In this paper an exploratory investigation to the concept of varying the parameters of the turbo-generator mechanical system for the purpose of avoiding the occurrence of the coincidence between electrical and mechanical modal interactions at their natural frequencies is performed. The study involved both the steam and hydro mechanical system parameters of three basic cases namely steam plant with rotating exciter; steam plant with static exciter and finally a hydro plant system were developed. The results confirm the possibility of maintaining system stability, this avoiding the development of subsynchronous resonance instability.