Patent Publication Number: US-2015084439-A1

Title: Shorting assembly and method for wind turbine power supply

Description:
FIELD OF THE INVENTION 
     The present disclosure is directed to wind turbine power supplies, and more particularly to shorting devices, shorting assemblies and methods for shorting wind turbine power supplies. 
     BACKGROUND OF THE INVENTION 
     Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known airfoil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid. 
     In many instances, it may be desirable to stop the generator from operating or being capable of operating. For example, during routine maintenance or repairs, it is desirable to “lock out” the generator using a “lock out tag out” procedure to ensure that the generator does not injure a worker. Presently known procedures for locking out a generator, however, are cumbersome and time consuming. For example, workers are currently required to climb the wind turbine tower to access the generator in the nacelle directly. After climbing the wind tower, the workers can apply a rotor lock pin into the generator&#39;s shaft, to physically prevent spinning, or can apply locks to a generator in-line circuit breaker after visually verifying that the breaker contacts are open. Because they require workers to climb the wind turbine tower and directly access the generator, however, such procedures increase labor costs and wind turbine downtime, and can increase safety risks to the workers. 
     Accordingly, improved methods and apparatus for locking out wind turbine generators are desired in the art. In particular, methods and apparatus that increase worker safety while reducing labor costs and wind turbine downtime are desired. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In one embodiment, a shorting assembly for a wind turbine power supply is disclosed. The shorting assembly includes a generator, and a plurality of bus bars in electrical communication with and disposed downstream of the generator. The shorting assembly further includes a shorting device removably connectable to the plurality of bus bars. The shorting device includes a plurality of cables, each of the plurality of cables including a first end and a second end. The shorting device further includes a plurality of bus bar connectors, each of the plurality of bus bar connectors attached to the first end of one of the plurality of cables and removably connectable to one of the plurality of bus bars. The shorting device further includes a common cable connector, the second end of each of the plurality of cable attached to the common cable connector. 
     In another embodiment, a shorting device for shorting a power supply, the power supply including a generator and a plurality of bus bars downstream of the generator, is disclosed. The shorting device includes a plurality of cables, each of the plurality of cables including a first end and a second end. The shorting device further includes a plurality of bus bar connectors, each of the plurality of bus bar connectors attached to the first end of one of the plurality of cables and removably connectable to one of the plurality of bus bars. The shorting device further includes a common cable connector, the second end of each of the plurality of cable attached to the common cable connector. 
     In another embodiment, a method for shorting a wind turbine power supply is disclosed. The method includes locating a plurality of bus bars, the plurality of bus bars in electrical communication with a generator of the wind turbine power supply and disposed in a downtower location. The method further includes connecting the plurality of bus bars to a common shorting component. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a side view of a wind turbine in accordance with one embodiment of the present disclosure; 
         FIG. 2  is a schematic view of a wind turbine power supply in accordance with one embodiment of the present disclosure; 
         FIG. 3  is a front view of a shorting device in accordance with one embodiment of the present disclosure; 
         FIG. 4  is a cross-sectional view of a portion of a shorting device removably connected to a wind turbine power supply in accordance with one embodiment of the present disclosure; and 
         FIG. 5  is a perspective view of a shorting device removably connected to a wind turbine power supply in accordance with one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIG. 1  illustrates a wind turbine  10  of conventional construction. The wind turbine  10  includes a tower  12  with a nacelle  14  mounted thereon. A plurality of rotor blades  16  are mounted to a rotor hub  18 , which is in turn connected to a main flange that turns a main rotor shaft. The wind turbine power generation and control components are housed within the nacelle  14 . The view of  FIG. 1  is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration. 
     Referring now to  FIG. 2 , a power supply  50  for a wind turbine is illustrated. As shown, a generator  52  may be housed in the nacelle  14  (see  FIG. 1 ). The hub  18  may be rotatably coupled to the generator  52  via, for example, a shaft and optional gearbox to permit electrical energy to be produced. Rotation of the rotor blades  16  may cause rotation of the hub  18  and thus rotation of a rotor of the generator  52 , which may enable kinetic energy to be transferred from the wind into usable mechanical energy and subsequently electrical energy. 
     Generator  52  may be coupled to a power converter  54 . The power converter  54  may be in electrical communication with and disposed downstream (relative to the flow of electrical power) of the generator  52 . Output multiphase power, such as for example three-phase power, may be supplied from the generator  52 , such as from the rotor of the generator  52 , to the power converter  54 . Specifically, generator  52  may be coupled to a rotor side converter  56  of the power converter  54 . The rotor side converter  56  may in turn be coupled to a line side converter  58  of the converter  54 . After being supplied to the converter  54  from the generator  52 , power may flow to the grid. Additionally, in some embodiments, a main generator circuit breaker  60  may be provided between the generator  52  and the power converter  54 , as shown. 
     Referring still to  FIG. 2  as well as  FIG. 1 , various of the power supply  50  components may be disposed in uptower locations  62 , while others of the power supply components may be disposed in downtower locations  64 . An uptower location  62  is a location in a wind turbine  10  that is accessible generally by climbing up a majority of the tower  12 . Thus, the nacelle  14  and upper platforms in the tower are considered uptower locations  62 . A downtower location  64  is a location in a wind turbine  10  that is accessible generally without requiring climbing up a majority of the tower  12 . Thus, lower platforms in the tower, as well as base platforms and locations at the base of the tower both inside and outside of the tower, are considered downtower locations  64 . As shown, generator  52  may be disposed in an uptower location  62 , such as in nacelle  14 , while power converter  54  may be disposed in a downtower location  64 , such as on a base platform  66  of the tower  12 . Main circuit breaker  60  may in some embodiments additionally be disposed in an uptower location  62 . 
     Referring still to  FIG. 2  as well as to  FIGS. 4 and 5 , the power converter  54  may be disposed in a cabinet  70 . A plurality of bus bars  72 , which may also be disposed in the cabinet  70 , may be in electrical communication with and disposed downstream of the generator  52 . The bus bars  72  may further be in electrical communication with and disposed upstream of the power converter  54 , such as upstream of the rotor side converter  56 . In exemplary embodiments, three bus bars  72  are provided. Further, in some embodiments, ball stud  74  may extend from each bus bar  72 . As shown, a ball stud  74  may include a ball end  76  distal from the bus bar  72 . The bus bars  72  and ball studs  74  are in exemplary embodiments formed from a suitable metal or other suitable conductive material. 
     In some embodiments, a ground ball stud  80  may additionally be provided. The ground ball stud  80  may be similar to a ball stud  74 , and may include a ball end  82 , but may not be connected to and extending from a bus bar  72 . Rather, a ground ball stud  80  may be connected to the cabinet  70  or another suitable location for establishing a voltage reference to ground potential. 
     As discussed above, improved apparatus for locking out the generator  52  are desired in the art. Accordingly, and referring now to  FIGS. 2 through 5 , the present disclosure is further directed to shorting assemblies  100  and shorting devices  102 . A shorting assembly  100  according to the present disclosure may include, for example, a generator  52  and a plurality of bus bars  72 . A shorting assembly  100  may further include a converter  54 . In exemplary embodiments, the generator  52  may be disposed in an uptower location  62 , while the bus bars  72 , including the ball studs  74  thereon, as well as the converter  54  may be disposed in downtower locations  64 . 
     A shorting assembly  100  may further include a shorting device  102 . The shorting device  102  may be utilized to short the wind turbine  10  power supply  50 . Advantageously, use of shorting devices  102  according to the present disclosure may increase worker safety while reducing labor costs and wind turbine downtime, by allowing worker to short the power supply  50  at downtower locations  64 . 
     As shown, a shorting device  102  may include a plurality of cables  110 . In exemplary embodiments, three cables  110  may be provided. Generally, the number of cables  110  may for example match the number of bus bars  72 . Each cable  110  may include a first end  112  and a second end  114 . A cable  110  may be formed from any suitable conductive material, such as for example copper or another suitable metal. In exemplary embodiments, a cable is formed from a braided copper. 
     A shorting device  102  may further include a plurality of bus bar connectors  120 . Each bus bar connector  120  may be attached to the first end  112  of a cable  110 , and may be removably connectable to one of the plurality of bus bars  72 . Referring to  FIG. 4 , for example, one embodiment of a bus bar connector  120  is illustrated. The bus bar connector  120  may include a ball clamp  122 . The ball clamp  122  may include a socket  124  defined therein. The connector  120  may further include an adjustable bolt  126 . The bolt  126  may be threadably engaged with the ball clamp  122 , such that adjustment of the bolt  126  increases or decreases the usable size of the socket  124 . In these embodiments, the bus bar connector  120  may be removably connectable to the ball stud  74  of a bus bar  72 . For example, to connect the device  102  to a bus bar  72 , the ball end  76  may be placed into the socket  124 . The bolt  126  may then be adjusted to contact the ball end  76 , thus connecting the device  102  and bus bar  72 . It should be understood, however, that the present disclosure is not limited to the above-disclosed apparatus for removable connection to a ball stud  74 . Rather, any suitable connecting means for connecting a shorting device  102  to a bus bar  72  are within the scope and spirit of the present disclosure. 
     As mentioned, a bus bar connector  120  may be attached to a first end  112  of a cable  110 . For example, referring still to  FIG. 4 , a bus bar connector  120  may include a single-cable fitting  128 , to which the first end  112  of a cable  110  may be attached. The fitting  128  may further be attached to a ball clamp  122  as shown or other suitable component, such as through a threadable connection. Further, a bus bar connector  120  may include a compression lug  130 , which may attach the first end  112  of a cable  110  to the fitting  128 . For example, the first end  112  may be compression fit into the compression lug  130 , and the compression lug  130  may be attached to the fitting  128 , such as through a threadable connection as shown. Alternatively, however, any suitable attachment between the cable  110  and bus bar connector  120  is within the scope and spirit of the present disclosure. 
     A shorting device  102  according to the present disclosure may further include a common cable connector  140 . The common cable connector  140  may be attached to the second ends  114  of each cable  110  of the shorting device  102 . Further, in some embodiments, the common cable connector  140  may be removably connectable to a point of zero electrical potential, such as the cabinet  70  or ground ball stud  80 . However, it should be understood that the shorting device  102  need not necessarily be connected to a point of zero electrical potential in order to achieve a shorting effect on the generator. Referring to  FIGS. 3 and 5 , for example, one embodiment of a common cable connector  140  is illustrated. The common cable connector  140  may include a ball clamp  142 , similar to the ball clamp of a bus bar connector  120 . The ball clamp  142  may include a socket  144  defined therein. The connector  140  may further include an adjustable bolt  146 . The bolt  146  may be threadably engaged with the ball clamp  142 , such that adjustment of the bolt  146  increases or decreases the usable size of the socket  144 . In these embodiments, the common cable connector  140  may be removably connectable to the ground ball stud  80 . For example, to connect the device  102  to the ground ball stud  80 , the ball end  82  may be placed into the socket  144 . The bolt  146  may then be adjusted to contact the ball end  82 , thus connecting the device  102  and ground ball stud  80 . It should be understood, however, that the present disclosure is not limited to the above-disclosed apparatus for removable connection to a ground ball stud  80 . Rather, any suitable connecting means for connecting a shorting device  102  to a point of zero electrical potential are within the scope and spirit of the present disclosure. Further, it should be understood that shorting device  102  need not be connected to a point of zero electrical potential, and rather that shorting device  102  operates to achieve a shorting effect on the generator merely by connecting cables  110  to the common cable connector  140 . 
     As mentioned, the common cable connector  140  may be attached to a second end  114  of each cable  110 . For example, referring still to  FIGS. 3 and 5 , a common cable connector  140  may include a multiple-cable fitting  148 , such as a tri-cable fitting in exemplary embodiments, to which the second end  114  of each cable  110  may be attached. The fitting  148  may further be attached to the ball clamp  142  as shown or other suitable component, such as through a threadable connection. Further, a common cable connector  140  may include a plurality of compression lugs  150 , which may attach the second end  114  of each cable  110  to the fitting  148 . For example, the second end  114  of each cable  110  may be compression fit into the compression lug  150 , and each compression lug  150  may be attached to the fitting  148 , such as through a threadable connection as shown. Alternatively, however, any suitable attachment between the cables  110  and common cable connector  140  is within the scope and spirit of the present disclosure. 
     As mentioned, in some embodiments, the common cable connector  140  need not be connected to a point of zero electrical potential. In these embodiments, the common cable connector  140  still acts as the point of commonality for the shorting device  102  and shorting assembly  100 . In other embodiments, the common cable connector  140  may be connected to a ground source, such as discussed above. 
     Connection of the shorting device  102  to the bus bars  72  may advantageously short the power supply  50 , generally preventing the generator  52  from spinning fast enough to create a dangerous voltage level. Such shorting is caused because the various phases of power being generated by the generator  52  are shorted together by the shorting device  102  when the shorting device  102  is connected to each phase through connection to the bus bars  72 . When shorted, the generator  52  is prevented from spinning at a relatively high rotational speed, because the shorting device  102  introduces a resistive rotational torque in a direction opposite to the direction in which the generator  102  is spinning. 
     Further, advantageously, use of a shorting device  102  and shorting assembly  100  according to the present disclosure may increase worker safety while reducing labor costs and wind turbine downtime, because the shorting device  102  can be utilized to short the power supply  50  from a downtower location  64 , as discussed herein. 
     It should be understood that shorting devices  102  according to the present disclosure are not limited to use in wind turbines  10  with wind turbine power supplies  50 , but rather that use with any suitable power supply  50  is within the scope and spirit of the present disclosure. 
     The present disclosure is further directed to methods for shorting a wind turbine power supply  50 . A method may include, for example, the step of locating a plurality of bus bars  72 . The plurality of bus bars  72  may be in electrical communication with a generator  52  of the wind turbine power supply  50  and disposed in a downtower location  64 . A method may further include, for example, connecting the plurality of bus bars  72  to a common shorting component. In exemplary embodiments, for example, such connection may include removably connecting a shorting device  102  to each of the plurality of bus bars  72 . 
     In some embodiments, the generator  52  is disposed in an uptower location  62 . Further, in some embodiments, the wind turbine power supply  50  further comprises a converter  54 , the converter comprising the plurality of bus bars  72 . 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.