The aim of the present paper is 10 investigate two types of SSR countermeasures: a) Phase shifters used to modulate the generator real power b) Static VAR compensator (SVC) and its auxiliary controllers. An eigenvalue analysis method is used to study the effectiveness of these countermeasures in damping SSR on the second system of the second IEEE SSR Benchmark model. The method is based on the linearization of the coupled electrical and mechanical equations under small perturbations. An analytical expression of the electrical subsynchronous frequency is expressed as a function of different parameters of the power system. Results concerning the variations of the decrement factors (real part of the eigenvalues) of the torsional modes are presented for different cases.