36 kV: a new standard voltage level for the connection of renewable energy sources to the Italian National Transmission Grid

The introduction of a new voltage level for integrating renewable energy sources into the National Transmission Grid (NTG) offers several advantages to the current energy landscape. In compliance with European and national regulations, including the integration of the Italian National Recovery and Resilience Plan (PNRR), the production from renewable energy sources (RES) has significantly grown, resulting in a substantial increase in the demand for NTG connection from RES plants. Until now, the standard practice in Italy for bulk harvesting of renewable energy sources involved the connection of RES plants to the NTG at 150 kV level; typically, each power plant developed its own medium voltage network and its own substation with a MV/HV transformer that was then connected through a dedicated bay in a Terna’s substation. However, Terna’s 150 kV bays are designed to accommodate much higher power (about 250 MVA) if compared to the average size of typical wind farms or PV plants. To address these inefficiencies and technical challenges, Terna has identified an optimized solution—the utilization of a new unified voltage level for the NTG, set at $\mathrm{U_{n}=36 kV}$. This enables the direct connection of renewable energy production plants with a rated power capacity of up to 100 MW, without the need for a power MV/HV transformer, reduces land occupation, streamlines connection request management, and optimizes costs for both producers and the NTG.