a further power line which for the sake of clarity is not depicted in fig1 connects the generator 128 with the electricity network 190 via this non depicted power line the electrical power which is produced by the wind turbine 100 is transferred to the electricity network 190 fig2 shows a circuit diagram for the rotational speed controlling device 140 which is now denominated with reference numeral 240 the rotational speed controlling device 240 comprises three input nodes a first input node 241 is used for receiving a signal being indicative for the actual rotational speed of the rotor of a wind turbine a second input node 242 is used for receiving a signal being indicative for a reference rotational speed for the rotor a third input node 243 is used for connecting the device 240 to an electricity network 290 the electricity network 290 is the same network in which the electrical power is fed which is generated by the wind turbine a can be seen from fig2 the reference signal being applied to the second input node 242 can represent a a time independent rotational speed having a predefined nominal value speednom b a time independent rotational speed having a zero value speedzero or c a trigger signal which is used for initiating a ramping down of a speed reference being provided by a speed reference unit 248 starting from the predefined nominal value speednom and ending at a zero value speedzero as can.