5.2.1. Train Performance

The train performance has been performed for each direction of travel: from Station A to Station B and vice versa. Figure 11 shows the speed profile from Station A to Station B, highlighting that the train that travels the line from one stop to another, accelerating until the speed limit is reached and decelerating accordingly of stops.

**Figure 11.** Speed profile from Station A to Station B.

Starting from the speed profile, it is possible to obtain the power profile of each direction of travel, as shown in Figures 12 and 13. For each single section present between one stop and another, the train uses all the effort theoretically available only in the acceleration phases until the limit speed of the track is reached. Subsequently, in the steady state phase, the tractive effort applied at the wheels follows the trend of the resistance offered by the various accidentalities present in the track, influencing the power requested by the train. It is also noted that the maximum power at the pantograph in the traction phase is 3.7 MW and the maximum power in the regenerative braking phase is 2 MW. During stops, the only power consumed by the train is related to auxiliary services.

**Figure 12.** Power profile from Station A to Station B.

**Figure 13.** Power profile from Station B to Station A.

From Station A to Station B, the energy consumption is about double respect of the opposite direction, where the regenerative braking energy is high as the rolling stock must brake to contain its speed. It is due to the negative sign of the track resistance since the train goes downhill.

Figure 14a shows the energy consumption of the train and the regenerative braking energy, for each direction of travel. Figure 14b reports the timetable of the railway line under study (26 min and 51 s from Station A to Station B and 26 min, and 38 s in the opposite direction).

**Figure 14.** Energy required by trains: (**a**) Energy data; (**b**) Traffic conditions of the railway line.

### 5.2.2. Electrification at 3 kV DC

The electrification of the section under study include the installation of a traction power substation and the contact line. Therefore, it is necessary to determine the nominal power of the transformer groups present in the substation and the catenary to be used, considering the limits allowed by the CEI EN 50163 standards. For the TPS, located at Stop 2, it has been analyzed the use of two different types of substations: 2 AC/DC conversion units with a nominal power of 3.6 MVA or 5.4 MVA each. For the catenary, it has been considered the use of an equivalent section of 320 mm<sup>2</sup> or 440 mm2. For simplicity purposes, only the numerical results related to the 2 × 3.6 MVA TPS with a 320 mm<sup>2</sup> are here reported.

Figure 15 reports the minimum line voltage, highlighting that the voltage drop along the line is critical only at 7:30 and 8:30, at the departure of the train from Station B, towards Station A. In this case, the TPS must feed the train that is more than 11 km away. In fact, it is necessary to limit the power to the pantograph to 3 MW in order to contain the voltage drop on the line, obtaining a voltage at the pantograph is 2.19 kV. However, this minimum voltage is present only for a single sample of the simulation (10 s).

**Figure 15.** Minimum line voltage.

Figure 16 shows the TPS power absorption and given that the power required to the primary network does not exceed 10 MVA, it is possible to provide for the medium voltage connection to the primary network.

**Figure 16.** Power absorbed by the traction power substation between 7 a.m. and 8 a.m.
