Ricerc@Sapienza

We investigate the improvement of the lightning performance of overhead power lines through the use of additional ground wires placed below the phase conductors. The analysis of the electrical system is carried out through a method based on the conventional multiconductor transmission-line formalism. In the presence of a direct lightning, both the currents flowing in phase conductors and ground wires and the overvoltages across insulator strings can easily be evaluated. The main effects of such additional ground wires are here pointed out through an accurate numerical analysis.

The improvement of the lightning performance of overhead distribution lines, hit by direct strokes, is investigated considering the use of additional shield wires beneath the phase conductors. The frequency-domain theory of multiconductor transmission lines with periodical grounding is adopted permitting a rigorous evaluation of the phase and shield wire currents and of the overvoltages across insulators. These can be minimized by careful positioning of the underbuilt shield wires.

The proper monitoring and operation and maintenance (O&M) of solar photovoltaic (PV) systems are an integral part of the service tasks required to ensure long-term reliability and prolonged lifetime of the installation. In the recent years, with the end of the feed-in-tariff legislation, the PV stakeholders and operators shifted their focus from the design and construction of utility-scale grid-connected PV plants to the development of monitoring and more efficient O&M practices.

The probability of flashovers due to indirect lightning on overhead lines is us ually calculated assuming a statistical distribution for the induced voltages, and a deterministic and specified value for the insulation level of the line. However, more accurate practices of insulation coordination suggest a statistical treatment for the insulation level too, in order to relate the probabilistic nature of both electrical stress (induced voltage) and the electrical strength (insulation level).

Large-scale ground-mounted PV plants, because of their large extend and localization, can be subject to lightning strikes. When a lightning strike falls into the area of the PV plant, the earthing system is affected by the current flowing in the lightning channel and potentially dangerous overvoltages may occur. Thus, the investigation on the performance of the grounding system is of paramount interest for the prediction of the potential threats either for people working in (or animals passing through) the solar farm area and for the installed electric and electronic equipments.

Lightning meteorology investigates the dynamic and microphysical evolution of convective meteorological systems through
the monitoring of lightning. The timely information provided by the distribution of electrical discharges in the atmosphere is
closely related to atmospheric convection, which is often followed by the arrival of hailstorms. However, the distribution of
electrical discharges in the atmosphere also provides information on the production of nitrogen compounds, natural soil