Determining a phase and a frequency of an electric quantity of an operating electrical device

A method and an apparatus for determining a phase (¸) and a frequency (É) of an electric quantity being associated with an operation of an electrical device are described. The method comprises extracting a fundamental component (V ±1 , V ²1 ) of the electric quantity, calculating a positive sequence component (V + ±1 , V + ²1 ) of the electric quantity based on the extracted fundamental component (V ±1 , V ²1 ), and determining the phase and the frequency of the electric quantity based on the calculated positive sequence component (V + ±1 , V + ²1 ).