Technical Field

The present disclosure generally relates to an electric conductor. In particular, an electric conductor, and a high voltage arrangement comprising an electric conductor, are provided.

Background

A high voltage arrangement may comprise various electric apparatuses connected to each other in order to form an electrical circuit. Such connections are often done by means of aluminium wires. The geometry of the wires is however difficult to control when the electric apparatuses move relative to each other. The wires may adopt uncontrolled shapes and thereby jeopardizing electric clearance. The wires can also create corona discharges due to narrow radiuses. This behavior of aluminium wires is particularly undesirable for higher electric fields and/or compact arrangements.

EP 2555358 Ai discloses a telescopic busbar device having a first conducting member and a second conducting member that are telescopically assembled so that the second conducting member can reversibly extend from an end part of the first conducting member along an axial direction for adjusting the length of the telescopic busbar. The telescopic busbar may also be integrated with functions such as expansion movement, damping of oscillation movements of the telescopic busbar and surge protection. Flexible connectors for connecting the telescopic busbar to connection points with integrated radial damping function are also described. Summary

One object of the present disclosure is to provide an electric conductor that has a durable design. A further of the present disclosure is to provide an electric conductor that can withstand a high number of stress cycles, such as at least ten million stress cycles.

A still further object of the present disclosure is to provide an electric conductor that reduces a risk for corona discharge.

A still further object of the present disclosure is to provide an electric conductor that enables an aggressive dielectric design.

A still further object of the present disclosure is to provide an electric conductor that has a compact design. A still further object of the present disclosure is to provide an electric conductor that has a cost-effective design.

A still further object of the present disclosure is to provide an electric conductor that has a simple design.

A still further object of the present disclosure is to provide an electric conductor that is physically stable.

A still further object of the present disclosure is to provide an electric conductor that solves several or all of the foregoing objects in combination.

A still further object of the present disclosure is to provide a high voltage arrangement comprising an electric conductor, which high voltage arrangement solves one, several or all of the foregoing objects.

According to one aspect, there is provided an electric conductor comprising an electrically conductive rigid elongated element defining a longitudinal axis and having a primary end and a secondary end opposite to the primary end; a primary connection arrangement having a primary mechanical connection device for mechanically connecting the primary end to a primary external structure, and a primary electric connection device for electrically connecting the primary end to the primary external structure; and a secondary connection arrangement having a secondary mechanical connection device for mechanically connecting the secondary end to a secondary external structure, and a secondary electric connection device for electrically connecting the secondary end to the secondary external structure; wherein the primary mechanical connection device comprises two primary joints; and wherein the secondary mechanical connection device comprises a secondary joint.

By means of the primary connection arrangement and the secondary connection arrangement, the electric conductor can adapt to varying distances between the primary external structure and the secondary external structure with well-defined movements of the electric conductor and with well-defined geometries of the electric conductor, while maintaining an electric connection between the primary external structure and the secondary external structure through the electric conductor. The electric conductor according to the present disclosure is physically stable. That is, when the primary external structure moves relative to the secondary external structure, the electric conductor only adopts well-defined geometries, in particular in contrast to prior art wire conductors associated with narrow radiuses and shapelessness. The electric conductor is thus stable and has a high dimensional control.

The primary mechanical connection device and the secondary mechanical connection device the electric conductor to be configured such that relative movements between the primary external structure and the secondary external structure parallel with the longitudinal axis, result in movements of the elongated element substantially along the longitudinal axis. The primary mechanical connection device and the secondary mechanical connection device may thus allow movement of the elongated element substantially along the longitudinal axis when the primary external structure moves relative to the secondary external structure. Varying distances between the primary external structure and the secondary external structure may occur if a high voltage arrangement, in which the electric conductor is arranged, is provided in an offshore application. In an offshore platform application (such as a floating platform or a platform resting on the seabed), the high voltage arrangement may be subjected to more or less continuous relative movements between the primary external structure and the secondary external structure for several years. The frequency of such movement cycles may be below l hertz.

A further scenario where relative movements between the primary external structure and the secondary external structure occur is when a high voltage arrangement comprising the electric conductor is subjected to an earthquake Other types of scenarios where the primary external structure moves relative to the secondary external structure, and which can be addressed by the electric conductor, are conceivable.

Due to the ability of the electric conductor to adapt to varying distances between the primary external structure and the secondary external structure with well-defined movements of the electric conductor and with well-defined geometries of the electric conductor, while maintaining an electric connection between the primary external structure and the secondary external structure, the electric conductor according to the present disclosure can be installed in an insulation environment within relatively small spaces without risk for underpassing air clearance requirements. In this way, the electric conductor enables a more dielectrically aggressive design.

Furthermore, due to the provision of two primary joints at the primary end of the elongated element and one secondary joint at the secondary end of the elongated element, the electric conductor enables movements of the elongated element adjacent to the secondary end to be very small. This also contributes to enabling a dielectrically aggressive design.

The electric conductor according to the present disclosure may comprise a galvanically connected electrically conductive path through the entire electric conductor. For example, solid metal may be provided along the entire electrically conductive path of the electric conductor. Alternatively, or in addition, the electric conductor may provide a continuous electrically conductive path with a cross-sectional area of at least 500 mm ² along the entire electric conductor.

The primary external structure and the secondary external structure may be a primary electric terminal member and a secondary electric terminal member, respectively. By means of the primary mechanical connection device and the secondary mechanical connection device, the electric conductor can adapt to varying distances between the primary external structure and the secondary external structure to provide flexibility, e.g. in order to compensate for tolerances during installation. The electric conductor may for example enable relative movement between the primary external structure and the secondary external structure of at least too mm.

Optionally, the primary connection arrangement may comprise a primary terminal member and a secondary terminal member. In this case, the primary terminal member and the secondary terminal member may be attached to the primary external structure and the secondary external structure, respectively, for example by means of one or more fasteners. Thus, the primary terminal member and the secondary terminal member may be configured to provide mechanical support and current connection to the primary external structure and the secondary external structure, respectively. The primary mechanical connection device may be mechanically connected to the primary end and to the primary terminal member, the primary electric connection device may be electrically connected to the primary end and to the primary terminal member, the secondary mechanical connection device may be mechanically connected to the secondary end and to the secondary terminal member, and the secondary electric connection device may be electrically connected to the secondary end and to the secondary terminal member.

The elongated element may be made of aluminium or an aluminium alloy comprising at least 95%, such as at least 99%, aluminium. Alternatively, or in addition, the elongated element may have a circular exterior profile. In contrast to a telescopic electric conductor, the elongated element of the electric conductor is rigid and thereby also non-telescopic.

The entire electric conductor may have a generally cylindrical shape. The cylindrical shape reduces the risk for corona discharge and is dielectrically favorable. The electric conductor can thereby be installed in an environments with high electric fields with no or limited risk for partial discharge or flashover.

The primary electric connection device may comprise an electrically conductive primary flexible conductive element connected to the primary end. Alternatively, or in addition, the secondary electric connection device may comprise an electrically conductive secondary flexible conductive element connected to the secondary end.

Due to the flexibility of the primary flexible conductive element, the primary end can move relative to the primary external structure while the primary flexible conductive element maintains an electric path through solid material between the primary end and the primary external structure. Conversely, due to the flexibility of the secondary flexible conductive element, the secondary end can move relative to the secondary external structure while the secondary flexible conductive element maintains an electric path through solid material between the secondary end and the secondary external structure.

The primary flexible conductive element may be fixedly connected to the primary end, e.g. to a primary connection member thereof, and fixedly connected to the primary external structure. In this way, the primary electric connection device can transmit current between the primary external structure and the elongated element without any sliding contacts.

Conversely, the secondary flexible conductive element may be fixedly connected to the secondary end, e.g. to a secondary connection member thereof, and fixedly connected to the secondary external structure. In this way, the secondary electric connection device can transmit current between the elongated element and the secondary external structure without any sliding contacts.

The primary electric connection device may comprise a plurality of primary flexible conductive elements, each connected to the primary end and for electric connection to the primary external structure. The plurality of primary flexible conductive elements may be arranged in parallel between the primary end and the primary external structure.

Conversely, the secondary electric connection device may comprise a plurality of secondary flexible conductive elements, each connected to the secondary end and for electric connection to the secondary external structure. The plurality of secondary flexible conductive elements may be arranged in parallel between the secondary end and the secondary external structure.

Each primary flexible conductive element and/or each secondary flexible conductive element may be a braid, i.e. comprising a plurality of solid conductors. Alternatively, or in addition, each of the primary flexible conductive element and the secondary flexible conductive element may be made of aluminium or an aluminium alloy comprising at least 95%, such as at least 99%, aluminium. The two primary joints may comprise a first primary joint and a second primary joint. Although the first primary joint and the second primary joint may both be arranged at the primary end of the elongated element, the first primary joint may be spatially separated from the second primary joint. Alternatively, or in addition, the first primary joint and the second primary joint may be arranged in series. For example, the first primary joint may be arranged between the primary end and the second primary joint, the second primary joint may be arranged between the first primary joint and the primary external structure, and one member of the first primary joint may be fixed to one member of the second primary joint. The first primary joint may comprise a first primary bearing and the second primary joint may comprise a second primary bearing. The secondary joint may comprise a secondary bearing. Each of the first primary bearing, the second primary bearing and the secondary bearing may be configured to withstand at least ten million movement cycles, such as at least too million movement cycles, e.g. during the entire lifetime of a high voltage arrangement, comprising the electric conductor, arranged in an offshore application.

The first primary joint may allow relative rotation about two axes perpendicular to the longitudinal axis. The first primary joint may be a two- rotational-degrees-of-freedom kinematic pair or a three-rotational-degrees- of-freedom kinematic pair. By means of the first primary joint, the elongated element is free to move angularly relative to the primary external structure. The first primary joint may be a ball joint. Alternatively, the first primary joint may be a universal joint.

The second primary joint may define a second primary rotation axis. The second primary rotation axis may be arranged to be perpendicular to the longitudinal axis, e.g. at least for some relative positions between the primary external structure and the secondary external structure. The second primary joint may be a hinge or pin joint. The second primary joint may thus be a one-rotational-degree-of-freedom kinematic pair. The electric conductor may in this case be referred to as a hinged conductor.

The primary mechanical connection device may comprise a rigid member between the first primary joint and the second primary joint. In this case, the first primary joint and the second primary joint may be held at a fixed distance by means of the rigid member.

The rigid member may be elongated and define a rigid member axis. In this case, the electric conductor may be configured to operate with the rigid member axis substantially perpendicular to the longitudinal axis. The secondary joint may allow relative rotation about two axes perpendicular to the longitudinal axis. The secondary joint may be a two-rotational-degrees- of-freedom kinematic pair or a three-rotational-degrees-of-freedom kinematic pair. By means of the secondary joint, the elongated element is free to move angularly relative to the secondary external structure. The secondary joint may be a ball joint. Alternatively, the secondary joint may be a universal joint. The secondary joint may provide axial rigidity (along the longitudinal axis) between the elongated element and the secondary external structure.

The primary mechanical connection device may be configured to electrically isolate the primary end from the primary external structure. In this way, a primary electric connection device can electrically bypass the primary mechanical connection device and it can be made sure that the major current path (e.g. at least 99% of the current) is through the primary electric connection device. Alternatively, or in addition, the secondary mechanical connection device may be configured to electrically isolate the secondary end from the secondary external structure. In this way, a secondary electric connection device can electrically bypass the secondary mechanical connection device and it can be made sure that the major current path (e.g. at least 99% of the current) is through the secondary electric connection device. Each of the primary mechanical connection device and the secondary mechanical connection device may comprise plastic or other electrically insulating material.

The elongated element may have a circular exterior profile. For example, the elongated element may have a uniform, or substantially uniform circular exterior profile, i.e. with the same (or substantially the same) external diameter. Alternatively, or in addition, the elongated element may be hollow. The elongated element may for example be a cylindrical tube, i.e. a pipe. A cylindrical shape of the elongated element reduces the risk for corona discharge and is dielectrically favorable. Although the elongated element may be non-hollow with a solid cross-sectional profile, a hollow elongated element enables the exterior profile to be relatively large with relatively low material use. In case the elongated element is hollow, the elongated element may comprise stacked sheet metal, such as stacked aluminium sheets. Each metal sheet may have a thickness of less than 1 mm and/or at least ten metal sheets may be stacked.

The electric conductor may have a current-carrying capacity of at least 500 amperes. The electric conductor may thus be a high current conductor.

According to a further aspect, there is provided a high voltage arrangement comprising an electric conductor according to the present disclosure. The high voltage arrangement may comprise a primary high voltage unit including the primary external structure and a secondary high voltage unit including the secondary external structure. In this case, the primary mechanical connection device may be mechanically connected to the primary end and to the primary external structure such that the elongated element is allowed to move relative to the primary external structure by means of the two primary joints, and the secondary mechanical connection device may be mechanically connected to the secondary end and to the secondary external structure such that the elongated element is allowed to move relative to the secondary external structure by means of the secondary joint. Furthermore, the primary electric connection device may be electrically connected to the primary end and to the primary external structure and the secondary electric connection device may be electrically connected to the secondary end and to the secondary electric connection device. The electric conductor according to the present disclosure may thus be suitable for use in a high voltage arrangement according to the present disclosure.

A high voltage unit according to the present disclosure may for example be constituted by a high voltage direct current (HVDC) semiconductor valve. Further examples of high voltage units are capacitors and breakers. A high voltage within the present disclosure may be a voltage of at least too kV. Thus, a high voltage arrangement according to the present disclosure may have a system voltage of at least too kV. Either the primary high voltage unit or the primary connection arrangement may comprise the primary external structure. Either the secondary high voltage unit or the secondary connection arrangement may comprise the secondary external structure. In any case, the electric conductor enables an electric path through solid electrical connections to be established and maintained despite relative movements between the primary external structure and the secondary external structure.

The high voltage arrangement may further comprise one or more corona shields. For example, one corona shield may be provided around the primary connection arrangement and one corona shield may be provided around the secondary connection arrangement.

Brief Description of the Drawings

Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

Fig. 1: schematically represents a high voltage arrangement comprising two high voltage units and an electric conductor;

Fig. 2: schematically represents a perspective view of the electric conductor; Fig. 3: schematically represents a partial enlarged view of a primary connection arrangement of the electric conductor; and

Fig. 4: schematically represents a partial enlarged view of a secondary connection arrangement of the electric conductor.

Detailed Description In the following, an electric conductor, and a high voltage arrangement comprising an electric conductor, will be described. The same or similar reference numerals will be used to denote the same or similar structural features. Fig. l schematically represents a high voltage arrangement to. The high voltage arrangement to of this example comprises a primary high voltage unit 12 and a secondary high voltage unit 14. Each high voltage unit 12, 14 is here exemplified as a HVDC semiconductor valve. The high voltage arrangement 10 has a system voltage of at least 100 kV.

The primary high voltage unit 12 comprises a primary external structure 16 and the secondary high voltage unit 14 comprises a secondary external structure 18. Each external structure 16, 18 is here exemplified as an electric terminal member. The high voltage arrangement 10 further comprises an electric conductor 20. The electric conductor 20 is a high current conductor having a current- carrying capacity of at least 500 amperes, such as at least 1000 amperes.

The electric conductor 20 is mechanically and electrically connected to the primary external structure 16 and mechanically and electrically connected to the secondary external structure 18. In this example, the external structures 16, 18 are structures external to the electric conductor 20. The electric conductor 20 allows relative movements between the high voltage units 12, 14 while maintaining the electric connection therebetween. The high voltage arrangement 10 may further comprise one or more corona shields, for example one at each end of the electric conductor 20.

The high voltage arrangement 10 may for example be provided in an offshore platform application. Thus, a distance between the primary external structure 16 and the secondary external structure 18 may vary during operation of the high voltage arrangement 10. The distance may for example vary cyclically with a frequency of less than 1 hertz for several years. Thus, the high voltage arrangement 10 may be subjected to over ten million stress cycles.

Fig. 2 schematically represents a perspective view of the electric conductor 20. The electric conductor 20 comprises an electrically conductive and rigid elongated element 22. The elongated element 22 defines a longitudinal axis 24. The elongated element 22 comprises a primary end 26 and a secondary end 28. The primary end 26 is opposite to the secondary end 28.

The electric conductor 20 further comprises a primary connection arrangement 30. The primary connection arrangement 30 comprises a primary mechanical connection device 32 and a primary electric connection device 34. The primary mechanical connection device 32 is mechanically connected to the primary end 26 and mechanically connected to the primary external structure 16 (not shown in Fig. 2). The primary electric connection device 34 is electrically connected to the primary end 26 and electrically connected to the primary external structure 16.

The electric conductor 20 further comprises a secondary connection arrangement 36. The secondary connection arrangement 36 comprises a secondary mechanical connection device 38 and a secondary electric connection device 40. The secondary mechanical connection device 38 is mechanically connected to the secondary end 28 and mechanically connected to the secondary external structure 18 (not shown in Fig. 2). The secondary electric connection device 40 is electrically connected to the secondary end 28 and electrically connected to the secondary external structure 18.

Fig. 3 schematically represents a partial enlarged view of the primary connection arrangement 30 of the electric conductor 20. Fig. 4 schematically represents a partial enlarged view of the secondary connection arrangement 36 of the electric conductor 20.

With collective reference to Figs. 2 to 4, the primary mechanical connection device 32 comprises a first primary joint 42 and a second primary joint 44. The secondary mechanical connection device 38 comprises a secondary joint 46.

The elongated element 22 of this example is a hollow pipe. The elongated element 22 has a uniform circular exterior profile, which is dielectrically favorable. The elongated element 22 is made of an aluminium alloy comprising at least 99% aluminium. The primary mechanical connection device 32 of this example further comprises a rigid member 48. The rigid member 48 is elongated and thereby defines a rigid member axis 50. The first primary joint 42 is connected to one end of the rigid member 48 and the second primary joint 44 is connected to the opposite end of the rigid member 48. The first primary joint 42 and the second primary joint 44 are thereby kept at a fixed distance by means of the rigid member 48.

In Figs. 2 to 4, the electric conductor 20 is illustrated in an intended installation state or neutral state. In this state of the electric conductor 20, the rigid member axis 50 is substantially perpendicular to the longitudinal axis 24.

The first primary joint 42 is spatially separated from the second primary joint 44. Moreover, the first primary joint 42 and the second primary joint 44 are arranged in series. That is, the first primary joint 42 is arranged between the primary end 26 and the rigid member 48, and the second primary joint 44 is arranged between the rigid member 48 and the primary external structure 16. One member of the first primary joint 42 is fixed with respect to one member of the second primary joint 44 by means of the rigid member 48.

The first primary joint 42 of this example is a ball joint, i.e. a three- rotational-degrees-of-freedom kinematic pair. The first primary joint 42 thereby allows relative rotation between the rigid member 48 and the elongated element 22 about two axes, each axis being perpendicular to each other and perpendicular to the longitudinal axis 24.

The second primary joint 44 of this example is a hinge, i.e. a one-rotational- degree-of-freedom kinematic pair. The second primary joint 44 thereby defines a second primary rotation axis 52. The rigid member 48 is thereby allowed to rotate relative to the primary external structure 16 about the second primary rotation axis 52. In the installation state or neutral state of the electric conductor 20 in Figs. 2 to 4, the second primary rotation axis 52 is perpendicular to the longitudinal axis 24. The secondary joint 46 of this example is a ball joint, i.e. a three-rotational- degrees-of-freedom kinematic pair. The secondary joint 46 thereby allows relative rotation between the elongated element 22 and the secondary external structure 18 about two axes, each axis being perpendicular to each other and perpendicular to the longitudinal axis 24.

By means of the secondary joint 46, the elongated element 22 is free to move angularly relative to the secondary external structure 18. Furthermore, the secondary joint 46 provides axial rigidity between the elongated element 22 and the secondary external structure 18 along the longitudinal axis 24. The primary electric connection device 34 of this example comprises a plurality of primary flexible conductive elements 54, here four primary flexible conductive elements 54. One end of each primary flexible conductive element 54 is fixedly and electrically connected to the primary end 26, for example by means of welding. An opposite end of each primary flexible conductive element 54 is fixedly and electrically connected to the primary external structure 16 (not shown in Figs. 2 and 3). The primary flexible conductive elements 54 are thereby arranged in parallel between the primary end 26 and the primary external structure 16. Each primary flexible conductive element 54 is bent in the illustrated intended installation state or neutral state of the electric conductor 20. In this way, margin for an increased distance between the primary end 26 and the primary external structure 16, without tensioning the primary flexible conductive elements 54, is provided. In this example, each primary flexible conductive element 54 is a braid of electrically conductive material, such as an aluminium alloy comprising at least 99% aluminium.

As shown in Fig. 3, the primary end 26 of this example comprises a primary connection member 56. The primary flexible conductive elements 54 are attached to the primary connection member 56. The primary connection member 56 of this example is a rod extending perpendicular to the longitudinal axis 24. Two primary flexible conductive elements 54 are connected to the primary connection member 56 at one side of the longitudinal axis 24 and two primary flexible conductive elements 54 are connected to the primary connection member 56 at the opposite side of the longitudinal axis 24.

The secondary electric connection device 40 of this example comprises a plurality of secondary flexible conductive elements 58, here four secondary flexible conductive elements 58. One end of each secondary flexible conductive element 58 is fixedly and electrically connected to the secondary end 28. An opposite end of each secondary flexible conductive element 58 is fixedly and electrically connected to the secondary external structure 18. The secondary flexible conductive elements 58 are thereby arranged in parallel between the secondary end 28 and the secondary external structure 18. Each secondary flexible conductive element 58 is bent in the illustrated intended installation state or neutral state of the electric conductor 20. In this way, margin for an increased distance between the secondary end 28 and the secondary external structure 18, without tensioning the secondary flexible conductive elements 58, is provided. In this example, each secondary flexible conductive element 58 is a braid of electrically conductive material, such as an aluminium alloy comprising at least 99% aluminium.

As shown in Fig. 4, the secondary end 28 of this example comprises a secondary connection member 60. The secondary flexible conductive elements 58 are attached to the secondary connection member 60. The secondary connection member 60 of this example has a flat shape parallel with the longitudinal axis 24. Two secondary flexible conductive elements 58 are connected to the secondary connection member 60 at one side of the longitudinal axis 24 and at opposite sides of the secondary connection member 60, and two secondary flexible conductive elements 58 are connected to the secondary connection member 60 at the opposite side of the longitudinal axis 24 and at opposite sides of the secondary connection member 60. The primary mechanical connection device 32 is configured to electrically isolate the primary end 26 from the primary external structure 16. The secondary mechanical connection device 38 is configured to electrically isolate the secondary end 28 from the secondary external structure 18. To this end, the primary mechanical connection device 32 and the secondary mechanical connection device 38 comprises electrically insulating material, such as plastic. In this way, the primary electric connection device 34 electrically bypasses the primary mechanical connection device 32 and the secondary electric connection device 40 electrically bypasses the secondary mechanical connection device 38.

In case of relative movement between the primary external structure 16 and the secondary external structure 18 parallel with the longitudinal axis 24, from the illustrated neutral state, the elongated element 22 will at least initially move along the longitudinal axis 24. After further movement, the elongated element 22 will move substantially along the longitudinal axis 24. The second primary joint 44 will rotate about the second primary rotation axis 52 and the first primary joint 42 will rotate about an axis parallel with the second primary rotation axis 52. Moreover, for small such relative movements, there will only be a very small movement of the secondary end 28 relative to the secondary external structure 18 by means of the secondary joint 46. The electric conductor 20 is therefore physically stable and performs well-defined movements with well-defined geometries. Thereby, the electric conductor 20 enables a more dielectrically aggressive design, e.g. the electric conductor 20 can be installed in insulation environments within relatively small spaces without risk for underpassing air clearance requirements.

During relative movements between the primary external structure 16 and the secondary external structure 18, the primary flexible conductive element 54 and the secondary flexible conductive element 58 flex, while the electric conductor 20 maintains an electric path through solid material all the way between the primary external structure 16 and the secondary external structure 18. Thus, no sliding contacts are needed. While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.