EP0212832B1 - Electric cable jointing or terminating method - Google Patents
Electric cable jointing or terminating method Download PDFInfo
- Publication number
- EP0212832B1 EP0212832B1 EP86305370A EP86305370A EP0212832B1 EP 0212832 B1 EP0212832 B1 EP 0212832B1 EP 86305370 A EP86305370 A EP 86305370A EP 86305370 A EP86305370 A EP 86305370A EP 0212832 B1 EP0212832 B1 EP 0212832B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- semi
- conducting
- electric cable
- over
- 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
Definitions
- This invention relates to a method of making an electric cable termination or joint.
- 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- conducting layer is to prevent electrical discharges occurring due to voids being 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 allowed to form a path between the current carrying conductor and earth in the joint or termination. Removal of the semi-conducting layer over the insulating layer therefrom is a difficult operation which involves the risk of damage being caused to the insulation layer.
- the present invention seeks an alternative solution in which the semi-conducting layer over the insulating layer is replaced by an alternative layer which can be readily extruded over the insulating layer but which does not have to be removed during jointing or terminating.
- GB-A-2095024 there is disclosed an electric cable in which respective layers of material having a relative permittivity which is higher than the relative permittivity of the insulating layer are provided under and over the insulating layer in order to reduce dielectric losses.
- EP-A-0076579 discloses an electric cable having at least one current carrying conductor provided with an extruded insulating layer, over the whole length of which is applied a layer of material having a relative permittivity which is higher than the relative permittivity of the material of the first-mentioned layer, the second mentioned layer being covered with a semi-conducting tape in contact therewith.
- EP-A-0076579 is a method of making a cable termination with such a cable which method includes stripping back the semi-conducting tape along an end portion of the cable.
- the semi-conducting tape is removed prior to cable termination most of the second-mentioned layer is removed with it and to this end the second-mentioned layer adheres strongly to the tape and modestly to the first-mentioned layer and preferably comprises a paint-type material which is applied by spraying, dipping, washing or wiping although it may comprise a material which is extruded over the first-mentioned layer.
- the present invention provides an electric cable termination or joint including: (a) providing an electric cable having at least one current carrying conductor provided with an extruded polymeric insulating layer, over the whole length of which is an extruded layer of a material having a relative permittivity which is higher than the relative permittivity of the material of the first-mentioned layer, the second-mentioned layer being covered with a semi-conducting tape in contact therewith; and (b) stripping back the semi-conducting tape along an end portion of the cable; characterised in that the relative permittivity of the material of said second layer is at least 15 and in that none of said second-mentioned layer exposed by the stripping back of said tape is stripped from said first-mentioned layer.
- the embodiment comprises a method of making an electrical termination or joint with a high voltage electric cable having: a single current carrying conductor; a layer of semi-conducting material extruded over the conductor; a layer of polymeric insulating material extruded over the layer of semi-conducting material; and a layer of high permittivity material, that is a material with a relative permittivity of at least 15 and preferably for example 20 to 30, or even more, extruded over the layer of insulating material. All three extruded layers extend the whole length of the conductor and the insulating layer is bonded to the layers on each side of it. The three layers may be co-extruded or extruded in separate operations on the cable length.
- the high permittivity layer is covered with semi-conducting tape which is lapped or longitudinally wrapped around the high permittivity layer in contact with the outer surface thereof.
- the semi-conducting tape may include a dessicant. Whilst it is preferable that the entire surface of the high permittivity layer be 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 conventional metallic earth screen is provided over the semi-conducting tape.
- the semi-conducting tape over the high permittivity layer is stripped back by simple unwinding or unwrapping thereof to the termination of the earth screen, but since the high permittivity layer will carry negligible current if left in a position at a joint or termination, it does not have to be stripped from the insulation layer. 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 within the joint or termination as the high permittivity layer tends to reduce the surface gradient at the earth screen termination.
- An example of a suitable high permittivity material is nitrile rubber containing anatase.
Abstract
Description
- This invention relates to a method of making an electric cable termination or joint.
- 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- conducting layer is to prevent electrical discharges occurring due to voids being 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 allowed to form a path between the current carrying conductor and earth in the joint or termination. Removal of the semi-conducting layer over the insulating layer therefrom is a difficult operation which involves the risk of damage being caused to the insulation layer.
- To avoid this problem, it has been proposed to provide over the whole length of the insulation layer a layer of highly resistive material whose resistance is voltage dependent instead of a semi-conducting layer since such a voltage dependent resistive layer does not have to be removed during jointing or termination. However, this solution suffers from the disadvantage that material with the appropriate voltage dependent resistivity is not suitable for application by conventional extrusion equipment.
- The present invention seeks an alternative solution in which the semi-conducting layer over the insulating layer is replaced by an alternative layer which can be readily extruded over the insulating layer but which does not have to be removed during jointing or terminating.
- In GB-A-2095024 there is disclosed an electric cable in which respective layers of material having a relative permittivity which is higher than the relative permittivity of the insulating layer are provided under and over the insulating layer in order to reduce dielectric losses.
- EP-A-0076579 discloses an electric cable having at least one current carrying conductor provided with an extruded insulating layer, over the whole length of which is applied a layer of material having a relative permittivity which is higher than the relative permittivity of the material of the first-mentioned layer, the second mentioned layer being covered with a semi-conducting tape in contact therewith.
- Also disclosed in EP-A-0076579 is a method of making a cable termination with such a cable which method includes stripping back the semi-conducting tape along an end portion of the cable. When the semi-conducting tape is removed prior to cable termination most of the second-mentioned layer is removed with it and to this end the second-mentioned layer adheres strongly to the tape and modestly to the first-mentioned layer and preferably comprises a paint-type material which is applied by spraying, dipping, washing or wiping although it may comprise a material which is extruded over the first-mentioned layer.
- The present invention provides an electric cable termination or joint including: (a) providing an electric cable having at least one current carrying conductor provided with an extruded polymeric insulating layer, over the whole length of which is an extruded layer of a material having a relative permittivity which is higher than the relative permittivity of the material of the first-mentioned layer, the second-mentioned layer being covered with a semi-conducting tape in contact therewith; and (b) stripping back the semi-conducting tape along an end portion of the cable; characterised in that the relative permittivity of the material of said second layer is at least 15 and in that none of said second-mentioned layer exposed by the stripping back of said tape is stripped from said first-mentioned layer.
- In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described
The embodiment comprises a method of making an electrical termination or joint with a high voltage electric cable having: a single current carrying conductor; a layer of semi-conducting material extruded over the conductor; a layer of polymeric insulating material extruded over the layer of semi-conducting material; and a layer of high permittivity material, that is a material with a relative permittivity of at least 15 and preferably for example 20 to 30, or even more, extruded over the layer of insulating material. All three extruded layers extend the whole length of the conductor and the insulating layer is bonded to the layers on each side of it. The three layers may be co-extruded or extruded in separate operations on the cable length. - In order to fulfil its functions of preventing electrical discharges the high permittivity layer is covered with semi-conducting tape which is lapped or longitudinally wrapped around the high permittivity layer in contact with the outer surface thereof. The semi-conducting tape may include a dessicant. Whilst it is preferable that the entire surface of the high permittivity layer be 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 conventional metallic earth screen is provided over the semi-conducting tape.
- When making a joint or termination the semi-conducting tape over the high permittivity layer is stripped back by simple unwinding or unwrapping thereof to the termination of the earth screen, but since the high permittivity layer will carry negligible current if left in a position at a joint or termination, it does not have to be stripped from the insulation layer. 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 within the joint or termination as the high permittivity layer tends to reduce the surface gradient at the earth screen termination.
- An example of a suitable high permittivity material is nitrile rubber containing anatase.
Claims (1)
- A method of making an electric cable termination or joint including: (a) providing an electric cable having at least one current carrying conductor provided with an extruded polymeric insulating layer, over the whole length of which is an extruded layer of a material having a relative permittivity which is higher than the relative permittivity of the material of the first-mentioned layer, the second-mentioned layer being covered with a semi-conducting tape in contact therewith; and (b) stripping back the semi-conducting tape along an end portion of the cable; characterised in that the relative permittivity of the material of said second layer is at least 15 and in that none of said second-mentioned layer exposed by the stripping back of said tape is stripped from said first-mentioned layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT86305370T ATE72497T1 (en) | 1985-08-08 | 1986-07-14 | METHOD OF CONNECTING OR TERMINATING ELECTRICAL WIRES. |
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 (3)
| Publication Number | Publication Date |
|---|---|
| EP0212832A2 EP0212832A2 (en) | 1987-03-04 |
| EP0212832A3 EP0212832A3 (en) | 1988-12-28 |
| EP0212832B1 true EP0212832B1 (en) | 1992-02-05 |
Family
ID=10583522
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP86305370A Expired - Lifetime EP0212832B1 (en) | 1985-08-08 | 1986-07-14 | Electric cable jointing or terminating method |
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 |
|---|---|---|---|---|
| ZA734019B (en) * | 1972-06-29 | 1974-05-29 | Pirelli General Cable Works | 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 |
| BR8600498A (en) * | 1985-02-06 | 1986-10-21 | Raychem Corp | HIGH FREQUENCY ATTENUATION CABLE AND BEAM |
| BR8600492A (en) * | 1985-02-06 | 1986-10-21 | Raychem Corp | HIGH FREQUENCY ATTENUATION CABLES AND CABLE WHIP |
-
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 |
|---|---|
| DK360386A (en) | 1987-02-09 |
| BR8603745A (en) | 1987-03-10 |
| NO863120L (en) | 1987-02-09 |
| GB8519967D0 (en) | 1985-09-18 |
| EP0212832A3 (en) | 1988-12-28 |
| AU6075586A (en) | 1987-02-12 |
| EP0212832A2 (en) | 1987-03-04 |
| AU582259B2 (en) | 1989-03-16 |
| ATE72497T1 (en) | 1992-02-15 |
| DE3683813D1 (en) | 1992-03-19 |
| GB2179196A (en) | 1987-02-25 |
| NO863120D0 (en) | 1986-08-01 |
| DK360386D0 (en) | 1986-07-29 |
| CA1266102A (en) | 1990-02-20 |
| GB2179196B (en) | 1989-01-11 |
| ES2000395A6 (en) | 1988-02-16 |
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