Ricerc@Sapienza

The lightning performance evaluation of overhead lines (OHLs) is a very important task, since the vast majority of line outages are due to backflashover caused by a direct lightning stroke. The paper presents results concerning the lightning performance evaluation of existing Italian 150 kV OHLs. An ATP-EMTP Monte Carlo procedure is used to assess the OHL backflashover rate (BFOR): main feature of the procedure is a simplified pi-circuit model able to simulate the transient grounding system behavior with high accuracy and very low computational effort.

A significant majority of overhead transmission lines' (OHLs) outages is due to backflashovers caused by direct lightning strikes: the realistic assessment of the lightning performance is thus an important task. The paper presents the analysis of the lightning performance of an existing 150kVItalian OHL, namely, its backflashover rate (BFOR), carried out by means of anATP-EMTP-based Monte Carlo procedure.

The lightning performance of an EHV overhead transmission line (OHL) largely depends on tower grounding behavior; when high ground flash density values are expected, a proper design of grounding arrangements, focused on their high frequency behavior instead of the conventional power frequency analysis, can significantly reduce the backflashover rate (BFR) of the OHL. A technical optimization is reported, aiming at improving the BFR of an EHV OHL in Brazil, which crosses a region with widely different soil resistivity values, resulting in a compact tower grounding system design.