Abstract:
A wind turbine generator includes a tower, a nacelle mounted on the tower, at least one cable suspended downward from the nacelle inside the tower, a protective tube attached to the cable to surround the cable, and a cable swing restraint support attached to the tower and provided in a position opposed to the protective tube to surround the protective tube. The protective tube is relatively movable with respect to the cable swing restraint support.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of International Application No. PCT/JP2010/055961, filed on Mar. 31, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a wind turbine generator, more particularly, to a cable holding structure for holding a cable suspended from the nacelle of the wind turbine generator. 
     2. Description of the Related Art 
     One distinctive feature of a wind turbine generator is that main components constituting the wind turbine generator, such as a generator, a pitch control system and a yaw control system, are provided away from the ground. More specifically, a nacelle is provided on the top of a tower so that the nacelle is rotatable in the azimuth direction, and the nacelle is installed with a generator, the gear box, a pitch control system and a yaw control system. 
     Cables are suspended inside the tower to connect the components installed in the nacelle to facilities provided on the ground (such as in-site transmission lines and a SCADA (Supervisory Control And Data Acquisition)). The suspended cables include a power cable connected to the generator, and a control cable used for controlling the components installed in the nacelle. It is important in increasing the reliability of the wind turbine generator to appropriately design a cable holding structure which suspends and holds these cables. 
     One difficulty of the cable holding structure is how to deal with the rotation of the nacelle. Since a twist is given to the cable by the rotation of the nacelle, it is desirable that the cable holding structure is so designed as to structurally absorb the twist of the cable. U.S. Pat. No. 6,713,891 B2 discloses a cable holding structure that gives a downwards curve to a cable by using a fixing device provided with an upward curved plate so that the twist of the cable is absorbed by this downwards curve. Further, U.S. Pat. No. 6,713,891 B2 also discloses a cable holding structure for maintaining adjacent cables to be spaced at a constant distance. 
     Another difficulty of the cable holding structure is that, when the wind turbine generator is driven, the tower is largely shaken and hence the cables are largely swung. When the cables are largely swung, it may cause a contact between a structural member (e.g., a ladder) in the tower and the cables, resulting in damages of the cables. U.S. Patent Publication No. 2009/0206610 (A1) discloses a wind turbine generator provided with a first cable guard for covering a ladder and a second cable guard of a tubular shape for suppressing a movement of a cable in a tower. 
     However, there is room for improvement in these known cable holding structures in view of avoiding the cables being damaged. 
     SUMMARY 
     Therefore, an objective of the present invention is to provide a cable holding structure which effectively avoids a cable being damaged. 
     In one aspect of the present invention, a wind turbine generator includes a tower, a nacelle mounted on the tower, at least one cable suspended downward from the nacelle inside the tower, a protective tube attached to the cable to surround the cable, and a cable swing restraint support attached to the tower and provided in a position opposed to the protective tube to surround the protective tube. The protective tube is relatively movable with respect to the cable swing restraint support. 
     In a case where said at least one cable includes first and second cables, the wind turbine generator is preferably further provided with an inter-cable spacing retention mechanism including a spacer for retaining a spacing between the first and second cables. Preferably, the inter-cable spacing retention mechanism is relatively movable with respect to the tower. 
     Preferably, the spacing between the first cable and the second cable retained by the protective tube is substantially the same as that between the first cable and the second cable retained by the spacer tube. 
     In one embodiment, the wind turbine generator further includes a cable guide coupled to a lower frame of the nacelle and a cable securing cleat attached to the cable guide to support the cable. The cable securing cleat includes an elastic spacer attached to the cable to surround the cable and first and second members for holding the elastic spacer clamped therebetween, wherein the first and second members are attached to the cable guide. 
     In one embodiment, the cable securing cleat further includes a coil spring, a bolt and a nut screwed with the bolt. The first member includes a tubular sleeve. The sleeve has a first opening through the bottom portion thereof while the coil spring is inserted to the sleeve. Meanwhile, the second member has a second opening. The bolt and nut are fastened in a state in which the bolt is put through the coil spring and the first and second openings, whereby the first and second members are coupled. 
     In the case where the wind turbine generator further includes a cable drum for providing a downwards curve for the cable, the protective tube and the cable swing restraint support are preferably positioned between the downwards curve and the nacelle. 
     The present invention provides a cable holding structure which effectively avoids a cable being damaged. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view showing the configuration of a wind turbine generator in one embodiment of the present invention; 
         FIG. 2  is a perspective view showing the inner structure of a tower in one embodiment; 
         FIG. 3A  is a side view showing the structure of a cable swing restraint structure in one embodiment; 
         FIG. 3B  is a top plan view showing the structure of the cable swing restraint structure in  FIG. 3A ; 
         FIG. 4A  is a top plan view showing the structure of securing a cable to a protective tube in one embodiment; 
         FIG. 4B  is a side view showing a structure for securing a cable to a protective tube; 
         FIG. 5A  is a sectional view showing the configuration of an inter-cable spacing retention structure in one embodiment; 
         FIG. 5B  is a side view showing the configuration of the inter-cable spacing retention structure in  FIG. 5A ; 
         FIG. 6A  is a side view showing the structure of the part A in  FIG. 2 ; 
         FIG. 6B  is a diagram when seeing downward from the plane a-a in  FIG. 6A ; 
         FIG. 7A  is a side view showing a structure of a cable securing cleat in one embodiment; 
         FIG. 7B  is a sectional view showing the structure of the cable securing cleat in  FIG. 7A ; 
         FIG. 7C  is a top plan view showing the structure of the cable securing cleat in  FIG. 7A ; 
         FIG. 7D  is a side view showing a structure of an elastic spacer of the cable securing cleat in  FIG. 7A ; 
         FIG. 7E  is a top plan view showing the structure of the elastic spacer of the cable securing cleat in  FIG. 7A ; 
         FIG. 8A  is a side view showing a structure of a cable securing cleat in one embodiment; 
         FIG. 8B  is a top plan view of a spacer main body in  FIG. 8A ; and 
         FIG. 8C  is a side view of the spacer main body in  FIG. 8A . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is a side view showing the configuration of a wind turbine generator  1  in one embodiment of the present invention. The wind turbine generator  1  includes a tower  2  stood on a foundation  6 , a nacelle  3  provided on the top end of the tower  2 , a rotor head  4  rotatably attached to the nacelle  3 , and wind turbine blades  5  attached to the rotor head  4 . The rotor head  4  and the wind turbine blades  5  constitute a wind turbine rotor. When the wind turbine rotor is rotated by wind power, the wind turbine generator  1  generates electric power and supplies the power to the utility grid connected with the wind turbine generator  1 . 
       FIG. 2  is a perspective view showing the inner structure of the tower  2 . In this embodiment, two bundles of cables  7  and  8  are suspended from the nacelle  3 . The cables  7  are used for supplying control signals to equipment provided in the nacelle  3  (e.g., a nacelle control panel, a generator and the like) and sending control signals from the equipment to an external control device (e.g., SCADA (Supervisory Control And Data Acquisition)). Meanwhile, the cables  8  are power cables for connecting the generator provided in the nacelle  3  and the utility grid. Herein, the number of the bundles of the cables is not limited to two. In the following, a detailed description is given of the structure provided in the tower  2  and the structure for holding the cables  7  and  8 . 
     A ladder  11  is vertically attached to the inner face of the tower  2 , and an upper landing  12  and a lower landing  13  are further provided. The upper landing  12  and the lower landing  13  have openings, respectively, and the ladder  11  passes through the openings. A worker can reach the upper landing  12  by climbing the ladder  11 . 
     A lower frame  14  of the nacelle  3  has an opening  14   a  used for a worker to get in and out therethrough and, in the proximity thereof, a cable guide  15  is attached to the undersurface of the lower frame  14 . An access ladder  16  is attached to the cable guide  15 . A worker can enter the inside of the nacelle  3  by climbing the access ladder  16  from the upper landing  12 . The cable guide  15  is attached so that the rotation axis of the nacelle  3  is vertically extended to pass through the inside the cable guide  15 . The cables  7  and  8  are routed through the cable guide  15  and attached to the cable guide  15  and suspended therefrom. The structures for attaching the cables  7  and  8  to the cable guide  15  are described later. The cables  7  and  8  are extended downward from the cable guide  15  to pass through the opening provided through the upper landing  12 . 
     A cable drum  17  is attached to a position between the upper landing  12  and the lower landing  13  on the inner face of the tower  2 . The cables  7  and  8  suspended from the cable guide  15  are routed along the upper surface of the cable drum  17  and further guided downward the cable drum  17 . The cable drum  17  has a function of providing a downward curve  18  for the cables  7  and  8  suspended from the cable guide  15 . The existence of the downward curve  18  is useful for accepting a twist of the cables  7  and  8  when the nacelle  3  is rotated. Even when the cables  7  and  8  are twisted by the rotation of the nacelle  3 , the twist is absorbed by the downward curve  18  so that the rotation of the nacelle  3  does not cause displacements of the cables  7  and  8  below the cable drum  17 . This effectively facilitates the connection of the cables  7  and  8  to the facilities built on the ground. 
     In order to restrict the swing of the cables  7  and  8 , a cable swing restraint structure  20  is provided between the cable guide  15  and the cable drum  17 . The cable swing restraint structure  20  is attached to the ladder  11 . In addition, an inter-cable spacing retention structure  30  is attached to the cables  7  and  8  to appropriately retain the spacing between the cables  7  and  8 . In this embodiment, the cable swing restraint structure  20  and the inter-cable spacing retention structure  30  mainly provide a function of preventing the cables  7  and  8  from being damaged. It should be noted that, although one cable swing restraint structure  20  and one inter-cable spacing retention structure  30  are shown in  FIG. 2 , two or more cable swing restraint structures  20  and two or more inter-cable spacing retention structures  30  may be attached to the cables  7  and  8 . In the following, a description is given of the cable swing restraint structure  20  and the inter-cable spacing retention structure  30 . 
       FIG. 3A  is a side view showing the structure of the cable swing restraint structure  20 , and  FIG. 3B  is a top plan view thereof. The cable swing restraint structure  20  includes a pair of arms  21  fixed to the ladder  11  and a cable swing restraint support  22 . The cable swing restraint support  22  has a ring shape, and the cables  7  and  8  are suspended to pass through the cable swing restraint support  22 . The arms  21  and the cable swing restraint support  22  are made of metal material, for example, steel. A cylindrical protective tube  23  is attached to the cables  7  and  8  at a position opposed to the cable swing restraint support  22 . The protective tube  23  is made of resin (typically, vinyl chloride), and the cables  7  and  8  are bound and fixed to the inner face of the protective tube  23  by binding bands  24  and  25 . 
       FIG. 4A  is a top plan view showing the structure for securing the cables  7  and  8  to the protective tube  23 , and  FIG. 4B  is a side view thereof. Referring to  FIG. 4A , the protective tube  23  includes two semi-cylindrical members  23   a  and  23   b . Each of the members  23   a  and  23   b  is provided with openings so that the members  23   a  and  23   b  are coupled by binding bands  23   c . The structure in which the protective tube  23  is dividable into two members allows easily attaching the protective tube  23  to the cables  7  and  8 . A band made of elastic material, specifically a rubber band  26  is wrapped around the cable bundle  7  so that the cables  7  are bundled together by the rubber band  26 . Further, openings are formed through the protective tube  23  in the vicinity of the position where the cable bundle  7  is secured, so that binding bands  24  are routed through the openings from the outside of the protective tube  23 . The cables  7  are bound to the inner surface of the protective tube  23  on the face of the rubber band  26  by the binding bands  24 . Similarly, a rubber band  27  is wrapped around the cable bundle  8  so that the cables  8  are bundled together by the rubber band  27 . Further, openings are formed through the protective tube  23  in the vicinity of the position where the cables  8  are secured, so that the binding bands  25  are routed through the openings from the outside of the protective tube  23 . The cables  8  are bound to the inner surface of the protective tube  23  on the rubber band  27  by the binding band  25 . 
     The cable swing restraint structure  20  restrains movements of the cables  7  and  8  by the cable swing restraint support  22  so as to reduce the swings of the cables  7  and  8 . This is effective to reduce the damages of the cables  7  and  8  in the positions where the cables  7  and  8  are attached to the cable guide  15 . It should be noted, however, that the cable swing restraint structure  20  accepts the swings of the cables  7  and  8  to some degrees and is not a structure of securely holding the cables. This aims to accept the twists of the cables  7  and  8  when the nacelle  3  is rotated. When the nacelle  3  is rotated, the cables  7  and  8  are twisted. Here, the twists of the cables  7  and  8  are accepted, since the cables  7  and  8  are mechanically separated from the cable swing restraint support  22 . As described above, the twists of the cables  7  and  8  are absorbed by the downward curve  18  formed by the cable drum  17 . 
     In this configuration, the protective tube  23  provides a function of preventing damages of the cables  7  and  8  when the cables  7  and  8  are swung. In this embodiment, when the cables  7  and  8  are swung, the protective tube  23  comes into contact with the cable swing restraint support  22  so that the cables  7  and  8  do not come into contact with the cable swing restraint support  22 . Thus, the cables  7  and  8  are effectively protected. 
     Meanwhile,  FIG. 5A  is a sectional view showing the structure of the inter-cable spacing retention structure  30 , and  FIG. 5B  is a side view thereof. As shown in  FIG. 5A , a band made of elastic material, specifically a rubber band  31  is wrapped around the cables  7  so that the cables  7  are bundled by the rubber band  31 . Similarly, a rubber band  32  is wrapped around the cables  8  so that the cables  8  are bundled by the rubber band  32 . 
     The inter-cable spacing retention structure  30  includes a spacer tube  33 . The spacer tube  33  provides a function for retaining a constant spacing between the cables  7  and  8 . The spacer tube  33  is provided with openings formed in the vicinity of a portion to which the cables  7  are abutted so that the cables  7  are bound to the outer face of the spacer tube  33  by a binding band  34  which is routed through the openings. Similarly, the spacer tube  33  is also provided with openings formed in the vicinity of a portion to which the cables  8  are abutted so that the cables  8  are bound to the outer face of the spacer tube  33  by a binding band  35  which is routed through the openings. 
     The cable swing restraint structure  20  and the inter-cable spacing retention structure  30  mechanically couple the cables  7  and  8  with a constant spacing kept between the cables  7  and  8 , preventing the cables  7  and  8  from coming into contact with each other. The use of the inter-cable spacing retention structure  30  makes it unlikely that the cables  7  and  8  come into contact with each other when the cables  7  and  8  are twisted by the rotation of the nacelle  3 . This effectively prevents damages of the cables  7  and  8  when the nacelle  3  is rotated. In order to effect such a function, it is preferable that the spacing between the cables  7  and  8  retained by the protective tube  23  of the cable swing restraint structure  20  is substantially the same as the spacing between the cables  7  and  8  retained by the spacer tube  33  of the inter-cable retaining structure  30 . 
     Various structures may be used for attaching the cables  7  and  8  to the cable guide  15 . It is important not to be applied an excessive force to the coatings of the cables  7  and  8  while the cables  7  and  8  are securely fixed. In the following, a description is given of preferred structures for attaching the cables  7  and  8  to the cable guide  15 . 
       FIG. 6A  is a side view of the structure of the part A shown in  FIG. 2 , particularly the structure of attaching the cables  7  and  8  to the cable guide  15 , and  FIG. 62  is a diagram viewed downward from the plane a-a. As shown in  FIG. 66 , the cables  7  and  8  are secured to the cable guide  15  by cable securing cleats  40  and  50 , respectively, in this embodiment. 
       FIGS. 7A to 7E  are diagrams showing the structure of the cable securing cleat  40  for securing the cable bundle  7 . With reference to  FIG. 7A , the cable securing cleat  40  includes an elastic spacer  41 , a subsidiary plate  42 , a U-shaped cleat main body  43 , bolts  44  and nuts  45 . The elastic spacer  41  is made of elastic material such as rubber. The elastic spacer  41  is provided with an opening  41   b  having a shape corresponding to the bundle of the cables  7 . In addition, the elastic spacer  41  is provided with a slit  41   c  so that the bundle of the cables  7  can be put through the opening  41   b  by opening the slit  41   c . As shown in  FIGS. 7D and 7E , the elastic spacer  41  includes a spacer main body  41   a  and side plate portions  41   d  and  41   e  provided on both sides thereof. The side plate portions  41   d  and  41   e  are outwardly protruded from the spacer main body  41   a  and the cleat body  43  is abutted to the spacer main body  41   a  between the side plate portions  41   d  and  41   e . These side plate portions  41   d  and  41   e  have a function of preventing the elastic spacer  41  from displacing in the axial direction of the cables  7 . 
     As shown in  FIGS. 7B and 7C , the subsidiary plate  42  and the cleat body  43  are provided with openings through which the bolts  44  are put. The elastic spacer  41  is clamped between the cleat body  43  and the subsidiary plate  42  in a state that the cables  7  are put through the opening  41   b  (see  FIG. 7B ), and further the cleat body  43 , the subsidiary plate  42  and the cable guide  15  are clamped by the bolts  44  and nuts  45 , whereby the cable securing cleat  40  is attached to the cable guide  15 . 
     It is preferable to use so-called “a hard lock nut” as the nuts  45 . The hard lock nut is a nut assembly including an upper nut having a recess and a lower nut having a protrusion engaged with the recess. The hard lock nut is disclosed, for example, in U.S. Pat. No. 6,609,867. 
     The cable securing cleat  40  shown in  FIGS. 7A to 7E  supports the cables  7  by surrounding the cables  7  with the elastic spacer  41 , and further clamping the elastic spacer  41  between the cleat body  43  and the subsidiary plate  42 . The cable securing cleat  40  having such a structure can support the cables  7  with an optimum strength, while restraining the coatings of the cables  7  from being damaged. 
     On the other hand,  FIGS. 8A to 8C  are diagrams showing the structure of the cable securing cleat  50  for supporting the cables  8 . The cable securing cleat  50  has a structure different from that of the cable securing cleat  40  mentioned above as to be described below. With reference to  FIG. 8A , the cable securing cleat  50  includes an elastic spacer  51 , a main body lower part  52 , a main body upper part  53 , bolts  54 , nuts  55 , coil springs  56 , bolts  57 , nuts  58  and washers  59 . Although only one bolt  54 , one nut  55 , one coil spring  56 , one bolt  57 , one nut  58  and one washer  59  are shown in  FIG. 8A , it should be understood that that these parts are provided in pairs provided across the elastic spacer  51 . 
     The elastic spacer  51  is provided with an opening  51   b  having a shape corresponding to the bundle of the cables  8 . In addition, the elastic spacer  51  is provided with a slit  51   c  so that the bundle of the cables  8  can be put through the opening  51   b  by opening the slit  51   c . As shown in  FIGS. 8B and 8C , the elastic spacer  51  includes a spacer main body  51   a  and side plate portions  51   d  and  51   e  provided on both sides thereof. The side plate portions  51   d  and  51   e  are outwardly protruded from the spacer main body  51   a , and the main body lower part  52  and the main body upper part  53  are abutted to the spacer main body  51   a  between the side plate portions  51   d  and  51   e . These side plate portions  51   d  and  51   e  provide a function of preventing the elastic spacer  51  from displacing in the axial direction of the cables  8 . 
     Referring back to  FIG. 8A , the main body lower part  52  and the main body upper part  53  are clamped by the coil springs  56 , the bolts  57  and the nuts  58 . More specifically, the main body upper part  53  is provided with cylindrical sleeves  53   a , and openings  53   b  are formed through the bottom portions of the respective sleeve  53   a . In addition, the main body lower part  52  is provided with openings  52   b  opposing to the openings  53   b . The coil springs  56  are inserted into the sleeves  53   a  of the main body upper part  53 , and the bolts  57  are so inserted through the coil springs  56  and the openings  53   b  and  52   b . The washers  59  are provided between the bolts  57  and the coil springs  56 . The cables  8  are fixed to the cable securing cleat  50  by tightening the bolts  57  and the nuts  58  in a state in which the cables  8  are surrounded with the elastic spacer  51 . Here, the force of clamping the elastic spacer  51  between the main body lower part  52  and the main body upper part  53  is adjusted by the spring constant of the coil springs  56  and the tightening torque of the bolts  57 . 
     Moreover, the main body lower part  52  is provided with openings  52   a  through which the bolts  54  are inserted. The cable securing cleat  50  is attached to the cable guide  15  by clamping the main body lower part  52  and the cable guide  15  with the bolts  54  and the nuts  55 . A hard lock nut mentioned above may be preferably used as the nuts  55 . 
     The cable securing cleat  50  shown in  FIGS. 8A to 8C  supports the cable bundle  8  by surrounding the cables  8  with the elastic spacer  51 , and further clamping the elastic spacer  51  between the main body lower part  52  and the main body upper part  53 . Here, the force of clamping the elastic spacer  51  between the main body lower part  52  and the main body upper part  53  is adjusted by the spring constant of the coil springs  56  and the clamping torque of the bolts  57 . The cable securing cleat  50  having such a structure can support the cables  8  with an optimum strength while suppressing the damage of the coatings of the cables  8 , even when the bundle of the cables  8  is thick. 
     Referring back to  FIG. 6A , a cable protection structure  60  is provided in a position opposing to the upper landing  12  of the cables  7  and  8 . The cable protection structure  60  provides a function of preventing a contact between the upper landing  12  and the cables  7  and  8  to thereby protect the cables. Specifically, a cylindrical cable swing restraint tube  61  is fixed to the circumference of the opening formed through the upper landing  12  for routing the cables  7  and  8  therethrough. The cables  7  and  8  are routed through the cable swing restraint tube  61  so that the cable swing restraint tube  61  also provides a function of restraining the movements of the cables  7  and  8  and thereby reducing the swings of the cables  7  and  8 . Meanwhile, a protective tube  62  is attached to the cables  7  and  8  at a position opposing to the cable swing restraint tube  61 . The structure of attaching the cables  7  and  8  to the protective tube  62  is the same as the structure shown in  FIGS. 4A and 4B . When the cables  7  and  8  are swung, the protective tube  62  comes into contact with the cable swing restraint tube  61 , avoiding the cables  7  and  8  being in direct contact with the cable swing restraint tube  61 . Thus, the swings of the cables  7  and  8  are restrained while the cables  7  and  8  are prevented from being damaged. 
     Although the embodiments of the present invention are described above in specific, the present invention should not be interpreted as being limited to the embodiments and it would be apparent for those skilled in the art that various changes or modifications may be made.