Monitoring system for a wind turbine blade, wind turbine arrangement and method for monitoring of a wind turbine blade

1. A system, comprising:

a wind turbine blade, wherein the wind turbine blade comprises at least one electrically conducting or semi-conducting structural component and a lightning protection system having a down conductor electrically connected to at least one lightning receptor, wherein the down conductor is electrically connected to the at least one structural component by at least one equipotential connector, such that, in the wind turbine blade, a network of electrical impedances comprising the at least one structural component, the at least one equipotential connector, and the down conductor is formed;

a sensing device for the network, comprising at least one transmitter for emitting an electrical pulse into the network via at least one first terminal and at least one receiver for receiving at least one reception pattern of the electrical pulse from the network via at least one second terminal; and

an evaluation device for evaluating the at least one reception pattern, to determine a first health information regarding the lightning protection system, and a second health information regarding the at least one structural component;

wherein the sensing device and evaluation device together provide monitoring of both the lightning protection system and the structural health of the at least one structural component.

2. The system according to claim 1 , wherein the at least one structural component is a beam and/or a spar cap, and/or the evaluation device is at least partly located external to the wind turbine blade, and connected to the sensing device and/or a remaining part of the evaluation device by a communication link.

3. The system according to claim 1 , wherein the evaluation device is adapted to determine, as the first health information and/or the second health information, the location and/or at least one property of a discontinuity, described by at least one received pulse of the reception pattern and/or wherein the evaluation device and/or a control device receiving the respective health information is configured to generate at least one control signal for the wind turbine based on the respective health information.

4. The system according to claim 1 , wherein the down conductor is connected to ground via a ground connection at a root terminal at a root of the wind turbine blade, wherein the ground connection at the blade root and/or a ground connection from a hub of a wind turbine to a nacelle of the wind turbine comprises a spark gap or a switching device for galvanically disconnecting the down conductor from ground while a reception pattern is measured, and/or wherein at least one second terminal is located at a root side end of the down conductor.

5. The system according to claim 1 , wherein the at least one first terminal and the at least one second terminal are located at a blade root-side edge of the network and/or the sensing device comprises at least one control unit and/or the sensing device is completely installed in the wind turbine blade.

6. The system according to claim 1 , wherein one or more equipotential connectors of the at least one equipotential connector, which is located at a root side of the wind turbine blade, comprises a spark gap.

7. The system according to claim 1 , further comprising at least one temperature sensor, wherein the evaluation device and/or the sensing device are configured to compensate the reception patterns for temperature effects with reference to a reference temperature, and/or the evaluation device is configured to take temperature data of the temperature sensor into account when determining the first health information and/or the second health information.

8. The system according to claim 1 , further comprising at least one lightning strike sensor, wherein the evaluation device is adapted to also use sensor data of the lightning strike sensor to determine at least the first health information.

9. The system according to claim 1 , wherein at least one lightning surge protection element and/or at least one retracting connector is provided at one or both of the first and second terminals.

10. A wind turbine arrangement comprising at least one wind turbine, in which multiple wind turbine blades are installed, and at least one system according to claim 1 .

11. The wind turbine arrangement according to claim 10 , wherein one respective system is associated with each combination of first and second terminals designated for measuring a reception pattern or with each single wind turbine blade or with each single wind turbine.

12. The wind turbine arrangement according to claim 10 , wherein at least one of the at least one system is partly installed in a hub and/or a nacelle and/or a tower of at least one of the at least one wind turbine.

13. A method, comprising:

providing a wind turbine blade, wherein the wind turbine blade comprises at least one electrically conducting or semi-conducting structural component and a lightning protection system having a down conductor electrically connected to at least one lightning receptor, wherein the down conductor is electrically connected to the at least one structural component by at least one equipotential connector, such that, in the wind turbine blade, a network of electrical impedances comprising the at least one structural component, the at least one equipotential connector, and the down conductor is formed;

providing at least one transmitter for emitting an electrical pulse into the network via at least one first terminal and at least one receiver for receiving at least one reception pattern of the electrical pulse from the network via at least one second terminal;

emitting the electrical pulse into the network;

receiving the at least one reception pattern; and

evaluating the at least one reception pattern to determine a first health information regarding the lightning protection system and a second health information regarding the at least one structural component.

14. The method according to claim 13 , further comprising: evaluating the at least one reception pattern when

a lightning strike sensor of the wind turbine detects a lightning strike, and/or

a measurement criterion describing a non-standard and/or heightened aerodynamic and/or structural loading condition of the wind turbine blade is fulfilled, and/or

a change in energy production of the wind turbine or a wind turbine park, in which the wind turbine is installed, is detected, and/or

continuously over a defined period of time, and/or

periodically.

15. The method according to claim 13 , wherein the wind turbine blade is not installed to a wind turbine and is quality-controlled and/or tested, wherein at least one additional first or second terminal is used for evaluating the at least one reception pattern.