Evaluation method and system for a lightning protection system of a wind turbine comprising a plurality of blades made of carbon fiber reinforced plastic or polymer

1. An evaluation method for a lightning protection system of a wind turbine comprising a plurality of blades made of carbon fiber reinforced plastic or polymer, the lightning protection system comprising a down conductor connected to earth and to each of the plurality of blades by a plurality of conductor plates that are embedded in a corresponding blade of the plurality of blades, that are longitudinally distributed in said corresponding blade, each of the plurality of conductor plates extending along an entire width of said corresponding blade, wherein the evaluation method is configured for determining a quality of connections between the plurality of conductor plates and the corresponding blade and comprises the following successive steps:

injecting direct current between two conductor plates of the plurality of conductor plates that are embedded in the corresponding blade by generating a flow of current through a segment of the corresponding blade comprised between the two conductor plates,

measuring a voltage with respect to a certain common reference point at a plurality of surface measurement points of said segment of the corresponding blade and distributed in a substantially linear manner along the width of said corresponding blade,

comparing measured voltages measured in said step of measuring the voltage to one another, and

determining the quality of the connections between said two conductor plates and said corresponding blade depending on a result of said comparison, better quality being determined the closer measured values are to one another.

2. The evaluation method according to claim 1 , wherein each of the measured voltages measured in the step of measuring the voltage is taken by contact of at least one sensor with respect to a corresponding measurement point of the corresponding blade, the at least one sensor comprising a metal measuring tip, an end of which contacts with the corresponding measurement point, the contact of said at least one sensor with the corresponding blade being caused to measure the voltages.

3. The evaluation method according to claim 2 , comprising a preparation step prior to the step of injecting direct current, wherein the segment of the corresponding blade between the two conductor plates and the at least one sensor are arranged with respect to one another such that the segment of the corresponding blade and the at least one sensor are facing one another, and the at least one sensor is configured to move towards the corresponding blade in that situation to cause contact with the corresponding blade and to adjust a contact force between said at least one sensor and said corresponding blade.

4. The evaluation method according to claim 3 , wherein the at least one sensor remains stationary during the step of measuring the voltage.

5. The evaluation method according to claim 1 , comprising determining whether the quality of the connections is suitable when maximum dispersion between the measured voltages is equal to or less than 10%.

6. The evaluation method according to claim 1 , wherein during the step of measuring the voltage, the direct current injected in the step of injecting direct current comprises a substantially constant magnitude and is comprised between an upper limit and a lower limit which are determined depending on a geometry of a carbon laminate used to manufacture the corresponding blade.

7. The evaluation method according to claim 1 , wherein during the step of injecting direct current, a temperature is further measured at measurement points or areas of the corresponding blade distributed in a substantially linear manner along the width of said corresponding blade, between the two conductor plates, temperatures measured are compared to one another, the quality of the connections between the two conductor plates and said corresponding blade is determined depending on a result of said comparisons, better quality being determined the closer the measured values are to one another, a quality determined from the temperature measured is compared with the quality determined from the measured voltages, and said determination is validated if the quality determined from the temperature measured is close or equal to the quality determined from the measured voltages.

8. The evaluation method according to claim 1 , wherein the method is implemented while the corresponding blade is being manufactured, before installing the corresponding blade in a corresponding wind turbine.

9. An evaluation system of a lightning protection system of a wind turbine comprising a plurality of blades made of carbon fiber reinforced plastic or polymer, the lightning protection system comprising a down conductor connected to earth and to each of the plurality of blades by a plurality of conductor plates that are embedded in the carbon fiber laminates of a corresponding blade of the plurality of blades, that are longitudinally distributed in said corresponding blade, each of the plurality of conductor plates extending along an entire width of said corresponding blade, and the evaluation system being configured for determining a quality of connections between the plurality of conductor plates and the corresponding blade, wherein the evaluation system comprises:

an injection device configured for injecting direct current between two conductor plates of the plurality of conductor plates that are embedded in the corresponding blade by generating a flow of current through a segment of the corresponding blade comprised between the two conductor plates,

a measuring device configured for measuring a voltage with respect to a certain common reference point at a plurality of surface measurement points of said segment of the corresponding blade and distributed in a substantially linear manner along the width of the corresponding blade, and

a control device communicated with the measuring device for receiving said voltage measured by the measuring device and configured for comparing said the voltage measured by the measuring device to one another and for determining the quality of the connection between said two conductor plates and said corresponding blade depending on a result of said comparison, better quality being determined the closer measured values are to one another.

10. The evaluation system according to claim 9 , wherein the measuring device comprises at least one sensor with respect to a corresponding measurement point of the corresponding blade, the at least one sensor comprising a metal measuring tip, an end of which contacts with the corresponding measurement point, the contact of said at least one sensor with the corresponding blade being caused to measure the voltages.

11. The evaluation system according to claim 10 , wherein the measuring device comprises a first element and a second element which are attached to one another, between which there is defined a gap for receiving the corresponding blade, the measuring device being suitable for measuring the voltage at the plurality of surface measurement points of an area of the corresponding blade which is arranged in said gap.

12. The evaluation system according to claim 11 , wherein the first and second elements of the measuring device comprise two facing surfaces, each of the first and second elements comprising one of the two facing surfaces, between which the corresponding blade is arranged when said corresponding blade is housed in the gap, the at least one sensor being arranged on one of said surfaces for contacting with the corresponding blade when said blade is in said gap.

13. The evaluation system according to claim 12 , wherein the first element and the second element of the measuring device are attached to one another with relative freedom of movement in the sense of the respective facing surfaces moving closer to or away from one another, to be able to adjust a contact force between the at least one sensor and the corresponding blade.

14. The evaluation system according to claim 13 , wherein the first element of the measuring device is suitable and configured for being coupled to the corresponding blade, when said corresponding blade goes through the gap defined between the first and second elements of said measuring device, the second element being suitable and configured for moving with respect to the first element to adjust the contact force, and the at least one sensor being arranged in said second element such that corresponding measuring tips project from the surface of said second element facing the first element, towards said first element.

15. The evaluation system according to claim 9 , comprising a thermographic camera suitable for measuring a temperature at measurement points of the corresponding blade distributed in a substantially linear manner along the width of said corresponding blade between the two conductor plates, the control device being suitable for receiving said temperature measured and configured for comparing said temperature measured to one another, for determining the quality of the connections between said conductor plates and the corresponding blade depending on a result of said comparisons, better quality being determined the closer measured values are to one another, for comparing the quality determined from the temperature measurements with the quality determined from the measured voltages, and for validating said determination if the quality determined from the temperature measured is close or equal to the quality determined from the measured voltages.