Resonance at the front of lightning impulse voltage waveforms caused by the load capacitor

During the impulse voltage comparison test, it is important to keep the waveforms smooth for obtaining consistent experiment results, especially for the front time parameter. However, steps or oscillations are often found on the front of the waveforms. The authors propose a theory that these oscillations can be caused by the resistors in the damped capacitive voltage divider, which often serves as the load capacitor in the impulse voltage generation circuit. The theoretical analysis, numerical simulation, and experimental results are performed, and a good agreement has been found in support of the proposed theory. Furthermore, the waveform parameters measured by two resistive reference standard systems were found to be influenced by the shape of the waveform and the oscillation on the front. It is recommended to avoid using a damped capacitive divider as the load capacitor but use an impulse capacitor with low equivalent series resistance instead. This would help to eliminate this common cause of oscillation on the front of the lightning impulse voltage waveform. Waveform uniformity and uncertainty of the result could then be improved during the comparison of reference measuring systems.