Electric power cable

1. An electric power dynamic sea cable ( 1 ), comprising:

at least one cable core ( 3 ) comprising a conductor ( 2 ), an electric insulation ( 6 ) surrounding the conductor ( 2 ), and a water barrier comprising a protective sheath ( 7 ) surrounding the electric insulation ( 6 ),

at least one outer layer ( 8 ) surrounding the at least one cable core ( 3 ), and

at least one friction reducing layer ( 9 ) surrounding the at least one cable core ( 3 ), wherein

the at least one friction reducing layer ( 9 ) comprises a wound layer of a polymer tape,

at least one surface ( 10 ) of the at least one friction reducing layer ( 9 ) has a friction coefficient in an interval of 0.1-0.3,

the at least one friction reducing layer ( 9 ) is at least partially arranged between the water barrier ( 7 ) and the at least one outer layer ( 8 ),

the at least one friction reducing layer ( 9 ) and the at least one outer layer ( 8 ) are not bonded or interlocked with one another, and

the at least one friction reducing layer ( 9 ) and the water barrier ( 7 ) are not bonded or interlocked with one another, such that

sliding movement between the water barrier ( 7 ) and the at least one outer layer ( 8 ) occurs upon bending of the cable ( 1 ) beyond a threshold and prevents transferring bending force of the at least one outer layer ( 8 ) to the water barrier ( 7 ).

2. The electric power dynamic sea cable according to claim 1 , wherein the water barrier comprises a corrugated metallic sheath.

3. The electric power dynamic sea cable according to claim 1 , wherein the at least one friction reducing layer is completely arranged between the water barrier of the at least one cable core and the at least one outer layer.

4. The electric power dynamic sea cable according to claim 1 , wherein the at least one cable core comprises three parallel cable cores and the friction reducing layer surrounds the three cable cores.

5. The electric power dynamic sea cable according to claim 1 , further comprising:

a cable core binder surrounding the at least one cable core, wherein the friction reducing layer is arranged radially outside the cable core binder.

6. The electric power dynamic sea cable according to claim 1 , wherein the at least one cable core comprises three parallel cable cores and wherein the friction reducing layer is arranged radially outside each cable core.

7. The electric power dynamic sea cable according to claim 1 , wherein the polymer tape comprises at least one of the following: polypropylene, high density polyethylene, Teflon, silicone or polyester.

8. The electric power dynamic sea cable according to claim 1 , wherein the friction reducing layer has a thickness in an interval 0.01-1 mm.

9. The electric power dynamic sea cable according to claim 8 , wherein the friction reducing layer has a thickness in an interval 0.05-0.3 mm.

10. The electric power dynamic sea cable according to claim 1 , wherein the polymer tape is an extruded tape.

11. The electric power dynamic sea cable according to claim 1 , wherein the at least one cable core further comprises an inner conducting layer arranged between the conductor and the electric insulation and an outer conducting layer outside the electric insulation.

12. The electric power dynamic sea cable according to claim 1 , wherein the electric power dynamic sea cable comprises a plurality of cable cores, the electric power dynamic sea cable further comprising:

an outer friction reducing layer surrounding all of the cable cores;

a binder layer surrounding the outer friction reducing layer;

an armor layer surrounding the binder layer; and

an outer jacket surrounding the armor layer.

13. An off-shore installation ( 21 ) comprising:

an electric power dynamic sea cable ( 1 ) extending freely in the sea between two fixing points ( 22 , 23 ), wherein the electric power dynamic sea cable ( 1 ) comprises at least one cable core ( 3 ) comprising a conductor ( 2 ), an electric insulation ( 6 ) surrounding the conductor ( 2 ), and a water barrier comprising a protective sheath ( 7 ) surrounding the electric insulation ( 6 ),

at least one outer layer ( 8 ) surrounding the at least one cable core ( 3 ), and

at least one friction reducing layer ( 9 ) surrounding the at least one cable core ( 3 ), wherein

the at least one friction reducing layer ( 9 ) comprises a wound layer of a polymer tape,

at least one surface ( 10 ) of the at least one friction reducing layer ( 9 ) has a friction coefficient in an interval of 0.1-0.3,

the at least one friction reducing layer ( 9 ) is at least partially arranged between the water barrier ( 7 ) and the at least one outer layer ( 8 ),

the at least one friction reducing layer ( 9 ) and the at least one outer layer ( 8 ) are not bonded or interlocked with one another, and

the at least one friction reducing layer ( 9 ) and the water barrier ( 7 ) are not bonded or interlocked with one another, such that

sliding movement between the water barrier ( 7 ) and the at least one outer layer ( 8 ) occurs upon bending of the cable ( 1 ) beyond a threshold and prevents transferring bending force of the at least one outer layer ( 8 ) to the water barrier ( 7 ).

14. A method for transmitting electric power to an off-shore installation ( 21 ), the method comprising:

extending an electric power dynamic sea cable ( 1 ) in the sea between two fixing points ( 22 , 24 ), wherein the electric power dynamic sea cable ( 1 ) comprises at least one cable core ( 3 ) comprising a conductor ( 2 ), an electric insulation ( 6 ) surrounding the conductor ( 2 ), and a water barrier comprising a protective sheath ( 7 ) surrounding the electric insulation ( 6 ),

at least one outer layer ( 8 ) surrounding the at least one cable core ( 3 ), and

at least one friction reducing layer ( 9 ) surrounding the at least one cable care ( 3 ), wherein

the at least one friction reducing layer ( 9 ) comprises a wound layer of a polymer tape,

at least one surface ( 10 ) of the at least one friction reducing layer 9 ) has a friction coefficient in an interval of 0.1-0.3,

the at least one friction reducing layer ( 9 ) is at least partially arranged between the water barrier ( 7 ) and the at least one outer layer ( 8 ),

the at least one friction reducing layer ( 9 ) and the at least one outer layer ( 8 ) are not bonded or interlocked with one another, and

the at least one friction reducing layer ( 9 ) and the water barrier ( 7 ) are not bonded or interlocked with one another, such that

sliding movement between the water barrier ( 7 ) and the at least one outer layer ( 8 ) occurs upon bending of the cable ( 1 ) beyond a threshold and prevents transferring bending force of the at least one outer layer ( 8 ) to the water barrier ( 7 ).

15. An electric power dynamic sea cable ( 1 ), comprising:

three cable cores ( 3 , 4 , 5 ), each said cable, core ( 3 , 4 , 5 ) comprising a conductor ( 2 ), an electric insulation ( 6 ) surrounding the conductor ( 2 ), and a water barrier comprising a protective, sheath ( 7 ) surrounding the electric insulation ( 6 ),

an outer friction reducing layer ( 9 ) surrounding said three cable cores ( 3 , 4 , 5 ),

a binder layer ( 14 ) surrounding the outer friction reducing layer ( 9 ),

an armor layer ( 17 ) surrounding the binder layer ( 14 ),

an outer jacket ( 18 ) surrounding the armor layer ( 17 ), and

filler profiles ( 13 ) arranged between said three cable cores ( 3 , 4 , 5 ), with the outer friction reducing layer ( 9 ) also surrounding the filler profiles ( 13 ), wherein

the outer friction reducing layer ( 9 ) comprises a wound layer of a polymer tape,

at least one surface ( 10 ) of the at least one friction reducing layer ( 9 ) has a friction coefficient in an interval of 0.1-0.3, and

the outer friction reducing layer ( 9 ) is at least partially arranged between the water barrier ( 7 ) and the binder layer ( 14 ).