith~ The semi-conductive jacket is cut back at a 15 predetermined distance from the cable tip, as is the cable insulation, exposing a predetermined length of the bared current carrying conductor~ A series of different tapes are wound about defined sections of the prepared cable end. Vinyl plastic electrical tape~
20 semi-conducting tape, and stress control tape, for example, are employed.
A porcelain insulator is disposed about the prepared cable end and a mounting ring is slid underneath the porcelain insulator before its insertion in the 25 bo~tom end cap. A top cap includes a recess for receiving the current-carrying conductor, and includes a threaded hole ~or receiving a pour spout. An elastomeric compound commercially available as SCOTCHCAST 2100 is poured through the top cap to fill the interior o~ the 30 porcelain insulator. The hole i5 plugyed with a threaded sealing plug. The entire assembly of the termination, including pouring of the elastomeric compound i performed in the field and is therefore subject to different temperature and humidity condition67 ~or 35 example.

3 ;~ ~ 5 ~ 3 . ~ ~

It has been found during development of the present invention, that the ~irst 20 hours or so of the curing of an elastomeric compound is p~rticularly critical to the subsequent performance of that cast compound in a high voltage electrical insulation system.
As those skilled in the art will recognize, it is difficult to maintain carefully controlled conditions in the field, let alone for an extended period of time such as a 20-hour period ~ubsequent to the casting of th~
elastomeric compound. As described, the cable is inserted in the porcelain insulator before the elastomeric compound is poured and thus, the resulting cured compound structure takes on the diameter of the cable portions disposed within the porcelain insulator.
Experience has shown that elastomeric fillers applied in ~he field do not offer good performance at low temperatures and that, due to different coefficients of thermal expansion, a gap between the filler and the cable might result.
A terminator commercially available from Joslyn 20 Manufacturing Company, Stock Item #E5200 provides a porcelain termination with a stress relief cone which is loaded inside the porcelain insulator at the lower end thereof, and an elastomer sleeve is inserted between the prepared cable end and the porcelain insulator bore. In 25 order to eliminate air gaps between the sleeve and porcelain and the sleeve and cable insulation, a compression ~pring of considerable strength is loaded into the top of the porcelain insulator, surrounding the upper end of the prepared cable end. An upper cap is 30 secured to the porcelain insulator to maintain the spring in compression. A relatively large number of components and a higher level of expertise are required for assembly. Further, neither the stress relief cone nor the elastomer ~leeve bond to the porcelain insulator and 35 thus, air voids at the interface between these members . , , .. ,, , .. ~ .. , , .. , . ... ~ ., ~ .. . .... . .

-4~

and the porcelain insulator may ultimately lead to dielectric failure.
A porcelain termination sold hy the G & W
Electric Company, assignee of the present invention, is commercially available under the trade designation "Slip On Terminator." This termination employs a porcelain insulator which slips o~er a prepared cable end. A len~th of sponge tubing is inserted between the prepared cable end and the inner bore of the porcelain insulator, and also in a mounting base which is disposed 10 below the insulator, also surrounding the prepared cable end. The sponge does not bond to the inner bore of the porcelain insulator and greater retention strength at low temperaturPs is desired.
As mentioned above, it is important to control 15 the electrical stress at the prepared cable end. Of particular interest is the control of electrical stress at abrupt changes in the cable shielding system. One araa of concern is the point whers the semi-conducting layer is cut away, thus creating a discontinuity in the 20 electrical field surrounding the cable. Heretofore, measures have been taken to directly bond metallic base mountings at the bottom end of a cable termination, so as to position the ground plane at a portion o the cable termination which is designed to handle the electrical 25 stress. It i5 desirable to provide a ground plane at the bottom of the cable termination which extends through the various termination components and which adapts to thermal changes in cable size, to eliminate interstices that may form between the various termination components, 30 particularly the cable and a metallic support base. It may also be desirable in some circumstances to establish a ground plane without direct contact with the cable components.
Further improvement~ in metallic support bases 35 are desirable to insure an hermetic sealing between the ... ~, , , .. , , . . . , .. . ~.. , ,.. " .... . .. .. . .

Z~5~
metallic base and the porcelain insulator resting thereon. To be commercially attractive, such hermetic sealing should be easy to install and economical to fabricate. Heretofore, oil-filled terminations have been provided to address many of the above concerns. For a 5 variety of reasons, which have long been recognized in the industry, it is desirable to eliminate liquid-~illed terminations.

SUNNARY OF ~H~ INVEN~ION
It is an object according to the present invention to provide a method of manufacturing a cable termination which is economical, which uses a minimum number of inexpensive parts and which maintains a tight grip on the cable over a variety of cable operating 15 temperatures and environmental temperatures.
Another object according to the present invention is to provide a cable termination o~ the above-described type which is fabricated in a factory under controlled conditions and which is quickly and 20 easily installed in the field with a minimum amount o~
expertise and without requiring special tools.
A further object of the present invention is to provide a cable termination having a metallic base member which forms a ground plane passing through a precisely 25 located medial portion of the ceramic insulator to provide efficient electrical stress control.
Another object according to the present invention is to provide an electric termination having a metallic base member which provides an effective ground 30 plane of the above-described type, but which is encapsulated within a ~iller which maintains a void-free engagement with the cable and porcelain insulator despite temperature changes.
~nother object according to the present 35 invention is to provide a cable termination in which air ~ . . . . ..

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pockets and interstices internal to the porcelain bushing are avoided, thus precluding ionization, especially in regions of high electric field.
The~e and other objects of the present .invention which will become apparent from studying the appended description and drawings are provided in a method of fabricating a cable termination, comprising the steps of:
providing a rigid housing having a bore wall defining an inner bore;
providing a mandrel;
coaxially disposing said mandrel within the housing bore;
pouring a dielectric polymer betwean the mandrel and the housing bore wall;
curing the polymer so as to fo~m a substantially incompressible, but nonetheless deformable, flexible dielectric liner having a cable-receiving bore; and removing the mandrel so as to open the conductor-receiving bore.

BRIEF D~SCRIYTION OF TH~ DR~WING~
In the drawings, wherein like elements are referenced alike:
FIG. 1 is a fragmentary cross-sectional elevational view of a portion of a cable termination assembly illustrating principles according to the present invention:
FIG. 2 is a perspective view of a termination assembly with the top cap removed;
FIGS. 3 and 4 are fragmentary cross-sectional elevational views thereof;
FIG. 5 is an electrical field plot overlaid on a schematic outline of a fragment of the cross-sectional view of FIG. 1:
FIG. 6 is an exploded elevational view of a 35 mandrel assembly according to the present invention; and 3~

FI&. 7 is a cross-sectional elevational view of a housing and mandrel assembly according to the present invention.

DETAIL~D D~SCRIPTI0~ OF qH~ P~FERR~D ~NEODIN~NTS
Referring now to the drawings, and initially to FIGS. 1 and 2, a cable termination constructed according to the assembly method of the present invention is generally indicated at 10. As will be seen herein, the cable termination is a "dry" termination, that is, n~t oil-filled and is fitted on a prepared cable end without requiring special tools or expertise. Essentially, the cable termination subassembly is comprised of a porcelain housing 12 and a dielectric liner or filler 14~ The filler 14 is cast in the porcelain housing at the factory, under controlled conditions, and is shipped to the field, fully assembled, for installation as required.
Referring now to FIG. 1, the completed cable termination assembly 10 includes a porcelain housing generally indicated at 12 defining a central bore, a dielectric liner 14 of substantially incompressible, but nonetheles~ deformable, resilient or flexible material, and a metallic support base generally indicated at 16.
The housing 12 is preferably o~ conventional porcelain construction, comprising a generally tubular wall 20, and 25 a series of skirts 22, outwardly extending from the wall.
The inner surface 24 of wall 20 as shown is cylindrical, but can have other shapes, if desired. Wall ~0 include~
upper and lower generally annular end members 30, 32.
FIG. 1 shows a completed terminator assembly 30 with a high voltage electrical cable generally indi~ated at 36, installed therein. Cable 36 may be of the concentric neutral or embedded wire type, for example, as is commonly used in electrical distribution systems for Underground Residential Distribution (U~) applications.
35 In the preferred embodiment illustrated in the figures, -8- ~ 5~ ~

cable 36 has a semiconductor layer 40 disposed around an insulating layer 41 covering a cen~ral metallic conductor 42. The cable 36 further includes an outer diele~tric jacket 44.
As can be seen in FIG. 1, the multi-layer cable 36 has been prepared for assembly with the cable termination 10. For example, the outer dielectric jacket 44 has an upper free end 46 disposed n~ar the bottom of the termination, and the semi-conductive layer 40 has an upper free end 48 forming a step with respect to insulating layer 41. The conductor 42 and insulating layer 41 together comprise a conductor means or cable inner layer which is inserted in the termination, as will be seen herein. As those skilled in the art will appreciate, termination 10 allows the central 15 current-carrying conductor 42 to be bared at 43, and to extend beyond the electrical shielding system of the cable, which otherwise controls the electrical stress and electrical fields present when the conductor is energized.
According to an important aspect of the present invention, hou ing 20 is filled with an elastomer material which is cast in plase, within housing 20, prior to insertion of cable 36. ~he generally tubular liner 14 is produced by this casting. The elastomer material of 25 liner 14, when cured, preferably comprises a substantially incompressibl~ but nonetheless deformable, resilient material which maintains the shape over the operating range of cable temperatures, so as to follow motion of the cable sur~ace as the cable expands and 30 contracts. The following are examples of suitable elastomer materials: low durometer polyurethane, low durometer silicones and flexibilized epoxies. The preferred material is a low durometer polyurethane commercially available as a potting and encapsulating 35 compound under the trade designation of CASTALL UX~7544, -9~ ~,",,~j availa~le from CASTALL, Inc., of East Weymouth, Massachusetts. Those skilled in the art will be abl~ to readily determine other suitable elastomer materials, based upon teachings of the present invention.
As one feature of the present invention, the elastomer materi~l, when cast within ho-~sing wall 20, forms a bonding with the inner wall surface 24.
Preferably, the bonding is substantially continuous throughout the interface between the liner 14 and the wall surace 24 so as to prevent pockets or other interstices which might break down electrically under the high electric fields set up by the current-carrying conductor 42~ At a minimum, the bonding eliminates large size voids, large numbers of linearly aligned smaller size voids, and large numbers of closely spaced smaller size voids. Such would, of course, degrade the insulation value of the termination and if breakdown were to occur, might significantly shorten the useful life of the termination assembly.
As mentioned above, electrical terminations have 20 been proposed and are in use today, which have elastomeric compounds poured into the space between a porcelain insulator and an electrical cable previously inserted therein. Such elastomeric compounds are poured in the field, under field conditions. In contrast, the 25 liner 14 according to the present invention, is cast within insulator housing 20 prior to insertion of an electrical cable therein. The liner 14 is cast to ~orm an inner bore, when cured, has a neck portion of size slightly less than the size of the current-carrying 30 cable, a feature not possible with elastomers cast in the field to surround a cable previously inserted in an insulator housing.
With the precast liner of the present invention, a certain amount of insertion force must be exerted on 35 the cable inner layer to install the cable in the -10- 2~ J~3.

termination assembly. However, the liner material is flexible and deformable without sacrificing substantial incompressibility, shape retention and resilience, and thus, an intimate void-free engagement of the liner throughout the length of the conductor is assured and minor irregularities in the outer surface of insulating layer 41 may be accommodated by liner 1~, assuring an intimate engagement which is not compromised over the useful life of the termination assembly. Such engagement is important to prevent electrical breakdown and also to prevent intrusion of contamination within the termination assembly.
Provision is made when casting liner 14 to accommodate the increased size of the upper end of semi-conductive layer 40. Referring to FIG. 3, a pocket 49 is formed with an upper wall 51. The pocket 49 is generally cylindrical to reduce push-out of the cable.
The pocket 49 forms an enlarged end of the cable-receiving bore to aid in cable insertion. In the preferred embodiment, a plurality of annular ribs 53 20 provide an elastomeric seal with the cable, and in particular, the semiconductor layer 40 thereof. The ribs 53 are formed such that their root portions are of ~enerally the same size as the semiconductor layer~ with the protruding portions of the ribs being flattened when 25 the cable is inserted. A dielectric grease may be employed when insexting the cable to displace any trapped air in pocket 49. The cable is inserted until the free end of the semiconductor layer engages wall 51.
As can be seen in FIG. 3, a generally 30 cylindrical neck portion 55 is located above pocket 49.
The neck portion 55 is undersized relative to the cable insulating layer 410 An upwardly expanding tapered portion 59 is located above neck portion 55. The tapered portion has an upper free end 61, which is recessed ~elow 35 the upper surface of housing wall 20. A protective cap ,q~,t~

63 (see FIG. 1), preferably of stainless steel, prevents water and air borne contaminants from settling in this recessed area, the upper cap being particularly desirable when the termination assembly is installed outdoors. A
compression terminal 45 is crimped onto conductor 42 after the tip of the conductor is pushed through cap 63.
A conductive rubber sealing boot 67 covers the upper end of the a~sembly and a non-conductive rubber sealing boot 65 covers the lower end, as will be seen herein.
According to another aspect of the present invention, a base support generally indicated at 16 is provided to support the cable and the termination 10.
The base 16 includes a lower, generally horizontal plate member 52 having an aperture 54 for receiving a screw fastener to provide a convenient mounting for the termination to a supporting structure. The base 16 includes an annular portion 56 underlying the insulator housing so as to engage the lower enlarged annular end 32 thereof. Annular portion S6 is preferably merged with plate 52. As those skilled in the art will appreciate, the joint 57 between the bottom end of the insulator housing and the base 16 may experience intrusion of moisture and contaminants which might migrate inwardly toward the center of the termination assembly, over a prolonged period of time.
Accordingly, it is desirable to eliminate such intrusion at the ioint between the housing and base and according to one aspect of the present invention, an upstanding annular collar 60 is provided to surround the joint between the housing and base member. The collar 60 has an upper surface 62 extending above the bottom of the insulator housing, preferably extending to the top of the enlarged annular end 32 of the housing. Collar 60 forms a recess into which a sealant 66 is cast. The sealant may be of any suitable material, but preferably bonds to 35 the base 16 and the housing 12, so as to provide an -12~

hermetic seal. Preferably, the sealant will maintain the bond with the insulator housing and base, despite temperature variations causing expansion and contraction associated with the thermal coefficients of expansion of economical housing and ~ase materials.
According to another aspect of the present invention, the base 16 includes an optional upstanding shield 70 extending part way into housing 20. The shield 70 is preferably provid~d as an integral portion of base 16, which as mentioned, is made of a conductive, preferably metallic material. The base 16 is electrically grounded, and thus, the upstanding shield 70 i5 at ground potential. The shield 70 extends above the upper end 48 of semi~conductive layer 40 sufficiently to minimize the electrical stresses at upper end 48. In the preferred embodiment, the upper end 72 of shield 70 is located adjacent an enlarged thickness portion of housing 20, herein the lowermost skirt 22a. As can be seen in the electric field plot of FIG. 5, the electric field lines 76 emanating from the free end of the 20 semi-conductive layer are concentrated at the increased thickness portion of housing 20, which is better able to withstand the electrical stress than thinner portions of the housing. The shield ~ree end 72 can be located elsewhere, if desired, away from a skirt member. Thus, 25 the relatively expensive porcelain material can be reduced in thickness with the optional upstanding shield according to the present invention. Also, quite importantly, as can be seen in FIG. 5, the joint between the insulator housing and base is effectively shielded 30 from electrical stress.
If desired, the upstanding shield 70 can be installed after liner 14 is cured. However, the factory casting of liner 14 made possible with the present invention provides significant advantages if an 35 electrical shield member or a simpler base without an -13~

electric shield member is desired for the termination assembly. In the preferred embodiment, the base member 16 is installed prior to casting o~ liner 14, the liner material flowing to surround the shield 70, and to provide an intimate void-free seal between the shield, housing and cable, and optionally the annular support portion of base 16.
Contrary to a commonly held belief in this art, the electric shield 70 has been found to function very well as an electric shield, even though it is separated from semi-conductive layer 40 by a thickness o~
dielectric liner 14. Of course, the semi-conductive shield 40 must be bonded to a circuit element which is at ground potential, according to currently accepted practices in the industry. Thus, the semi-conductive layer ~O and shield 70 are both at ground potential and the innermost electric field line 76a plotted in FIG. 5, represents a line of approximately zero potential, i.e., the receding ground plane, when conductor 42 is energized.
As mentioned above, the neck portion 55 is undersized relative to the cable insulating layer 41.
The cable end is prepared as explained above, with various outer layers removed at appropriate points along the cable length. For example, the semiconductor layer 25 40 is cut back from the cable free end at a distance which ensures the cut end 48 engages wall 51 of pocket 49 (see FIG. 3), thus provi.ding a convenient tactile indication that desired orientation relative to shield 70 has been achieved. The inner layer of the cable, 30 comprising the conductor 42 and sur.rounding insulating layer 41, is inserted in the lower, enlarged end of the liner bore and is pushed through the neck portion 55, displacing liner material 14a from the neck into the tapered portion 59 as indicated by arrow 71 of FIG. 4.
35 The liner material is incompressible and flexible and -14~ 3.~

exhibits sufficient compression set resistanc~, so as to retain its cured shape despite deformation, and hence the cable is securely gripped by liner 14 despite changes in temperature and variations in conductor size. Thus, an interference fit can be Pnsured under all expec~ed cable operating conditions. The liner is ~oft, but still tear resistant and easily follows motion of the sable surface maintaining a "dry" void-free engagement therewith, as the cable expands and contracts with temperature changes.
Turning now to FIGS. 6-7, a method of fabricating the termination assembly will now be described in greater detail. ~s mentioned above, the liner is cast before insertion of the cable in the termination assembly, the liner having a central bore slightly smaller in size than the cable insulation layer.
FIGS. 6-7 illustrate a further refinement to the casting of the liner so as to provide certain advantages as will be described herein. FIG. 6 shows a mandrel assembly generally indicated at 86. The mandrel assembly includes a post member 88, an end member 90 and a bolt fastener 92. According to one aspect of the present invention, the post member 88 has a tapered, part conical portion 96. The conical portion 96 of post 88 is disposed between generally cylindrical end portions 98, 100 disposed at the outer free end and inner end of the post 25 member, respectively. End portion 100 defines a threaded bore 102 for receiving bolt 92. End member 90 has a generally cylindrical configuration with a series of annular indentations 104 formed therein, and includes a central bore through which bolt 92 is inserted. The 30 annular indentations 104 form the series of ribs 53 which function like 0 rings, providing an elastomeric sealing o~ the semiconductor portions of the cable.
Referring no~ to FIG. 7, the mandrel assembly 8 is disposed along the central axis 103 of housing 12.
35 Preferably, end member 90 is seated within a tapered bore ~15- 2~

portion 108 o~ base 16. An 0-ring gasket 105 is located at the bottom of end member 90. An elastomsr material such as that described above is poured into the inner bore of housing 12, filling the space between the mandrel assembly, the housing wall and the shield portion of base 16. It has been found that approximately the fixst 20 hours of curing of the elastomer is critical to the proper functioning of the resulting solid liner.
According to one aspect of the present invention, the elastomer is preferably cured in one stage, but may also be cured in two stages. If a two-stage cure is employed, the first stage will provide a room temperature cure for at least several hours. The entire termination assembly (with the mandrel assembly installed) is then placed in an oven, and the second stage of curing is completed, the temperature in the oven preferably comprising a temperature at least as great as the maximum temperature of the termination assembly to be expected during its operation, usually determined by the maximum overload condition of the current-carryin~ conductor~
The elevated temperature cure is carried out for several additional hours with the mandrel optionally remaining in position throughout the entire curing operation. Thereafterl the termination assembly is removed from the oven and allowed to cooled~ The mandrel is then disassembled by removing bolt fastener 92, and separating the mandrel post member and mandrel end members in the directions indicated by arrows 112, 114, respectively. With installation of top cap 63, the cable termination assembly is then ready for shipment to the field, where the prepared electrical cable is inserted through the central bore of the liner, herein indicated by the reference num~ral 120.

-16- ~r~ 3~

When a single stage cure is preferred, the terminator assembly is immediately placed in an oven after assembly, and is cured at a temperature which is at least as high, and preferably higher than the highest expected operating temperature of the cable and terminator assembly.
Several important features of the liner 120 will now be described. As mentioned above, it is desirable to have the central bore of the dielectric liner dimensioned smaller than at least the insulating layer 41 portion of the electric cable 36~ For the liner fabricated according to the method of the present invention, a reduced bore size occurs at the neck portion formed around portion lO0 of post member g6. As mentioned, the portion 100 is preferably cylindrical and as can now be seen is dimensioned to have a diameter substantially less 15 than the diameter of insulating layer 41.
In order to aid the insertion of the insulating layer through the liner 14, the end member 90 is provided with an enlarged diameter, so as to create an enlarged opening or pocket at the lower end of the liner.
20 According to one aspect of the present invention, the enlarged opening is preferably provided with one or more ribs 53 which function as 0-ring structures to provide a sealing with the semi-conducting layer 40, although the rib structures 53 can be omitted if desired. The pocket 25 may be tapered if desired, but it has been found that significant push-out forces result, which tend to expel the prepared cable end from liner 14. Accordingly, it is preferred that the pocket be made generally cylindrical with a significant step wall 51 which provides a 30 pronounced stop for abutting engagement with the cut free end of semiconductor layer 40, so as to provide a tactile indication that the semiconductor end is spaced a preferred distance from the tip 72 of shield 70, which positioning cannot be readily visually determined. Due 3.~

to the soft, deformable nature of the liner, as the inner cable layer is inserted in the inner liner bore, liner material is displaced in the direction of cable insertion, indicated by the arrow 124 of FIG. 3.
According to one aspect of the present S invention, the tapered portion 96 of post member 88 has cross-sectional sizes larger than that of the insulation layer, and thus, forms a cavity at a downstream portion of the undersized liner segment. This cavity allows liner material to "flow" or be displaced in the direction of cable insertion, without generating forces within the housing or tearing the liner. As a result, an intimate engagement between the liner and inner cable layer can easily be achieved throu~hout the axial length of the liner and such has been readily verified during the course of developing the present invention~ If desired, however, the kapered portion 96 can be reduced or eliminated i~ the bore of the liner is undersized only a slight amount, although it is generally preferred to provide the tapered portion as described above.
The liner material, despite being deformabl~ and flexible, is sufficiently tough, so a~ to resist tearing, especially at the displaced portions. Further, the material is substantially incompressible, exhibiting compression set resistance, particularly in the neck 25 portion even when subjected to elevated temperatures for prolonged periods of time, as might be expected in most service conditions. Pulling grease is optionally used to reduce the possibility of tearing the liner. A
dielectric grease may be used to purge pocket 49 of air.
The drawings and the foregoing descriptions are not intended to represent the only forms of the invention in regard to the details of its construction and manner of operation. Changes in form and in the proportion of parts, as well as the substitution of equivalents, are 35 contemplated as circumstances may suggest or rend~r ~ ~t~

expedient; and although specific terms have been employed, they are intended in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being delineated by the following Claims.

Claims (10)

1. A method of fabricating a cable termination, comprising the steps of:
providing a rigid housing having a bore wall defining an inner bore;
providing a mandrel;
coaxially disposing said mandrel within the housing bore;
pouring a dielectric polymer between the mandrel and the housing bore wall;
curing the polymer so as to form a substantially incompressible, but nonetheless deformable, flexible dielectric liner having a cable-receiving bore; and removing the mandrel so as to open the conductor-receiving bore.

2. The method of Claim 1 further comprising the steps of:
providing a cable comprising an inner layer larger than the liner bore, surrounded by an outer dielectric covering:
baring an end portion of the cable conductor;
and inserting the bared end of the conductor through the liner bore and hold the conductor captive therein.

3. The method of Claim 1 the method further comprising the steps of:
providing a two piece mandrel having enlarged ends with a mid-portion therebetween:
coaxially aligning the mandrel pieces end-to-end in abutting relationship; and releasably joining the mandrel pieces together.

4. The method of Claim 1 for retaining an electrical cable having an electrical conductor of predetermined cross-sectional diameter surrounded by a dielectric covering, further comprising the step of forming at least one mandrel portion having an enlarged end larger than the dielectric covering and an intermediate portion abutting the other mandrel portion which is smaller in cross section than the dielectric covering, the mandrel used to form a bore in the liner when removed therefrom.

5. The method of Claim 4 further comprising the step of:
providing a cable having an electrical conductor surrounded by a dielectric covering and at least one outer covering;
removing the outer covering from an end portion of the cable;
inserting the end portion in the liner bore; and pushing the end portion through the liner bore so as to displace a portion of the liner toward the part of the bore formed by the enlarged end portion of the mandrel.

6. The method of Claim 1 further comprising the steps of:
partially curing the cast polymeric liner at a generally ambient temperature for a first time period:
and completing the curing of the cast polymeric liner at an elevated temperature for a second time period so that the polymeric liner remains substantially incompressible and resilient but nonetheless deformable despite warming of the cable above the ambient temperature.

7. The method of Claim 5 further comprising the steps of forming a plurality of O-ring sealing means at the entrance end of the liner bore for sealing engagement with the at least one outer covering of the cable, by forming a series of annular recesses in the mandrel prior to casting the polymeric material.

8. The method of Claim 1 further comprising the steps of:
providing a rigid conductive base having an annular portion and a shielding portion extending upwardly therefrom;
inserting the shielding portion part way into the housing bore so as to electrically shield a part of the housing from an electric field emanating from said cable; and casting the polymeric material around the shielding portion to bond the shielding portion and the housing with a void-free interface between the shielding portion and the housing bore wall.

9. The method of Claim 8 further comprising the steps of:
forming an upstanding collar surrounding the joint between the base annular portion and the housing:
forming a recess between the collar and the housing by spacing the collar from the housing outer surface: and filling at least a portion of the recess with a sealant to protect the joint from exposure to the ambient environment.

10. A method of fabricating a cable termination, comprising the steps of:
providing a rigid housing having a bore wall defining an inner bore;
providing a mandrel;
coaxially disposing said mandrel within the housing bore;
pouring a dielectric polymeric material between the mandrel and the housing bore wall;
removing the mandrel so as to expose the conductor-receiving bore:
partially curing the cast polymeric liner at a generally ambient temperature for a first time period;
and completing the curing of the cast polymeric liner at an elevated temperature for a second time period so as to form a dielectric liner which is substantially incompressible, but nonetheless deformable despite warming of the cable above the ambient temperature.