Achievements in the Measurement of Tower-footing Impulse Impedance of Transmission Lines

This paper presents results obtained from field measurements of tower-footing impulse impedance carried out in real transmission lines. Tests were performed using an impulsive voltage generator, measuring the ground potential rise and the impressed current to determine the impulsive grounding impedance. The results of the harmonic impedance measured for the same towers with a 25-kHz instrument showed to be consistent with the 25-kHz impedance derived from the impulsive GPR and current waveforms by applying FFT.