*3.1. Architecture*

The system under analysis is in Bergamo (Italy). The pattern has a full length of 12 km, and it is characterized by 10 feeding electrical substations (ESSs), whose positions are in Figure 2.

**Figure 2.** Position of the electrical feeding substations (ESSs) in blue and stops in red along the path (distances from the terminal are indicated in meters).

The main technical data of this system are in the next Table 1.


**Table 1.** Main features of the system.

The feeding supply system is schematically represented in the next Figure 3. How visible, each ESS has a MV/LV transformer (TR1) with its converter, in order to feed energy needed for propulsion. Then, a second transformer (TR2) feeds the LV auxiliary loads, e.g., visual and acoustic signals of each ESS and of the nearest train stop. As always depicted in Figure 3, energy meters were installed in each ESS to measure energy flows, and also additional data logger were introduced, to measure instantaneous DC voltage and current. Measurement devices are also indicated in Figure 3.

**Figure 3.** Scheme of ESS, including measurement system.

The main characteristics of the transformer TR1 are in the next Table 2.


**Table 2.** Main parameters of the standard transformer (TR1).
