Blade deflection monitoring system

A blade deflection monitoring system for installation on a wind turbine blade, the wind turbine blade comprising an airfoil profile body having a pressure side and a suction side, and a leading edge and a trailing edge with a chord length extending therebetween, the blade having a tip end and a root end, the monitoring system comprising:

• at least one tip communication device for installation towards the tip end of a wind turbine blade,
• at least one root communication device for installation towards the root end of a wind turbine blade, and
• a controller to operate said communication devices in wireless communication to monitor the distance between said at least one tip communication device and said at least one root communication device when installed on a wind turbine blade to determine a movement of said at least one tip communication device relative to said at least one root communication device indicative of a blade deflection, wherein
• said at least one root communication device is arranged to be located spaced from an external surface of the wind turbine blade at said root end, and
• wherein the at least one root communication device comprises a first root communication device provided on a first bracket and a second root communication device provided on a second bracket, the first and second root communication devices provided towards either the leading or trailing edge of the blade, wherein said first root communication device is located on the pressure side of the leading edge or the trailing edge of the blade and said second root communication device is located on the suction side of the leading edge or the trailing edge of the blade.

A method of monitoring the deflection of a wind turbine blade, the wind turbine blade having a pressure side and a suction side, and a leading edge and a trailing edge with a chord length extending therebetween, the blade having a tip end and a root end, the method comprising the steps of:

• providing at least one tip communication device located towards the tip end of a wind turbine blade,
• providing at least one root communication device located towards the root end of said wind turbine blade, said at least one root communication device in wireless communication with said at least one tip communication device via a wireless communication path,
• transmitting a signal between said at least one tip communication device and said at least one root communication device along said wireless communication path,
• calculating a distance measurement between said at least one tip communication device and said at least one root communication device based on said signal, and
• determining a current blade deflection value based on said distance measurement, wherein the method further comprises the step of
• adjusting a signal gain level of said signal based on at least one of the following:
• the current blade deflection value, a predicted blade deflection value based at least in part upon said current blade deflection value, or a signal strength level of a signal received via said communication path,
• wherein the at least one root communication device comprises a first root communication device provided on a first bracket and a second root communication device provided on a second bracket, the first and second root communication devices provided towards either the leading or trailing edge of the blade, wherein said first root communication device is located on the pressure side of the leading edge or the trailing edge of the blade and said second root communication device is located on the suction side of the leading edge or the trailing edge of the blade.