5-phases solution and series compensation: a cost-effective strategy for OHLs power transfer capacity increase under stability margin

In the light of the decarbonization process, modern power systems pose multiple challenges to transmission network planners. In the Italian context, increasing network congestions are expected in the medium/long-term horizon across long corridors from South, where connection applications for new renewable power plants are concentrated, to North, where main load consumptions are located: in these scenarios, the angle stability constraint become an additional subject to be addressed in the EHV transmission system planning. For this purpose, the reduction of equivalent reactance of strategic transmission paths enables operational limits extension and becomes a crucial topic in planning framework. In this paper, the innovative "5-phases" solution, developed by Terna (the Italian TSO), is combined with the capacitive series compensation in a wider pilot network affected by stressful power transfer conditions. The main benefits in terms of transfer capacity increase between relevant market section and voltage phase shifts reduction are assessed in different cases study both in normal conditions and during critical contingencies.