Electrical cable comprising a filling compound

Abstract

An electrical cable (100, 101) includes at least one elongated electrical conductor (1), at least one protective element (4, 41, 42) surrounding the elongated electrical conductor (1), and at least one filling compound (5) surrounded by said protective element (4, 41, 42). The filling compound (5) has more than 20.0% by weight of a mineral oil, relative to the total weight of the filling compound, and at least one nanofiller.

Claims

1. Electrical cable comprising: at least one elongated electrical conductor, at least one protective element surrounding said elongated electrical conductor, and at least one filling compound surrounded by said protective element, wherein the filling compound comprises: more than 20.0% by weight of a mineral oil, relative to the total weight of the filling compound, and at least one nanofiller.

2. Cable according to claim 1, wherein the filling compound comprises more than 50.0% by weight of mineral oil, and preferably at least 60.0% by weight of mineral oil, relative to the total weight of the filling compound.

3. Cable according to claim 1, wherein the filling compound comprises less than 50.0% by weight of nanofiller, and preferably at most 40.0% by weight of nanofiller, relative to the total weight of the filling compound.

4. Cable according to claim 1, wherein the viscosity of the filling compound is at least 100 Pa.Math.s, determined at 100 C. according to standard ASTM D 4440.

5. Cable according to claim 1, wherein the mineral oil is chosen from naphthenic oils, paraffinic oils, and mixtures thereof.

6. Cable according to claim 1, wherein at least one of the dimensions of the nanofiller is at most 2000 nm, and preferably at most 1000 nm.

7. Cable according to claim 1, wherein the nanofiller is a treated filler.

8. Cable according to claim 1, wherein the nanofiller is a silanized filler.

9. Cable according to claim 1, wherein the nanofiller has a specific surface area (BET) of at least 70 m.sup.2/g, and preferably of at least 100 m.sup.2/g.

10. Cable according to claim 1, wherein the nanofiller is a mineral filler, preferably chosen from alkaline-earth metal carbonates, alkaline-earth metal sulfates, metal oxides, metalloid oxides, metal silicates, and siloxanes.

11. Cable according to claim 1, wherein said cable also comprises an insulating element (2) surrounded by the protective element.

12. Cable according to claim 11, wherein the insulating element comprises at least one propylene polymer.

13. Cable according to claim 11, wherein the filling compound is in direct physical contact with the insulating element.

14. Cable according to claim 1, wherein the protective element is chosen from a polymeric layer, a metallic layer, and a combination thereof.

15. Cable according to claim 1, wherein the cable is a remotely operated submersible vehicle cable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0101] FIG. 1 represents a schematic view of an electrical cable according to a first particular embodiment in accordance with the invention.

[0102] FIG. 2 represents a schematic view of an electrical cable according to a second particular embodiment in accordance with the invention.

DETAILED DESCRIPTION

[0103] For reasons of clarity, only the elements essential for understanding the invention have been represented schematically, without being to scale.

[0104] FIG. 1 represents an electrical cable 100 according to a first particular embodiment of the invention.

[0105] The electrical cable 100 comprises several elongated electrical conductors 1, each of said elongated electrical conductors 1 being surrounded by at least one electrically insulating layer 2, thus forming insulated electrical conductors 3.

[0106] The assembly of the insulated electrical conductors 3 is surrounded by a protective element 4 of the extruded polymeric layer type.

[0107] A filling compound 5 according to the invention is positioned inside the zone delimited by the protective element 4, and in particular in the gaps or voids between the various insulated electrical conductors 3. The protective element 4 therefore surrounds the filling compound 5.

[0108] FIG. 2 represents an electrical cable 101 according to a second particular embodiment of the invention.

[0109] The electrical cable 101 is in particular a remotely operated vehicle cable, and comprises a first assembly 31 of insulated electrical conductors 3, this first assembly 31 being surrounded by a separation layer 6. The separation layer 6 comprises a polymeric layer of a propylene polymer, surrounded by a metallic layer of the wound copper layer type. The metallic layer of the separation layer 6 is a metallic screen used to ground the first assembly 31.

[0110] The electrical cable also comprises a second assembly 32 of insulated electrical conductors 3, this second assembly 32 being positioned around said first assembly 31.

[0111] The electrical cable also comprises a protective element, said protective element surrounding the first assembly 31 of insulated electrical conductors, the second assembly 32 of insulated electrical conductors, and the separation layer 6.

[0112] The protective element comprises a first polymeric layer 41 of the polyester thermoplastic layer type, surrounded by a first metallic layer 42 comprising a plurality of steel conductors, preferably helically twisted together.

[0113] The protective element may also comprise a second metallic layer (not represented) of the wound copper layer type, surrounded by the first polymeric layer 41. Said second metallic layer of the protective layer is a metallic screen used to ground the second assembly 32.

[0114] The protective element may also comprise a second polymeric layer (not represented) of the wound polyurethane layer type, surrounding the first metallic layer 42.

[0115] The electrical cable may also comprise non-insulated electrical conductors (not represented), termed grounding conductors, positioned in the first assembly and in the second assembly.

[0116] A filling compound 5 according to the invention is positioned inside the zone delimited by the protective element, and in particular in the gaps or voids between the various insulated and non-insulated electrical conductors of the first assembly 31 and of the second assembly 32. The protective element, composed at least of the layers 41 and 42, thus surrounds the filling compound 5.

Examples

[0117] 1. Preparation of a Filling Compound According to the Invention

[0118] A filling compound (I1) in accordance with the invention is prepared with the following constituents:

[0119] 73% by weight of mineral oil, and

[0120] 27% by weight of nanofiller,

the percentages (%) by weight being expressed relative to the total weight of the filling compound.

[0121] The origin of the constituents described in the example above is the following:

[0122] the mineral oil is a mineral oil of naphthenic type sold by the company Nynas under the reference Nyflex 820, the oil comprising 7% of aromatic carbon atoms, 40% of naphthenic carbon atoms and 53% of paraffinic carbon atoms; and

[0123] the nanofiller is silicon oxide particles surface-treated with dimethyl dichlorosilane (DDS), sold by the company Aerosil under the reference Aerosil R 974, this nanofiller having the following characteristics: spherical elementary particles with an aspect ratio substantially equal to 1, the diameter of which is less than 100 nm, and the specific surface area (BET) of which is 17020 m.sup.2/g.

[0124] The filling compound I1 is prepared by mixing the nanofiller with the mineral oil, in a mixer, at ambient temperature (25 C.), for approximately 5 minutes at a speed of approximately 2200 revolutions per minute.

[0125] 2. Characterizations

[0126] In order to study the viscosity of the filling compound of the invention, tests are prepared with the compound I1, and with a comparative filling compound (C1) of the hot-melt adhesive type. The hot-melt adhesive used is that sold by the company Henkel under the reference Technomelt PS 8673L.

[0127] In this respect, discs of compounds I1 and C1, with a radius of 25 mm and a thickness of approximately 2 mm, are formed using a mould.

[0128] The viscosity of the compounds I1 and C1 is determined according to standard ASTM D 4440 using a dynamic viscometer in plate-plate configuration under a frequency of 50 Hz, with a deformation of 5% and a temperature gradient of 5 C./min.

[0129] The viscosity results in pascal second (Pa.Math.s) are collated in Table 1 below, as a function of the temperature in C.

TABLE-US-00001 TABLE 1 40 C. 50 C. 60 C. 70 C. 80 C. 90 C. 100 C. I1 423 415 397 372 338 316 326 C1 770 498 417 394 377 337 294

[0130] In order to study the breakdown strength of an insulating layer in contact with the filling compound, the following tests are prepared:

[0131] Test 1 (test according to the invention): an insulating layer in contact with the compound I1,

[0132] Test 2 (comparative test): an insulating layer in contact with the compound C1, and

[0133] Test 3 (comparative test): an insulating layer alone, the insulating layer being a layer of a propylene copolymer sold by Borealis under the reference PP4821.

[0134] In this respect, about ten sheets of the insulating layer alone (i.e. layer of a propylene copolymer according to Test 3), 75 mm in diameter and 500 m thick, are formed for each test (in order to verify the repeatability of the results regarding the breakdown measurements).

[0135] For Test 1, 10 grams of compound I1 are deposited on each face of the insulating layer of Test 3.

[0136] For Test 2, 10 grams of compound C1 are deposited on each face of the insulating layer of Test 3.

[0137] Thus, Tests 1 and 2 comprise a trilayer (i.e. the insulating layer of Test 3 sandwiched between two layers of the compound I1 or C1). The trilayers of Test 1 and of Test 2 are placed in an oven under 100 C. for 10 days.

[0138] The two layers of compound I1 and the two layers of compound C1 are then removed from the trilayers in question, after the 10 days. The breakdown strength is then measured on the residual insulating layer of Test 1 and on the residual insulating layer of Test 2.

[0139] With regard to Test 3, the sheet of insulating layer alone, which does not comprise compound I1 or C1, is not placed in the oven, and the breakdown strength is directly measured on about ten of these sheets.

[0140] The breakdown (dielectric) strength of Tests 1 to 3 is determined according to standard ASTM D 149 by means of an alternating current breakdown bench.

[0141] The results are collated in Table 2 below.

TABLE-US-00002 TABLE 2 Test 1 Test 2 Test 3 Alternating current dielectric breakdown 98 78 89 strength (expressed in kV/mm) at 25 C.