Development of a Rogowski Coil-Based Lightning Current Measuring System with Wide Frequency Bandwidth for Wind Turbines

Abstract

Accurate monitoring of lightning currents is critical for incident assessment and the implementation of protective measures in wind turbines. Owing to the complex geometry of turbines, direct measurement is impractical, making indirect approaches, such as the Rogowski coil, a promising alternative. The Rogowski coil provides galvanic isolation, fast transient response, and high current capacity; however, achieving broadband performance with a very low cut-off frequency remains a significant challenge. This article proposes a broadband Rogowski coil-based lightning current measuring system (RLMS) with an exceptionally low cut-off frequency. The system comprises a Rogowski coil, hybrid integrator, and digital filter. The coil was designed and optimized using transmission line theory and a distributed parameter model. The hybrid integrator, which combines the Sallen-Key and T-feedback topologies, ensures effective compensation, whereas the digital filter suppresses high-frequency noise. The feasibility of the RLMS was confirmed by a frequency response analysis in the frequency domain and time-domain comparison of lightning current waveform measurements against the reference system. The experimental results confirmed the effectiveness of the system for lightning current measurements. This demonstrates the strong potential for integration into wind turbines to enhance the accuracy of lightning detection and protection strategies.