Oscar Diaz

Sensitivity analysis of leader channel models used in long air gap positive discharge modelling

Leader models used in electrical discharge simulation have been proposed in theoretical works by different authors. Their application can be found in the study of lightning upward connecting leaders or long air gap laboratory testing, and can be considered engineering or physical according to their detail level. Based on simplifications and assumptions, these models are capable of predicting the 50% breakdown voltage for certain electrode arrangements, time evolution of physical phenomena like particle densities, temperatures, electric fields, leader and streamer progress, among others. An important parameter in a leader model is the potential distribution along the channel as it propagates. In present work, we compare an engineering and a physical leader model against experimental data recorded while testing a rod-to-plane 10 m gap with switching-like voltage impulse. A sensitivity analysis was done with some basic input parameters of two leader models in order to compare the outcome for different cases. The results showed a strong dependence of the leader channel evolution with the assumed constant average potential gradient used in most of the leader models.

Experimental study of leader tortuosity and velocity in long rod-plane air discharges

Long air gap electrical discharges are of particular interest among scientists and engineers working on high voltage techniques and lightning research. In the present work we report experimental results obtained while testing a long rod-plane air gap with positive switching-like voltage impulses to study the velocity and tortuous progression of the leader discharge. Voltage and current waveforms were recorded. Two still digital cameras were used to track the leader tortuous path. By using a fast digital camera, the leader temporal evolution was recorded and its propagation velocity was estimated. Three angles were used to describe the leader tortuous progression.

Cold-electrode voltage fall for impulse arcs in argon between copper electrodes

The full electric arc discharge in gases for short gaps in homogeneous electric field and pressure·distance (pd) below 150 Torr·cm, can be described as a transition between different discharge mechanisms such as: Townsend, glow, and arc. Once the arc is achieved the measured voltage drops to some volts and the current density increases several orders of magnitude. Depending upon the type of gas used, the electrode surface characteristics and type of electrical excitation, the cathode and anode voltage fall might change. The present work is directed to study the electrode fall (sum of anode and cathode falls) during a current impulse arc discharge between copper electrodes in ceramic tubes filled with argon between 0.01 and 6.5 Torr·cm. The copper electrodes were cleaned, degassed and hydrogen reduced. The arc voltages were measured with fast/slow rise times and short/long duration current impulses produced by a RLC circuit. An increasing variation of the electrode fall was found at the pressure·distance range analyzed.

Energy dissipation in a new flat low voltage surge protective gas discharge tube

The presented study deals with the behavior of a new flat low voltage surge protective gas discharge tube (GDT) while tested with different electric currents and how it dissipates the energy generated during operation.

Spark gap resistance for an electrostatic discharge at different pressures

Summary form only given. Most of the experimental data available in the literature on electrical discharges is referred to the breakdown characteristics of discharge gaps for different geometries in air. However, in order to understand the physical processes associated with the electrical discharges, it is necessary to obtain experimental data on the temporal variation of current- voltage during the pre-breakdown and the spark stage. This information is necessary to understand how the resistance of the discharge channel varies as a function of time and the energy dissipation during the discharge. The aim of this work present a study performed on a self- breakdown pressured gap, where voltage and current were measured when a fast electrostatic discharge (ESD) occurred between two electrodes. This fast ESD was produced by a floating electrode charged with corona currents, obtaining some hundreds of amperes of peak-current amplitude and a few nanoseconds of risetime and pulse width. The internal gas was dry air at different pressures.