A. Paolucci

Gas insulated transmission lines in railway galleries

This paper deals with the possibility of installing a double-circuit gas insulated transmission line (GIL) in the pilot tunnel of the planned new railway galleries Bolzano (Italy)- Innsbruck (Austria). This EHV transmission line could represent a new fundamental step in reconstructing the transnational networks. The high GIL power ratings together with very low power losses would be a strong and highly efficient transmission tie between Italy and Austria particularly useful for the future European Market. The steady-state regime of the line and the electro-magnetic field impact are analyzed. Moreover, the paper discusses the necessary studies to be carried out and the problems that have to be faced.

Resonance phenomena on line-to-ground fault current harmonics in MV networks

High levels of harmonic components measured on MV line fault currents have prompted a detailed investigation of the phenomena in order to develop models to accurately reproduce the observed harmonic currents and clarify the resonance characteristics of the system under line-to-ground fault conditions. A procedure which can predict the fault current wave-form of a whatsoever complex distribution system supplying a variety of loads, enabling identification of potentially harmonic resonance conditions, is presented. It may be applied, for instance, to verify the performance of networks adopting suppressing coil (which is normally tuned on the fundamental frequency) or zero-sequence protection relays. A parametric analysis on typical MV distribution systems shows how it is possible to identify critical fault locations which may give rise to very high harmonic currents.