Systematic Design and Circuit Analysis of Lightning Impulse Voltage Generation on Low-Inductance Loads

The well-known circuit for the generation of lightning impulse voltage (LIV) on low-inductance loads was introduced by Glaninger in 1975, and the circuit component selection was proposed by Feser. However, the circuit and the approach for the component selection have some difficulties for which further adjustment is required for obtaining the waveform parameters according to the standard requirement. In this paper, an extended Glaninger’s circuit with an additional series resistor is proposed. Furthermore, a systematic design and circuit analysis of LIV generation for low-inductance loads are developed. With the help of a circuit simulator, the circuit analysis for the component selection is described. The validity of the proposed circuit was confirmed by some experimental results in comparison with the simulated ones. The proposed circuit and component selection provide not only the generation waveform according to the standard requirement but also other promising performances in terms of the wide inductance load range from 400 μH to 4 mH, a voltage efficiency of over 80%, an overshoot voltage of below 5%, an undershoot voltage of below 40%, and a maximum charging capacitance of 10 μF. From the simulated and experimental results, the proposed circuit and component selection approach is very useful for the LIV tests on low-inductance loads instead of using the conventional approach based on trial and error.

Oscillation of Gas Density in the Gas Filament Remained by a Streamer Discharge in Water

When a streamer discharge occurs in water, several luminous plasma filaments will be created in the water during the discharge. After the discharge, these plasma filaments turn into neutral gas phase and remain in water. The gas filament remained in water is a good object for studying the basic processes involved in the streamer propagation. We investigated the evolution of the gas filaments remained in water after a streamer discharge at different experimental conditions. We recorded eight successive images during one discharge pulse. The density of gas in the gas filament and the radius of the gas filament were measured from the obtained images. We found that the radius of the gas filament and the density of gas in the gas filament are almost not influenced by the impulse voltage within the range studied. While the conductivity of water has strong effect on the radius of the gas filament and the density of gas in the gas filament. The radius of the gas filament becomes thicker and expands faster as the conductivity of water becomes larger. The density of gas in the gas filament remained in water oscillates between 400 to 800 kg/m3 with an duration of ~10 μs during the expansion period of 4–39 μs after the HV pulse starts. Both the impulse voltage and the conductivity of water do not affect the oscillation duration of the density of gas in the gas filament.