# Dynamic Thermal Rating and Development of Renewable Energy Zones in Sicily
## 4 Methodology
### Identification of Renewable Energy Zones  
In this context, some typical requirements have been identified for a portion of land to qualify as a Renewable Energy Zone:  
* A high concentration of renewable energy systems (RES) connected to the transmission grid within the same geographical area;
* Distribution of electricity flows generated by these RES through common transmission channels for all installations in the REZ. This condition allows the REZ to be treated as a kind of single equivalent grid node, which simplifies the management of the network outside the REZ;
* Analysis of the relationships between all the network elements that make up the REZ. If a REZ is properly identified and managed, it should be possible to minimize the need for flow management interventions within it. The evaluation starts with a real scenario identified in 2024, characterized by high renewable energy production using the TDV software (version 3.7.5). This is the software used by Terna to constantly monitor the electricity system. From TDV, it is possible to extrapolate the measurements of the current capacity over a given period. In the case study, it refers to the situation on 19 April at 16:00-17:00. It is noted that under these conditions, the RES plants connected to the transmission grid in Sicily produced about 2000 MW, and the region's high-voltage energy requirements were about 1350 MW. Another software (Wincreso, also owned by Terna) was used. This program allows the carrying out of \"Load Flow\" analyses taking into account different network assets, boundary conditions, and fault simulations. The WinCreso software (version 7.69.01) was used to simulate n-1 operating scenarios under the network conditions of 19 April at 16:00. Therefore, the loss of an additional element during maintenance conditions could lead to greater overloads. The software makes it possible to simulate the intervention of the protective system following a fault on all transmission lines. Due to the high production of energy from renewable sources, several lines were overloaded, and the protection system intervened by disconnecting some of the lines from the grid. The disconnection of each line leads to the distribution of energy flows to other lines in the transmission system, causing further grid overloads. The lines that overload frequently and with greater intensity were therefore identified. In Table 1, the overloaded lines are indicated with numbering to avoid showing sensitive data. Each overload was detected following the simulation of the opening of the corresponding power line. The disconnection of the line caused an increase in the required flow rate on the numbered line. As can be seen, the nominal current limit is exceeded by a large margin. Observing the location of each of the lines potentially subject to frequent and high overloads, one characteristic common to all the lines becomes evident: they are located in the north-western part of Sicily. The distribution of the overloaded lines is, in fact, closely linked to the uneven presence of RES plants in the territory. Network congestions, which are local phenomena, almost always occur in the vicinity of such areas characterized by numerous RES plants. Based on these analyses, it was possible to identify the lines that are typically overloaded under n \(-\) 1 network conditions. Based on the geographical distribution of the overloaded lines, four REZs were determined: A, B, C, and D. As observed, the current Sicilian REZs are located exclusively in the western part of the region, mainly due to the higher concentration of RES plants in this area. However, by consulting development scenarios for the coming years [2], potential REZs have also been identified on the eastern side of Sicily: REZs E and F (Figure 2). To identify them, the same methodology was applied; first, the expected renewable power in the coming years was implemented on WinCreso, then the most overloaded lines were identified, and finally, the expected new REZs were circumscribed.