Induced voltage measurements on an experimental distribution line during nearby rocket triggered lightning flashes

Rocket triggered lightning flashes were triggered near a de-energized experimental distribution line while simultaneous measurements of the induced phase to neutral voltage were performed. Electric field, magnetic field and lightning stroke current characteristics associated with the triggered flashes were also measured. Analysis of 63 stroke currents and corresponding induced voltages reveals that the peak induced voltages are roughly 63% larger than predicted by the commonly used Rusck theory but in fairly good agreement with modern coupling theory using measured electric and magnetic fields as inputs. The induced voltages had peak magnitudes between about 8 and 100 kV for stroke magnitudes ranging from a few kiloamperes up to about 44 kA. The vertical electric field resulting from the lightning flash was found to play a dominant role in the induction process, but the magnetic field also contributed significantly to the total induced voltage. These measurements suggest that induced voltages on distribution lines are larger than expected and may lead to more flashovers than expected.