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.

We study the shielding performance of shield wires in overhead power lines. We propose a novel chain matrix formulation, that employs longitudinally symmetric transmission-line cells to more efficiently, and correctly, simulate the propagation behaviour over the line accounting for the periodical grounding. The analysis is performed in the frequency domain and results in time domain are obtained through inverse Fourier transform. In the case of direct lightning, we can easily compute overvoltages across insulator strings for insulation coordination purposes.