# Evaluating the Flexibility Benefits of Smart Grid Innovations in Transmission Networks
## 1 Introduction  
Electricity infrastructure projects are capital intensive and face several public objections before and during their implementation phases [1]. Decision-making during planning phases is something that requires comprehensive tools to evaluate costs and benefits with various KPIs (key performance indicator). In this context, CBA (cost-benefit analysis) approaches have been introduced worldwide, providing analytic methodologies to quantify the effects of specific electricity projects [2, 3, 4]. The implementation of innovation technology into the electricity networks is a complex issue and can be expressed in different ways [5, 6]. Clean energy targets have been the main driver for the disruption occurring in the electricity sector the last couple of decades. Electrification and digitalization areemerging as additional major challenges for the future years, dictating the maximization of assets capacity and controllability, so as to defer costly infrastructure investments with significant footprint on the environment, i.e., new OHLs (overhead line), substations, fossil fuel plants [7; 8]. With more and more intermittent or variable sources from renewable energy and new patterns of demand resulting from electric vehicle charging, power systems critically need different flexibility means to maintain security of supply [9; 10]. The need for flexibility in a decarbonizing electricity sector was consistently and broadly understood. Without an increase in flexibility, likely situation of power balance violates and increases levels of renewable energy curtailment. There are also needs for conventional reinforcement to deal with congestion, and a greater reliance on cross border trading and energy flows to accommodate regional power fluctuations [11; 12]. An increase in system risk is also highlighted, which is associated with increasing the breadth of participation in system services, and with applying commercial pressure to that participation. Overall, by increasing the number of participants, the system will become more difficult to manage which may result in a less secure or a less stable grid configuration. There is also increased uncertainty in the network's ability to deal with infrequent but high impact events, such as storms or floods. Mechanisms should be put in place to ensure that the system can deal with such events without passing unnecessary costs onto consumers [13]. Flexibility is a necessary part of a low carbon electricity network, rather than an end in itself. Benefits resulting from increased flexibility lie in different aspects such as the ability to have a greater proportion of distributed renewable generation on the network without incurring significant additional network reinforcement costs and increased efficiency of electricity grid operation without oversizing generation capacity [14; 15; 16]. This was highlighted as an important aspect for grid owners and system development planners, as they focus on keeping electricity bills at reasonable levels. Electrical energy storage was seen as a key enabler for flexibility [17; 18; 19]. Note that flexibility resources can include both centralized resources connected to the transmission system, as well as distributed resources connected to the distribution network. In the latter case, aggregation will be required, as well as appropriate coordination, in order to provide flexibility services from the distribution network to the transmission system. The current work deals with the assessment of the flexibility benefits coming from smart grid innovations, developed in the H2020 project FLEXITRANSTORE [20]. The project includes pilots in various sites across the Europe, where appropriate technologies have been developed in an effort to enhance the flexibility of the systems examined in the context of the project. To this direction, the paper focuses on a specific use case, considering a bulk system, i.e., the electrical power system of Cyprus and evaluates the benefits that the implemented technologies provide.