원래 이름 기록: Siemens Gamesa Renewable Energy A/S

A method of determining a value of a stress related quantity of a rotor blade of a wind turbine is provided, the method including: emitting a primary radar signal towards a portion of the blade; receiving a secondary radar signal emanating from the blade due to interaction with the primary radar signal; analyzing at least the received secondary radar signal; and deriving, based on the analysis, the value of the stress related quantity as related to or indicating a blade acceleration and/or a first temporal derivative of the blade acceleration and/or a higher temporal derivative of the blade acceleration.