Field-Time Breakdown Characteristics of Air, N₂, CO₂, and SF₆

Abstract

The dielectric performance of gases in insulation systems used in high voltage power and pulsed power applications is a subject of intensive theoretical and experimental investigation. Transient breakdown processes in gases stressed with short, high-field impulses, have been studied for many decades. However, there are still significant gaps in the understanding of the main breakdown processes and mechanisms associated with fast transient breakdown processes in gases. This knowledge is important for optimisation of gaseous insulating systems and for coordination of gaseous insulation in power and pulsed power apparatuses. This information is also required for the development of gas-filled components such as circuit breakers and plasma closing switches. The present work is aimed at analysis of the field-time breakdown characteristics of air, N 2 , CO 2 , and SF 6 , using kinetic and drift-diffusion approaches. The kinetic approach is based upon the avalanche-to-streamer transition criterion, while the fluid drift-diffusion model requires self-consistent numerical solution of the continuity equations for charged species, and the Poisson equation for the electric field. The time to breakdown as a function of the applied field was obtained for all investigated gases. The obtained analytical results agree well with the experimental data reported in the literature, which suggests that both approaches can be used for insulation coordination, and for the development of gas-insulated power and pulsed power systems and components. Index Terms-Transient breakdown in gases, ionization front, time-field breakdown characteristics.

The Nanosecond Impulsive Breakdown Characteristics of Air, N2 and CO2 in a Sub-mm Gap

“…The numerical values of the fitting parameters, C and D, obtained in OriginPro graphing software for each gas are given in Table 2. 11 shows Nt as a function of E/N for air, N2 and CO2 and includes: the results obtained in the present work (Ntbr as a function of Etip/N), the kinetic model results (Ntf as a function of E/N), and the results previously published in the literature, [10,11,[22][23][24], and [34][35][36][37]. Each experimental point shown in Figure 11 represents the average value obtained using 20 individual data points, the error bars show the 95% confidence interval values, (some original experimental points do not appear to have error bars as a result of these bars being too small to display relative to the size of the point).…”

“…To obtain the analytical "breakdown field-formative time to breakdown" characteristics, a kinetic model can be used. The kinetic model discussed in detail in [34] links the formative time and the normalised breakdown field, E/N:…”

“…where, t f is the formative time, α eff is the effective ionization coefficient and µ e is the mobility of electrons; the numerical values of α eff and µ e used in the present analysis are listed in [34].…”

“…The literature data are based on both formative and (in some cases) total time to breakdown and were obtained under various experimental conditions (type of electrodes, inter-electrode distances, gas pressures, high-voltage pulse characteristics). Details of each specific set of experimental conditions can be found in [10,11,[22][23][24][34][35][36][37]. -positive polarity (monocone) [24]; - [23]; solid line, fitting curve, Equation ( 6).…”

Automatic Optimization of Gas Insulated Components Based on the Streamer Inception Criterion

“…As a matter of fact, the computation of streamer integrals (15) requires knowledge ofᾱ for a large range of operational parameters. For common insulating gases empirical relations well-fitting experimental data over a wide range of E/P are listed in the literature [21,26]. Using the ideal gas law, relating gas pressure and density N [1/m 3 ], the reduced effective ionization coefficient of SF 6 , can be expressed as [26]:…”