Connection interface and method for electrical connection of a rotational part and a stationary part of a wind turbine

The invention disclosed herein relates to a connection inter face and a method for electrical connection of a rotational part and a stationary part of a wind turbine.

Connection interfaces based on electrical connection ele ments, such as copper brushes are used in wind turbines to transfer the current from stationary part to the rotational part, vice versa during a lightning strike, for example.

Springs are used to hold a brush firmly against a rotary part to keep the brush intact and in position. If the pressure of the spring is too light, imperfect contact results in spark over and threading may occur on the rotatory part. As springs weaken with age, rapidly if overheated, low spring pressure is a common problem. Thus, brushes may momentarily separate from the rotating surface when struck by an irregularity.

Further, brush wear increases when the pressure falls below the recommended lower limit. This wear is more severe than a wear caused by high pressures.

Very often, brushes are used for the purpose of transferring lightning current, which may have a magnitude of up to 200kA. If the brushes do not work properly, a flashover may occur, which results in a high chance of a fire accident.

If the contact resistance of a connection interface using a brush increases, sensitive equipment in a particular wind turbine may fail and the connection interface may be damaged.

In earlier turbine design, the brushes where placed in loca tions where the lateral movement was minimal. However, newer lightning protection designs demand brushes to be placed in locations where lateral displacement is increased. Thus, load and fatigue on the spring is also increased such that the risk of spring failure is high.

In order to prevent damage of a wind turbine from damaged springs, the springs have to be manually checked on a regular basis.

It is an object of the present invention to provide for a possibility to maximize a service interval for manual check of a connection interface for electrical connection of a ro tational part and a stationary part of a wind turbine.

This object is solved by the subject-matter of the claims. In particular, the object is solved by a connection interface, a wind turbine and a method according to the independent claims. Further details of the invention unfold from the oth er claims as well as the description and the drawings. There by, the features and details described in connection with the connection interface apply in connection with the wind tur bine and the method, so that the disclosure of the individual aspects of the invention can be referred to one another.

According to a first aspect of the invention, a connection interface for maintaining an electrical connection of a rota tional part and a stationary part of a wind turbine is dis closed. The connection interface comprises a first connection element for electrical connection with the rotational part, a second connection element for electrical connection with the stationary part, an elastic element for pressing the first connection element in a first direction towards the rotation al part, and a clamping element for clamping the first con nection element in a clamped position. The clamping element comprises a number of locking elements that are configured to allow movement of the first connection element in the first direction and that are configured to block movement of the first connection element in a second direction towards the stationary part. In the context of the present invention, a brush is an ele ment for establishing an electrical connection between two elements, such as a rotational part and a stationary part of a wind turbine.

In the context of the present invention, a rotational part is a part that is movable with respect to a stationary part. A rotational part may be a nacelle moving with respect to a tower. Of course, a rotational part may also be a tower that moves relative to a nacelle, for example.

In the context of the present invention, an elastic element may be any structure providing a dynamic pressure force, such as a spring or a flexible part made from rubber and/or plas tic, for example.

The connection interface described herein is based on the principle that a clamping element is used for clamping a first connection element, which may be a brush, in a clamped position. The clamped position may be a position where the first connection element is in contact with a rotational part of a wind turbine such that electrical connectivity between the rotational part and the first connection is maintained as the rotational element moves.

For clamping the first connection element in the clamped po sition, the clamping element comprises a number of locking elements. The locking elements are configured to allow move ment of the first connection element in a first direction to wards the rotational part. Thus, the first connection element may be moved along the locking elements in the first direc tion, in order to be pressed against the rotational part by the elastic element and/or by lateral movement, i.e. movement along an axis in which the elastic element presses the first connection element, for example.

Further, the locking elements are configured to block move- ment of the first connection element in a second direction towards the stationary part. Thus, the first connection ele ment cannot move along the locking elements in the second di rection. Accordingly, the locking elements reduce or minimize a force with which the first connection element pushes back on the elastic element in the second direction, such that the elastic element is saved from being worn out early. Accord ingly, the elastic element lasts longer and a service inter val for manual check of the connection interface can be lengthened with respect to known connection interfaces.

Since the locking elements of the connection interface ac cording to the present invention reduce or even minimize a force of the first connection element pushing back in the second direction, i.e. against a spring force or pushing force provided by the elastic element, the elastic element of the connection interface may be construed very small and/or light. Thus, a block of an elastic material, such as rubber and/or plastic, may be used as elastic element, which is less prone to being worn out than a mechanical spring, for exam ple.

According to an example, the locking elements each comprise a movable part that is movable from a standard position in the first direction and that is immovable from the standard posi tion in the second direction.

By using locking elements comprising movable parts that are movable from a standard position in the first direction, a movement of the first connection element in the first direc tion can be facilitated. Thus, as the first connection ele ment moves along the locking elements in the first direction, the locking elements may be urged in the first direction to gether with the first connection element, thereby providing a space in which the first connection element can move.

In order to block movement of the first connection in the second direction, the locking elements may be immovable in the second direction. Thus, as the first connection element is pushed in the second direction, a force pushing the first connection element is transmitted on the locking elements, which may transmit the force further into surrounding ob jects, such as a body or a screw. For blocking movement of the locking elements in the second direction, the locking el ements may be shaped in a way that minimizes movement of the locking elements in the second direction and enables movement in the first direction, such as a wedge-shape, a sawtooth- shape or a triangle-shape, for example.

According to another example, the locking elements are placed at a connecting side of the clamping element pointing to the first connection element, and the locking elements are ar ranged in an angle pointing towards the rotational part.

By using locking elements that are arranged in an angle pointing towards the rotational part, i.e. pointing in the first direction, movement of the locking elements and, there fore, movement of the first connection element moving along the locking elements is facilitated.

By using a locking element that is arranged in an angle pointing towards the rotational part, a distance between an outer point of a locking element and a plate carrying the locking element is minimized in the first direction and max imized in the second direction. Accordingly, an amount of en ergy needed to move the locking element in the first direc tion is very small, whereas an amount of energy needed to move the locking in the second direction opposite the first direction, is very high.

According to another example, the locking elements are wedge- shaped with an outer part pointing towards the first connec tion element.

Wedge-shaped locking elements facilitate an engagement of the locking elements with the first connection element as the first connection element moves in the second direction. Thus, movement of the first connection element in the second direc tion is blocked as wedge-shaped elements are immovable in the second direction. Moreover, wedge-shaped locking elements guide the first connection element towards their thicker part as the first connection element pushes in the second direc tion, thereby protecting themselves from being cracked.

According to another example, the clamping element comprises at least two plates configured to at least zonally surround the first connection element, wherein each of the at least two plates provide a plurality of locking elements, wherein the locking elements of opposing plates face each other, wherein a first distance between the at least two plates is wider than a width of the first connection element, and wherein a second distance between the locking elements facing each other is smaller than the width of the first connection element.

By using plates carrying locking elements to surround a first connection element, a space in which the first connection is moving, can be defined. By defining the space such that a first distance between the at least two plates is wider than a width of the first connection element, and a second dis tance between the locking elements facing each other is smaller than the width of the first connection element, a movement of the first connection element towards the first direction pushing the locking elements towards the plates is facilitated, and a movement of the first connection towards a second direction opposite the first direction pushing the locking elements away from the plates into the space and over the first connection element is blocked.

According to an example, the locking elements of the plurali ty of locking elements are arranged one underneath another along each of the at least two plates.

By using a plurality of locking element arranged one under- neath another, layers of locking elements are provided that provide a block in the second direction. Thus, the first con nection element may move in the first direction passing a number of locking elements but will be blocked by the nearest locking element, in case the first connection element moves in the second direction.

According to another example, the connection interface com prises a body having at least two parts that are configured to hold the first connection element, the second connection element, the elastic element and the clamping element togeth er, such that the elastic element pushes the first connection element in the first direction towards the rotational part of the wind turbine and the clamping element surrounds the first connection element at least zonally, thereby blocking move ment of the first connection element in the second direction towards the stationary part.

A body having two parts allows for assembling the connection interface disclosed herein in a way that provides the first connection element at a clamping position, i.e. a position where the first connection element is in contact with a rota tional part of a wind turbine. This means, the first connec tion element may be arranged in the clamping position, and the body together with the elastic element and the clamping element is arranged around the first connection element, thereby securing the first connection element in the clamping position. Alternatively, the body may be assembled together with the elastic element and the clamping element, such that the first connection can be inserted in the body afterwards.

The body may be connected to the stationary part of a partic ular wind turbine.

According to another example, the first connection element comprises a number of counter locking elements that are con figured to clamp the first connection element in the clamping position by engaging with the locking elements. By using counter locking elements, which may be negatively shaped with respect to the locking elements, a strong connec tion that stands a high pushing force may be provided as the first connection element moves in the second direction.

Moreover, by using a plurality of counter locking elements, the first connection element may be secured by the locking elements, even in case the first connection element partially passes the locking elements due to a very high force pushing the first connection in the second direction.

According to a second aspect of the present invention, a wind turbine comprising an embodiment of the connection interface disclosed herein is provided.

The connection interface disclosed herein preferably serves to provide the wind turbine disclosed herein.

According to a third aspect of the present invention, a meth od for maintaining an electrical connection of a stationary part and a rotational part of a wind turbine using an embodi ment of the connection interface disclosed herein is provid ed. The method comprises a first connection step for connect ing the first connection element to the rotational part, a second connection step for connecting the second connection element to the stationary part, and an arrangement step for arranging the clamping element around the first connection element such that the clamping element allows for a movement of the first connection element in the first direction to wards the rotational part and blocks movement of the first connection element in the second direction towards the sta tionary part.

The method disclosed herein preferably serves to provide the wind turbine disclosed herein.

Further advantages, features and details of the invention un- fold from the following description, in which embodiments of the present invention are described in detail. Thereby, the features from the claims as well as the features mentioned in the description can be essential for the invention as taken alone or in an arbitrary combination. In the drawings, there is schematically shown:

Fig. 1 a connection interface according to an embodiment in a first view,

Fig. 2 the connection interface according to Fig. 1 in a second view,

Fig. 3 the connection interface according to Fig. 1 and Fig. 2 in a detailed drawing,

Fig. 4 a wind turbine according to an embodiment, and

Fig. 5 a method according to an embodiment.

In Fig. 1, a connection interface 100 is shown. The connec tion interface 100 comprises a first connection element 101 in form of a brush, a second connection element 103 in form of a cable, an elastic element 105 in form of a spring, and a clamping element 107 with locking elements 109.

The first connection element 101, the second connection ele ment 103, the elastic element 105 and the clamping ele ment 107 are kept in a predetermined relative position with respect to each other by a body 111.

The body 111 comprises a first body part 113 and a second body part 115. Thus, the first connection element 101, the second connection element 103, the elastic element 105 and the clamping element 107 may be arranged at predetermined po sitions relative to each other in a first step. In a sec ond step, the first connection element 101, the sec ond connection element 103, the elastic element 105 and the clamping element 107 may be surrounded by the first body part 113 and the second body part 115 in order to fixate the first connection element 101, the second connection ele ment 103, the elastic element 105 and the clamping ele ment 107 in their predetermined positions.

Of course, the first connection element 101, the second con nection element 103, the elastic element 105 and the clamping element 107 may be arranged in the first body part 113 in the first step and the second body part 115 may be arranged at the first body part 115 in the second step.

The first connection element 101 is configured to be mechani cally and electrically connected to a rotational part of a wind turbine, such as a nacelle, for example. Thus, the first connection element 101 may comprise a metal, such as copper. In particular, the first connection element 101 may be made from graphene and copper, thereby forming a brush, as shown in Fig. 1.

As the length of the first connection element 101 reduces due to movement of the rotational part, the first connection ele ment has to be pressed against that rotational part in order to maintain an electrical and mechanical connection with the rotational part using the elastic element 105.

The second connection element 103 is configured to be con nected to a stationary part of a wind turbine, such as a tow er for example. Thus, the connection interface 100 electri cally connects the stationary part and the rotational part of a wind turbine.

In Fig. 2, the connection interface 100 is shown in a sec tional view, where the body 111 is drawn intersected, such that the elastic element 105 can be seen in detail.

The elastic element 105 comprises a spring element 106, which provides a spring force that acts on the first connection el- ement 101.

The elastic element 105 is arranged at the body 111 such that the spring force provided by the spring element 106 forces the first connection element 101 in a direction away from the spring element 106, relative to the body 111 and towards a rotational part beneath the first connection element 101.

In Fig. 3, the connection interface 100 is shown in detail.

As can be seen in Fig. 3, a first plate 201 and a second plate 203 of the clamping element 107 are surrounding the first connection element 101. Each of the two plates 201 and 203 comprises a number of locking elements 109.

The locking elements 109 are wedge-shaped and pointing in a first direction towards a rotational part. Thus, as the first connection element 101 moves in the first direction, the locking elements 109, which are flexible in the first direc tion, are moved closer to the plates 201 and 203, respective ly, thereby forming a gap in which the first connection ele ment 101 can move.

In contrast to a movement in the first direction, when the first connection element 101 moves in a second direction op posite the first direction, the first connection element 101 is pushed against the locking elements 109, which are immova ble in the second direction.

Since the locking elements 109 extend into a space between the plates 201 and 203, the space between the plates 201 and 203 is limited such that the first connection element cannot move into this space. Accordingly, the locking ele ments 109 block a movement of the first connection ele ment 101 in the second direction.

As the locking elements 109 are wedge-shaped, the locking el ements 109 comprise a smaller part and a thicker part. As the locking elements 109 point in the first direction by an in- clination angle, less material of a particular locking ele ment has to be moved when moving the locking element 109 in the first direction than in the second direction. Thus, the locking elements 109 are stiff with respect to a movement in the second direction.

In Fig. 4, a wind turbine 300 is shown. The wind turbine 300 comprises a rotational part 301, which is a nacelle, and a stationary part 303, which is a tower.

The rotational part 301 and the stationary part 303 are elec trically connected by a connection interface 100, as shown in Fig. 1.

In Fig. 5, a method 400 for maintaining an electrical connec tion of a stationary part 303 and a rotational part 301 of a wind turbine 300 as shown in Fig. 4 using the connection in terface 100 shown in Fig. 1, for example, is shown.

The method 400 comprises a first connection step 401 for con necting the first connection element 101 to the rotational part 301, a second connection step 403 for connecting the second connection element 103 to the stationary part 303, and an arrangement step 405 for arranging the clamping ele ment 107 around the first connection element 101 such that the clamping element 107 allows for a movement of the first connection element 101 in the first direction towards the ro tational part 301 and blocks movement of the first connection element 101 in the second direction towards the stationary part 303.