Abstract: A method for detecting mechanical damage to a rotor blade of a wind turbine includes measuring vibrations of the rotor blade and generating a frequency-dependent vibration signal. A value of the signal energy over a predetermined frequency range of the vibration signal is determined at each of a number of measuring times and the respectively determined signal energy values are evaluated with respect to time in order to detect mechanical damage.

Abstract: A method for detecting a state of change of an installation includes rotating at least one first component around a rotatable connection using a drive such that at least part of the at least one first component carries out an oscillation. The at least one first component is mechanically connected to a second component via the rotatable connection. The method further includes recording the oscillation using a third component. The method includes investigating the recorded oscillation for changes based on a reference value. The method further includes detecting the state of change of the installation in reference to the changes to based on the reference value.