# US 2021/0277874 A1 · A method of balancing turbine blades > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0277874 A1 - Document ID: US20210277874A1 - Status: Published application - Kind: A1 - Application number: 17/261,236 - Filed: 2019-07-19 - Published: 2021-09-09 - Earliest claimed: 2018-07-20 - Assignees: Vestas Wind Systems A/S - Applicants: Vestas Wind Systems A/S - Inventors: Anton Bech - Web page: https://patentgrep.com/patent/US20210277874A1 ## CPC - F03D 13/35: Balancing static or dynamic imbalances - F03D 1/0675: {of the blades} - F05B 2230/60: Assembly methods - F05B 2240/302: Segmented or sectional blades - F05B 2260/966: by correcting static or dynamic imbalance - Y02E 10/72: Wind turbines with rotation axis in wind direction - F03D: WIND MOTORS - F05B: INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract There is disclosed a method of balancing a set of first and second modular blade sections for a set of blades of a rotor of a wind turbine. The method comprises determining a mass moment of the first and second blade sections, the mass moment being deter-mined about an axis equivalent to an axis of rotation of a hub of the turbine when the blade section is assembled onto the hub. A plurality of blade section groups 10 are defined, each comprising a first blade section of the set and at least one second blade section of the set, each blade section group having a blade section group mass moment about the axis. The first blade section and the at least one second blade section in each group are selected so as to satisfy a minimised total ballast condition, to minimise balancing ballast to be added to the set as a whole, or a minimised 15 ballasting difference condition, to minimise the difference in balancing ballast added to different blades, or both. ## Claims ### Claim 1 A method of balancing a set of modular blade sections for a set of blades of a rotor of a wind turbine, the method comprising the steps of: providing the set of modular blade sections, the set comprising a plurality of first blade sections and a plurality of second blade sections; determining a mass moment of each first blade section and of each second blade section, the mass moment being determined about an axis equivalent to an axis of rotation of a hub of the turbine when the blade section is assembled onto the hub; and defining a plurality of blade section groups, each comprising a first blade section of the set and at least one second blade section of the set, each blade section group having a blade section group mass moment (MMu) about the axis, the first blade section and the at least one second blade section in each group being selected so as to: minimise a sum of differences between: the group mass moment of the blade section group having the highest group mass moment of the plurality of blade section groups; and the group mass moment of each of the remaining blade section groups; or minimise a difference in mass moment between: the group mass moment of the blade section group or groups having the highest group mass moment of the plurality of blade section groups; and the group mass moment of the blade section group or groups having the lowest group mass moment of the plurality of blade section groups. ### Claim 2 (depends on 1) The method according to claim 1, further comprising the step of providing identifying means, identifying each first blade section and each second blade section of the set as belonging to its respective blade section group. ### Claim 3 (depends on 1) The method according to claim 1, further comprising the step of providing ballast to at least one of the plurality of blade section groups to provide a mass moment equal to the blade section group having the highest mass moment. ### Claim 4 (depends on 3) The method according to claim 3, wherein no ballast is added to the blade section group having the highest group mass moment of the plurality of blade section groups. ### Claim 5 (depends on 1) The method according to claim 1, wherein the step of defining a plurality of blade section groups includes providing a blade section group comprising: a first blade section having the highest mass moment of the first blade sections; and a second blade section having the lowest mass moment of the second blade sections. ### Claim 6 (depends on 1) The method according to claim 1, wherein determining the mass moment of a first or second blade section comprises weighing the first or second blade section. ### Claim 7 (depends on 1) The method according to claim 1, wherein ballast is provided at or adjacent: an outer end of one or more inner blade sections; and/or an inner end of one or more outer blade sections. ### Claim 8 (depends on 1) The method according to claim 1, wherein ballast is added to a shear web portion of one or more of the first or second blade sections. ### Claim 9 (depends on 1) The method according to claim 1, wherein addition of ballast to a blade section group comprises adding one or more of: granular material such as sand; a solid material such as a metal; a liquid; a curable fluid, such as a curable polymer, preferably curable polyurethane. ### Claim 10 (depends on 1) The method according to claim 1, further comprising the step of assembling the first blade section and the at least one second blade section within each blade section group to one another to form a set of blades for a rotor of a wind turbine. ### Claim 11 (depends on 1) The method according to claim 1, further comprising the step of assembling the plurality of blade section groups onto a wind turbine hub, such that each blade section group forms a wind turbine blade, the wind turbine blades having an equivalent mass moment, about an axis of rotation of a hub of the turbine, to one another. ### Claim 12 A set of blades for a rotor of a wind turbine, wherein each blade comprises a blade section group comprising a first blade section and at least one second blade section, each blade section group having a blade section group mass moment about an axis equivalent to an axis of rotation of a hub of the turbine when the blade section is assembled onto the hub; wherein, excluding any supplementary balancing mass added to the blades, the first blade section and the at least one second blade section in each group are selected so as to: minimise a sum of the differences between: the group mass moment of the blade section group having the highest group mass moment of the plurality of blade section groups; and the group mass moment of each of the remaining blade section groups; or minimise a difference in mass moment between: the group mass moment of the blade section group or groups having the highest group mass moment of the plurality of blade section groups; and the group mass moment of the blade section group or groups having the lowest group mass moment of the plurality of blade section groups. ### Claim 13 (depends on 12) The set of blades according to claim 12, further comprising ballast provided to at least one of the plurality of blade section groups, to provide a mass moment equal to the blade section group having the highest mass moment. ### Claim 14 (depends on 13) The set of blades according to claim 13, wherein the ballast comprises one or more of the following: granular material such as sand, a block or plate of material such as a steel block or plate, a liquid such as a curable polymer, specifically curable polyurethane.