Abstract: In a method and devices for assessing the stability of an electric power network, for each of a plurality of measurement locations with associated voltage and current measurements, a normalized power margin value dSn is computed, which is defined as a result of dividing an associated power margin value by an associated maximum allowable power flow. In a preferred embodiment of the invention, the normalised power margin value dSn is computed from an apparent load impedance Za and a Thévenin impedance Zt, that are perceived from the measurement location, as 1 dSn = ( Za - Zt Za + Zt ) 2 .