A method of protecting a wind turbine against a sub-synchronous resonance, SSR, event acting on the wind turbine, wherein the method comprises: measuring a plurality of power-output values or current-output values over a given period of time that corresponds to a measurement cycle, determining, whether power-output values or current-output values measured in the at least one measurement cycle are indicative of an SSR-event critical for further operation of the wind turbine, wherein the determining comprises monitoring whether at least one oscillation-parameter exceeds at least one oscillation-parameter threshold for at least one measurement cycle (A7, B7, C4, D4), wherein the oscillation-parameter is obtained using the power output values or the current output values and is representative of a power output oscillation or current output oscillation (A3-A6, B3-B6, C1-C3, D1-D3), shutting down the wind turbine in response to the measured power-output values or the measured current-output values being determined to be indicative of an SSR-event critical for further operation of the wind turbine (A9, B9, C5, D5), characterized in that the wind turbine is a wind turbine with a doubly-fed induction generator, DFIG,, and the monitored oscillation-parameter is calculated based on differences between (i) measured power-output values or current-output values of a measurement cycle and (ii) a reference power-output value or a reference current-output value, wherein these differences are integrated over time to obtain a power-output deviation-energy value or an integrated current-output-deviation value of a measurement cycle (A3, B3), wherein the power-output deviation-energy value or integrated current-output deviation value is compared with a given energy-threshold or a given integrated current-deviation threshold and the power-output deviation-energy value or the integrated current-output-deviation value of the measurement cycle is stored if said power-output deviation-energy value or integrated current-output-deviation value exceeds said given energy-threshold or integrated current-deviation threshold (A5, B5), wherein an accumulated power-output deviation-energy value or an accumulated integrated current-output-deviation value is calculated using stored power-output deviation-energy values or stored integrated current-output-deviation values obtained over a given number of successive measurement cycles, said accumulated power-output deviation-energy value or accumulated integrated current-output-deviation value corresponding to the oscillation-parameter, wherein the oscillation parameter is compared with an oscillation-parameter threshold, wherein a condition for determining the presence of an SSR-event critical for further operation of the wind turbine is that the at least one oscillation-parameter exceeds the oscillation-parameter threshold. measuring a plurality of power-output values or current-output values over a given period of time that corresponds to a measurement cycle, determining, whether power-output values or current-output values measured in the at least one measurement cycle are indicative of an SSR-event critical for further operation of the wind turbine, wherein the determining comprises monitoring whether at least one oscillation-parameter exceeds at least one oscillation-parameter threshold for at least one measurement cycle (A7, B7, C4, D4), wherein the oscillation-parameter is obtained using the power output values or the current output values and is representative of a power output oscillation or current output oscillation (A3-A6, B3-B6, C1-C3, D1-D3), shutting down the wind turbine in response to the measured power-output values or the measured current-output values being determined to be indicative of an SSR-event critical for further operation of the wind turbine (A9, B9, C5, D5),