The scientific problem identified in this dissertation is the problem of overloading parts of the electricity transmission network, in market conditions of its operation, with a high share of electricity production from renewable energy sources. The problem that builds on this is the problem of coordinating the operation of local relay protection systems in a wide area. The dissertation investigates the possibility of solving the described scientific problems by applying the technology of synchronized phasor measurements, in the form of system integrity protection schemes (SIPS). A method for designing transmission power network SIPS has been developed. It is based on synchronized phasor measurements and safety assessment. Method is described with a block diagram and allows the division of SIPS into schemes that maintain existing production and consumption of protected system part and into load shedding or production reduction schemes. The method defines criteria for initiating SIPS as well as calculations that need to be performed, in order to assess safety of the observed network part. A heuristic model for changing network topology, based on synchronized phasor measurements, was developed with the aim of preserving safety. This model is based on the principle of redistribution power flows, in order to mitigate loads in endangered network parts. The operation verification of the developed heuristic model was performed on the IEEE test system. After a successful operation verification, SIPS application is presented on a part of the Croatian transmission network near wind power plant Vrataruša. A software algorithm for SIPS application was developed within given example. The developed algorithm is described by a flow diagram and its operation is shown, according to the steps of performing the algorithm. Optimal network topology switching and load shedding models, based on linear calculation and synchronized phasor measurements, have been developed. Model verifications were performed on the IEEE test system. Tests determined correct operation and exceptional accuracy. SIPS application of the optimal load shedding model is shown on a part of the Croatian power system, Istrian subsystem.