Joints for high voltage cables insulated with impregnated paper or paper-polypropylene laminate (PPL)

Patent metadata

Field	Value
Publication number	US-9306382-B2
Application number	US-201114001789-A
Country	US
Kind code	B2
Filing date	Mar 1, 2011
Priority date	Mar 1, 2011
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A method of jointing two high voltage impregnated cables may include exposing an impregnated cable insulation layer of cable ends by removing at least one protecting layer and an outer semiconducting layer; exposing a terminal length of conductors of the cable ends by cutting a portion of the impregnated cable insulation layer and by removing an inner semiconducting layer; mechanically and electrically connecting the conductors; filling at least in part a space left by the removed impregnated cable insulation layer with a conductive insert; providing an intermediate semiconducting layer to surround the conductive insert and abutting on portions of cable insulation layers adjacent to the conductive insert; applying a stratified insulation, impregnated with a second viscous compound, overlapping the exposed impregnated cable insulation layer of the cable ends and covering the intermediate semiconducting layer; electrically screening the conductors; and tightly containing the first and/or second viscous compounds.

First claim

The invention claimed is:

1. A method of jointing two high voltage impregnated cables, each comprising a conductive core, made of a conductor wrapped in an inner semiconducting layer, a cable insulation layer, impregnated with a first viscous compound, radially external to the conductive core, an outer semiconducting layer radially external to the cable insulation layer, and at least one protecting layer radially external to the outer semiconducting layer, the method comprising:
exposing a length of the impregnated cable insulation layer of each cable end by removing the at least one protecting layer and the outer semiconducting layer;
exposing a terminal length of the conductor of each cable end by cutting essentially perpendicularly to a longitudinal axis of each cable a portion of the impregnated cable insulation layer and by removing the inner semiconducting layer;
mechanically and electrically connecting the conductors;
filling at least in part a space left by the removed impregnated cable insulation layer with a conductive insert;
providing an intermediate semiconducting layer to surround the conductive insert and abutting on portions of cable insulation layers adjacent to the conductive insert;
applying a stratified insulation, impregnated with a second viscous compound, longitudinally overlapping the exposed length of the impregnated cable insulation layer of each cable end and covering the intermediate semiconducting layer;
electrically screening the conductors; and
tightly containing the first viscous compound, the second viscous compound, or the first and second viscous compounds.

2. The method according to claim 1 , wherein the filling at least in part the space left by the removed impregnated cable insulation layer with a conductive insert comprises:
arranging a metal insert having substantially a same outer diameter as an outer diameter of the impregnated cable insulation layer.

3. The method according to claim 1 , wherein the applying the stratified insulation comprises:
providing rolls of impregnated insulation at both sides of the intermediate semiconducting layer, the rolls having substantially a same outer diameter as the intermediate semiconducting layer so as to form an even cylindrical surface.

4. The method according to claim 3 , wherein the applying the stratified insulation further comprises:
arranging at least one further layer of impregnated insulation material over the rolls of impregnated insulation and the intermediate semiconducting layer.

5. The method according to claim 1 , further comprising:
shaving the stratified impregnated insulation at longitudinal edges to obtain an even surface with a sigmoid profile.

6. The method according to claim 1 , wherein the electrically screening the conductors is carried out by wrapping the stratified insulation with a layer of semiconductive material.

7. The method according to claim 1 , further comprising:
providing a volume compensating device.

8. The method according to claim 1 , wherein the first viscous compound is the same as the second viscous compound.

9. A joint for splicing two high voltage impregnated cables comprising respective conductive cores made of conductors wrapped in inner semiconducting layers, cable insulation layers, impregnated by a first viscous compound, radially external to the conductive cores, outer semiconducting layers surrounding the cable insulation layers, and protecting layers radially external to the outer semiconducting layers, the joint having a longitudinal axis and comprising:
mechanically and electrically connected conductors;
impregnated cable insulation layers having faces cut essentially perpendicular to the longitudinal axis of the joint and being shorter than the respective conductors;
a conductive insert interposed between the faces of the impregnated cable insulation layers;
an intermediate semiconducting layer surrounding the conductive insert and abutting on portions of the cable insulation layers adjacent to the conductive insert;
a stratified insulation, impregnated with a second viscous compound, longitudinally overlapping the impregnated cable insulation layers and covering the intermediate semiconducting layer;
an external semiconducting layer wrapping the impregnated stratified insulation and the impregnated cable insulation layers;
a metal casing enclosing the external semiconducting layer and extending over the outer semiconducting layers; and
the first viscous compound, the second viscous compound, or the first and second viscous compounds contained in the metal casing.

10. The joint according to claim 9 , wherein the joint splices two high voltage direct current cables.

11. The joint according to claim 9 , wherein the conductive insert comprises a metal insert.

12. The joint according to claim 9 , wherein the intermediate semiconducting layer has edges with a tapering degree of at most 1:10.

13. The joint according to claim 9 , wherein the intermediate semiconducting layer overlaps portions of the cable insulation layers to an extent covering an interface between such layers and the conductive insert.

14. The joint according to claim 9 , wherein the impregnated stratified insulation comprises at least two rolls of wrapped sheet impregnated insulation material.

15. The joint according to claim 9 , wherein the impregnated stratified insulation comprises at least three rolls of wrapped sheet impregnated insulation material.

16. The joint according to claim 15 , wherein edges of a first roll of the at least three rolls of one layer of the impregnated stratified insulation are longitudinally offset with respect to edges of a second roll of the at least three rolls of a radially adjacent layer.

17. The joint according to claim 9 , wherein windings of stretch paper are interposed in spaces between edges of longitudinally adjacent rolls.

18. The joint according to claim 9 , further comprising:
a volume compensating device within the metal casing.

19. A power supply line comprising at least one joint according to claim 9 .

20. The joint according to claim 9 , wherein the first viscous compound is the same as the second viscous compound.

Assignees

• Ladié Pierluigi
• Ravasio Mario
• Prysmian Spa

Inventors

• Ladié Pierluigi
• Ravasio Mario

Classifications

• H02G1/14

  for joining or terminating cables · CPC title

• Y10T29/49195

  with end-to-end orienting · CPC title

• H02G15/184 Primary

  with devices for relieving electrical stress · CPC title

• H02G15/24 Primary

  Cable junctions · CPC title