Clarifications on the Behavior of Alternative Gases to SF6 in Divergent Electric Field Distributions under AC Voltage

Abstract

Negative and positive partial discharge inception voltages and breakdown measurements are reported in a needle-plane electrode system as a function of pressure under AC voltage for natural gases (N2, CO2, and O2/CO2), pure Novec TM gases (C4F7N and C5F10O) and Novec TM in different natural gas admixtures. For compressed 4% C4F7N–96% CO2 and 6% C5F10O–12% O2–82% CO2 gas mixtures, the positive-streamer mode is identified as the breakdown mechanism. Breakdown and negative partial discharge inception voltages of 6% C5F10O–12% O2–82% CO2 are higher than those of 4% C4F7N–96% CO2. At 8.8 bar abs, the breakdown voltage of 6% C5F10O–12% O2–82% CO2 is equal to that of 12.77% O2–87.23% CO2 (buffer gas). Synergism in negative partial discharge inception voltage/electric field fits with the mean value and the sum of each partial pressure individually component for a 20% C4F7N–80% CO2 and 6% C5F10O–12% O2–82% CO2, respectively. In 9% C4F7N–91% CO2, the comparison of partial discharge inception electric fields is Emax (CO2) = Emax(C4F7N), and Emax (12.77% O2–87.23% CO2) = Emax(C5F10O) in 19% C5F10O–81%(12.77% O2–87.23% CO2). Polarity reversal occurs under AC voltage when the breakdown polarity changes from negative to positive cycle. Polarity reversal electric field EPR was quantified. Fitting results show that EPR (CO2) = EPR(9% C4F7N–91% CO2) and EPR(SF6) = EPR (22% C4F7N–78% CO2). EPR (4% C4F7N–96% CO2) = EPR (12.77% O2–87.23% CO2) and EPR (6% C5F10O–12% O2–82% CO2) <EPR (4% C4F7N–96% CO2) <EPR (CO2).

Trace Analysis of C4F7N Insulating Gas Mixtures by Spontaneous Raman Spectroscopy and Gas Chromatography

“…39 It was also found that the breakdown voltage for mixtures of 20% C 4 F 7 N and 80% CO 2 follows a nonlinear pattern as pressure increases. 40 When it comes to general-purpose chemical trace analysis, GC has been the default laboratory technique for separating and analyzing mixtures. Components are separated by moving through a chromatography column before being analyzed by a detector.…”

“…These parameters also affect the insulating ability of C 4 F 7 N. For example, as the distance between the arc contacts in a circuit breaker increases, the insulating efficiency of the gas is improved . It was also found that the breakdown voltage for mixtures of 20% C 4 F 7 N and 80% CO 2 follows a nonlinear pattern as pressure increases …”

“… 39 It was also found that the breakdown voltage for mixtures of 20% C 4 F 7 N and 80% CO 2 follows a nonlinear pattern as pressure increases. 40 …”

3D particle-in-cell simulations of negative and positive streamers in C4F7N–CO2 mixtures

“…Swarm parameters such as ionization and attachment coefficients have been experimentally measured to determine the reduced critical electric field and to estimate the dielectric strength of C 4 F 7 N mixtures [15][16][17][18][19][20]. Furthermore, their breakdown characteristics and dielectric properties have been extensively investigated through experimental measurements [21][22][23][24][25][26][27][28][29][30] as well as theoretical calculations [31][32][33]. C 4 F 7 N-CO 2 mixtures with approximately 10%-20% C 4 F 7 N have been found to achieve a comparable dielectric strength to SF 6 under varying conditions.…”