Presentations

Abstract

Lightning damage is a critical concern for wind turbines, potentially leading to catastrophic failure if the Lightning Protection System (LPS) suffers from uncontrolled discontinuities in the internal down conductor system. According to DNV, lightning damage is the leading cause of unplanned downtime in wind turbines and the most frequent basis for insurance claims filed by wind farm operators. Detecting discontinuities in glass-fibre reinforced polymer (GFRP) blades is feasible using continuity measurements, but localising the damage is only possible if the discontinuity is visible from the blade root. To repair damaged down conductors in otherwise inaccessible blade regions, precise localisation is necessary, requiring blade surface cuts at the exact site of the damage. This paper introduces a novel method to accurately locate discontinuities in wind turbine LPS, supporting repair strategies and minimising operational downtime. The proposed approach is performed by injecting high-frequency pulses into the LPS and analysing the reflected signal. When these pulses encounter a discontinuity, a part of the signal is reflected, providing a clear signature of the damage. By comparing signatures, the system can pinpoint the location of the fault with remarkable precision. The developed prototype was evaluated on 18 blades in a controlled ground setting and installed for six weeks in a blade test facility for continuous LPS condition monitoring. Additionally, a 50-meter-long mock-up LPS system was constructed to validate the method further. Results from these trials demonstrate that the system achieves a spatial resolution of 20 to 30 cm in detecting discontinuities. It effectively identifies the absence of critical components, such as a missing solid metal tip, and detects resistive changes in the LPS exceeding 5 ohms. This localisation method proves compatible with various blade designs, including single-down conductor blades like those made from GFRP, as well as complex configurations using carbon-fibre reinforced polymer (CFRP) and expanded metal foils (EMF). These findings highlight the versatility and robustness of the system across diverse turbine architectures. In conclusion, this paper presents a breakthrough in LPS fault localisation for wind turbine blades. It overcomes the limitations of continuity measurements which cannot localise the faults and are not able to detect discontinuities in complex blades. If upcoming full-scale turbine tests are successful, the prototype will be rapidly developed into a serial production kit which will be available as a permanent installation for continuous monitoring or as a portable measurement kit for periodic maintenance. The permanently installed system facilitates rapid diagnostics, allowing checks to be completed within seconds, providing an effective method for LPS integrity validation after a lightning strike. This innovation holds therefore the potential to validate the integrity of the LPS in a wind turbine blade on an on-demand basis, drastically reduce unplanned downtime, optimize repair efficiency, and enhance the operational reliability of wind turbines.