Ionization and Attachment Coefficients in C4F7N Gas Measured by the Steady-State Townsend Method

Abstract

The normalized Townsend first ionization coefficient α/N and normalized attachment coefficient η/N in pure C4F7N were measured by using the steady-state Townsend (SST) method for a range of reduced electric fields E/N from 750 to 1150 Td at room temperature (20 °C). Meanwhile, the effective ionization coefficients are obtained. All SST experimental results show good agreement with pulsed Townsend (PT) experiment results. Comparisons of the critical electric fields of C4F7N with SF6 and other alternative gases such as c-C4F8 and CF3I indicate that C4F7N has a better insulation performance with a much higher normalized critical electric field at 959.19 Td.

Electron Swarms Parameters in CF3SO2F as an Alternative Gas to SF6

“…Figure 4 presents the value of (α−η)/N as a function of E/N in CF 3 SO 2 F and the comparison to that of SF 6 gas 3 and C 4 F 7 N gas. 12 Similar to the other two gases, the value of (α−η)/N in CF 3 SO 2 F shows an obvious linear growing trend with the E/N increasing from 400 to 750 Td at 20 °C. Notably, the value of E/N in CF 3 SO 2 F is between those for SF 6 and C 4 F 7 N for the same (α−η)/N, which suggests that the insulation performance of CF 3 SO 2 F is better than that of SF 6 while weaker than that of C 4 F 7 N.…”

“…To evaluate the ionization performance more directly, the reduced effective ionization coefficients (α–η)/ N was obtained as well. Figure presents the value of (α–η)/ N as a function of E / N in CF 3 SO 2 F and the comparison to that of SF 6 gas and C 4 F 7 N gas . Similar to the other two gases, the value of (α–η)/ N in CF 3 SO 2 F shows an obvious linear growing trend with the E / N increasing from 400 to 750 Td at 20 °C.…”

“…This important value of ( E / N ) lim could help evaluate the dielectric strength quantitatively. The comparisons of ( E / N ) lim in CF 3 SO 2 F, SF 6 , and C 4 F 7 N have been listed in Table . It can be found that CF 3 SO 2 F has better performance as gas insulation than SF 6 as its ( E / N ) lim is 578.8 Td, which is about 1.6 times that of pure SF 6 gas.…”

“…The SST experimental setup in the present work is the same as that in our former work. − As described, the SST experimental setup consists of five parts including the vacuum system, the discharge current measuring system, and so on. The background vacuum degree in the ionization chamber is better than 1.0 × 10 –5 Pa at 20 °C and the leak rate of gas pressure is less than 0.07 Pa/h.…”

Measurement of Ionization and Attachment Coefficients in C4F7N/CO2 Gas Mixture as Substitute Gas to SF6

“…The measurements of the C 4 F 7 N/CO 2 mixtures were performed on the SST apparatus setup in Wuhan University [13], [14]. The accuracy of the measurement is less than 2%.…”