Comparative analysis of external lightning protection systems for small-scale wind turbines

Should a small wind turbine owner invest in premium lightning protection, or will basic measures suffice? This practical question confronts the rapidly growing small-scale wind energy sector in Taiwan, where high keraunic levels create significant lightning strike risk yet economic constraints limit available protection budgets. The present investigation compared the effectiveness and cost-efficiency of five external lightning protection system configurations for small-scale wind turbines (15-35m hub height) through field monitoring, laboratory simulation, and economic analysis conducted at the Taipei Institute of Technology High Voltage Laboratory between January 2023 and October 2024. Protection systems evaluated included conventional Franklin rod configurations (Class I and Class II per IEC 62305), early streamer emission (ESE) air terminals, mesh/cage systems, and combined approaches integrating multiple protection elements. Field monitoring of seventeen instrumented turbines across northern Taiwan recorded 43 confirmed lightning attachment events over the 22-month observation period, enabling comparison of actual versus theoretical protection performance. Laboratory impulse testing validated rolling sphere method predictions for each protection geometry. Results demonstrated that mesh/cage systems achieved the highest protection efficiency (96.8-99.1% depending on turbine height), followed closely by ESE terminals (91.8-97.8%) and Franklin Class I rods (89.4-98.2%). Cost-benefit analysis over a 20-year turbine lifespan revealed that combined systems, despite highest initial investment, delivered optimal economic returns in regions with ground flash density exceeding 6 strikes/km²/year due to superior damage prevention. For lower-risk installations, Franklin Class I systems provided adequate protection at substantially lower cost. The findings establish selection criteria enabling site-specific optimization of lightning protection investment for Taiwan's expanding small wind energy fleet.