Generation and measurement of oscillatory current impulses up to 470 kA

Investigations into the characteristics of spark discharges have been made for impulse currents of up to 100 kA peak. The generation of such currents is based on the techniques developed for surge-testing purposes to simulate lightning-stroke conditions. For oscillatory impulses the current is determined primarily by the discharge energy of the generator and the total effective inductance. The generator described in the paper has been constructed to have a low inductance (0.1 μH) and gives a peak current of 470 kA for a discharge energy of 18000 joules at 25 kV. It is being used for studies of the spark channel under different conditions.The measurement of impulse currents is normally made with the aid of a low-resistance shunt. A shunt of coaxial form, giving a small time-constant and freedom from unwanted coupling with the main current circuit, has been used with the above generator and is described.