FDTD Analysis of the Unit Step Response of a Circuit Measuring Chopped Lightning Impulse Voltages

Unit step response (USR) parameters of a circuit for measuring chopped lightning impulse voltages are calculated using the finite-difference time-domain method for solving Maxwell's equations, and compared with those of a USR-measuring circuit recommended by the International Electrotechnical Commission (IEC). Although the circuit for measuring chopped lightning impulse voltages is quite different from the IEC-recommended USR measuring circuit, USR parameters calculated for the former circuit are not much different from those calculated for the latter circuit except the case when the former circuit includes both a low-impedance impulse high voltage generator and a damping resistor.