CA1266102A - Electric cables - Google Patents
Electric cablesInfo
- Publication number
- CA1266102A CA1266102A CA000514944A CA514944A CA1266102A CA 1266102 A CA1266102 A CA 1266102A CA 000514944 A CA000514944 A CA 000514944A CA 514944 A CA514944 A CA 514944A CA 1266102 A CA1266102 A CA 1266102A
- Authority
- CA
- Canada
- Prior art keywords
- layer
- cable
- semi
- conducting
- extruded
- 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 - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B9/00—Power cables
- H01B9/02—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients
- H01B9/027—Power cables with screens or conductive layers, e.g. for avoiding large potential gradients composed of semi-conducting layers
Landscapes
- Insulated Conductors (AREA)
- Resistance Heating (AREA)
- Cable Accessories (AREA)
- Organic Insulating Materials (AREA)
- Ignition Installations For Internal Combustion Engines (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
- Laminated Bodies (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
- Processing Of Terminals (AREA)
- Coupling Device And Connection With Printed Circuit (AREA)
Abstract
ABSTRACT
ELECTRIC CABLES
An electric cable having a current carrying conductor provided with an extruded polymeric insulating layer, has a layer of a high permittivity material extruded over the whole length of the insulating layer, which layer is covered with semi-conducting tape in contact therewith.
ELECTRIC CABLES
An electric cable having a current carrying conductor provided with an extruded polymeric insulating layer, has a layer of a high permittivity material extruded over the whole length of the insulating layer, which layer is covered with semi-conducting tape in contact therewith.
Description
lZ6610Z
ELECTRIC CABLES
This in~ention relates to electric cables, and more particularly to electric cables in which the current carrying conductors are provided with extruded polymeric insulating layers.
In known high voltage cables in which the current carrying conductors are provided with extruded polymeric insulation, a layer of polymeric insulation is disposed over the conductor with a first semi-conducting layer between the conductor and insulation and a second semi-conducting layer over the insulation, and a conducting sheath is provided over the second semi-conducting layer to provide an earth screen. It is conventional to co-extrude the semi-conducting layers with the insulating layer whereby the semi-conducting layers are bonded to the insulating layer. The purpose of the semi- conduct-ing layer is to prevent electrical discharges occurring due to voids bein present between the inner surface of the insulating layer and the conductor and between the outer surface of the insulating layer and the conducting sheath-The semi-conducting layer over the insulating layer has to be removed during jointing or termination of the cable in the region of the joint or termination as it normally has a resistance such that it would carry unacceptable high currents if it were allvwed to form a ~2~61~
path bet~en the ~rrent ~arr~in~ conductor and earth in the joint or t~rmination. Remo a~ of the ~emi-condurtin~ ~a~er o~er the insu]atin~ ]a~r ~herefrom is a diffjcu]t operation ~hich in ol~es th~ ris~ of damage b~ing caused to the insu~ation ]a~er.
~ o a~oid this prob]em it has been prop~sed to pro~id~ o ~r the ~ho~e length of the insu~ation la~er a ~a~er of hi~hl~ resisti e materia] ~lose resistance is ~o~ta~e depend~nt instead of a se~i-conductin~ ~ayer '~ ~ince ~u~h a ~o~ta~e dependent resisti~ la~er does not ha~e to be remo~ed d~rin~ jointin~ or termination.
Ho~ er this soluti~n suffers from the disad antage that material ~ith the appropriate ~oltage dependent re-sisti~it~ is not suitab~e for application by con ention-'S a~ extrusion equipment.
~ he present in ention seeks an a3ternati~e solu-tion in ~hich the semi-conducting la~er o er the insu~-ating ~a~er is rep~aced b~ an alternati-~e la~er hhich can be readil~ extruded o er the insulating la~er but hich does not ha-e t-o be remo ed during jointing or terminating.
~ he pres~nt in~entio~ provides an electric cable ha ing at least one current carr~in~ conductor pro~ided hith an extrud~d pol~meric insulating la~er o~er the
ELECTRIC CABLES
This in~ention relates to electric cables, and more particularly to electric cables in which the current carrying conductors are provided with extruded polymeric insulating layers.
In known high voltage cables in which the current carrying conductors are provided with extruded polymeric insulation, a layer of polymeric insulation is disposed over the conductor with a first semi-conducting layer between the conductor and insulation and a second semi-conducting layer over the insulation, and a conducting sheath is provided over the second semi-conducting layer to provide an earth screen. It is conventional to co-extrude the semi-conducting layers with the insulating layer whereby the semi-conducting layers are bonded to the insulating layer. The purpose of the semi- conduct-ing layer is to prevent electrical discharges occurring due to voids bein present between the inner surface of the insulating layer and the conductor and between the outer surface of the insulating layer and the conducting sheath-The semi-conducting layer over the insulating layer has to be removed during jointing or termination of the cable in the region of the joint or termination as it normally has a resistance such that it would carry unacceptable high currents if it were allvwed to form a ~2~61~
path bet~en the ~rrent ~arr~in~ conductor and earth in the joint or t~rmination. Remo a~ of the ~emi-condurtin~ ~a~er o~er the insu]atin~ ]a~r ~herefrom is a diffjcu]t operation ~hich in ol~es th~ ris~ of damage b~ing caused to the insu~ation ]a~er.
~ o a~oid this prob]em it has been prop~sed to pro~id~ o ~r the ~ho~e length of the insu~ation la~er a ~a~er of hi~hl~ resisti e materia] ~lose resistance is ~o~ta~e depend~nt instead of a se~i-conductin~ ~ayer '~ ~ince ~u~h a ~o~ta~e dependent resisti~ la~er does not ha~e to be remo~ed d~rin~ jointin~ or termination.
Ho~ er this soluti~n suffers from the disad antage that material ~ith the appropriate ~oltage dependent re-sisti~it~ is not suitab~e for application by con ention-'S a~ extrusion equipment.
~ he present in ention seeks an a3ternati~e solu-tion in ~hich the semi-conducting la~er o er the insu~-ating ~a~er is rep~aced b~ an alternati-~e la~er hhich can be readil~ extruded o er the insulating la~er but hich does not ha-e t-o be remo ed during jointing or terminating.
~ he pres~nt in~entio~ provides an electric cable ha ing at least one current carr~in~ conductor pro~ided hith an extrud~d pol~meric insulating la~er o~er the
2~ ~hole ~en~th of hhich is an extruded layer. of materia~
having a re]at.ive permitt.ivity of at least 15 said ~atter ~ayer heing co~ered with semi-conducting tape in contact. there~ith.
The present inverl~ion in another aspect resides
having a re]at.ive permitt.ivity of at least 15 said ~atter ~ayer heing co~ered with semi-conducting tape in contact. there~ith.
The present inverl~ion in another aspect resides
3 in a meth~ ~r making a joint or termination for a cable as described above including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
~LZ~
-2a-ln order that the invention may be well understood an embodimen~ t~hereof, hhich is given by h~ay of example only,h~ no~ be described ~ith reference to the accom-pan~ing drawing in ~hich the single figure schematica]ly shohs in radial cross-section a high ~oltage electric cable. Referring to the figure, the high voltage ~lectric cable ~ has a sing~e current carrying, stranded .
i6~
conduct.or 2. A ~ayer 3 of semi-cond~cting material i5 ex-truded o~er the conductor Z. A layer 4 of polymeric in-sulating material is extruded over the layer 3 of semi-conducting material and a layer 5 of high permittivity mat-5 erial, that is a material with a relative permittivity ofat least. 15 and preferably for example 20 to 30, or even more, is extruded over the layer 4 of insulating material.
All three extruded layers 3,4 and 5 extend the whole length of the conduct.or 2 and t.he insulating layer 4 is bonded to 1~ the layers 3 and j on each side of it. The three layers 3,4 and 5 may be co-extruded or extruded in separate oper-ations on t.he cable length.
In order to fulfil its functions of preventing elec-trical discharges the high permittivity layer 5 is covered ~5 with semi-conducting tape 6 which is lapped or longitudin-ally wrapped around the high permittivity layer 5 in con-tact with the outer surface thereof. The semi-conducting tape 6 may include a desi~cant. Whilst it is preferable that the entire surface of the high permittivity layer be ~0 contacted by the semi-conducting tape small breaks in such contact will not give rise to electrical discharges because of the high permittivity of the layer. A convent-ional metallic earth screen 7 is provided over the semi-conducting tape and an outer plastics sheath 8 is provided over the screen 7.
~ 'hen making a Joint or termination the semi-conduc-ting tape 6 over the high permittivity layer 5 is stripped back by simple unwinding or unwrapping thereof to the termination of the earth screen 7, but since the high permittivity layer 5 will carry negligble current if left in a position at a joint or termination, it does not have to be stripped from the insulation layer 4. This not only simplifies jointing and terminating operations and eliminates the possibility of damage to the insulation layer's outer surface but also assists stress distribution ~ 26 within the joint or termination as the high permittivity layer tends t,o reduce the surface gradient at the earth screen terminat,ion.
An example of a suitable high permittivity material j is nitrile rubber containing anatase.
~LZ~
-2a-ln order that the invention may be well understood an embodimen~ t~hereof, hhich is given by h~ay of example only,h~ no~ be described ~ith reference to the accom-pan~ing drawing in ~hich the single figure schematica]ly shohs in radial cross-section a high ~oltage electric cable. Referring to the figure, the high voltage ~lectric cable ~ has a sing~e current carrying, stranded .
i6~
conduct.or 2. A ~ayer 3 of semi-cond~cting material i5 ex-truded o~er the conductor Z. A layer 4 of polymeric in-sulating material is extruded over the layer 3 of semi-conducting material and a layer 5 of high permittivity mat-5 erial, that is a material with a relative permittivity ofat least. 15 and preferably for example 20 to 30, or even more, is extruded over the layer 4 of insulating material.
All three extruded layers 3,4 and 5 extend the whole length of the conduct.or 2 and t.he insulating layer 4 is bonded to 1~ the layers 3 and j on each side of it. The three layers 3,4 and 5 may be co-extruded or extruded in separate oper-ations on t.he cable length.
In order to fulfil its functions of preventing elec-trical discharges the high permittivity layer 5 is covered ~5 with semi-conducting tape 6 which is lapped or longitudin-ally wrapped around the high permittivity layer 5 in con-tact with the outer surface thereof. The semi-conducting tape 6 may include a desi~cant. Whilst it is preferable that the entire surface of the high permittivity layer be ~0 contacted by the semi-conducting tape small breaks in such contact will not give rise to electrical discharges because of the high permittivity of the layer. A convent-ional metallic earth screen 7 is provided over the semi-conducting tape and an outer plastics sheath 8 is provided over the screen 7.
~ 'hen making a Joint or termination the semi-conduc-ting tape 6 over the high permittivity layer 5 is stripped back by simple unwinding or unwrapping thereof to the termination of the earth screen 7, but since the high permittivity layer 5 will carry negligble current if left in a position at a joint or termination, it does not have to be stripped from the insulation layer 4. This not only simplifies jointing and terminating operations and eliminates the possibility of damage to the insulation layer's outer surface but also assists stress distribution ~ 26 within the joint or termination as the high permittivity layer tends t,o reduce the surface gradient at the earth screen terminat,ion.
An example of a suitable high permittivity material j is nitrile rubber containing anatase.
Claims (12)
1. An electric cable having at least one current carrying conductor provided with an extruded polymer insulating layer, over the whole length of which is an extruded layer of material having a relative permittivity of at least 15, said latter layer being covered with semi-conducting tape in contact therewith.
2. A cable as claimed in claim 1, wherein said semi-conducting tape includes a desiccant.
3. A cable as claimed in claim 1, wherein said relative permittivity is at least 20.
4. A cable as claimed in claim 3, wherein said semi-conducting tape includes a desiccant.
5. A cable as claimed in claim 1, wherein said polymeric insulating layer is extruded on to a layer of semi-conducting material which is extruded over said at least one current carrying conductor.
6. A cable as claimed in any one of claims 2, 3 and 4, wherein said polymeric insulating layer is extruded onto a layer of semi-conducting material which is extruded over said at least one current carrying conductor.
7. A method of making a joint or termination for a cable as claimed in claim 1, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
8. A method of making a joint or termination for a cable as claimed in claim 2, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
9. A method of making a joint or termination for a cable as claimed in claim 3, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
10. A method of making a joint or termination for a cable as claimed in claim 4, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
11. A method of making a joint or termination for a cable as claimed in claim 5, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable.
12. A method of making a joint or termination for a cable as claimed in claim 2, 3 or 4, including stripping back the semi-conducting tape over said layer of material having a relative permittivity of at least 15 along an end portion of the cable but not stripping said latter layer from the insulation layer of the cable, and wherein said polymeric insulating layer is extruded onto a layer of semi-conducting material which is extruded over said at least one current carrying conductor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08519967A GB2179196B (en) | 1985-08-08 | 1985-08-08 | Electric cables |
| GB8519967 | 1985-08-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266102A true CA1266102A (en) | 1990-02-20 |
Family
ID=10583522
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000514944A Expired - Lifetime CA1266102A (en) | 1985-08-08 | 1986-07-30 | Electric cables |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0212832B1 (en) |
| AT (1) | ATE72497T1 (en) |
| AU (1) | AU582259B2 (en) |
| BR (1) | BR8603745A (en) |
| CA (1) | CA1266102A (en) |
| DE (1) | DE3683813D1 (en) |
| DK (1) | DK360386A (en) |
| ES (1) | ES2000395A6 (en) |
| GB (1) | GB2179196B (en) |
| NO (1) | NO863120L (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU5686773A (en) * | 1972-06-29 | 1974-12-19 | Pirelli General Cable Works | High voltage electric cables high voltage electric cables |
| US3828115A (en) * | 1973-07-27 | 1974-08-06 | Kerite Co | High voltage cable having high sic insulation layer between low sic insulation layers and terminal construction thereof |
| US3885085A (en) * | 1974-06-11 | 1975-05-20 | Gen Cable Corp | High voltage solid extruded insulated power cables |
| US4361723A (en) * | 1981-03-16 | 1982-11-30 | Harvey Hubbell Incorporated | Insulated high voltage cables |
| EP0076579A1 (en) * | 1981-10-07 | 1983-04-13 | Cable Technology Laboratories, Inc. | Insulation shield for a high-voltage cable |
| AU5323686A (en) * | 1985-02-06 | 1986-08-14 | Raychem Corporation | High frequency attenuation cable |
| BR8600498A (en) * | 1985-02-06 | 1986-10-21 | Raychem Corp | HIGH FREQUENCY ATTENUATION CABLE AND BEAM |
-
1985
- 1985-08-08 GB GB08519967A patent/GB2179196B/en not_active Expired
-
1986
- 1986-07-14 DE DE8686305370T patent/DE3683813D1/en not_active Expired - Lifetime
- 1986-07-14 AT AT86305370T patent/ATE72497T1/en active
- 1986-07-14 EP EP86305370A patent/EP0212832B1/en not_active Expired - Lifetime
- 1986-07-29 DK DK360386A patent/DK360386A/en not_active Application Discontinuation
- 1986-07-30 CA CA000514944A patent/CA1266102A/en not_active Expired - Lifetime
- 1986-07-31 AU AU60755/86A patent/AU582259B2/en not_active Ceased
- 1986-08-01 NO NO863120A patent/NO863120L/en unknown
- 1986-08-06 BR BR8603745A patent/BR8603745A/en not_active IP Right Cessation
- 1986-08-07 ES ES8601530A patent/ES2000395A6/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BR8603745A (en) | 1987-03-10 |
| NO863120L (en) | 1987-02-09 |
| ES2000395A6 (en) | 1988-02-16 |
| EP0212832A3 (en) | 1988-12-28 |
| GB8519967D0 (en) | 1985-09-18 |
| NO863120D0 (en) | 1986-08-01 |
| AU6075586A (en) | 1987-02-12 |
| DE3683813D1 (en) | 1992-03-19 |
| AU582259B2 (en) | 1989-03-16 |
| GB2179196A (en) | 1987-02-25 |
| EP0212832A2 (en) | 1987-03-04 |
| DK360386D0 (en) | 1986-07-29 |
| DK360386A (en) | 1987-02-09 |
| GB2179196B (en) | 1989-01-11 |
| ATE72497T1 (en) | 1992-02-15 |
| EP0212832B1 (en) | 1992-02-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |