Submarine power cable system with reduced losses

Abstract

To provide a submarine power cable system with reduced losses.SOLUTION: The submarine power cable system includes: a first cable section 5 in the form of a dynamic submarine power cable; and a second cable section in the form of a static submarine power cable. The first cable section has a first cable section first power core 19a including a first cable section first insulation system 19c, a first cable section first metal sheath 19d and a first electrically insulating sheath 19e. The second cable section has a second cable section first power core including a second cable section first insulation system, a second cable section first metal sheath and a first semiconducting sheath. The first cable section first metal sheath and the second cable section first metal sheath are electrically connected to each other, thereby providing a ground point of the first cable section first metal sheath.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to power cables, such as submarine power cables. [Background technology]

[0002] A power cable may comprise a power core, including a conductor and an insulation system surrounding the conductor. The insulation system may be surrounded by a metallic sheath or screen, which acts as a water barrier to protect the insulation system from water penetration if the power cable is typically a high voltage submarine cable. The metallic sheath may be covered by another polymer sheath, typically a semiconducting sheath. In longer cables, the sheath is always a semiconducting sheath.

[0003] Particularly in AC power cables, circulating and eddy currents can be induced in the metallic sheath by the alternating magnetic field around the conductor. The semiconducting sheath uniformizes the capacitive currents.

[0004] Losses in the metallic sheath can be as much as 20-30% of the total losses in some types of cables. The temperature of the power cable is therefore significantly increased by the losses. The temperature of the power cable can be increased even more if the power cable is a dynamic submarine cable with leads passing through bending reinforcements. The maximum allowable power cable conductor temperature limits the amount of current that can be carried by the power cable at a given time.

[0005] Furthermore, if the metal sheath is damaged, in particular if a circumferential crack appears, rapid failure can occur as a result of degradation of the insulation system, especially due to sparking across gaps in the metal sheath. Summary of the Invention

[0006] In view of the above, it is a general object of the present disclosure to provide a submarine power cable that solves or at least alleviates problems in the prior art.

[0007] Thus, according to a first aspect of the present disclosure, there is provided a cable conductor comprising a first cable section in the form of a dynamic submarine power cable and a second cable section joined to the first cable section, the second cable section being a static submarine power cable, the first cable section having a first cable section first power core including a first cable section first insulation system, a first cable section first metallic sheath covering the first cable section first insulation system, and a first electrical insulation sheath provided around the first cable section first metallic sheath, the second cable section having a first cable section first power core including a first cable section first insulation system, a first cable section first metallic sheath covering the first cable section first insulation system, and a first electrical insulation sheath provided around the first cable section first metallic sheath, A submarine power cable system is provided having a second cable section first power core joined to a first power core, the second cable section first power core including a second cable section first insulation system, a second cable section first metallic sheath covering the second cable section first insulation system, and a first semiconducting sheath disposed around the second cable section first metallic sheath, the first cable section first metallic sheath and the second cable section first metallic sheath being electrically connected to each other, thereby providing a ground point for the first cable section first metallic sheath, and the first cable section being shorter than the second cable section.

[0008] If the power cable system is installed in such a manner that the first metal sheath of the first cable section is connected to ground via a single point bond, a significantly reduced screen loss will occur along the first cable section, especially since the first metal sheath of the first cable section is electrically insulated from its surroundings by the first electrically insulating sheath. Thereby, it may be possible to reduce the conductor size and / or increase the transmission power of the first cable section in the design phase. Furthermore, since no circulating screen currents are induced in the first metal sheath of the first cable section, a failure of the first metal screen of the first cable section will be less critical.

[0009] The first semiconducting sheath has a higher electrical conductivity, and therefore a lower resistivity, than the first electrically insulating sheath.

[0010] The first electrical insulation sheath may be provided directly on the first cable section first metallic sheath. Alternatively, an adhesive layer may be disposed between the first electrical insulation sheath and the first cable section first metallic sheath, which bonds the first electrical insulation sheath and the first cable section first metallic sheath to one another.

[0011] The first semiconducting sheath may be provided directly on the second cable section first metal sheath. Alternatively, a semiconducting adhesive layer may be disposed between the first semiconducting sheath and the second cable section first metal sheath, which bonds the first semiconducting sheath and the second cable section first metal sheath to one another.

[0012] The first electrically insulating sheath may be joined, such as directly joined, to the first semiconducting sheath.

[0013] According to one embodiment, the first electrically insulating sheath comprises or consists of a polymer.

[0014] According to one embodiment, the polymer is a polyethylene, such as high density polyethylene (HDPE), medium density polyethylene (MDPE) or low density polyethylene (LDPE). Other examples of suitable polymers are polyvinyl chloride, polyamides and polyurethanes.

[0015] The first semiconducting sheath may, for example, include a polymer mixed with a semiconducting material such as carbon black.

[0016] According to one embodiment, the first cable section has a first cable section second power core including a first cable section second insulation system, a first cable section second metallic sheath covering the first cable section second insulation system, and a second electrically insulating sheath provided around the first cable section second metallic sheath, and the second cable section has a second cable section second power core joined to the first cable section second power core, the second cable section second power core including a second cable section second insulation system, a second cable section second metallic sheath covering the second cable section second insulation system, and a second electrically insulating sheath provided around the second cable section second metallic sheath, and the first cable section second metallic sheath and the second cable section second metallic sheath are electrically connected to each other, thereby providing a ground point for the second cable section second metallic sheath.

[0017] The second semiconducting sheath has a higher electrical conductivity, and therefore a lower resistivity, than the second electrically insulating sheath.

[0018] The second electrically insulating sheath may be provided directly on the second metallic sheath of the first cable section. Alternatively, an adhesive layer may be disposed between the second electrically insulating sheath and the second metallic sheath of the first cable section, which bonds the second electrically insulating sheath and the second metallic sheath of the first cable section to one another.

[0019] The second semiconducting sheath may be provided directly on the second cable section second metal sheath. Alternatively, a semiconducting adhesive layer may be disposed between the second semiconducting sheath and the second cable section second metal sheath, which bonds the second semiconducting sheath and the second cable section second metal sheath to one another.

[0020] The second electrically insulating sheath may be bonded, such as directly bonded, to the second semiconducting sheath.

[0021] According to one embodiment, the first cable section has a first cable section third power core including a first cable section third insulation system, a first cable section third metallic sheath covering the first cable section third insulation system, and a third electrically insulating sheath provided around the first cable section third metallic sheath, and the second cable section has a second cable section third power core joined to the first cable section third power core, the second cable section third power core including the second cable section third insulation system, the second cable section third metallic sheath covering the second cable section third insulation system, and a third electrically insulating sheath provided around the second cable section third metallic sheath, and the first cable section third metallic sheath and the second cable section third metallic sheath are electrically connected to each other, thereby providing a ground point for the first cable section third metallic sheath.

[0022] The third semiconducting sheath has a higher electrical conductivity, and therefore a lower resistivity, than the third electrically insulating sheath.

[0023] The third electrical insulation sheath may be provided directly on the third metallic sheath of the first cable section. Alternatively, an adhesive layer may be disposed between the third electrical insulation sheath and the third metallic sheath of the first cable section, which bonds the third electrical insulation sheath and the third metallic sheath of the first cable section to one another.

[0024] The third semiconducting sheath may be provided directly on the third metal sheath of the second cable section. Alternatively, a semiconducting adhesive layer may be disposed between the third semiconducting sheath and the third metal sheath of the second cable section, which bonds the third semiconducting sheath and the third metal sheath of the second cable section to one another.

[0025] The third electrically insulating sheath may be bonded, such as directly bonded, to the third semiconducting sheath.

[0026] According to one embodiment, for the first cable section first insulation system, the first cable section second insulation system and the first cable section third insulation system, the first electrical insulation sheath covers only the first cable section first insulation system, the second electrical insulation sheath covers only the first cable section second insulation system and the third electrical insulation sheath covers only the first cable section third insulation system.

[0027] According to one embodiment, the second electrically insulating sheath comprises or consists of a polymer and the third electrically insulating sheath comprises or consists of a polymer.

[0028] According to one embodiment, the polymer is a polyethylene, such as high density polyethylene (HDPE), medium density polyethylene (MDPE) or low density polyethylene (LDPE). Other examples of suitable polymers are polyvinyl chloride, polyamides and polyurethanes.

[0029] According to one embodiment, the submarine power cable system is an AC power cable system.

[0030] According to one embodiment, the power cable is a submarine power cable.

[0031] According to one embodiment, the first metal sheath of the first cable section is a corrugated metal sheath.

[0032] According to one embodiment, the first cable section comprises a first armour surrounding a first power core of the first cable section, and the second cable section comprises a second armour surrounding a first power core of the second cable section.

[0033] According to one embodiment, the first cable section is at least an order of magnitude shorter than the second cable section.

[0034] According to one embodiment, the first metal sheath of the first cable section is configured to be connected to ground only in the area where the first metal sheath of the first cable section connects with the first metal sheath of the second cable section, whereby the first metal sheath of the first cable section has a single point ground.

[0035] Thus, the first metallic sheath of the first cable section is, according to this example, connected to ground only in the transition region between the first cable section and the second cable section.

[0036] According to a second aspect of the present disclosure, there is provided an offshore system comprising a floating structure and a submarine power cable system of the first aspect, wherein a dynamic submarine power cable is suspended from the floating structure to the seabed, and a first cable section first metal sheath is connected to ground only in the area where the first cable section first metal sheath is connected to the second cable section first metal sheath, whereby the first cable section first metal sheath has a single point ground.

[0037] In general, all terms used in the claims should be interpreted according to their customary meaning in the art, unless expressly defined otherwise herein. All references to "a / an / the element, device, component, means, etc." should be openly interpreted as referring to at least one instance of that element, device, component, means, etc., unless expressly stated otherwise.

[0038] Specific embodiments of the inventive concept will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 illustrates a schematic conceptual layout of an offshore system. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an example of a first cable section. [Diagram 3] FIG. 2 is a schematic cross-sectional view of an example of a second cable section. [Figure 4] FIG. 2 is a schematic diagram showing the interior of a joint. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The inventive concepts will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. However, the inventive concepts may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein, but rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concepts to those skilled in the art. Like numbers refer to like elements throughout the description.

[0041] 1 shows a conceptual layout of an example of an offshore system 1. The offshore system 1 comprises a submarine power cable system 3. The submarine power cable system 3 may be an AC power cable system. The offshore system 1 also comprises a floating structure 13.

[0042] The submarine power cable system 3 comprises a first cable section 5 and a second cable section 7. The first cable section 5 is a dynamic submarine power cable and the second cable section 7 is a static submarine power cable. The submarine power cable system 3 further comprises a joint 9. The first cable section 5 and the second cable section 7 are joined by a joint 9. The joint 9 can be a vulcanised factory joint, a flexible transition joint or a rigid sea joint. The rigid sea joint can be constructed offshore. The first cable section 5 extends between the joint 9, which is on the seabed 11, and a topside floating structure 13, such as a floating platform, a floating substation, a floating power transformer, a floating power converter or a floating wind turbine. According to the example shown in FIG. 1 , the first cable section 5 extends through a bending stiffener 15 connected to the floating structure 13 to limit bending of the first cable section 5, e.g. due to movement of the floating structure 13.

[0043] One or more buoyancy devices 17 may be attached to the first cable section 5 to reduce wave-related shocks to the first cable section 5 .

[0044] The first cable section 5 is shorter than the second cable section 7. For example, the first cable section 5 can be at least an order of magnitude shorter than the second cable section 7. The first cable section 5 is typically shorter than 2000 meters. The second cable section 7 is typically longer than 5000 meters, such as longer than 10000 meters.

[0045] The submarine power cable system 3 is hereinafter illustrated by a three-phase power cable, but may alternatively have fewer electrical phases, such as a single electrical phase, or four or more electrical phases.

[0046] 2 shows a cross-section of one example of a first cable section 5. The cross-section may be taken anywhere between the offshore structure 13 and the joint 9.

[0047] The first cable section 5 comprises a plurality of first cable section power cores, namely, a first cable section first power core 19a, a first cable section second power core 21a, and a first cable section third power core 23a. In this example, the three first cable section power cores 19a-23a are arranged in a stranded configuration along the axial direction of the first cable section 5.

[0048] The first cable section first power core 19a comprises a first cable section first electrical conductor 19b. The first cable section first power core 19a further comprises a first cable section first insulation system 19c configured to electrically insulate the first cable section first electrical conductor 19b. The first cable section first power core 19a also comprises a first cable section first metal sheath 19d surrounding / covering the first cable section first insulation system 19c. The first cable section first metal sheath 19d may be made of, for example, copper, stainless steel, lead or a copper alloy. The first cable section first metal sheath 19d may be corrugated in the axial direction of the first cable section 5. The first cable section first power core 19a comprises a first electrical insulation sheath 19e surrounding the first cable section first metal sheath 19d. The first electrically insulating sheath 19e may be extruded over the first cable section first metallic sheath 19d. The first electrically insulating sheath 19e may be electrically insulating and may include or consist of a polymer, such as, for example, polyethylene.

[0049] The first cable section second power core 21a comprises a first cable section second electrical conductor 21b. The first cable section second power core 21a further comprises a first cable section second insulation system 21c configured to electrically insulate the first cable section second electrical conductor 21b. The first cable section second power core 21a also comprises a first cable section second metal sheath 21d surrounding / covering the first cable section second insulation system 21c. The first cable section second metal sheath 21d may be made of, for example, copper, stainless steel, lead or a copper alloy. The first cable section second metal sheath 21d may be corrugated in the axial direction of the first cable section 5. The first cable section second power core 21a comprises a second electrical insulation sheath 21e surrounding the first cable section second metal sheath 21d. The second electrically insulating sheath 21e may be extruded over the first cable section second metallic sheath 21d. The second electrically insulating sheath 21e is electrically insulating and may include or consist of a polymer, such as, for example, polyethylene.

[0050] The first cable section third power core 23a comprises a first cable section third electrical conductor 23b. The first cable section third power core 23a further comprises a first cable section third insulation system 23c configured to electrically insulate the first cable section third electrical conductor 23b. The first cable section third power core 23a also comprises a first cable section third metal sheath 23d surrounding / covering the first cable section third insulation system 23c. The first cable section third metal sheath 23d may be made of, for example, copper, stainless steel, lead or a copper alloy. The first cable section third metal sheath 23d may be corrugated in the axial direction of the first cable section 5. The first cable section third power core 23a comprises a third electrical insulation sheath 23e surrounding the first cable section third metal sheath 23d. The third electrically insulating sheath 23e may be extruded over the first cable section third metallic sheath 23d. The third electrically insulating sheath 23e is electrically insulating and may include or consist of a polymer, such as, for example, polyethylene.

[0051] The first cable section 5 may further comprise a plurality of filler profiles 25a-25c extending along and positioned between the three first cable section power cores 19a-23a to limit radial deformation of the first cable section 5.

[0052] The first cable section 5 may further include a plurality of first armor wires 27 forming a first armor of the first cable section 5. The first armor wires 27 are disposed radially outside the three first cable section power cores 19a-21a and extend axially along the first cable section 5 in a helical manner.

[0053] The first cable section 5 further comprises an outer sheath or outer serving 29 which forms the outermost layer of the first cable section 5. The outer sheath or serving 29 is thus disposed radially outwards of the first armor wire 27.

[0054] FIG. 3 shows a cross-section of an example of a second cable section 7 .

[0055] The second cable section 7 comprises a plurality of second cable section power cores, namely, a second cable section first power core 31a, a second cable section second power core 33a, and a second cable section third power core 35a. In this example, the three second cable section power cores 31a-35a are arranged in a stranded configuration along the axial direction of the second cable section 7.

[0056] The second cable section first power core 31a comprises a second cable section first electrical conductor 31b. The second cable section first power core 31a further comprises a second cable section first insulation system 31c configured to electrically insulate the second cable section first electrical conductor 31b. The second cable section first power core 31a also comprises a second cable section first metal sheath 31d surrounding / covering the second cable section first insulation system 31c. The second cable section first metal sheath 31d may be made of, for example, stainless steel, copper, copper alloy, aluminum, or lead. The second cable section first power core 31a comprises a first semiconducting sheath 31e surrounding the second cable section first metal sheath 31d. The first semiconducting sheath 31e may be extruded onto the second cable section first metal sheath 31d. The first semiconducting sheath 31e may, for example, comprise or consist of a polymer, such as polyethylene, mixed with a conductive material, such as carbon black, to obtain its semiconducting properties.

[0057] The second cable section second power core 33a comprises a second cable section second electrical conductor 33b. The second cable section second power core 33a further comprises a second cable section second insulation system 33c configured to electrically insulate the second cable section second electrical conductor 33b. The second cable section second power core 33a also comprises a second cable section second metal sheath 33d surrounding / covering the second cable section second insulation system 33c. The second cable section second metal sheath 33d may be made of, for example, stainless steel, copper, copper alloy, aluminum, or lead. The second cable section second power core 33a comprises a second semiconducting sheath 33e surrounding the second cable section second metal sheath 33d. The second semiconducting sheath 33e may be extruded onto the second cable section second metal sheath 33d. The second semiconducting sheath 33e may, for example, comprise or consist of a polymer, such as polyethylene, mixed with, for example, carbon black, to obtain its semiconducting properties.

[0058] The second cable section third power core 35a comprises a second cable section third electrical conductor 35b. The second cable section third power core 35a further comprises a second cable section third insulation system 35c configured to electrically insulate the second cable section third electrical conductor 35b. The second cable section third power core 35a also comprises a second cable section third metal sheath 35d surrounding / covering the second cable section third insulation system 35c. The second cable section third metal sheath 35d may be made of, for example, stainless steel, copper, copper alloy, aluminum, or lead. The second cable section third power core 35a comprises a third semiconducting sheath 35e surrounding the second cable section third metal sheath 35d. The third semiconducting sheath 35e may be extruded onto the second cable section third metal sheath 35d. The third semiconducting sheath 35e may, for example, comprise or consist of a polymer, such as, for example, polyethylene, mixed with carbon black to obtain its semiconducting properties.

[0059] The second cable section 7 may further comprise a number of filler profiles 37a-37c extending along and positioned between the three second cable section power cores 31a-35a.

[0060] The second cable section 7 may include a plurality of second armor wires 39 forming a second armor of the second cable section 7. The second armor wires 39 are disposed radially outside the three second cable section power cores 31a-35a.

[0061] The second cable section 7 also includes an outer sheath or outer serving 41 which forms the outermost layer of the second cable section 7 .

[0062] 4 shows the inside of the joint 9 in a schematic way, as exemplified by a rigid sea joint. The first cable section first power core 19a is joined to the second cable section first power core 31a. The first cable section second power core 21a is joined to the second cable section second power core 33a. The first cable section third power core 23a is joined to the second cable section third power core 35a. Thus, the first cable section first conductor 19b is joined, for example, to the second cable section first conductor 31b, and the first cable section first insulation system 19c is joined to the second cable section first insulation system 31c.

[0063] The joint 9 in the form of a rigid sea joint may comprise a number of rigid inner casings 43a-47a, one for each electrical phase. The first cable section first metal sheath 19d and the second cable section first metal sheath 31d are joined to the first rigid inner casing 43a along their entire circumference, for example by soldering or welding, to make a watertight connection with the first rigid inner casing 43a. The electrical connection between the first cable section first electrical conductor 19b and the second cable section first electrical conductor 31b is made inside the first rigid inner casing 43a. The above described connections are made in the same way for the other two power cores 21a and 33a, as well as 23a and 35a.

[0064] The joint 9 may comprise a rigid outer casing 9a which contains all of the rigid inner casings 43a, 45a, and 47a.

[0065] The submarine power cable system 3 also includes a plurality of connection cables or leads 49, 51, 53 and breakouts 55, 57, 59. The connection cables 49-53 and the breakouts 55-59 may be disposed inside the rigid outer casing 9a. A first connection cable 49 is electrically connected to the second cable section first metal sheath 31d via a first breakout 55 in the second cable section first cable core 31a and electrically connected to the second cable section second metal sheath 33d via a second breakout 57 in the second cable section second cable core 33a. A second connection cable 51 is electrically connected to the second cable section first metal sheath 31d via the first breakout 55 and electrically connected to the second cable section third metal sheath 35d via a third breakout 59 in the second cable section third cable core 35a. The third connecting cable 53 is electrically connected to the second cable section second metal sheath 33d via a second breakout 57 and to the second cable section third metal sheath 35d via a third breakout 59. This configuration is a Delta connection. Alternatively, the leads 49, 51 and 53 may be connected in a Y connection, whereby circulating currents in the second cable section metal sheaths 31d, 33d, 35d in the joint area may be reduced or eliminated.

[0066] Alternatively, the connections by the connecting cables 49-53 may be between the first cable section metal sheaths 19d, 21d and 23d inside the rigid outer casing.

[0067] Each breakout 55, 57 and 59 may, according to one example, comprise a metal braid electrically connected to the underlying second cable section first metal sheath 31d, second metal sheath 33d or third metal sheath 35d and a sleeve or cylindrical connector disposed around and attached to the metal braid, for example by crimping or by one or more shear off screws. The metal braid and a portion of the sleeve or cylindrical connector may be covered by tape and / or one or more shrink tubes. The area of ​​the second cable section first power core 31a, second power core 33a or third power core 35a employing the breakouts 55, 57 and 59 may also comprise shrink tubes to ensure water tightness. The leads 49, 51, 53 are connected to the sleeve or cylindrical connector. In FIG. 4 showing the delta connection, two leads 49, 51, 53 are connected to each breakout 55, 57, 59. In the case of a Y-connection, each lead 49, 51, 53 is connected at one end to a respective breakout 55, 57, 59 and at their other ends to each other. The metal braids can be soft soldered to the underlying first metal sheath 31d, second metal sheath 33d, or third metal sheath 35d of the second cable section, for example, through openings made in the respective first semiconductor sheath 31e, second semiconductor sheath 33e, and third semiconductor sheath 35e. Alternatively, if the connection by the connecting cable 49-53 is between the first cable section metal sheaths 19d, 21d, and 23d, the metal braids can be electrically connected to the underlying first cable section first metal sheath 19d, second metal sheath 21d, or third metal sheath 23d. According to one example, the joint may be a vulcanized factory joint, provided with connecting cables for electrically connecting the metal sheaths 31d, 33d and 35d to each other, or alternatively to the metal sheaths 19d, 21d and 23d, in the area of ​​the joint.

[0068] When installed, the second cable section first metal sheath 31d, the second cable section second metal sheath 33d, and the second cable section third metal sheath 35d are grounded, for example at a landfall, i.e., at the other end of the second cable section 7. The first cable section first metal sheath 19d, the first cable section second metal sheath 21d, and the first cable section third metal sheath 23d are also grounded by their connection to the corresponding second cable section metal sheaths 31d-35d. This grounding forms a single-point bond or single-point ground of the first cable section first metal sheath 19d, the first cable section second metal sheath 21d, and the first cable section third metal sheath 23d. Therefore, when the submarine power cable system 3 is installed, at the other end of the first cable section 5, there is no grounding of the first cable section first metal sheath 19d, the first cable section second metal sheath 21d, and the first cable section third metal sheath 23d.

[0069] As mentioned above, the first cable section first metal sheath 19d, the first cable section second metal sheath 21d and the first cable section third metal sheath 23d are not connected to earth at the termination end of the first cable section 5, i.e., at the floating structure 13. Due to the electrical insulation properties of the first electrical insulation sheath 19e, the second electrical insulation sheath 21e and the third electrical insulation sheath 23e, the first cable section first metal sheath 19d, the second metal sheath 21d and the third metal sheath 23d will only have a single point connection / earth. Therefore, no circulating screen current will be induced in the metal sheaths 19d-23d, and therefore a significant reduction in losses will occur in the metal sheaths 19d-23d.

[0070] When designing the submarine power cable system 3, the length of the first cable section 5 should be, at most, such that the potential difference between the metal sheath 19d-23d at the single-point connection and the terminal end of the first cable section 5 is within an acceptable range.

[0071] The inventive concept has been described above primarily with reference to a few examples. However, as will be readily appreciated by those skilled in the art, other embodiments than those disclosed above are equally possible within the scope of the inventive concept as defined by the appended claims.

Claims

1. A submarine power cable system (3), comprising: a first cable section (5) in the form of a dynamic submarine power cable; a second cable section (7) joined to the first cable section (5), the second cable section being a static submarine power cable; Equipped with the first cable section (5) has a first cable section first power core (19a) including a first cable section first insulation system (19c), a first cable section first metallic sheath (19d) covering the first cable section first insulation system (19c), and a first electrical insulation sheath (19e) disposed around the first cable section first metallic sheath (19d); the second cable section (7) has a second cable section first power core (31a) joined to the first cable section first power core (19a), the second cable section first power core (31a) including a second cable section first insulation system (31c), a second cable section first metallic sheath (31d) covering the second cable section first insulation system (31c), and a first semiconducting sheath (31e) provided around the second cable section first metallic sheath (31d); 1. A submarine power cable system (3), wherein the first cable section first metal sheath (19d) and the second cable section first metal sheath (31d) are electrically connected to each other, thereby providing a ground point for the first cable section first metal sheath (19d), and the first cable section (5) is shorter than the second cable section (5).

2. 2. The submarine power cable system (3) according to claim 1, wherein the first electrically insulating sheath (19e) comprises or consists of a polymer.

3. 3. A submarine power cable system (3) according to claim 2, wherein the polymer is polyethylene.

4. the first cable section (5) has a first cable section second power core (21a) including a first cable section second insulation system (21c), a first cable section second metallic sheath (21d) covering the first cable section second insulation system (21c), and a second electrical insulation sheath (21e) disposed around the first cable section second metallic sheath (21d); the second cable section (7) has a second cable section second power core (33a) joined to the first cable section second power core (21a), the second cable section second power core (33a) including a second cable section second insulation system (33c), a second cable section second metal sheath (33d) covering the second cable section second insulation system (33c), and a second semiconducting sheath (33e) disposed around the second cable section second metal sheath (33d), the first cable section second metal sheath (21d) and the second cable section second metal sheath (33d) being electrically connected to each other, thereby providing a ground point for the second cable section second metal sheath (33d); A submarine power cable system (3) according to any one of claims 1 to 3.

5. the first cable section (5) has a first cable section third power core (23a) including a first cable section third insulation system (23c), a first cable section third metallic sheath (23d) covering the first cable section third insulation system (23c), and a third electrical insulation sheath (23e) disposed around the first cable section third metallic sheath (23d); the second cable section (7) has a second cable section third power core (35a) joined to the first cable section third power core (23a), the second cable section third power core (35a) including a second cable section third insulation system (35c), a second cable section third metal sheath (35d) covering the second cable section third insulation system (35c), and a third semiconducting sheath (35e) disposed around the second cable section third metal sheath (35d), the first cable section third metal sheath (23d) and the second cable section third metal sheath (35d) being electrically connected to each other, thereby providing a ground point for the first cable section third metal sheath (23d); A submarine power cable system (3) according to claim 4.

6. 6. The submarine power cable system (3) according to claim 5, wherein for the first cable section first insulation system (19c), the first cable section second insulation system (21c) and the first cable section third insulation system (23c), the first electrical insulation sheath (19e) covers only the first cable section first insulation system (19c), the second electrical insulation sheath (21e) covers only the first cable section second insulation system (21c), and the third electrical insulation sheath (23e) covers only the first cable section third insulation system (23c).

7. 7. A submarine power cable system (3) according to claim 5 or 6, wherein the second electrically insulating sheath (21e) comprises or consists of a polymer and the third electrically insulating sheath (23e) comprises or consists of a polymer.

8. 8. A submarine power cable system (3) according to claim 7, wherein the polymer is polyethylene.

9. 9. The submarine power cable system (3) according to any one of claims 1 to 8, wherein the power cable system (3) is an AC power cable system.

10. 10. A submarine power cable system (3) according to any one of claims 1 to 9, wherein the first metal sheath (19d) of the first cable section is a corrugated metal sheath.

11. 11. The submarine power cable system (3) according to any one of claims 1 to 10, wherein the first cable section (5) comprises a first exterior covering surrounding the first cable section first power core (19a) and the second cable section (7) comprises a second exterior covering surrounding the second cable section first power core (31a).

12. 12. A submarine power cable system (3) according to any one of claims 1 to 11, wherein the first cable section (5) is at least an order of magnitude shorter than the second cable section (7).

13. 13. A submarine power cable system (3) according to any one of claims 1 to 12, wherein the first cable section first metallic sheath (19d) is configured to be connected to ground only in the area where the first cable section first metallic sheath (19d) is connected with the second cable section first metallic sheath (31d), whereby the first cable section first metallic sheath (19d) has a single point ground.

14. An offshore system (1), comprising:

14. An offshore system (1) comprising a floating structure and a submarine power cable system (3) according to any one of claims 1 to 13, wherein a dynamic submarine power cable is suspended from the floating structure to the seabed, and a first cable section first metal sheath (19d) is connected to earth only in the area where the first cable section first metal sheath (19d) is connected with a second cable section first metal sheath (31d), whereby the first cable section first metal sheath (19d) has a single point earth.

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