A method of balancing turbine blades

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.