Failure analysis of a hydraulic power system in the wind turbine

Abstract The use of the wind energy is increasing as one of the eco-friendly alternative energies when clean (nonpolluting) energy is required due to the development of alternative energy caused by the fossil energy depletion recently and serious environmental pollution problems such as carbon dioxide and fine dust. The blades among the various components of the wind turbine convert the kinetic energy of the wind into mechanical rotational energy to drive the generator. This study tried to find out through the analysis of the fire on the wind turbine how the pilot check valve malfunction due to contamination and leakage of hydraulic oil in the hydraulic system for pitch control occurred. In order to analyze the failure, the circuit analysis of the hydraulic system was carried out, the characteristics of the hydraulic oil were analyzed, and the calorific value of friction was calculated in order to analyze the breakdown phenomenon which is the cause of the fire. Pitch control of the blade from the engineering brake position (feathering position) to the pitch fine position which receives the maximum drag is regulated by the position control of the hydraulic cylinder. The backward movement of the hydraulic cylinder immediately led the blades out of the feathering position and allowed the rotor to rotate, eventually reaching a maximum pitch angle of −5 degrees. As a result, this study explained that the friction heat was increased higher than the flash point of the hydraulic oil by rotating the shaft in the state where the blade rotated and the brake operated. As the disk brake was rotated in the same way as the fire occurred, the temperature of the disk plate was found to have risen about 1 °C per second and to have exceeded the flash point of the hydraulic oil, which was 250 °C at the temperature of a disk brake plate.