Wind turbine blade

1 . A blade for a wind turbine comprising a tip region, extending from a tip end to an intermediate spanwise position, a proximal region, extending from the intermediate spanwise position to a base portion, a lightning protection system and a non-conductive exterior surface, the lightning protection system comprising:

an internal down conductor for conducting lightning current towards the base portion of the blade; and

one or more lightning receptors, the one or more lightning receptors located on a suction side or a pressure side of the blade at a spanwise position of the blade, the one or more lightning receptors extending through the exterior surface of the blade and electrically connected to the internal down conductor;

wherein for a lightning receptor of the one or more of the lightning receptors:

for one or more points on an other of the suction side or pressure side of the blade at the spanwise position corresponding to the lightning receptor, an electrical insulation level for a leader along any path of lightning from any of the one or more points to the lightning receptor via an interior of the blade is greater than an electrical insulation level for a leader along an indirect path from the point to the lightning receptor around the exterior surface of the blade, wherein the leader is an ionized path, wherein, in the proximal region, all lightning receptors are located at a same suction side or pressure side of the blade.

2 . The blade according to claim 1 , wherein the blade comprises the tip region extending from a distal tip of the blade to the intermediate spanwise position, and the proximal region extending from the base portion of the blade to the intermediate spanwise position, wherein the one or more lightning receptors are provided in the proximal region of the blade.

3 . The blade according to claim 2 , wherein the proximal region comprises a plurality of the lightning receptors at different spanwise positions.

4 . The blade according to claim 3 , wherein the plurality of the lightning receptors are all provided on the suction side of the blade or the pressure side of the blade.

5 . The blade according to claim 2 , wherein the tip region comprises one or more lightning receptor pairs at a spanwise position in the tip region, each of the one or more lightning receptor pairs comprising a first lightning receptor located on the suction side of the blade and a second lightning receptor located on the pressure side of the blade, the first and second lightning receptors extending through the exterior surface of the blade and electrically connected to the internal down conductor.

6 . The blade according to claim 1 , wherein for, the lightning receptor is electrically connected to an electrically conductive block mounted to an interior surface of the blade at the spanwise position of the lightning receptor, wherein the electrically conductive block is electrically connected to the internal down conductor.

7 . The blade according to claim 6 , wherein for the lightning receptor, an electrical insulator covers the lightning receptor in the interior of the blade such that any path of lightning through the interior of the blade passes through the electrical insulator.

8 . The blade according to claim 7 , wherein at one or more spanwise positions of the blade, two or more lightning receptors are provided, both located on the suction side or the pressure side of the blade.

9 . The blade according to claim 8 , wherein one of the two or more lightning receptors is provided more proximal to a leading edge of the blade, and another of the two or more lightning receptors is provided more proximal to a trailing edge of the blade.

10 . The blade according to claim 8 , further comprising a structural support extending between the pressure side and the suction side of the blade, wherein one of the two or more lightning receptors is provided on a first side of the structural support, and another of the two or more lightning receptors is provided on a second side of the structural support opposite to the first side.

11 . The blade according to claim 10 , wherein the internal down conductor extends along the blade proximal to the pressure side along an entire length, or proximal the suction side along an entire length.

12 . A wind turbine comprising one or more blades according to claim 11 .

13 . A method of manufacturing a blade for a wind turbine, the method comprising:

providing a blade having a non-conductive exterior surface;

providing a down conductor for conducting lightning current towards a base portion of the blade and locating the down conductor in an interior of the blade;

providing one or more lightning receptors in an intermediate region of the blade all at the same suction side or pressure side of the blade and for each lightning receptor:

extending the lightning receptor through the exterior surface of the suction side or pressure side of the blade at a spanwise position of the blade and exposing the lightning receptor externally to the blade; and

electrically connecting the lightning receptor to the down conductor;

wherein a lightning receptor of the one or more of the lightning receptors:

for one or more points on the other of the suction side or pressure side of the blade at the spanwise position corresponding to the lightning receptor, an electrical insulation level for a path of lightning from any of the one or more points to the lightning receptor through the interior of the blade is greater than an electrical insulation level for an indirect path from the point to the lightning receptor around the exterior surface of the blade.

14 . The method according to claim 13 , wherein the step of providing the blade comprises separately forming the suction side of the blade and the pressure side of the blade and joining the suction side and pressure side to form the blade.

15 . The method according to claim 14 , wherein the one or more lightning receptors are extended through the exterior surface of the suction side or pressure side of the blade and electrically connected to the internal down conductor before the suction side and pressure side are joined.