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The monitoring and control of smart power transmission grid represents active infrastructure capable of obtaining increased transfer and distribution of electrical energy, with considerable rate of generation from renewable energy sources without compromising the stability, security and reliability of power grid in different operating conditions. The development concept of intelligent protection and control systems of the entire smart power transmission grid defines:x use of complex information and communication technology (ICT) system, x sending selected local information to a remote location where this information is processed and x implementation of accurately defined automated actions to neutralize and stop the spreading of major system disturbances. Wide area monitoring of electrical power system, which is the initial step in developing the smart power transmission grid has found its place around the world and it's expected increase of use in the daily work of system operators will result in more efficient and reliable use of ancillary functions during large scale disturbances. The intention of this paper is to point out the needs and developing possibilities of monitoring and control systems of the entire smart power transmission grid based on the System Integrity Protection Schemes (SIPS) and synchronized measurements technologies, to summarize accomplishments within ongoing projects and experience gathered worldwide, and to emphasize the need for making practical roadmap towards greater deployment of the technology. This paper will give the scheme of automatic transmission control system that aims to mitigate the possible overloading of existing transmission lines while maintaining the same rate of generation.

In order to analyze the operation of the protection system during induced fault testing in the Croatian power system, a simulation using the CAPE software has been performed. The CAPE software (Computer-Aided Protection Engineering) is expert software intended primarily for relay protection engineers, which calculates current and voltage values during faults in the power system, so that relay protection devices can be properly set up. Once the accuracy of the simulation model had been confirmed, a series of simulations were performed in order to obtain the optimal fault location to test the protection system. The simulation results were used to specify the test sequence definitions for the end-to-end relay testing using advanced testing equipment with GPS synchronization for secondary injection in protection schemes based on communication. The objective of the end-to-end testing was to perform field validation of the protection settings, including verification of the circuit breaker operation, telecommunication channel time and the effectiveness of the relay algorithms. Once the end-to-end secondary injection testing had been completed, the induced fault testing was performed with three-end lines loaded and in service. This paper describes and analyses the test procedure, consisting of CAPE simulations, end-to-end test with advanced secondary equipment and staged-fault test of a three-end power line in the Croatian transmission system.

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In the territory of the western part of the Croatian electrical power system (EPS) lines 110 kV of the transmission network have been reconstructed for the purpose of improvement of safety and drive quality. The particularity of the observed part of the EPS is that its environment includes only one powerful power supply source. Those are two thermal power plants on the same location, Plomin 1 with the voltage level of 110 kVand Plomin 2 with the voltage level of 220 kV. The fault which occurred in the observed network is charged almost entirely from one supply point. The said inconsistence in the fault currents distribution often results in the occurrence of such conditions that do not guarantee proper operation of the transmission lines’ protection relays. Relay protection of the transmission lines has become a complex system. The use of telecommunication resources together with numerical protection relays has given rise to the need for verification of the entire system as a whole and not only its individual parts. The performance of primary trials in the transmission network 110 kV was used to test the operation of the protection system in the fault ambience. The work describes the preparatory work and the very performance of primary trials at the T-junction of the 110 kV transmission line of Plomin thermal power plant − Šijana substation − Vinčent substatio.