CA2240203A1 - Methods and apparatus for adapting paper insulated lead cables for use with polymeric attachments - Google Patents
Methods and apparatus for adapting paper insulated lead cables for use with polymeric attachments Download PDFInfo
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- CA2240203A1 CA2240203A1 CA 2240203 CA2240203A CA2240203A1 CA 2240203 A1 CA2240203 A1 CA 2240203A1 CA 2240203 CA2240203 CA 2240203 CA 2240203 A CA2240203 A CA 2240203A CA 2240203 A1 CA2240203 A1 CA 2240203A1
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- cable
- sealant
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- tubing
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G15/00—Cable fittings
- H02G15/02—Cable terminations
- H02G15/06—Cable terminating boxes, frames or other structures
- H02G15/064—Cable terminating boxes, frames or other structures with devices for relieving electrical stress
- H02G15/068—Cable terminating boxes, frames or other structures with devices for relieving electrical stress connected to the cable shield only
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- Gas Or Oil Filled Cable Accessories (AREA)
- Cable Accessories (AREA)
- Connector Housings Or Holding Contact Members (AREA)
Abstract
A paper insulated lead cable includes a conductor, paper oil insulation disposed around the conductor, and a lead sheath disposed around the insulation. An oil barrier assembly is formed on an end of the cable by removing respective components of the cable to form axially spaced first and second junctions between the insulation and other respective components of the cable. A soft, tacky, oil resistant sealant is applied to form first and second oil barriers across the first and second junctions respectively. First and second elastomeric gaskets are positioned against the first and second barriers to oppose axial movement of the barriers.
A heat shrink tubing is heat shrunk around the gaskets and barriers to press the barriers against the cable, and to press the gaskets against the barriers.
A heat shrink tubing is heat shrunk around the gaskets and barriers to press the barriers against the cable, and to press the gaskets against the barriers.
Description
METHODS AND APPARATUS FOR ADAPTING
PAPER INSULATED LEAD CABLES FOR USE
WITH POLYMERIC ATTACUM~NTS
Background of the Invention The present invention relates to paper insulated lead (PILC) cables and to methods and apparatus for enabling such cables to be connected to attachments formed of polymeric materials such as EPDM rubber, polyolefin heat shrink material, and silicone rubber.
Paper insulated lead cable (PILC) has been used for many years, with a high degree of success. Such a cable 10 is depicted in Fig. 16 wherein strand shielding 12 is interposed between a conductor 14 and a paper oil insulation layer 16 (i.e., paper impregnated with mineral oil) of the cable. A conductive wrap 18 is interposed between the paper oil insulation 16 and a lead sheath 20 of the cable.
When used together, the paper and oil (mineral oil) have exceptional dielectric strength, adequate heat resistance, and when isolated from moisture by the lead sheath, form a very reliable cable. However, because of the presence of the oil and because of the difficulties encountered in working with the lead sheath, extruded solid dielectric cables, made from cross linked polyethylene (XLPE) and Ethylene Propylene Rubber (EPR) have been replacing paper lead cable throughout the world.
The XLPE cable is much lower in cost and can be used with a wide array of premolded polymeric attachments, such as terminations, connectors and joints which make installation and operation of the system safer and easier.
As utilities have become familiar with those premolded attachments they wish to utilize them on the paper lead cable. However, the preferred polymeric materials for making such attachments, namely, EPDM
rubber, polyolefin heat shrink materials and silicone rubbers, are subject to chemical attack by the mineral oil used to impregnate the paper. Therefore, it would be desirable to enable such premolded polymeric attachments to be used on PILC cable.
In order to use these premolded devices on PILC
cable, however, it is necessary to establish a barrier preventing the mineral oil of the paper insulation 16 from coming in contact with the polymeric attachments and/or leaking out of the cable. Leaked oil can cause dielectric failure of the cable and environmental damage.
Achieving such a sealing-in of the mineral oil is complicated by the fact that, in some cases, the oil inside the cable is pressurized. At medium voltage, this is usually not the case. However, since the cable can vary in elevation as it enters buildings or subterranean vaults, gravity can induce pressure in the cable. This pressure is normally less than 103 kPa (15 PSIG). Higher pressures may result in leaks through the lead sheath at weak or thin spots.
Also, when fully loaded, the cable will experience elevated temperatures, as the load current flows through the cable resistance.
Thus, in addition to resisting heat and oil pressure, an oil barrier must resist the electrical stress within the cable and its associated connection. At the lead sheath and outer wrap ending, a concentrated electrical field appears when the lead sheath and conductive wrap are interrupted. Over time, this field, if not controlled, would over stress the cable and result in failure. Therefore, the barrier would have to control this stress.
Summary of the Invention The present invention relates to a method of forming an oil barrier at a end of a paper insulated lead cable. The cable includes a conductor, paper oil insulation disposed around the conductor, and a lead sheath disposed around the insulator. The method includes the steps of:
A) exposing the insulation to form axially spaced first and second junctions between the insulation and respective components of the cable;
B) applying a soft, tacky, oil-resistant sealant to form an oil barrier around the first and second junctions;
C) positioning heat-shrink tubing around the cable to cover the sealant disposed at the first and second junctions; and D) heat-shrinking the tubing to compress the sealant against the first and second junctions.
Preferably, step B comprises applying sealant comprised of mastic.
Preferably, prior to step C, first and second elastomeric gaskets are positioned against the sealant at the first and second junctions to oppose axial movement thereof and step D includes positioning the heat shrinked tubing around the first and second gaskets.
The present invention also relates to a paper insulated lead cable having an oil barrier assembly made according to the method.
Brief Description of the Drawings The objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawing in which like numerals designate like elements and in which:
Fig. 1 depicts a conventional paper insulated lead cable positioned next to a bushing to which it is to be terminated in accordance with the present invention;
Fig. 2 is a view similar to Fig. 1 after a section of lead sheath has been removed from the cable, with the bushing not shown;
Fig. 3 is a view similar to Fig. 2 after a section of the carbon conductive paper has been removed;
Fig. 4 is a view similar to Fig. 3 after a section of paper oil insulation has been removed;
Fig. 5 is a view similar to Fig. 4 after a metal connector has been attached to a conductor of the cable, and an O-ring gasket has been inserted onto the cable;
Fig. 6 is a view similar to Fig. 5 after another gasket has been inserted onto the connector;
Fig. 7 is a view similar to Fig. 6 after oil barriers have been positioned around first and second junctions of the cable;
Fig. 7A is a side elevational view of the cable depicted in Fig. 7;
Fig. 8 is a view similar to Fig. 7 after heat shrinked tubing has been applied to the cable;
Fig. 8A is a side elevational view of the cable depicted in Fig. 8;
Fig. 9 is a view similar to Fig. 8A after additional mastics have been applied to the cable;
Fig. 10 is a view similar to Fig. 9 after a ground lead has been attached to the cable;
Fig. 11 is a view similar to Fig. 10 depicting a further mounting of the ground lead;
Fig. 12 is a view similar to Fig. 11 after additional layers of mastic have been applied to the ground lead;
Fig. 13 is a view similar to Fig. 12 after an additional heat shrink tube has been loosely fit to the conductor, and a cylindrical adapter has been mounted on the cable;
Fig. 14 is a view similar to Fig. 13 after the additional heat shrink tubing has been heat shrunk, and an additional heat shrink tube has been applied to the cable;
Fig. 15 is a view similar to Fig. 14 after a T-shaped connector has been mounted to the cable, and a copper wire of the ground lead has been fastened to the connector; and Fig. 16 is a side view of a conventional paper insulated lead cable with sections thereof removed.
Detailed Description of Preferred Embodiments of the Invention A paper insulated lead cable (PILC) 10 of the type described earlier in connection with Fig. 16 is depicted in Fig. 1. A procedure for providing that cable with an oil barrier, enabling the cable to be used with attachments (e.g., connectors, terminations, joints etc.) formed of a polymeric material will now be described with reference to the connection of the cable with a bushing 30.
The cable 10 is moved to its final position and is cut off a given distance D from the center line of the apparatus bushing 30 at which the cable is to be terminated. After cleaning an end section of the lead sheath 20, a first sealing gasket 32 in the form of an O-ring is placed on the lead sheath, behind (i.e., axially inwardly of) a region where the lead sheath is to be removed (see Fig. 2). The O-ring 32 is preferably formed of an oil-resistant elastomer, such as a fluorocarbon based compound. Then, a section of the lead sheath is removed, thereby exposing the outer wrap of conductive carbon paper 18 (Fig. 2)-.
A region of the carbon paper 18 is then removed, thereby exposing the oil-impregnated insulation paper 16, as shown in Fig. 3. A portion of the carbon paper 18 projecting out of the lead sheath should remain.
A region of the insulation paper and strand shielding is then removed, thereby exposing the conductor 14, as shown in Fig. 4. The conductor wires are then cleaned.
A conventional metallic compression connector 34 is inserted onto the conductor and crimped thereto, as shown in Fig. 5.
Then, an annular shaped second sealing gasket 36 in the form of a shaped annular member, having large and small inside diameters, is slid over the end of the connector 34 such that the large diameter sits on the connector 34, and a radially outwardly facing surface 35 abuts an end of the connector. The second gasket 36, like the first gasket 32, is preferably formed of a fluoro-elastomer.
Then a first mastic 38, preferably a polysulfide or epicholorhydrin, is wrapped in such a way as to overlap a junction 15 between the paper oil insulation 16 and the connector (see Figs. 7, 7A). The mastic is formulated to have a high dielectric constant ("K") to provide electrical stress control (reduction). The mastic 38 overlaps slightly onto the paper oil insulation and touches the second gasket 36 without covering the outside of the gasket 36.
Then a second mastic 40 (preferably a polysulfide or epichlorhydren) is wrapped around the conductive paper 18 while overlapping junctions 17 and 19 between the paper oil insulation 16 on the one hand and the carbon paper 18 and lead sheath 20 on the other hand. The mastic wraps 38, 40 are then squeezed to form each of the mastic wraps into a solid mass.
The O-ring 32 is then positioned against the axially inwardly facing end of the second mastic 40 as shown in Figs. 8, 8A. An oil-resistant heat shrink tubing 42, preferably a polyvinylidene fluoride (PVDF) or (FEP) TeflonTM, is slid over the assembly such that one end thereof surrounds an axially inner section of the connector 34, and another end of the tubing overlaps the lead sheath, as shown in Figs. 8, 8A.
By using a torch, the tubing 4 is shrunk (from left to right in Fig. 8).
The result is a very effective barrier or adaptor assembly 50 which prevents the leaking of oil, even pressurized oil, while resisting electrical stress. The tubing 42, formed of a fluorinated polymeric material that is shrunk tightly to conform to the underlying structures, such as the paper oil insulation. That material is also tough, wear resistant, and able to withstand temperatures in excess of 150~C, and possess excellent dielectric strength. The tubing provides a primary oil barrier in the adaptor, blocking any oil from flowing through it.
The mastics 38, 40 are highly oil resistant and have a dielectric constant (preferably 10-20) which is high enough to perform the needed stress grading. Being tacky, the mastics amalgamate when pressed together. This means they can block the oil flow by forming a single mass. The mastics also stick to other materials that they come in contact with, preventing leaks around themselves.
They can withstand the elevated temperatures experienced in cable connection systems without significant degradation. The mastics effectively prevent the leakage of oil through the ends of the tubing 42.
The gaskets 32, 36 block the movement of the mastics 38, 40 when exposed to heat and pressure, ensuring that the seal is maintained. These gaskets butt against the mastics and are captured under the oil barrier tubing.
By preventing movement and flow of the oil sealing mastics, long term seal integrity is ensured at a minimum cost. Since no additional parts are placed over the cable insulation for achieving the oil barrier, excessive build-up of the cable diameter is avoided. This allows largersize cable to be terminated using premolded polymeric connectors.
To terminate the adaptor assembly 50, a ring of copper tape 52 is wrapped around the lead sheath 20 at a location spaced from the axial inner end of the adaptor assembly 50, and then a ring of mastic 54 is wrapped around the lead sheath at a location spaced axially inwardly from the copper tape 52, as shown in Fig. 9.
CA 02240203 l998-06-09 A grounding lead 56 (Fig. 10) is then provided, which is comprised of a copper strip or a braided copper cable 56 ' having an oil blocking region and a solid copper wire 56 " . A section 58 of the cable 56 ' iS soldered for 5 water blocking, and that section is pressed into the mastic 54. Another section of the grounding lead 56 iS
secured over the copper tape 52 by an annular spring 60, so that the braid 561 and the wire 561' are pressed against the copper tape 52 and the lead sheath, as shown in Fig. 10. Then, the front end of the grounding lead 56 is folded back over itself at 62, and is positioned within the spring 60, as shown in Fig. 11. Thereafter, as shown in Fig. 12, a first layer 64 of mastic is wrapped around the mastic 54 to cover the mastic 54 and the soldered 15 section 58 of the grounding lead 56, including the wire 56 " . A second layer 66 of mastic is wrapped to cover the spring 60 and provide a smooth transition thereover.
As shown in Fig. 13, an electrically insulative heat-shrink tube 70 iS then slid axially inwardly over 20 the cable 10 until an axial outer end of that tube 70 iS
positioned inwardly of the adapter assembly 50, and a molded-rubber cable adapter cylinder 72 iS installed by being slid axially inwardly. If necessary, silicone grease can be applied to selected portions of the adapter 25 assembly to facilitate such sliding movement.
Then, as shown in Fig. 14, the heat-shrink tube 70 iS axially advanced to be disposed almost at the inner end of the adaptor cylinder 72, and is heat-shrunk by means of a torch.
CA 02240203 l998-06-09 Then, a shorter insulative heat-shrink tube 74 is slid onto the end of the adaptor assembly so that it substantially abuts the adaptor cylinder 72, and that tube 74 iS heat shrunk, as shown in Fig. 14.
A premolded connector, such as an EPDM "Tee"
connector 76 iS slid onto the end of the adaptor assembly to abut the outer end of the heat-shrunk tube 70, as shown in Fig. 15, again using silicone grease if necessary.
A hole 78 of the connector 34 is centered within the transverse section 80 of the Tee 76. The tee connector 76 includes a plurality of apertured grounding tabs 82. The solid copper wire 56" of the grounding lead 56 iS bent up and inserted through one of those tabs 82. The end of the wire is twisted to complete the securement. The grounding lead 56 thus effectively earths the connector and prevents the build-up of capacitive charge on the outside of the Tee 76.
It will be appreciated that the present invention provides a novel adaptor assembly which enables a PILC
cable to be attached to premolded polymeric attachments by creating a barrier preventing oil from leaking out of the PILC cable and contacting the attachment. The barrier also resists heat and electrical stress occurring within the PILC cable. Furthermore, an effective earthing for the PILC cable and the attachment is provided.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.
PAPER INSULATED LEAD CABLES FOR USE
WITH POLYMERIC ATTACUM~NTS
Background of the Invention The present invention relates to paper insulated lead (PILC) cables and to methods and apparatus for enabling such cables to be connected to attachments formed of polymeric materials such as EPDM rubber, polyolefin heat shrink material, and silicone rubber.
Paper insulated lead cable (PILC) has been used for many years, with a high degree of success. Such a cable 10 is depicted in Fig. 16 wherein strand shielding 12 is interposed between a conductor 14 and a paper oil insulation layer 16 (i.e., paper impregnated with mineral oil) of the cable. A conductive wrap 18 is interposed between the paper oil insulation 16 and a lead sheath 20 of the cable.
When used together, the paper and oil (mineral oil) have exceptional dielectric strength, adequate heat resistance, and when isolated from moisture by the lead sheath, form a very reliable cable. However, because of the presence of the oil and because of the difficulties encountered in working with the lead sheath, extruded solid dielectric cables, made from cross linked polyethylene (XLPE) and Ethylene Propylene Rubber (EPR) have been replacing paper lead cable throughout the world.
The XLPE cable is much lower in cost and can be used with a wide array of premolded polymeric attachments, such as terminations, connectors and joints which make installation and operation of the system safer and easier.
As utilities have become familiar with those premolded attachments they wish to utilize them on the paper lead cable. However, the preferred polymeric materials for making such attachments, namely, EPDM
rubber, polyolefin heat shrink materials and silicone rubbers, are subject to chemical attack by the mineral oil used to impregnate the paper. Therefore, it would be desirable to enable such premolded polymeric attachments to be used on PILC cable.
In order to use these premolded devices on PILC
cable, however, it is necessary to establish a barrier preventing the mineral oil of the paper insulation 16 from coming in contact with the polymeric attachments and/or leaking out of the cable. Leaked oil can cause dielectric failure of the cable and environmental damage.
Achieving such a sealing-in of the mineral oil is complicated by the fact that, in some cases, the oil inside the cable is pressurized. At medium voltage, this is usually not the case. However, since the cable can vary in elevation as it enters buildings or subterranean vaults, gravity can induce pressure in the cable. This pressure is normally less than 103 kPa (15 PSIG). Higher pressures may result in leaks through the lead sheath at weak or thin spots.
Also, when fully loaded, the cable will experience elevated temperatures, as the load current flows through the cable resistance.
Thus, in addition to resisting heat and oil pressure, an oil barrier must resist the electrical stress within the cable and its associated connection. At the lead sheath and outer wrap ending, a concentrated electrical field appears when the lead sheath and conductive wrap are interrupted. Over time, this field, if not controlled, would over stress the cable and result in failure. Therefore, the barrier would have to control this stress.
Summary of the Invention The present invention relates to a method of forming an oil barrier at a end of a paper insulated lead cable. The cable includes a conductor, paper oil insulation disposed around the conductor, and a lead sheath disposed around the insulator. The method includes the steps of:
A) exposing the insulation to form axially spaced first and second junctions between the insulation and respective components of the cable;
B) applying a soft, tacky, oil-resistant sealant to form an oil barrier around the first and second junctions;
C) positioning heat-shrink tubing around the cable to cover the sealant disposed at the first and second junctions; and D) heat-shrinking the tubing to compress the sealant against the first and second junctions.
Preferably, step B comprises applying sealant comprised of mastic.
Preferably, prior to step C, first and second elastomeric gaskets are positioned against the sealant at the first and second junctions to oppose axial movement thereof and step D includes positioning the heat shrinked tubing around the first and second gaskets.
The present invention also relates to a paper insulated lead cable having an oil barrier assembly made according to the method.
Brief Description of the Drawings The objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawing in which like numerals designate like elements and in which:
Fig. 1 depicts a conventional paper insulated lead cable positioned next to a bushing to which it is to be terminated in accordance with the present invention;
Fig. 2 is a view similar to Fig. 1 after a section of lead sheath has been removed from the cable, with the bushing not shown;
Fig. 3 is a view similar to Fig. 2 after a section of the carbon conductive paper has been removed;
Fig. 4 is a view similar to Fig. 3 after a section of paper oil insulation has been removed;
Fig. 5 is a view similar to Fig. 4 after a metal connector has been attached to a conductor of the cable, and an O-ring gasket has been inserted onto the cable;
Fig. 6 is a view similar to Fig. 5 after another gasket has been inserted onto the connector;
Fig. 7 is a view similar to Fig. 6 after oil barriers have been positioned around first and second junctions of the cable;
Fig. 7A is a side elevational view of the cable depicted in Fig. 7;
Fig. 8 is a view similar to Fig. 7 after heat shrinked tubing has been applied to the cable;
Fig. 8A is a side elevational view of the cable depicted in Fig. 8;
Fig. 9 is a view similar to Fig. 8A after additional mastics have been applied to the cable;
Fig. 10 is a view similar to Fig. 9 after a ground lead has been attached to the cable;
Fig. 11 is a view similar to Fig. 10 depicting a further mounting of the ground lead;
Fig. 12 is a view similar to Fig. 11 after additional layers of mastic have been applied to the ground lead;
Fig. 13 is a view similar to Fig. 12 after an additional heat shrink tube has been loosely fit to the conductor, and a cylindrical adapter has been mounted on the cable;
Fig. 14 is a view similar to Fig. 13 after the additional heat shrink tubing has been heat shrunk, and an additional heat shrink tube has been applied to the cable;
Fig. 15 is a view similar to Fig. 14 after a T-shaped connector has been mounted to the cable, and a copper wire of the ground lead has been fastened to the connector; and Fig. 16 is a side view of a conventional paper insulated lead cable with sections thereof removed.
Detailed Description of Preferred Embodiments of the Invention A paper insulated lead cable (PILC) 10 of the type described earlier in connection with Fig. 16 is depicted in Fig. 1. A procedure for providing that cable with an oil barrier, enabling the cable to be used with attachments (e.g., connectors, terminations, joints etc.) formed of a polymeric material will now be described with reference to the connection of the cable with a bushing 30.
The cable 10 is moved to its final position and is cut off a given distance D from the center line of the apparatus bushing 30 at which the cable is to be terminated. After cleaning an end section of the lead sheath 20, a first sealing gasket 32 in the form of an O-ring is placed on the lead sheath, behind (i.e., axially inwardly of) a region where the lead sheath is to be removed (see Fig. 2). The O-ring 32 is preferably formed of an oil-resistant elastomer, such as a fluorocarbon based compound. Then, a section of the lead sheath is removed, thereby exposing the outer wrap of conductive carbon paper 18 (Fig. 2)-.
A region of the carbon paper 18 is then removed, thereby exposing the oil-impregnated insulation paper 16, as shown in Fig. 3. A portion of the carbon paper 18 projecting out of the lead sheath should remain.
A region of the insulation paper and strand shielding is then removed, thereby exposing the conductor 14, as shown in Fig. 4. The conductor wires are then cleaned.
A conventional metallic compression connector 34 is inserted onto the conductor and crimped thereto, as shown in Fig. 5.
Then, an annular shaped second sealing gasket 36 in the form of a shaped annular member, having large and small inside diameters, is slid over the end of the connector 34 such that the large diameter sits on the connector 34, and a radially outwardly facing surface 35 abuts an end of the connector. The second gasket 36, like the first gasket 32, is preferably formed of a fluoro-elastomer.
Then a first mastic 38, preferably a polysulfide or epicholorhydrin, is wrapped in such a way as to overlap a junction 15 between the paper oil insulation 16 and the connector (see Figs. 7, 7A). The mastic is formulated to have a high dielectric constant ("K") to provide electrical stress control (reduction). The mastic 38 overlaps slightly onto the paper oil insulation and touches the second gasket 36 without covering the outside of the gasket 36.
Then a second mastic 40 (preferably a polysulfide or epichlorhydren) is wrapped around the conductive paper 18 while overlapping junctions 17 and 19 between the paper oil insulation 16 on the one hand and the carbon paper 18 and lead sheath 20 on the other hand. The mastic wraps 38, 40 are then squeezed to form each of the mastic wraps into a solid mass.
The O-ring 32 is then positioned against the axially inwardly facing end of the second mastic 40 as shown in Figs. 8, 8A. An oil-resistant heat shrink tubing 42, preferably a polyvinylidene fluoride (PVDF) or (FEP) TeflonTM, is slid over the assembly such that one end thereof surrounds an axially inner section of the connector 34, and another end of the tubing overlaps the lead sheath, as shown in Figs. 8, 8A.
By using a torch, the tubing 4 is shrunk (from left to right in Fig. 8).
The result is a very effective barrier or adaptor assembly 50 which prevents the leaking of oil, even pressurized oil, while resisting electrical stress. The tubing 42, formed of a fluorinated polymeric material that is shrunk tightly to conform to the underlying structures, such as the paper oil insulation. That material is also tough, wear resistant, and able to withstand temperatures in excess of 150~C, and possess excellent dielectric strength. The tubing provides a primary oil barrier in the adaptor, blocking any oil from flowing through it.
The mastics 38, 40 are highly oil resistant and have a dielectric constant (preferably 10-20) which is high enough to perform the needed stress grading. Being tacky, the mastics amalgamate when pressed together. This means they can block the oil flow by forming a single mass. The mastics also stick to other materials that they come in contact with, preventing leaks around themselves.
They can withstand the elevated temperatures experienced in cable connection systems without significant degradation. The mastics effectively prevent the leakage of oil through the ends of the tubing 42.
The gaskets 32, 36 block the movement of the mastics 38, 40 when exposed to heat and pressure, ensuring that the seal is maintained. These gaskets butt against the mastics and are captured under the oil barrier tubing.
By preventing movement and flow of the oil sealing mastics, long term seal integrity is ensured at a minimum cost. Since no additional parts are placed over the cable insulation for achieving the oil barrier, excessive build-up of the cable diameter is avoided. This allows largersize cable to be terminated using premolded polymeric connectors.
To terminate the adaptor assembly 50, a ring of copper tape 52 is wrapped around the lead sheath 20 at a location spaced from the axial inner end of the adaptor assembly 50, and then a ring of mastic 54 is wrapped around the lead sheath at a location spaced axially inwardly from the copper tape 52, as shown in Fig. 9.
CA 02240203 l998-06-09 A grounding lead 56 (Fig. 10) is then provided, which is comprised of a copper strip or a braided copper cable 56 ' having an oil blocking region and a solid copper wire 56 " . A section 58 of the cable 56 ' iS soldered for 5 water blocking, and that section is pressed into the mastic 54. Another section of the grounding lead 56 iS
secured over the copper tape 52 by an annular spring 60, so that the braid 561 and the wire 561' are pressed against the copper tape 52 and the lead sheath, as shown in Fig. 10. Then, the front end of the grounding lead 56 is folded back over itself at 62, and is positioned within the spring 60, as shown in Fig. 11. Thereafter, as shown in Fig. 12, a first layer 64 of mastic is wrapped around the mastic 54 to cover the mastic 54 and the soldered 15 section 58 of the grounding lead 56, including the wire 56 " . A second layer 66 of mastic is wrapped to cover the spring 60 and provide a smooth transition thereover.
As shown in Fig. 13, an electrically insulative heat-shrink tube 70 iS then slid axially inwardly over 20 the cable 10 until an axial outer end of that tube 70 iS
positioned inwardly of the adapter assembly 50, and a molded-rubber cable adapter cylinder 72 iS installed by being slid axially inwardly. If necessary, silicone grease can be applied to selected portions of the adapter 25 assembly to facilitate such sliding movement.
Then, as shown in Fig. 14, the heat-shrink tube 70 iS axially advanced to be disposed almost at the inner end of the adaptor cylinder 72, and is heat-shrunk by means of a torch.
CA 02240203 l998-06-09 Then, a shorter insulative heat-shrink tube 74 is slid onto the end of the adaptor assembly so that it substantially abuts the adaptor cylinder 72, and that tube 74 iS heat shrunk, as shown in Fig. 14.
A premolded connector, such as an EPDM "Tee"
connector 76 iS slid onto the end of the adaptor assembly to abut the outer end of the heat-shrunk tube 70, as shown in Fig. 15, again using silicone grease if necessary.
A hole 78 of the connector 34 is centered within the transverse section 80 of the Tee 76. The tee connector 76 includes a plurality of apertured grounding tabs 82. The solid copper wire 56" of the grounding lead 56 iS bent up and inserted through one of those tabs 82. The end of the wire is twisted to complete the securement. The grounding lead 56 thus effectively earths the connector and prevents the build-up of capacitive charge on the outside of the Tee 76.
It will be appreciated that the present invention provides a novel adaptor assembly which enables a PILC
cable to be attached to premolded polymeric attachments by creating a barrier preventing oil from leaking out of the PILC cable and contacting the attachment. The barrier also resists heat and electrical stress occurring within the PILC cable. Furthermore, an effective earthing for the PILC cable and the attachment is provided.
Although the present invention has been described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (19)
1. A method of forming an oil barrier assembly at an end of a paper insulated lead cable, the cable including a conductor, paper oil insulation disposed around the conductor, and a lead sheath disposed around the insulation, the method including the steps of:
A) exposing the insulation to form axially spaced first and second junctions between the insulation and respective components of the cable;
B) applying a soft, tacky, oil-resistant sealant to form an oil barrier around the first and second junctions;
C) positioning heat-shrink tubing around the cable to cover the sealant disposed at the first and second junctions; and D) heat-shrinking the tubing to compress the sealant against the first and second junctions.
A) exposing the insulation to form axially spaced first and second junctions between the insulation and respective components of the cable;
B) applying a soft, tacky, oil-resistant sealant to form an oil barrier around the first and second junctions;
C) positioning heat-shrink tubing around the cable to cover the sealant disposed at the first and second junctions; and D) heat-shrinking the tubing to compress the sealant against the first and second junctions.
2. The method according to claim 1 wherein step B comprises applying sealant comprised of mastic.
3. The method according to claim 1, further comprising, prior to step C, the step of positioning first and second elastomeric gaskets against the sealant at the first and second junctions to oppose axial movement thereof; step D including positioning the heat-shrink tubing around the first and second gaskets.
4. The method according to claim 3 wherein the positioning step comprises positioning gaskets formed of an oil resistant material.
5. The method according to claim 3 wherein the positioning step comprises positioning gaskets formed of a fluorocarbon-based material.
6. The method according to claim 1 further comprising, prior to step C, the step of positioning first and second elastomeric gaskets against the sealant at the first and second junctions to oppose axial movement thereof; step D including positioning the heat-shrink tubing around the first and second gaskets.
7. The method according to claim 6 wherein the positioning step comprises positioning the first gasket against an axial outwardly facing end of sealant at the first junction, and positioning the second gasket against an axial inwardly facing end of the sealant at the second junction.
8. The method according to claim 7 wherein step B comprises applying two separate axially spaced masses of the sealant at the first and second junctions, respectively.
9. The method according to claim 7, further comprising, prior to step C, the step of attaching a metallic connector to the conductor; step C including positioning the tubing around an axially inner end of the connector.
10. The method according to claim 7, wherein the heat shrink tubing comprises a first heat shrink tubing, and further comprising the steps of connecting a ground lead to the cable at a location disposed axially inwardly of the first heat-shrink tubing; heat shrinking a second heat shrink tubing over the cable to cover a connection between the ground lead and the cable and to also cover a portion of the first heat shrink tubing covering the second gasket and the sealant disposed at the second junction; sliding a resilient cylindrical adaptor over a portion of the first heat shrink tubing disposed axially between the first and second junctions, and heat shrinking a third heat-shrink insulative tubing over a portion of the first tubing covering the first gasket, the sealant at the first junction, and an axially inner portion of the connector; and mounting a terminating member onto the connector, the third tubing, and the adapter; the terminating member formed of a polymer.
11. The method according to claim 1 further including the step of mounting a terminating member onto an axially outer end of the heat shrink tubing, the terminating member formed of a polymer.
12. A paper insulated lead cable comprising a conductor paper oil insulation surrounding the conductor, and a lead sheath surrounding the insulation; axially spaced first and second junctions formed between the insulation and respective components of the cable; a soft, tacky, oil-resistant sealant disposed around the first and second junctions to form an oil barrier around the first and second junctions, respectively; and a heat shrink tubing heat shrunk onto the cable to compress the sealant against the first and second junctions.
13. The paper insulated lead cable according to claim 12, wherein the sealant comprises mastic.
14. The paper insulated lead cable according to claim 12, further comprising first and second elastomeric gaskets positioned against the sealant at the first and second junctions to oppose axial movement thereof, the heat-shrink tubing surrounding the first and second gaskets.
15. The paper insulated lead cable according to claim 14 wherein the first gasket is positioned against an axial outwardly facing end of the sealant at the first junction, and the second gasket is positioned against an axial inwardly facing end of the sealant at the second junction.
16. The paper insulated lead cable according to claim 12, further comprising a metallic connector attached to the conductor, the tubing positioned around an axially inner end of the connector.
17. The paper insulated lead cable according to claim 14 wherein the first gasket includes an inner periphery having an axially outwardly facing surface facing an end of the connector.
18. The paper insulated lead cable according to claim 14 wherein the heat shrink tubing comprises a first heat shrink tubing; and further comprising a ground lead connected to the cable at a location axially inwardly of the first heat-shrink tubing, a second heat shrink tubing overlying a connection between the ground lead and the cable, and a portion of the first tubing covering the second gasket and the sealant disposed at the second junction; a resilient cylindrical adaptor overlying a portion of the first tubing disposed axially between the first and second junctions, and a third heat shrink tubing overlying a portion of the first tubing covering the first gasket, the sealant disposed at the first junction and an axially inner portion of the connector; and a termination member overlying the connector, the third tubing, and the adaptor, the terminating member formed of a polymeric material.
19. The paper insulated lead cable according to claim 12 further comprising a terminating member mounted on an axially outer end of the heat shrink tubing, the terminating member formed of a polymeric material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87206397A | 1997-06-10 | 1997-06-10 | |
| US08/872,063 | 1997-06-10 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2240203A1 true CA2240203A1 (en) | 1998-12-10 |
Family
ID=25358758
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2240203 Abandoned CA2240203A1 (en) | 1997-06-10 | 1998-06-09 | Methods and apparatus for adapting paper insulated lead cables for use with polymeric attachments |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA2240203A1 (en) |
| GB (1) | GB2327140A (en) |
| TW (1) | TW379333B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2911441B1 (en) * | 2007-01-16 | 2015-08-07 | Prysmian En Cables Et Systemes France | PROTECTIVE DEVICE FOR ELECTRICAL CABLE WITH INSULATION BASED ON IMPREGNATED PAPER |
| CN101340035B (en) | 2007-07-02 | 2010-08-25 | 3M创新有限公司 | Adapter, cable connector having the adapter and cable connector component |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4110550A (en) * | 1976-11-01 | 1978-08-29 | Amerace Corporation | Electrical connector with adaptor for paper-insulated, lead-jacketed electrical cables and method |
-
1998
- 1998-06-03 GB GB9811960A patent/GB2327140A/en not_active Withdrawn
- 1998-06-09 CA CA 2240203 patent/CA2240203A1/en not_active Abandoned
- 1998-06-10 TW TW87109206A patent/TW379333B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| TW379333B (en) | 2000-01-11 |
| GB9811960D0 (en) | 1998-07-29 |
| GB2327140A (en) | 1999-01-13 |
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| Date | Code | Title | Description |
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| FZDE | Dead |