Method and arrangement for operating a wind farm within voltage limit

It is described a method for determining a limit value of a wind turbine reference operational variable, the wind turbine being connected to a connection node to which a utility grid is connected, the method comprising: obtaining a first input signal indicative of a connection node limit voltage (Umaxref, Uminref); obtaining a second input signal indicative of a connection node voltage (Umeas); and determining the limit value (VMax, VMin) of the wind turbine reference operational variable (U_WTREF) based on the first signal and the second signal. Further a corresponding arrangement is described.