## 6 Results  
Table 3 reports the resulting occurrences of the three possible states of the calculated operating points into which are subdivided the maximum hourly range of the upward and downward bids (i.e., the market potential). A \"feasible point\" identifies an operating point (defined as a pair of active and reactive power for the whole feeder) fully feasible without any violations; a \"feasible point with Q control\" detects a technical condition where the Q support from DG (with additional costs) is fundamental to solve the electrical violations that happen in the network. Finally, an \"unfeasible point\" describes a condition where the technical violation cannot be avoided and, for this reason, the DSO will block this offer. The first case discussed in the following paragraphs is case A, which involves the DG units only. Therefore, the following comments are referred to in the first columns in Table 3 (case A). Table 3 highlights that, in the first feeder (R1--Figure 3), the reactive support from DG (i.e., their Q control) is mandatory to obtain an adequate flexibility level. By analysing Figure 2, it can be realised that R1 is the feeder with the biggest DG quantity (>50% of the total DG installed capacity in the substation). Consequently, more technical violations (e.g., overvoltages) can be expected in this feeder. On the contrary, the other feeders are fully feasibly capable of giving to the TSO all the flexibility potentially provided by the connected DG units. In the following, more details will be given about the flexibility potential offered by the feeder R1 (case A). In particular, in Figure 3, all the simulated operating points are shown: the different colours follow the definitions adopted in Table 3. Such points represent the operating points into which has been subdivided the market potential of the feeder, calculated as differences in the expected profile in each considered time interval. The (0, 0, \(t\)) points of the 3-D graph represent the expected profile without any variations in each time interval \(t\). For the comprehensive analysis of Figure 3, it is important to remark that positive \"Delta Active Power\" points identify a DG production curtailment, while negative \"Delta Active Power\" points represent an increase in DG production, which seems feasible for a given extent, 79.9% (green points) around the expected profile, and, for the remaining part of the potential range, become unfeasible (red points 17.4%) or feasible with the reactive support only (orange points, 2.7%). In detail, Figure 3 highlights that the market potential offered by the DG units can hypothetically reach +6 MW during the year, but this upper limit is unfeasible (red points in Figure 3), with the \"feasible flexibility quantity\" limited to about +4 MW (green points). As discussed above, positive \"Delta Active Power\" values detect a generation reduction that is easy to manage (green points--no technical violations). Still, if a large quantity of generation is switched off, some under-voltage conditions happen in the network. This contribution to flexibility becomes unfeasible (red points area in the upper part of Figure 3). In the negative part of the \"Delta Active Power\" axis (Figure 3), the offers that increase the DG production are represented: according to the availability shown in Table 2, these quantities are lower than the previous ones. Due to the high amount of installed DG in the feeder R1, a further increase in power injection is not suitable (the network suffers