Doctoral Thesis / Dissertation from the year 2015 in the subject Engineering - Power Engineering, Indian Institute of Engineering Science and Technology, Shibpur, course: PhD (Engineering), language: English, abstract: In this thesis methodologies to assist system operators in avoiding problems related to transmission line congestion, optimisation of operational standard management cost , social welfare optimisation and small signal stability optimisation in the context of traditional and smart power networks are been developed, illustrated and analyzed. The developed methodologies include operational standard management, contingency filtering and security control procedures. The contingencies analyzed in the assessment methodologies are those of N-1, N-2, N-3 and in some cases N-4 security criterion. The security assessment with contingencies are based on worst possible inadvertent state and for the identification of the same some sensitivity indices namely line loading index, congestion sensitivity index and demand sensitive loading factors have been developed. However, the security control methodologies are essentially re-dispatching techniques based on OPF solutions whose formulation includes constraints related to voltage profile, transmission line congestion, transmission line loss, load curtailment and small signal stability phenomena that limit system operation. The developed methodologies should be applied once a market dispatching solution is available.