The growing share of integrated renewable energy sources within the power system leads to instability and imbalance due to variable and erratic power production from renewable energy sources. A potential solution to the aforementioned issue is the utilization of energy storage systems in transmission networks, which is the main topic of this paper. The paper discusses the fundamental technologies of energy storage systems in which mechanical, electrical, chemical, electrochemical and thermal systems stand out. Furthermore, the paper provides a review of a comparison of relevant battery energy storage technologies. In addition, the paper discusses the application of battery energy storage systems in transmission network. In other words, it discusses the possibilities of using battery energy storage systems for integration within renewable energy sources and the consequent reduction of greenhouse gas emissions and also for increasing the quality of electricity and also for delaying the upgrade of the transmission network and also for ensuring N-1 safety criterion and also for achieving minimum system operating costs and also for provision of auxiliary services to the transmission system operator (congestion management in the network, balance of the power system, ensuring frequency stability and providing regulatory reserve, ensuring voltage stability and providing black start). Finally, the paper presents the application of the battery energy storage system on the simulation model of the Istrian subsystem, which resulted in the successful prevention of interruption of the power supply in the Istrian subsystem during the period of disturbed operating condition.