Abstract:
A power cable assembly device adapted to be arranged in the spaces between neighbouring power cores of a power cable, includes a profiled body made of a polymer material and adapted to the cross-sectional shape and elongation of the power cable, said profiled body including a chamber and a slit to the chamber, the chamber being adapted to receive a fibre optic cable via the slit. The profiled body is provided with a pair of transitions converging towards the slit, the transitions being adapted to supportingly receive a fibre optic cable to be introduced through the slit.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a power cable assembly device adapted to be arranged in the spaces between neighbouring power cores of a power cable, comprising a profiled body made of a polymer material and adapted to the cross-sectional shape and elongation of the power cable, said profiled body comprising a chamber and a slit to said chamber, said chamber being adapted to receive a fibre optic cable via said slit. 
         [0002]    It also relates to a power cable comprising such a power cable assembly device. 
       BACKGROUND OF THE INVENTION 
       [0003]    When putting a power cable in the ground, or on the sea floor, it is often practical to add a fibre optic cable in a space between the power cores. 
         [0004]    A power cable assembly device, a power cable and a tool is known from SE-C2-530 277, respectively. The known assembly device however suffers from a complicated access to the chamber containing a fibre optic cable. 
       OBJECT OF THE INVENTION 
       [0005]    The object is to provide a power cable assembly device having an improved design as regards access to the chamber of the profiled body. 
       SUMMARY OF THE INVENTION 
       [0006]    This object has been achieved by the assembly device and the power cable, further comprising the feature that said profiled body is provided with a pair of transitions at least partly defining said slit and converging towards said chamber, said transitions being adapted to supportingly receive a fibre optic cable to be introduced through said slit. 
         [0007]    Hereby is achieved a guided introduction of the fibre optic cable to the chamber. 
         [0008]    In particular, the cross-section of the profiled body includes a first wall, a second wall and a third wall, 
         [0009]    said first wall being convex and having first and second opposite end portions, 
         [0010]    said second wall being concave and having third and fourth opposite end portions, 
         [0011]    said third wall being concave and having fifth and sixth end portions, 
         [0012]    the third end portion of said second wall being connected to said first end portion of said first wall, 
         [0013]    the fifth end portion of said third wall being connected to said second end portion of the first wall, 
         [0014]    said fourth end portion of the second wall forming said first angled transition, 
         [0015]    said the sixth end portion of said third wall connecting to said second angled transition, 
         [0016]    said slit extending in the elongation of the profile for allowing introduction of a fibre optic cable into said chamber. 
         [0017]    Hereby, the profiled body is further defined. 
         [0018]    Suitably, the cross-section of the chamber is substantially annular. Hereby, an optimal shape of the chamber is achieved. Of course, the annular chamber could be polygonal rather than circular. 
         [0019]    Preferably, the diameter of the chamber ( 16 ) is in the range 11-25 mm, more preferably 12-23 mm. 
         [0020]    Suitably, the slit is open in a mounted state, and the distance between the fourth end portion of the second wall and the sixth end portion of the third wall defining the slit is in the range 1 mm-13 mm, more preferably 3-11 mm, even more preferably 4-6 mm, most preferably 5 mm. Hereby the insertion of a fibre optic cable is made allowed to be performed readily and easily. The slit width should be chosen such that the diameter of the fibre optic cable including cover is 1-5 mm larger than the slit width. 
         [0021]    Preferably, the wall thickness of either or all of the second wall, the third wall and a wall defining the chamber has a thickness in the range of 2-6 mm, more preferably 2,5-4 mm, most preferably 3 mm. 
         [0022]    Suitably, the first wall is adapted to face a jacket of the power cable, said a second and a third walls being adapted to face a pair of neighbouring power cores. 
         [0023]    In particular, the concavity of the outer surface of the second and third walls, respectively, is adapted to the number of power cores and the diameter of the power cores. Hereby, a tight fit will be achieved between the assembly profile and neighbouring power cores, and the power cores and the profiles will form a power cable with a substantially circular cross-section with high mechanical stability. 
         [0024]    Furthermore, the convexity of the outer surface of the first wall is adapted to an imaginary circle between a peripheral point of each power core in relation to the diametrical centre point of the power cable. Hereby is achieved a power cable with large form stability when assembled, i.e. the cross-section of the assembled power cable with be substantially circular also at the high pressures on the bottom of sea bottom at large depths. 
         [0025]    Preferably, said first angled transition connects to a first radial transition, said the sixth end portion of said third wall connecting to said second angled transition further connects to a second radial transition, 
         [0026]    said first and second radial transitions being substantially parallel to one another, wherein the first radial transition of the fourth end portion of the second wall and the second radial transition of the sixth end portion of the third wall define together at least a part of said slit. 
         [0027]    Suitably, said polymer material of the profiled body is PVC or PE. Hereby is achieved a profiled body with strong mechanical properties. 
         [0028]    Suitably, the number of power cores is three and the number of power cable assembly devices is three. The diameter of each power core is in the range of 30-140 mm, more preferably 40-130 mm. 
     
    
     
       DRAWING SUMMARY 
         [0029]    In the following, the invention will be described in more detail by reference to the enclosed drawings, in which 
           [0030]      FIG. 1  is a cross-section of a power cable assembly body according to a first embodiment of the invention; 
           [0031]      FIG. 2  is a cross-section of the interior of a power cable provided with the power cable assembly body shown in  FIG. 1 ; 
           [0032]      FIG. 3  is a cross-section of a power cable assembly body according to a second embodiment of the invention; 
           [0033]      FIGS. 4   a - 4   d  illustrate a tool for introduction of a fibre optic cable in a power cable assembly device shown in  FIGS. 1 and 3 ; and 
           [0034]      FIG. 5  illustrates a set up of tools in the assembly of a power cable. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  shows a power cable assembly device  2  in the form of an extruded profiled body  4  with a first wall  6 , a second wall  8 , a third wall  10 . The first wall  6  is convex while the second and third walls  8 ,  10  are concave, the reason for which will be discussed farther below. 
         [0036]    The first wall  6  has a first end  6   a  and a second end  6   b.  Likewise, the second wall  8  has a first end  8   a  and a second end  8   b,  and the third wall  10  has a first end  10   a  and a second end  10   b.  The first end  6   a  of the first wall  6  is connected to the first end  8   a  of the second wall, while the second end  6   b  of the first wall  6  is connected to the first end  10   a  of the third wall  10 . 
         [0037]    The second end  8   b  of the second wall  8  continues to a first angled transition  12   a  and further to a first radial transition  14   a.  Likewise, the second end  10   b  of the third wall  10  continues to a second angled transition  12   b  and further to a second radial transition  14   b.    
         [0038]    The first and second angled transitions  12   a,    12   b  are converging towards the first and second radial transitions  14   a,    14   b,  the latter being substantially parallel to one another and thus substantially radial to the convex first wall  6 . 
         [0039]    According to this embodiment, the first and second radial transitions  14   a,    14   b  are arranged at a distance from one another, defining an open slit  15 . 
         [0040]    Inside the profiled body  4 , a chamber  16  defined by a substantially annular wall  18  is arranged. The annular wall  18  extends from the first radial transition  14   a  to the second radial transition  14   b.  A pair of reinforcement members  20   a,    20   b  are arranged between the annular wall  18  and the first wall  6 . Of course, the number of reinforcement members could be less than two, i.e. one or zero (i.e. leaving an open space between the annular wall  18  and the first wall  6 ), or more than two, i.e. three, four, five or even more, depending on the space available between the circumferential walls. 
         [0041]    The assembly device  2  is made by extrusion of a polymer material, such as PE (e.g. MDPE or HDPE) or PVC and may have a length of several kilometres. 
         [0042]      FIG. 2  shows the interior of a power cable  22  provided with three neighbouring first, second and third power cores  24   a,    24   b,    24   c,  each provided—from the centre to the periphery—with a conductor  25   a,  a first second semi-conductive layer  25   b,  insulation  25   c,  a second semi-conductive layer  25   d,  a layer of swelling material  25   e,  a metal screen  25   f  made of led and a third semi-conductive mantle  25   g.    
         [0043]    The first and second semi-conductive layers  25   b,    25   d  form a smooth surface which controls the electric field strength. The swelling material  25   e  tightens against water in case the led screen  25   f  would start leaking. 
         [0044]    Each power core  24   a,    24   b,    24   c  has a peripheral point  26   a,    26   b,    26   c  in relation to the diametrical centre  19  of the power cable  22 , i.e. in the central space  27   d.  The three peripheral points  26   a,    26   b,    26   c  form together in relation to the centre point  19  an imaginary circle  26   d.    
         [0045]    The first and second power cores  24   a,    24   b  touch one another at a contact point  23   a  and define a peripheral space  27   a  together with the imaginary circle  26   d.  Likewise, the second and third power cores  24   b,    24   c  have a contact point  23   b  and define a second peripheral space  27   b  together with the imaginary circle  26   d.  Likewise, the third and first power cores  24   c  and  24   a  have a contact point  23   c  and define a third peripheral space  27   c  together with the imaginary circle. The first, second and third power cores  24   a,    24   b,    24   c  define between the contact points  23   a,    23   b,    23   c  a central space  27   d.    
         [0046]    In the peripheral space  27   a,  a first assembly device  2   a  is provided. Likewise, a second assembly device  2   b  is arranged in the second peripheral space  27   b,  and a third assembly device  2   c  is arranged in the third peripheral space  27   c.    
         [0047]    The power cable is provided with a jacket  28  to keep the power cores  24   a,    24   b,    24   c  and the assembly devices  2   a,    2   b,    2   c  together as one unit and to keep the circular cylindrical shape and mechanical protection. The jacket  28  comprises—from the periphery towards the centre point  19 —two layers  29   a  of yarn made of polypropylene (PP), a first steel wire armour layer  29   b,  a first soft layer  29   c  of laying bands, a second steel wire armour layer  29   d,  a second soft layer  29   e  of laying bands. 
         [0048]    As can be understood from  FIG. 2 , the concavity of the outer surface of the second and third walls  8 ,  10  of each assembly device  2   a,    2   b,    2   c  depends on the diameter of the power cores  24   a,    24   b,    24   c.  In the same manner, the convexity of the outer surface of the first wall  6  of each assembly device  2   a,    2   b,    2   c  depends on the radius of curvature of the imaginary circle  26   d.    
         [0049]    An elongated fibre optic cable  30  comprises a fibre optic wave conductor  31 , i.e. a bundle of optical fibres inside a metal tubing  32   a  together with a mass  32   b,  such as a gel. The metal tubing  32   a  is covered with a layer of semi-conductive layer  33 . The fibre optic cable  30  is put inside the chamber  16  of assembly device  2   a.    
         [0050]    Of course, this relates correspondingly to the case when a fibre optic cable is put inside the chamber of the assembly devices  2   b  and/or  2   c.    
         [0051]      FIG. 3  shows a second embodiment of an assembly device  2  made by extrusion of a polymer material, such as PE (e.g. MDPE or HDPE) or PVC. 
         [0052]    Also in this embodiment, the first wall  6  of the profiled body  4  is convex and has first and second ends  6   a,    6   b;  the second wall  8  is concave and has first and second ends  8   a ,  8   b;  and the third wall  10  is concave and has first and second ends  10   a,    10   b.  The first, second and third walls are connected to one another as described in connection with  FIG. 1  above. 
         [0053]    The second end  8   b  of the second wall  8  continues to a first angled transition  12   a  and further to a first radial transition  14   a.  Likewise, the second end  10   b  of the third wall  10  continues to a second angled transition  12   b  and further to a second radial transition  14   b.    
         [0054]    The first and second angled transitions  12   a,    12   b  are converging towards the first and second radial transitions  14   a,    14   b,  the latter being substantially parallel to one another and thus substantially radial to the convex first wall  6 . Also in this embodiment the first and second radial transitions  14   a,    14   b  are substantially parallel to one another and are thus substantially radial to the convex first wall  6 . 
         [0055]    However, according to this embodiment, the first and second radial transitions  14   a ,  14   b  are arranged without distance from one another, i.e. the slit  15  is closed at least when mounted, even though the slit for clarity reasons have been shown to be somewhat open. 
         [0056]    Also in this embodiment, the annular wall  18  defining the chamber  16  extends from the first radial transition  14   a  to the second radial transition  14   b.  However, no further reinforcement members are needed. Instead, the annual wall  18  is partly constituted by the first wall  6 . 
         [0057]    Equalisation of the electric potential between the fibre optic cable  30  and metal parts of any one of the power cores  24   a,    24   b,    24   c  could be equalised either by providing the surfaces of the chamber  18 , the radial transitions  14   a,    14   b,  the angled transitions  12   a ,  12   b  and at least a part of the exterior concave walls  8 ,  10  with a semi-conductive layer. Alternatively, the walls could be provided with holes for allowing sea water to circulate inside the chamber  18 . 
         [0058]    The first and second radial transitions  14   a,    14   b  have been shown in  FIGS. 1 and 3  to extend only to a small extent of the lateral extension of the walls  8 ,  10  in relation to the first and second angled transitions  12   a,    12   b.  It should be noted that the lateral extension of the first and second radial transitions may instead be larger than that of the first and second angled transitions  12   a,    12   b.  On the other hand, the first and second radial transitions  14   a,    14   b  may have a minimal lateral extension or no extension at all. 
         [0059]    Alternatively, the radial transitions  14   a,    14   b  may be differently shaped, such as rounded. 
         [0060]      FIG. 4   a  shows a tool  39  provided with support means  46  comprising four support members  48  in the form of double encapsulated ball-bearings  54 . Each ball-bearing  54  is rotatably connected via an axle  72  to a U-shaped bearing support  73  across an axis through the aligned ball-bearings  54 . The tool  39  is furthermore provided with guide means in the form of four pairs of guide wheels  41   a,    41   b  of encapsulated needle bearings  55   a,    55   b,  each rotatable about an axle  76 , said axle  76  being parallel to the axles  72  of the ball-bearings  54 . 
         [0061]    In order to position the four ball-bearings  54  in relation to one another and in relation to the guide wheels, the tool  39  comprises a grid of parallel plates  75  of a first frame part  74   a  of an interconnection means  44  in the form of a frame  74 , together forming a grid. Of course, the grid of parallel plates  75  could instead be constituted by a single plate. 
         [0062]    The frame further comprises a pair of side walls  74   b,    74   c,  connected perpendicularly to the first frame part  74   a  by screws  90 . The side walls  74   b,    74   c  are furthermore adjustably connected to a frame support  74   f  by screws  94  in a row of holes  96 . In this manner, the first frame part  74   a  can be moved in a direction across the row of holes  96 . Thus, the position of a plane through the axles  72  of the ball-bearings  54  can be adjusted in relation to the guide wheels  41   a,    41   b,  depending on the thickness of the profiled body  4 . 
         [0063]    The frame support  74   f  is provided with an entrance opening  92  for introduction of the profiled body  4  into the tool  39 . An access slot  93  in the frame support  74   e  allows for taking the tool  39  apart even if the profiled body  4  is still inside the tool  39 . 
         [0064]    The frame  74  further comprises a pair of plates  74   d,    74   e  each connected to extension plates  74   g,    74   h.  The plates  74   d,    74   e  are each provided with a slot  97   a,    97   b  in their opposing ends (the rear ends being hidden) for adjustable connection with screws  98   a ,  98   b  to a pair of rows of holes  99  in the frame support  74   f.  Hereby, the frame  74  is adjusted for the lateral dimension of the profiled body  4 . 
         [0065]    A pair of reinforcement members  74   i,    74   k  are each provided with four sets of screws  80   a.  Each guide wheel  41   a,    41   b  is independently movable in a slot  78  in the plates  74   d,    74   e  towards a plane through the axles  72  of the ball-bearings  54 , and is adjustable in the slot  78  by means of a corresponding set screw  80   a.  After performed adjustment, the position of the guide wheel  41   a  or  41   b  is fixed by means of a lock nut  80   b.    
         [0066]    The set of screws  80   a  and lock nuts  80   b  are adjusted in such a way that each guide wheel  41   a,    41   b  is positioned at a predetermined distance relative to the support member  48 . In this way, it is possible to adjust each pairs of guide wheels  41   a,    41   b  relative to the other pairs of guide wheels  41   a,    41   b  to bear against the edges of  5   a,    5   b  of the profiled body  4 . By said adjustment, the slit  15  will be widened and thus opened at a predetermined position between the first pair of wheels and the fourth pair of wheels. 
         [0067]    In  FIG. 4   b  is shown an elongated guide beam  82  having lateral sides  82   a,    82   b,  a guide side  82   c  and a connection side  82   d  (hidden). The guide beam  82  is to be arranged opposite to and facing the support members  48 . The guide beam  82  is provided with an elongated guide member  84  to be positioned parallel to a plane through the axles  72  of the ball-bearings  54 , by screws  83   a  in elongated slits  83   b,    83   c  in two pairs of arms  83   d,    83   e  connected to the side walls  74   b,    74   c  of the frame  74 . 
         [0068]    In  FIG. 4   c  is shown the guide beam  82  from the opposite direction. At a first end  82   e  of the guide beam, an elongated U-shaped guide member  85  is provided, while at a second end  82   f,  and on the same longitudinal side  82   c,  an elongated guide member  84  is provided. Between the elongated guide, the U-shaped member  85  and the elongated guide member  84 , a transition section  86   a  is provided between first and second sections  86   b,    86   c.  In the transition section  86   a,  the lateral extension of the elongated U-shaped member  85 , measured from the connection side  82   d  is reduced in a longitudinal direction from the first section  86   b  towards the elongated guide member  84 . Furthermore, in the transition section  86   a  the lateral extension of the elongated member  84 , measured from the connection side  82   d  is reduced in a longitudinal direction from the second section  86   c  towards the U-shaped member  85 . 
         [0069]    In  FIG. 4   d  is shown that the fibre optic cable  30  is controlled to keep a longitudinal orientation relative to the slit  15  of the profiled body by the U-shaped guide member  85  at the first section  86   b  extending from the first end  82   e  to the transition section  86   a . It also shows that the fibre optic cable is introduced into the profiled body  4  via slit  15  by the transition section  86   a  of the diminishing elongated U-shaped guide member  85  and the raising elongated guide member  84 , and that the fibre optic cable  30  is guided to stay inside the chamber by the elongated guide member  84  in the section  86   c  extending from the transition section  86   a  towards the second end  82   f.    
         [0070]      FIG. 5  shows the first step of assembly of the power cable. 
         [0071]    First, the power cores  24   a,    24   b,    24   c  are held 120° in relation to one another by means of not shown equipment in the periphery of an imaginary circle  100 . 
         [0072]    Then, between the power cores  24   a,    24   b,    24   c  three tools  39   a,    39   b,    39   c  of the kind shown in  FIGS. 5   a - d , are arranged 120° in relation to one another in the periphery of the imaginary circle  100  in relation to and between the power cores  24   a,    24   b,    24   c.    
         [0073]    As explained above in connection with  FIG. 4   a , the frame  74  is adjusted for the power cable assembly device  2  to be used, i.e. first frame part  74   a  is mounted in predetermined holes of the frame support  74   f,  and the pair of plates  74   d,    74   e  are mounted in predetermined holes  99 . 
         [0074]    In each tool  39   a,    39   b,    39   c,  a profiled body  4  is positioned between the four pairs of guide wheels  41   a,    41   b,  starting from the level of frame support  74   f  (i.e. seen from the lower part in  FIG. 5   a ) and the four support members  48 . 
         [0075]    The screws  80   a  of the first, second and third pairs of wheels  41   a,    41   b,  counted from the frame support  74   f,  are adjusted such that the slit  15  of the profiled body  4  of  FIG. 1  or  FIG. 3  is opened somewhat more than the diameter of the fibre optic cable  30 , while the fourth pair of wheels  41   a,    41   b  are adjusted to allow the slit  15  to be smaller, such that the width of the slit is less than the diameter of the fibre optic cable  30 , but wider than the transversal dimension of the guide member  84 . 
         [0076]    A fibre optic cable  30  is now introduced via the entrance opening  92  of the frame  74  (cf.  FIG. 4 ) in each profiled body  30  mounted in the tools  39   a,    39   b,    39   c,  and is introduced into the chamber  16  and through the end of the profiled body  4  and temporarily fixed inside the profiled body upon start. 
         [0077]    A guide beam  82  of the kind described above is then mounted. 
         [0078]    Each profiled body  4  is collected together with the power cores  24   a,    24   b,    24   c  at a distance from the tools  39   a,    39   b,    39   c  (above the tools as seen in  FIG. 4   a  and  FIG. 5 ) and are assembled while pulling the profiled bodies  4  and power cores  24   a,    24   b,    24   c  away from the tools  39   a,    39   b,    39   c.    
         [0079]    During this movement, the slit  15  is opened by the support members  48  and the guide members  41 , while fibre optic cables  30  are guided into the chamber by the guide beam  82 . 
         [0080]    It should also be noted that the tools  39   a,    39   b,    39   c  may be mounted for introduction of the fibre optic cable  30  through the entrance opening  92  of the frame  74  horizontally or vertically. 
         [0081]    In case of high torsional stiffness of the profiled body  4 , a higher pressure may have to be applied on one side  8  than the other  10  by the guide wheels  41   a,    41   b,  or a pressure may even only be applied on one side  8  by one or more guide wheels  41   a , while a lower or even no pressure may be applied on the other side  10  by one or more guide wheels  41   b.    
         [0082]    In  FIG. 5  is shown the simultaneous introduction of a fibre optic cable  30  into three power cable assembly devices  2  of a power cable  22 . However, in case only one or two fibre optic cables  30  are to be introduced into the power cable, the tools  39   a,    39   b,    39   c  will still be used as guide tools for the assembly of the cores  24   a,    24   b,    24   c  and the power cable assembly devices. The support members  48  and guide wheels  41   a,    41   b  of the tool or tools used only as guide tools will then preferably be adjusted in such a way that the slit of such profiled bodies  4  will not be opened. 
         [0083]    It should be noted that the guide beam  82  could instead be divided into three different items, corresponding to the sections  86   a,    86   b  and  86   c.  Alternatively, the first and second sections  86   b,    86   c  could instead be a pair of wheels with a peripheral shape corresponding to the cross-section of the first and second sections  86   b,    86   c , respectively. 
         [0084]    It should be noted that the encapsulated ball-bearing  54  could be exchanged to an encapsulated roller bearing, having circular cylindrical rollers, or to plain bearings. 
         [0085]    Likewise, the encapsulated needle-bearings could be exchanged to small ball-bearings or plain bearings. Of course the bearings could also be non-encapsulated.