LIGHTNING RECEPTOR ASSEMBLY

Abstract

The invention describes a lightning receptor assembly (1) for a wind turbine rotor blade (20), comprising a receptor unit (10R, 10B) comprising a receptor base (10B) for installation in the rotor blade interior (200) and a receptor (10R) for placement at an outer surface (20S) of the rotor blade (20); a threaded connector (11) to form a mechanical connection between the receptor (10R) and the receptor base (10B); and a conductive band (12) adapted to extend over the outer surface (20S) of the rotor blade (20) and to form an electrical connection to the receptor unit (10R, 10B) without requiring removal of the receptor (10R) from the receptor base (10B). The invention further describes a wind turbine (2) and a method of preforming a maintenance procedure on a lightning receptor assembly (1) of a rotor blade (20) of a wind turbine (2).

Claims

1. A lightning receptor assembly (1) for a wind turbine rotor blade (20), comprising a receptor unit (10R, 10B) comprising a receptor base (10B) for installation in the rotor blade interior (200) and a receptor (10R) for placement at an outer surface (20S) of the rotor blade (20); a threaded connector (11) to form a mechanical connection between the receptor (10R) and the receptor base (10B); and a conductive band (12) adapted to extend over the outer surface (20S) of the rotor blade (20), and comprising a cut-out (12U) extending inwards from an edge of the conductive band (12) and shaped to laterally receive a shaft (11S) of the threaded connector (11) to form an electrical connection to the receptor unit (10R, 10B) without requiring removal of the receptor (10R) from the receptor base (10B).

2. A lightning receptor assembly according to claim 1, wherein the cut-out (12U) is shaped to fit about a shaft (11S) of the threaded connector (11) in place between the receptor (10R) and the receptor base (10B).

3. A lightning receptor assembly according to claim 1, wherein the inner end of the cut-out (12U) is formed to abut the threaded connector (11).

4. A lightning receptor assembly according to claim 1, wherein the cut-out (12U) is formed as an elongate slit in the body of the conductive band (12).

5. A lightning receptor assembly according to claim 1, wherein the cut-out (12U) is formed as an angled slit in the body of the conductive band (12).

6. A lightning receptor assembly according to claim 1, wherein the cut-out (12U) is formed at an outer end of the conductive band (12).

7. A lightning receptor assembly according to claim 1, wherein the cut-out (12U) is formed half-way along one long edge of the conductive band (12).

8. A lightning receptor assembly according to claim 1, wherein the conductive band (12) comprises any of: a metal band, a slotted metal band, a segmented metal band, a metal braid, a metal-coated or metal-woven carbon fibre band, a metal-coated or metal-woven glass fibre band.

9. A lightning receptor assembly according to claim 1, wherein the conductive band (12) has a cross-sectional area in the order of 50 mm.sup.2.

10. A wind turbine (2) comprising a number of rotor blades (20), and wherein a rotor blade (20) is equipped with a lightning receptor assembly (1) according to claim 1.

11. A wind turbine according to claim 10, wherein a lightning receptor assembly (1) of a rotor blade (20) comprises two adjacent receptor units (10R, 10B) and wherein the conductive band (12) of that lightning receptor assembly (1) extends between those receptor units (10R, 10B).

12. A wind turbine according to claim 10, a lightning receptor assembly (1) of a rotor blade (20) comprises a first receptor unit (10R, 10B) on the pressure side and a second receptor unit (10R, 10B) on the suction side, and wherein the conductive band (12) of that lightning receptor assembly (1) extends between those receptor units (10R, 10B).

13. A method of preforming a maintenance procedure on a lightning receptor assembly (1) of a rotor blade (20) of a wind turbine (2) according to claim 10, which method comprises the steps of loosening the connector (11) of a receptor unit (10R, 10B); removing the conductive band (12) from under the receptor (10R) of that receptor unit (10R, 10B); inserting a replacement conductive band (12) under the receptor (10R) of that receptor unit (10R, 10B); tightening the connector (11) of the receptor unit (10R, 10B).

14. A method according to claim 13, comprising a step of forming a cut-out (12U) in the replacement conductive band (12) immediately prior to inserting the replacement conductive band (12) under the receptor (10R) of the receptor unit (10R, 10B).

15. A method according to claim 13, comprising a preparatory step of attaching a temporary holding means (40, 41) to the replacement conductive band (12) prior to its insertion under the receptor unit (10R, 10B), and a final step of detaching the temporary holding means (40, 41) from the replacement conductive band (12).

Description

[0026] Other objects and features of the present invention will become apparent from the following detailed descriptions considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention.

[0027] FIG. 1 is a schematic representation of a lightning protection system of a wind turbine;

[0028] FIG. 2 shows a cross-section through an exemplary receptor unit;

[0029] FIG. 3 shows an exemplary conductive band and a receptor unit of an embodiment of the inventive lightning receptor assembly;

[0030] FIG. 4 shows the lightning receptor assembly of FIG. 3 during a service procedure;

[0031] FIG. 5 shows an alternative form for the conductive band of an lightning receptor assembly according to the invention;

[0032] FIG. 6 shows an alternative lightning receptor assembly;

[0033] FIG. 7 shows a number of possible configurations of the inventive lightning receptor assembly for a wind turbine rotor blade;

[0034] FIGS. 8 and 9 show further alternative forms for the conductive band of an lightning receptor assembly according to the invention;

[0035] FIG. 10 illustrates a prior art LPS configuration of a rotor blade.

[0036] In the diagrams, like numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

[0037] FIG. 1 is a schematic representation of a lightning protection system (LPS) 3 of a wind turbine 2. Down conductors 30 of an LPS 3 are arranged throughout the various regions of the wind turbine 2. The drawing shows down-conductors 30 in the rotor blades 20, the hub 21, the nacelle 22, and in the tower 23, which is also provided with equipotential rings 31. The down-conductors 30 are all electrically connected so that a lightning currentfrom a lightning strike to any region of the wind turbine-will be guided through the shortest path to ground.

[0038] Each rotor blade 20 is equipped with a number of receptors 3R which in turn are electrically connected to the down-conductor in the rotor blade interior. Generally, it is advantageous to arrange receptors 3R towards the tip end of a rotor blade 20, since lightning strikes most frequently occur at the outer extremities of a tall structure.

[0039] FIG. 2 shows a cross-section through an exemplary receptor unit 10R, 10B, with a receptor block 10B arranged inside the rotor blade 20 and electrically connected to the down-conductor 30 in the rotor blade interior 200. A receptor 10R (functionally the same as the receptor 3R of FIG. 1) at the outside protrudes at least partially above the outer surface 20S of the rotor blade 20 and is connected to the base 10B by a threaded connector 11. All parts of the receptor unit 10R, 10B, 11 are made of a conductive metal such as stainless steel or a copper alloy, for example. The diagram shows a slight gap G between the receptor 10R and the base 10B. A component of the inventive lightning receptor assembly 1 will be inserted into this gap G, for example during a maintenance procedure, as will be explained below.

[0040] FIG. 3 is a plan view onto the surface of a rotor blade 20, showing an exemplary conductive band 12 and a receptor unit of an embodiment of the inventive lightning receptor assembly 1. The diagram shows the receptor 10R at the surface of the rotor blade 20, and the base 10B is concealed inside the interior of the rotor blade 20. An outer end of the conductive band 12 is to be placed into the gap G between receptor 10R and base 10B. The diagram shows that the conductive band 12 has a cut-out 12U in the form of an elongate slit that can accommodate the portion of the shaft 11S of the threaded connector 11 exposed in the gap G between receptor 10R and base 10B shown in FIG. 2 above. During assembly, the conductive band 12 can be pushed sideways into the gap between the receptor 10R and base 10B so that the cut-out 12U laterally receives the shaft 11S of the threaded connector 11.

[0041] FIG. 4 shows the lightning receptor assembly 1 of FIG. 3 during a service procedure. A technician 4 need only loosen the threaded connector 11 as shown in FIG. 2, without actually removing the receptor 10R. He then inserts one end of the conductive band 12 into the gap G between receptor 10R and base 10B, allowing the cut-out 12U to laterally receive the shaft 11S of the threaded connector 11 so that the shaft 11S of the screw 11 is positioned inside the cut-out 120, and then tightens the screw 11 once more. The process is repeatedas appropriateto clamp the other end of the conductive band 12 in a second receptor unit 10R, 10B.

[0042] The diagram illustrates another aspect of the invention. Here, a technician (not shown) has attached a temporary holding means 40 to the replacement conductive band 12 prior to its insertion into the receptor unit 10R, 10B. The temporary holding means 40 can be an elastic sleeve wrapped about the conductive band 12 and secured with a hook-and-loop fastener or similar, with a spiral cord 41 or similar for connecting to the technician's belt. The risk of the technician inadvertently dropping the conductive band 12 is therefore minimized. Of course, such a sleeve 40 can be realized in any suitable manner, for example from a rubber material, any non-slip material, a magnetic material, etc. Once the conductive band 12 has been secured, the technician can simply remove the temporary holding means 40, 41 from the conductive band 12.

[0043] FIG. 5 shows an alternative form for the conductive band 12 of an lightning receptor assembly according to the invention. Here, the cut-out 120 is angled, and the shape of the cut-out 12U allows the conductive band 12 to be hooked to a loosely fixed receptor 10R, thereby simplifying the replacement procedure.

[0044] FIG. 6 shows an alternative lightning receptor assembly. Here, the conductive band 12 is not inserted between receptor 10R and base 10B, but instead is held in place by a clamping plate 14. The clamping plate may be secured to the underside of the receptor 10R, for example by means of a cut-out that fits about the shaft of the threaded connector 11 as explained above. For replacement of the conductive band 12, the technician loosens the connector 11 between receptor 10R and base 10B at one end of the clamping plate 14 (or at both ends), thereby loosening the clamping plate 14. The technician then pulls out the conductive band 12 from underneath the loosened clamping plate 14, inserts a replacement conductive band 12 underneath the loosened clamping plate 14, and then tightens the threaded connector(s) 11. The advantage of this approach is that the conductive band 12 is less prone to fatigue from stress concentration in the press-fit realisations described in FIGS. 2-5 above. Optionally, the clamping plate 14 can be secured to the conductive band 12 by means of screws 140 as indicated here.

[0045] FIG. 7 shows a number of possible configurations of the inventive lightning receptor assembly 1 for a wind turbine rotor blade 20. For clarity, only the receptors of the receptor units 10R, 10B are shown. At the top of the diagram, a conductive band 12 extends between two receptor units; in the centre of the diagram, a conductive band 12 extends from a receptor unit on the pressure side of the rotor blade 20 to a receptor unit on the suction side of the rotor blade 20; at the bottom, two conductive bands 12 extend outward from a receptor unit.

[0046] FIGS. 8 and 9 show further alternative forms for the conductive band 12 of an lightning receptor assembly according to the invention. In FIG. 8, the conductive band 12 has an elongate oval form, and a cut-out is formed along one long edge. The conductive band can be pushed sideways between a receptor 10R and receptor base as indicated here.

[0047] FIG. 9 shows a conductive band 12 with several round holes 12H punched at various positions. During a maintenance routine, a technician can identify the most appropriate hole and, using an appropriate cutting tool 42, can cut a slit from the edge of the conductive band 12 to the punched hole 12U in order to complete the cut-out 12U.

[0048] FIG. 10 illustrates a prior art LPS configuration of a rotor blade. Here, the rotor blade 20 has been constructed to incorporate CFRP elements, in this case CFRP spar caps 20C on either side of a spar extending lengthwise through the rotor blade interior. The diagram indicates the position of a spar cap 20C under the skin of the rotor blade 20. During a lightning strike, electrical charge may collect in the region over the spar cap 20C, since CFRP is to some extent conductive. Instead of directly striking a receptor 3R, the lightning may be attracted towards the spar cap region instead. Equally, a direct strike to the receptor 3R may result in flashover to the CFRP spar cap 20C. Either way, the rotor blade may suffer severe damage leading to significant costs.

[0049] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. For example, a conductive band can be slotted as appropriate to improve adhesion of a fibreglass cover layer. A conductive band could also be realised in a segmented manner, with two or more strips converging to form a region with a cut-out for engaging with the threaded connector between receptor and base.

[0050] For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.