MONITORING METHOD AND MONITORING DEVICE

摘要

PROBLEM TO BE SOLVED: To more easily obtain a rotational speed of a power generator of a wind power generating system in monitoring of the wind power generating system.SOLUTION: A monitoring device 300 is a monitoring device of a wind power generating system that transfers a torque, generated due to that a wind mill blade receives wind, to a power generator via a speed increasing gear. The speed increasing gear is mounted in a relatively displaceable manner relative to a nacelle of the wind power generating system. The monitoring device 300 comprises: a displacement measurement result obtaining unit 306 for obtaining a measurement result of a displacement of a casing of the speed increasing gear relative to the nacelle; and a rotational speed calculating unit 340 for calculating a rotational speed of the power generator on the basis of the measurement result of the displacement obtained by the displacement measurement result obtaining unit 306.