The study considers an algorithm for determining a synchronous generator rotor mechanical speed rotation according to the data of ph as or measurement unit. The mechanical speed of the rotor is a key indicator in the organization of the power unit operating mode emergency control. In addition, the mechanical speed of the synchronous generator rotor is used in testing the unloading speed of the turbine. Testing of the proposed method for determining of a synchronous generator rotor mechanical speed was performed on a physical model of a power system consisting of three low- power synchronous generators. As a result, the error in determining the the synchronous generator rotor mechanical speed did not exceed 0.5%. © 2023 IEEE.