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EP-4283116-B1 - A WIND TURBINE BLADE WITH AN IMPROVED LIGHTNING PROTECTING SYSTEM

EP4283116B1EP 4283116 B1EP4283116 B1EP 4283116B1EP-4283116-B1

Inventors

  • BAVILOLIAIE, Mahdi
  • STEWART, IAN
  • HANSEN, LARS BO

Dates

Publication Date
20260506
Application Date
20220524

Claims (9)

  1. A lightning protection system for a wind turbine blade (10) including a pressure side (36) and a suction side (38), and a leading edge (18) and a trailing edge (20) with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end, the lightning protection system comprising at least one lightning receptor (70, 71) arranged at an outer surface of the blade and a down conductor extending within the blade, a first carbon fibre reinforced spar cap (64) extending substantially in the spanwise direction of the wind turbine blade and having a chamfered tip end (65) and an opposing chamfered root end (66), the first spar cap being arranged inside the blade along the pressure side, a second carbon fibre reinforced spar cap (67) extending substantially in the spanwise direction of the wind turbine blade and having a chamfered tip end (68) and an opposing chamfered root end (69), the second spar cap being arranged inside the blade along the suction side, wherein an electric connection between the at least one lightning receptor and the chamfered tip end and/or root end of the first and/or second spar cap comprises a conductive fabric (73), said conductive fabric comprising unidirectional carbon fibres bonded by an adhesive, characterized in that the fabric has a thickness of 0.01-0.5 mm and a fibre volume fraction (FVF) of at least 50%, wherein the electric connection between the at least one lightning receptor and the chamfered tip end and/or root end of the first and/or second spar cap further comprises a metallic mesh (72).
  2. A lightning protection system according to claim 1, wherein the thickness of the fabric (73) is 0.025-0.4 mm, preferably 0.05-0.3 mm.
  3. A lightning protection system according to claim 1 or 2, wherein the fibre volume fraction of the conductive fabric (73) is at least 55 %, such as at least 60 %, preferably at least 65%, more preferably at least 70%, yet more preferably at least 75%, even more preferably 80%, and preferably at least 85%, or at least 90%.
  4. A lightning protection system according to any of claims 1-3, wherein the conductive fabric (73) is provided without any stitching material and without weaving.
  5. A lightning protection system according to any of the preceding claims, wherein the conductive fabric (73) is arranged in between at least part of the metallic mesh (72) and at least part of the chamfered tip end and/or root end of the first and/or second spar cap.
  6. A lightning protection system according to any of the preceding claims, wherein the unidirectional carbon fibres in the conductive fabric are arranged in a spanwise direction between the chamfered tip end and root end of the first and/or second spar cap.
  7. A method of manufacturing a shell half structure with a lightning protection system (LPS) for a wind turbine blade, the wind turbine blade (10) having a profiled contour including a pressure side (36) and a suction side (38), and a leading edge and a trailing edge with a chord having a chord length extending therebetween, the wind turbine blade extending in a spanwise direction between a root end and a tip end, the method comprises: arranging one or more first layers of fibre fabrics, on the surface of a mould to form a first shell half structure, arranging one or more second layers of carbon fibres in a mould to form a spar cap having a chamfered tip end and an opposing chamfered root end, arranging at least one conductive fabric (73), comprising unidirectional carbon fibres bonded by an adhesive, wherein the carbon fabric has a thickness of 0.05-0.3 mm and a fibre volume fraction (FVF) of at least 50%, on at least part of the chamfered tip end and/or opposing chamfered root end of the spar cap, arranging at least one metallic mesh (72) on at least part of the conductive fabric, consolidating the one or more first layers of fibre fabrics, one or more second layers of carbon fibres, the conductive fabric and the metallic mesh.
  8. A method according to claim 7, wherein the unidirectional carbon fibres in the conductive fabric (73) are arranged in a spanwise direction between the chamfered tip end and root end of the first and/or second spar cap.
  9. A method according to claim 7 or 8, wherein the spar cap comprises precured elements, such as pultruded carbon fibre planks, comprising the unidirectional carbon fibres.

Description

Field of the Invention The present invention relates to a lightning protection system (LPS) for a wind turbine blade. In particular, the present invention relates to the use of a conducting fabric as part of an LPS system. Background of the Invention Wind power provides a clean and environmentally friendly source of energy. Wind turbines usually comprise a tower, generator, gearbox, nacelle, and one or more rotor blades. The wind turbine blades capture kinetic energy of wind using known airfoil principles. Modern wind turbines may have rotor blades that exceed 100 meters in length. Wind turbine blades are usually manufactured by forming two shell parts or shell halves (i.e. a pressure side shell half and a suction side shell half) from layers of woven fabric or fibres and resin. Spar caps, which are also called main laminates, are placed or integrated in the shell halves and may be combined with shear webs or spar beams to form structural support for the blade. Spar caps or main laminates may be joined to, or integrated within, the inside of the suction and pressure halves of the shell. The shell halves of the wind turbine blade are typically manufactured as fibre composite structures by means of VARTM (vacuum assisted resin transfer moulding), where liquid polymer, also called resin, is filled into the blade mould cavity, in which a fibre lay-up has been inserted together with the spar cap and typically a sandwich core material, and where a vacuum is generated in the mould cavity, hereby drawing in the polymer. The polymer can be thermoset or thermoplastics. Typically, the mould cavity is covered with a resilient vacuum bag. By generating a vacuum, the liquid resin can be drawn in and fill the mould cavity with the fibre material contained herein. In most cases, the resin applied is polyester or epoxy, and typically the fibre lay-up is based on glass fibres and/or carbon fibres. Usually, a shear web is arranged in between the first spar cap and the second spar cap. Each shear web may comprise a web body, a first web foot flange at a first end of the web body, and a second web foot flange at a second end of the web body. As wind turbines and wind turbine blades increase in size, the risk of a lightning strike hitting the wind turbine blades of the wind turbine increases. It is therefore of increasing interest to provide wind turbines and in particular wind turbine blades with lightning protecting measures. It is known to provide blades for wind turbines with lightning receptors, in electric connection with a down conductor that is able to connect a lightning current to ground. A lightning strike directly into the laminate may cause damage to a blade comprising electrically conductive fibres, as they would conduct the current and thereby would develop a substantial amount of heat. Thus, it is of increasing importance to provide a lightning protection system (LPS) and ways of integrating a lightning protection system, which protects components of the wind turbine blade from being damaged by lightning strikes. This is even more important, if the wind turbine blade comprises conductive parts, such as carbon fibre reinforced spar caps. Typically, a lightning protection system comprises at least one lightning receptor located at or near the tip end of the blade that is electrically connected to the down conductor. The current is transferred from the lightning receptor or lightning receptors via cables to the down conductor and ground. However, when a lightning strikes a lightning receptor, there is a substantial risk of arcs (i.e. current jumping) into e.g. the spar caps due to the presence of conductive carbon fibres, which may cause damage to the blade. Thus, LPS systems typically also comprise means to equalize a voltage build-up between the spar caps and down conductor in order to avoid current jumping by establishing an electrical connection between the LPS system and the spar caps. Spar caps are made from composite materials, often with carbon fabrics embedded in a cured resin matrix. While the carbon fibres in the fabric act as a conductive material the cured resin has insulating properties. The carbon fibres for spar caps are typically made from carbon rovings or tows, wherein the rovings or tows are either stitched and/or weaved together to form the fabric. Such fabrics may be in the form of precured elements, such as pultruded carbon planks. An additional carbon fibre fabric can be used for providing the potential equalising connection between the carbon fibres of the spar caps, e.g. the pultruded carbon planks, and the LPS system. Stitching and/or weaving are not desirable in terms of conductivity for this additional carbon fabric, as it introduces some disturbance in the fabric and creates small pockets that may be filled with insulating resin, thus reducing the contact surface between the potential equalising carbon fabrics and the carbon fibres of the spar cap. The conductivity of the fabric is also