Development of an On-line Insulation Degradation Diagnosis Technique for Wind Turbine Generators by Measurement and Analysis of Capacitive Leakage Current for Load Current Variation

Abstract

To construct a new inspection technique for insulation systems of wind turbine generators, we propose an on-line insulation degradation diagnosis system that monitors the load and capacitive leakage currents. Both currents with different service operation periods in the same wind firm were measured in the field. The SN ratio of the measured currents for a doubly fed generator driven by a power conditioning subsystem could be more than 40 dB using the developed diagnosis system. The difference between the off-line current converted from the capacitance and the on-line leakage current was evaluated. Furthermore, variational correlations between the load current and capacitive leakage currents of the generators were verified, indicating that signs of insulation degradation in the wind turbine generator could be detected using the proposed system.