Wet Design High Voltage Submarine Field and Repair Joint

Abstract

A joint assembly for two high voltage submarine cables (20, 30) of wet or semi wet design includes a water permeable enclosure (10) for receiving the two cables (20, 30) at opposite ends (16, 17) of the enclosure, and at least one joint unit (40, 50, 60) within said enclosure. Each joint unit connects corresponding phase conductors of each of the two cables (20, 30). A method of joining two three-phase high voltage submarine cables (20, 30) and a wet design electrical subsea pre-molded joint (100).

Claims

1. A pre-molded joint comprising: a tubular first layer made of a semiconducting material; a second layer made of an insulating material surrounding the outer surface of the first layer; and a third layer made of a semiconducting material surrounding the outer surface of the second layer wherein said first layer defines a tubular chamber suitable for surrounding an electrical joint between two cable conductors; and
wherein at least one of the layers of the joint are water permeable.

2. The pre-molded joint according to of claim 1, wherein all the layers of the joint are water permeable.

3. The pre-molded joint according to of claim 1, wherein the interface between said third layer and said second layer has a curved profile.

4. The pre-molded joint according to claim 1, wherein each of the layers comprises a same elastomeric material, selected from the group consisting of ethylene propylene diene monomer (EPDM), crosslinked polyethylene (XLPE), and silicon rubber.

5. A joint assembly for joining two high voltage submarine cables of wet or semi-wet design, comprising: a water permeable enclosure for receiving the two cables at opposite ends of the enclosure, and at least one joint unit within said enclosure.

6. The joint assembly according to claim 5, wherein the at least one joint unit is water permeable.

7. The joint assembly according to claim 5, wherein each cable is a three-phase high voltage submarine cables, and the joint assembly comprises at least three joint units, each joint unit for connecting corresponding phase conductors of each of the two cables.

8. The joint assembly according to claim 5, wherein the enclosure comprises two bend guides located at the opposite ends of the enclosure.

9. The joint assembly according to claim 5, wherein the enclosure comprises at least one aperture to facilitate flooding.

10. A joint assembly for joining two high voltage submarine cables of wet or semi-wet design, comprising: a water permeable enclosure for receiving the two cables at opposite ends of the enclosure, and at least one joint unit within said enclosure, wherein each of the joint units are a pre-molded joint according to claim 1.

11. A method for joining two high voltage submarine cables of wet or semi-wet design, the method comprising the steps of: a) providing the two cables; b) providing a joint assembly comprising a water permeable enclosure for receiving a connecting end section of each of the two cables at opposite ends of the enclosure, and at least a joint unit arranged within the enclosure, each joint unit for connecting corresponding phase conductors of each of the two cables; c) joining the corresponding phase conductors of each of the two cables using the at least a joint unit.

12. The method according to claim 11, wherein the joint assembly is a joint assembly according to claim 5.

13. The method according to claim 11, further comprising a step of lowering the joint assembly under water, after step c), such that the enclosure is flooded with water.

14. The cable joint comprising two high-voltage submarine cables, and a joint assembly according to claim 5.

15. The cable joint according to claim 14, wherein the joint assembly and/or the two high-voltage cables are fully saturated with water.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In the following description this invention will be further explained by way of exemplary embodiments shown in the drawings:

[0070] FIG. 1 shows a longitudinal cross-section of a pre-molded joint according to the first aspect of the invention.

[0071] FIG. 2 shows a longitudinal cross-section of a joint made with a pre-molded joint according to the first aspect of the invention.

[0072] FIG. 3 is a cross-sectional view of the joint assembly.

[0073] FIG. 4 is a front side view of the joint assembly.

[0074] FIG. 5 is an enlarged cross-sectional view of T-connectors assembled for use in a specific embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

[0075] FIG. 1 shows a longitudinal cross-section of a pre-molded joint 100 of the invention. This pre-molded joint 100 is double-ended to connect two electrical cables together.

[0076] The pre-molded joint 100 comprises [0077] a first layer 102 made of a semiconducting material; [0078] a second layer 103 made of an insulating material surrounding the first layer; and [0079] a third layer 104 made of a semiconducting material surrounding the second layer wherein said first layer define a chamber 110 suitable for surrounding an electrical joint between two cable conductors.

[0080] To make a cable joint, the end section of a first cable 120 is prepared for joining by stripping off the various layers (the semiconducting first layer 122, the insulation second layer 123 and the outer semiconductive third layer 124, obtaining a connecting end section of the cable 120 suitable for connecting to another connecting end section of a second cable 130, prepared in the same way. The pre-molded joint 100 is slided on one of the end section of the cables 120, 130.

[0081] The stripped conductor end 121, 131 of both cables are then connected using known techniques, such as pressing, welding or screwing the conductors ends 121,131 together, possibly using a connection ferrule, forming a conductor joint 125. The pre-molded joint is then slided over the conductor joint 125, so that the first layer 102 made of a semiconducting material covers the conductor joint. Further so that the second layer 103 made of an insulating material covers at least part of the insulation second layer 123, 133 and so that the third layer 104 made of a semiconducting material covers at least part of the outer semiconductive third layer 124 and is in electrical contact therewith.

[0082] To speed up the installation of the joint techniques based on welding may be avoided and a connection ferrule may be preferred as conductor joint.

[0083] The cross-section of the resulting joint is shown in FIG. 2.

[0084] According to the invention, the semiconducting layer 102 is surrounded by an insulating layer 103 surrounded itself by a second semiconducting layer 104.

[0085] The second semiconducting layer 104 extends all along the chamber 110 while the insulating layer 103 acting as insulating means and the first semiconducting layer 102 extend partially along the chamber 110.

[0086] The interface between insulating layer 104 and semiconducting layer 104 has a curved profile in order to prevent electrical breakdown. The curved profile of the interface has the same stress relieving effect as a deflector in a stress relief cone. Layers 102, 103 and 104 are moulded together in one single element 100 and can be made of a same elastomeric material, typically ethylene propylene diene monomer (EPDM), crosslinked polyethylene (XLPE) or silicon rubber except that the material used for layers 102 and 104 is also doped, for example with carbon black. Alternatively layers 102, 103 and 104 can be made of the same materials as at least one of the cable 120.

[0087] For transition joints, that is to say joints between two cables of different diameters, the pre-molded joint may be designed to so that each half of the chamber 110 has a cross-section matching the cross sections of each cable.

[0088] An exemplary joint assembly according to the invention is shown in FIG. 3. The joint assembly, comprises a first submarine three-phase power cable 20, a second submarine three-phase power cable 30. First cables 20 and second cable 30, may be two part of a damaged three-phase power cables that was damaged or broken and needs to be repaired. What is done at this point in the system is to electrically connect each phase 40,50,60 of the three-phase cable 20 to each corresponding phase 40,50, 60 of cable 30. This takes place inside an enclosure 10 shown in FIG. 3, FIGS. 4 and 5. The enclosure 10 may advantageously comprise at least one aperture 70 in order to ease the flooding of the enclosure 10. The at least one aperture 70 may be a hole or a slit. The enclosure 10 will be flooded when placed under the sea level. Before entering enclosure 10, the cables 20,30 may be each surrounded by a bend guide 21,31, respectively, according to known methods, as shown on FIG. 3. Alternatively, a bend restrictor or bend stiffener 23,33 may be used. Moreover, lead-in means 22,32 for entry of each cable into the enclosure may be provided, as shown on FIG. 5, also as known per se. Preferably, the lead-ins 22,32 are not sealed in a water-tight manner to the enclosure, such that water may easily enter the enclosure when submerged in water.

[0089] In the drawings the at least one aperture 70 are round holes, in alternative embodiments, the apertures may be of any shape or form or combination thereof, such as slits, provided the enclosure may be easily flooded with water when submerged in water.

[0090] The at least one aperture 70 may be spaced along the circumference of the enclosure, arranged close to each of the two ends of the enclosure etc. in order to achieve optimal flooding of the enclosure.

[0091] In FIGS. 3 and 4 the enclosure 10 is exemplified as being made of two cylinders connected at their end by a flange. In other embodiments, the enclosure 10 may be in any suitable shape or form, such as any type of splitable or openable box, such as a square box or a cylindrical box, for ease of access for installation of power cables.

[0092] The joint unit may advantageously be the pre-molded joint shown in FIGS. 1-2.

[0093] Another embodiment of the assembly 1 where the joint units 40,50,60 are couples of T-connectors is shown more detailed in FIG. 5.

[0094] As will be seen from FIG. 5, T-connectors are directly attached to one another by plugging together at their upper or transverse legs with a through-running electrically conductive path comprising conducting elements. In this manner conductors belonging to cable phases, are connected together.

[0095] The T-connectors are oriented so as to be opposed to each other 180 degrees along the axis between the two ends 16,17 of the enclosure 10 i.e. more or less in parallel to the direction of cables 20,30 when entering the enclosure, possibly through bend guides 21,31 and/or lead-ins 22,32.

[0096] Lead-ins 22,32 may be provided at both end or side wall 16,17 of enclosure 10. On a side wall there may be provided lifting means (not shown), for example in the form of an eye structure making possible deployment as well as retrieval of the whole assembly with power cables 20,30 connected thereto. It will be understood that depending on water depth at the site of installation, there may be a quite considerable weight to be carried by lifting eye during such operations. In many cases it may be considered advantageous to have the dimensions of enclosure 10 to be largest in a direction between the end or side walls 16 and 17.