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Italy, the country where the modern cities were born, suffer from the early ’90 of past century for a lack of vision and political address in terms of adoption of its urban agenda. The public debate about cities is focused only on administrative and insti aspects; not enough attention is dedicated to the problems of the Italian cities as development hubs. As a result, the law of 2014 that introduced the formal regulation of new metropolitan authorities lies unapplied. The paper gives some evidence about the economic specialization of the most important Italian metropolitan cities and about their relative room for innovation, using an hirschmanian index.

Positive, negative and zero sequence series impedances (in Ω/km units) are the first step for power flow and short circuit analyses and are also necessary for setting the distance relays. The paper is devoted to the computation of zero sequence series impedance (in Ω/km units) (self and mutual) in double-circuit overhead lines (OHLs) with one or more earth wires. A systematic comparison with matrix approaches demonstrates that IEC 60909-2 formula adds the zero sequence self and the zero sequence mutual impedance between the two circuits. This approximation of having a unique value of zero sequence impedance is misleading and gives great errors when phase-to-ground short circuit occurs along a circuit. It is worth noting that the zero sequence mutual impedance between parallel circuits installed on the same tower may be as high as 50% (or more) of the zero sequence self impedance of a circuit alone. Consequently, zero sequence mutual impedance between the two circuits cannot be neglected or mixed. MCA (Multiconductor Cell Analysis) shows that the simplified IEC approach underestimates heavily (more than 18%, depending upon the spacing between the circuits) the phase-to-ground fault current for a fault occurrence along one circuit of the double circuit.

The knowledge of ground return current in faulty occurrence plays a key role in the dimensioning of the earthing grid of substations and cable sealing end compounds, in the computation of rise of earth potential at substation sites and in electromagnetic interferences (EMIs) on neighbouring parallel metallic conductors (pipes, handrail, etc.). Moreover, the ground return current evaluation is also important in steady-state regime since this stray current can be responsible for EMIs and also for AC corrosion. In faulty situation and under some assumptions, the ground return current value at substation site can be computed by means of k-factors. The paper shows that these simplified and approximated approaches have a lot of limitations and only multiconductor approaches can show the ground return current behaviour along the cable (not only the two end values) both in steady-state regime and in short circuit occurrence (e.g. phase-to-ground and phase-to-phase-to-ground). Multiconductor Cell Analysis (MCA) considers the cable system in its real asymmetry without simplified and approximated hypotheses. The sensitivity of ground return current to circuit parameters (cross-bonding box resistances, substation earthing resistances, soil resistivity) is throughout presented.

The knowledge of ground return current in fault occurrence plays a key role in the dimensioning of the earthing grid of substations and of cable sealing end compounds, in the computation of rise of earth potential at substation sites and in electromagnetic interference (EMI) on neighbouring parallel metallic conductors (pipes, handrails, etc.). Moreover, the ground return current evaluation is also important in steady-state regime since this stray current can be responsible for EMI and also for alternating current (AC) corrosion. In fault situations and under some assumptions, the ground return current value at a substation site can be computed by means of k-factors. The paper shows that these simplified and approximated approaches have a lot of limitations and only multiconductor analysis can show the ground return current behaviour along the cable (not only the two end values) both in steady-state regime and in short circuit occurrence (e.g., phase-to-ground and phase-to-phase-to-ground). Multiconductor cell analysis (MCA) considers the cable system in its real asymmetry without simplified and approximated hypotheses. The sensitivity of ground return current on circuit parameters (cross-bonding box resistances, substation earthing resistances, soil resistivity) is presented in the paper.

Long–range transport of polluted air masses can significantly affect surface particulate matter levels. PM 10 and PM 2.5 daily-average ponderal values alone are not sufficient to investigate the occurrence of such phenomena and consequently do not give significant information for source apportionment. In this work, the analysis of aerosol size spectra and the study of the correlation of the fine and coarse modes of PM have been applied to individuate long–range transport episodes of polluted air masses. Dust-models and backward-trajectory analysis were supportive to local surface measurements of size distribution of PM in confirming the origins of remote sources of pollution. An application is discussed involving long range transport of desert dust over Italy that comparatively examined with a fine-PM pollution episode due to local sources. During the study, the atmospheric stability/unstability conditions were followed through the trend of the natural radioactivity considered as tracer of the Planetary Boundary Layer.