Influence of corona on the voltages induced by nearby lightning onoverhead distribution lines

摘要

A model for the calculation of lightning-induced voltages isnpresented with the aim of assessing the effect of corona when powerndistribution lines are illuminated by lightning electromagnetic fields.nCorona is taken into account by means of dynamic capacitance describingna charge-voltage diagram. Such an equivalent capacitance is thennintroduced in a model which describes a line illuminated by a lightningnelectromagnetic field. It is first concluded that the influence ofncorona on lightning induced overvoltages is of importance only fornparticularly severe strokes. It is also found that corona acts tonincrease the magnitude of these overvoltages, contrary to the case ofnvoltages due to direct strokes, which are attenuated by corona. Antheoretical explanation of such an amplitude increase is presented. Theneffect of the ground resistivity is also taken into account in thencalculations. The results show that such an effect is in general asnimportant as the effect of corona. This is different from thendirect-strike behavior, where corona, when present, affects the surgenpropagation more than the ground resistivity. This is due to the factnthat for the case of induced-voltages, the ground resistivity may affectnmore strongly the lightning-radiated fields rather than the surgenpropagation along the line, while corona affects only surge propagation.nThe need for experimental results to test the theoretical finding of thenpaper is stressed and some indication is given. Finally, a sensitivitynanalysis of the induced voltages as a function of the charge-voltagendiagram adopted to model corona is also performed