CA1113558A - Jointing electric cables with a mechanically rigid set compound - Google Patents
Jointing electric cables with a mechanically rigid set compoundInfo
- Publication number
- CA1113558A CA1113558A CA318,945A CA318945A CA1113558A CA 1113558 A CA1113558 A CA 1113558A CA 318945 A CA318945 A CA 318945A CA 1113558 A CA1113558 A CA 1113558A
- Authority
- CA
- Canada
- Prior art keywords
- inner casing
- cable joint
- compound
- discs
- filled
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- 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
- H02G15/003—Filling materials, e.g. solid or fluid insulation
-
- 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
- H02G15/08—Cable junctions
- H02G15/10—Cable junctions protected by boxes, e.g. by distribution, connection or junction boxes
Abstract
ABSTRACT
A cable joint comprises an inner casing enclosing the jointed conductors of the cables being jointed, this inner casing being filled with a com-pound serving as electrical insulation and an outer casing enclosing the inner casing and filled with a set compound serving as a mechanical support for the jointed conductors. Thus, the compound filling the inner casing is chosen purely for its electrical pro-perties and provides the electrical insulation of the joint and the compound filling the outer casing is chosen purely for its mechanical properties and prov-ides the mechanical strength of the joint.
A cable joint comprises an inner casing enclosing the jointed conductors of the cables being jointed, this inner casing being filled with a com-pound serving as electrical insulation and an outer casing enclosing the inner casing and filled with a set compound serving as a mechanical support for the jointed conductors. Thus, the compound filling the inner casing is chosen purely for its electrical pro-perties and provides the electrical insulation of the joint and the compound filling the outer casing is chosen purely for its mechanical properties and prov-ides the mechanical strength of the joint.
Description
\
This inventi~n relates to jointing ~lectric cables.
A method used in the jointing of low and high voltage elec-tric cables i~ to enclo6e the jointed conductors in a casing or shell and then pour a setting compound into the casing so as to embed the jointed conductors. This compound, when set, serves as the primary electrical insulation, but in addition it serves as a rigid support for the cables cores, ais protection against mechanical damage and as a barrier against the entry of water into the joint. ~esearch has shown that a rigid compound which willfully satisfy th~ important mechanical requirements is un-likely to have an electrical performa~ce adequate for the joint-~ng of high voltage cables rated at 7.2 kV and abo~e. In par-ticular it has been found that the inability of rigid thermo-setting compounds ( for exa~ple rigid silica-filled acrylic resins)to deform in sympathy with the expansion and contraction of polymeric core insulation during conductor load cycling can lead to a path of electrical weakness along the core surface between the conductor connector and the terminated core screen at earth potential.
This invention provides a cable joint comprising an inner casing enclosing the jointed conductors of the cables being jointed, this inner casing being filled with a compound serving as electrical insulation, and an outer casing enclosing the iDner caising and filled with a set compound serving as ~ mechanical support and Protection for the jointed conductors, the compound filling the inner casing having better electrically insulating properties than the compound filling the outer casing.
This inventi~n relates to jointing ~lectric cables.
A method used in the jointing of low and high voltage elec-tric cables i~ to enclo6e the jointed conductors in a casing or shell and then pour a setting compound into the casing so as to embed the jointed conductors. This compound, when set, serves as the primary electrical insulation, but in addition it serves as a rigid support for the cables cores, ais protection against mechanical damage and as a barrier against the entry of water into the joint. ~esearch has shown that a rigid compound which willfully satisfy th~ important mechanical requirements is un-likely to have an electrical performa~ce adequate for the joint-~ng of high voltage cables rated at 7.2 kV and abo~e. In par-ticular it has been found that the inability of rigid thermo-setting compounds ( for exa~ple rigid silica-filled acrylic resins)to deform in sympathy with the expansion and contraction of polymeric core insulation during conductor load cycling can lead to a path of electrical weakness along the core surface between the conductor connector and the terminated core screen at earth potential.
This invention provides a cable joint comprising an inner casing enclosing the jointed conductors of the cables being jointed, this inner casing being filled with a compound serving as electrical insulation, and an outer casing enclosing the iDner caising and filled with a set compound serving as ~ mechanical support and Protection for the jointed conductors, the compound filling the inner casing having better electrically insulating properties than the compound filling the outer casing.
- 2 -,;j., , ~'~ -.
. ~ , . ~ . ' .
An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a longitudinal section through a straight joint between two high voltage cables; and Figure 2 is a cross-section through the straight joint shown in Figure 1.
Referring to the drawings, there is shown a straight joint between two three-core high voltage cables. The individual conductors are insulated with extruded polymeric insulation, e.g. ethylene-propylene rubber (EPR) or cross-linked polyethylene, shown at 1.
Respective core conductors of the two cables are jointed by three connectors, two of which are ~hown in Figure 1 at 2. Individual screening layers for the conductors are shown at 3.
The joint comprises an inner casing ~0 which encloses the Jointed conductors and which is filled, by pouring through the inlet 11, with a compound whose function is solely to provide adequate electrical insulation over the conductor connectors and the lengths of extruded conductor insulation from which the cable screens have been stripped. The inlet 11 is closed, as shown, after the inner casing has been filled.
The inner casing includes a metal (e.g.
aluminiu~ sleeve 12 which is maintained at earth potential b~ connections 13 to the metal sheaths or screen~ of the cables themselves. Each end of the
. ~ , . ~ . ' .
An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a longitudinal section through a straight joint between two high voltage cables; and Figure 2 is a cross-section through the straight joint shown in Figure 1.
Referring to the drawings, there is shown a straight joint between two three-core high voltage cables. The individual conductors are insulated with extruded polymeric insulation, e.g. ethylene-propylene rubber (EPR) or cross-linked polyethylene, shown at 1.
Respective core conductors of the two cables are jointed by three connectors, two of which are ~hown in Figure 1 at 2. Individual screening layers for the conductors are shown at 3.
The joint comprises an inner casing ~0 which encloses the Jointed conductors and which is filled, by pouring through the inlet 11, with a compound whose function is solely to provide adequate electrical insulation over the conductor connectors and the lengths of extruded conductor insulation from which the cable screens have been stripped. The inlet 11 is closed, as shown, after the inner casing has been filled.
The inner casing includes a metal (e.g.
aluminiu~ sleeve 12 which is maintained at earth potential b~ connections 13 to the metal sheaths or screen~ of the cables themselves. Each end of the
3 inner casing is closed by a flexible moulded di~c 14 provided with three circular apertures for the core conductors, holding the three cores at their appropriate spacings. The disc 14 is moulded in a semi-conducting material such as carbon~loaded EPR and is made sufficiently flexible to fit over non-circular (e.g. sectoral) cores and in any event form a seal against loss of compound from the inner casing. This sealing can be assisted by a clip or binding around the periphery of the disc. Each such disc provides electric stre~s relief at the ends of the core screens by being positioned to embrace these screens at their ends and by being contoured as shown around the core apertures on its inwardly- -facing side.
The inner casing i~ completed at each end by a semi-conducting rubber shroud 15 which embraces and seals onto both the sleeve 12 and disc 14.
The joint further comprises an outer casing 20, which may comprise a vacuum-formed plastics sheet.
This outer casing is filled, by pouring through a subsequently-closed inlet 21, with a compound which sets rigid and which is chosen for itq ability to provide mechanical support and protection to the jointed conductors. There i~ no electrical requirement for this compound since the electric field i9 confined within the inner casing and within the core screens 3.
A core spreader element 22 is placed between the cores to maintain the correct spacings between the - . . ~ .
c~
three phases and also to support $he metal sleeve 12. The joint in accordance with the invention, whether for 3 core or single core cables, allows substantial cost savings over conventional joints using solidified resin as filling compound. This is because the volume of electrical grade compound is kept to a minimum (approximately 30% of the total volume of the 3 core joint) and because neither compound has to satisfy both electrical and mechanical requirements.
By way of example, the compound filling the inner casing may comprise a flexible polyurethane resin, and the compound filling the outer casing may comprise a rigid silica-filled polyester or polyurethane resin.
. . ~
The inner casing i~ completed at each end by a semi-conducting rubber shroud 15 which embraces and seals onto both the sleeve 12 and disc 14.
The joint further comprises an outer casing 20, which may comprise a vacuum-formed plastics sheet.
This outer casing is filled, by pouring through a subsequently-closed inlet 21, with a compound which sets rigid and which is chosen for itq ability to provide mechanical support and protection to the jointed conductors. There i~ no electrical requirement for this compound since the electric field i9 confined within the inner casing and within the core screens 3.
A core spreader element 22 is placed between the cores to maintain the correct spacings between the - . . ~ .
c~
three phases and also to support $he metal sleeve 12. The joint in accordance with the invention, whether for 3 core or single core cables, allows substantial cost savings over conventional joints using solidified resin as filling compound. This is because the volume of electrical grade compound is kept to a minimum (approximately 30% of the total volume of the 3 core joint) and because neither compound has to satisfy both electrical and mechanical requirements.
By way of example, the compound filling the inner casing may comprise a flexible polyurethane resin, and the compound filling the outer casing may comprise a rigid silica-filled polyester or polyurethane resin.
. . ~
Claims (11)
1. A cable joint comprising an inner casing enclosing the jointed conductors of the cables being jointed, this inner casing being filled with a compound serving as electrical insula-tion, and an outer casing enclosing the inner casing and filled with a set compound serving as a mechanical support for the jointed conductors, the compound filling the inner casing having better electrically insulating properties than the compound filling the outer casing.
2. A cable joint as claimed in claim 1, in which the compound filling the inner casing comprises a flexible poly-urethane resin.
3. A cable joint as claimed in claim 1 or 2, in which the compound filling the outer casing comprises a rigid silica-filled polyester resin.
4. A cable joint as claimed in claim 1 or 2, in which the compound filling the outer casing comprises a rigid silica-filled polyurethane resin.
5. A cable joint as claimed in claim 1 in which the inner casing is electrically conductive and is electrically connected to metal sheaths or screens of the respective cables.
6. A cable joint as claimed in Claim 5, in which the inner casing includes a pair of discs, closing the opposite ends of the inner casing, which discs are provided with apertures through which the respective cable conductors extend, the discs being flexible so as to seal around the conductors against loss of compound from the inner casing.
7. A cable joint as claimed in claim 6, in which said discs are formed of semi-conducting material.
8. A cable joint as claimed in claim 7, in which said discs are formed of carbon-loaded EPR.
9. A cable joint as claimed in Claim 6, 7 or 8 in which said inner casing further includes a metal sleeve and a pair of semi-conducting rubber shrouds, each shroud embracing, at its opposite ends, the metal sleeve and a respective said disc.
10. A cable joint as claimed in Claim 6, 7 or 8 in which said discs embrace individual screening layers of the cable con-ductors.
11. A cable joint as claimed in Claim 1, 2 or 6 in which the outer casing comprises a vacuum-formed plastics sheet.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB384278A GB1558657A (en) | 1978-01-31 | 1978-01-31 | Jointing electric cables |
| GB3842/78 | 1978-01-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1113558A true CA1113558A (en) | 1981-12-01 |
Family
ID=9765967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA318,945A Expired CA1113558A (en) | 1978-01-31 | 1979-01-02 | Jointing electric cables with a mechanically rigid set compound |
Country Status (5)
| Country | Link |
|---|---|
| AR (1) | AR219574A1 (en) |
| BR (1) | BR7900483A (en) |
| CA (1) | CA1113558A (en) |
| ES (1) | ES241385Y (en) |
| GB (1) | GB1558657A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5839216A (en) * | 1981-08-31 | 1983-03-07 | アイシン・エィ・ダブリュ株式会社 | Method and device for coupling and sealing wire in hydraulic equipment |
| US4647719A (en) * | 1985-06-21 | 1987-03-03 | At&T Technologies, Inc. | Termination closure for buried service cables and methods of installing |
| GB2284110B (en) * | 1991-03-25 | 1995-10-04 | Raychem Ltd | Cable closure arrangement |
| GB9106288D0 (en) * | 1991-03-25 | 1991-05-08 | Raychem Ltd | Cable joint |
| RU2752853C1 (en) * | 2020-10-30 | 2021-08-11 | Акционерное общество "Государственный Рязанский приборный завод" | Method for sealing low-frequency connectors of electrical harnesses and cables |
-
1978
- 1978-01-31 GB GB384278A patent/GB1558657A/en not_active Expired
-
1979
- 1979-01-02 CA CA318,945A patent/CA1113558A/en not_active Expired
- 1979-01-26 BR BR7900483A patent/BR7900483A/en unknown
- 1979-01-26 AR AR27530679A patent/AR219574A1/en active
- 1979-01-31 ES ES1979241385U patent/ES241385Y/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| ES241385U (en) | 1979-05-01 |
| BR7900483A (en) | 1979-08-21 |
| GB1558657A (en) | 1980-01-09 |
| AR219574A1 (en) | 1980-08-29 |
| ES241385Y (en) | 1979-11-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |