Ricerc@Sapienza

Auxiliary-battery-based substations (ABSs) can enhance conventional railway feeder systems. In particular, ABSs make dc feeders located in areas far from the ac grid able to power high-performance passenger and freight trains and store their braking energy. This paper proposes a techno-economic method to define size, position along the track, and control parameters of an ABS, with the goal to minimize the annual cost of energy. Our approach takes into account the replacements of battery modules within the ABS's expected lifetime in order to reduce costs.

The paper proposes a methodological approach to manage the electric vehicles recharging in an isolated power system characterized by low short circuit power. Focusing on harmonic disturbances, current harmonics injected in the network depend on the specific EV power converter. The model carried out allows for the evaluation of harmonic disturbances under variable conditions for non-linear loads and their harmonic spectra. The methodology allows estimating both current and voltage total harmonic distortion (THDV, THDI) at the point of common coupling (PCC).

A Cross-Country Fault (CCF) is the simultaneous occurrence of a couple of Line-to-Ground Faults (LGFs), affecting different phases of same feeder or of two distinct ones, at different fault locations. CCFs are not uncommon in medium voltage (MV) public distribution networks operated with ungrounded or high-impedance neutral: despite the relatively small value of LGF current that is typical of such networks, CCF currents can be comparable to those that are found in Phase-To-Phase Faults, if the affected feeder(s) consists of cables.

Since Lead-cooled Fast Reactors (LFR) have been conceptualized in the frame of Generation IV International Forum (GIF), great interest has focused on the development and testing of new technologies related to Heavy Liquid Metal (HLM) nuclear reactors. In this frame, ENEA developed one of the larger European experimental fleet of experimental facilities aiming at investigating HLM thermal-hydraulics, coolant chemistry control, corrosion behavior for structural materials, and at developing components, instrumentations and innovative systems, supported by experiments and numerical tools.

Transport is a main source of pollutants in cities, where air quality is a major concern. New transport technologies, such as electric vehicles, and public transport modalities, such as urban railways, have arisen as solutions to this important problem. One of the main difficulties for the adoption of electric vehicles by consumers is the scarcity of a suitable charging infrastructure. The use of the railway power supplies to charge electric vehicle batteries could facilitate the deployment of charging infrastructure in cities.

One of the parameters that has to be considered in designing underground cables is the thermal resistivity of the soil along their routes. In fact, the ampacity of the MV underground cables having different types of insulation is normally evaluated through the application of the IEC Standard 60287-x 'Electric cables - Calculation of the current rating'. This series of IEC Standard is formed of three parts as in the following: part 1: Formulae of ratings and power losses; part 2: Formulae for thermal resistance; part 3: Sections on operating conditions.

The paper reports a methodologie approach to analyze a new layout of 3 kV DC railway substation. An evaluation about the substations' (ESSs) filter, in order to reduce the reactor encumbrance has been carried out. By means of simulations with different filter configurations, the proposed approach allows to verify that the harmonic content of the released current in the return circuit is compatible with the safety and signalling devices and to evaluate the effect of new configurations on the fault current.

The paper shows the typical architecture of a 2×25 kV-50 Hz traction system, and the details that need to be considered and approximations that can safely be done, for power frequency studies. Power frequency models are important to allow simulations of long timespans, such as those needed when evaluation of trains acceleration/braking, for instance to analyse active and reactive power flows, voltages and currents. The proposed models are implemented in two ways: as data to be inputted to the well-known ATP Program, and as specific models written in the standard Modelica language.

Advanced guidelines have to support the design of every electric power systems in hunting performances of safety, dependability and costs saving. Particularly, power systems, critical for the mission of their loads and/or equalized to mission critical for the vulnerability of their supplying network, need a 'partition system', local fortified structure, interface between network and utilization, designed as a service continuity 'castle' and managed to guarantee an adequate response to every emergency.

Buildings with mixed residential and commercial units show relevant power peak that re further enhanced by shifting to electric source of nowadays gas-driven systems. The proposed solution is to organize a microgrid for such kind of buildings, aggregating different users with a common electric distribution system with a unique connection to the grid, a local common generation and a common heating/cooling system (electric-driven). This approach upgrades a group of independent several small users with rigid loads and chaotic behavior, to a large user with a flexible and controlled profile.