### IVDP

The case where the PDIV of the mixed gas changes with pressure under different mixing ratios and the case where the PDIV of the mixed gas changes with the mixing ratio under different pressures are shown in Figs. 5 and 6, respectively. Each experiment adopts the step-by-step voltage division method, and the voltage is applied slowly at a constant speed from 0 kV. Once the voltage is stable, observe the oscilloscope signal. When the voltage is high, it will cause the display board electrode to fail. At this time, the breakdown voltage is recorded, the voltage regulator is self-protected, the voltage drops to zero, and it is turned off. Then repeat the above operation for 5 tests and take the average of all test results as the final result in this condition.

It can be seen from the figure that the PDIV value of gas increases with increasing pressure and gas mixing ratio. Pure N_{2} has a PDIV value of 5.9 kV at 0.1 MPa and 7.2 kV at 0.2 MPa, with an increase of 1.3 kV. The PDIV value of the 2% gas mixture was 6.7 kV at 0.1 MPa and 10.1 kV at 0.2 MPa, with an increase of 3.4 kV. The PDIV values of the 4% and 6% mixed gas increased by 4 kV and 4.6 kV respectively in this pressure change. It can be concluded that the mixed gas of the high mixing ratio increases the PDIV value faster when the pressure changes.

The relationship between starting voltage and pressure is adjusted by the formula

$$ U_{PDIV} = AP + B. $$

(1)

*you*_{IVDP} is the PDIV value, *A* is the slope reflecting the rate of change of the PDIV value with pressure, and *P* is the pressure. The PDIV value of the mixed gas has a positive correlation with the pressure. Plus the value of *A*, the more the PDIV value of the gas mixture is visibly affected by the pressure. The results calculated after adjustment are: *A*_{0%}= 12.14; *A*_{2%}= 32.43; *A*_{4%}= 40; *A*_{6%}= 46.86. From this it can be concluded that the higher the mixing ratio, the greater the influence of pressure on the gas mixture.

In Fig. 6, when 2% C_{6} F_{12}O is added, the PDIV value of the gas increases rapidly. After adding 4% C_{6}F_{12}O gas, the PDIV value of the gas increases slowly. And the higher the pressure, the faster the PDIV value increases. It can be concluded that the PDIV value will increase faster after N_{2}is added with C_{6}F_{12} O under high pressure, but as the mixing ratio increases, the speed becomes slower at certain pressure.

Table 2 shows the ratio of the PDIV value at different pressures of each group of mixed gases to the PDIV value of N_{2} reflecting the increase in the ignition voltage of the partial discharge of the gas mixture obtained after the addition of C_{6} F_{12} O. It can be seen from the table that as pressure and mixing ratio increase, the ratio of the PDIV value of each mixed gas to the PDIV value of N_{2} is higher. At the same mixing ratio, as the pressure increases, the ratio of the PDIV value of the mixed gas to the PDIV value of N_{2}gradually increases. From Table 2, the ratio of 2% mixed gas to pure N_{2}increases from 1.14 times at 0.1 MPa to 1.40 times at 0.2 MPa with increasing pressure, at the same time, when the mixing ratio is 6%, the PDIV ratio of the mixed gas at PDIV of pure N2 increases from 1.20 times 0.1 MPa to 1.63 times 0.2 MPa. Thus, the mixed gas with high mixing ratio increases the PDIV value more obviously with increasing pressure, which is consistent with the results of the previous linear. At the same pressure, as the mixing ratio increases, the ratio of the PDIV value of the mixed gas to the PDIV value of N_{2} also gradually increases. When the pressure is 0.1 MPa and the mixing ratio of the mixed gas increases by 2-6%, the ratio of the PDIV value of the mixed gas to the PDIV value of N_{2}goes from 1.14 to 1.20, an increase of 5.3%; and when the pressure is 0.2 MPa, the data changes from 1.40 to 1.63, an increase of 16.4%. It can be concluded that the addition of C_{6}F_{12}Y to N_{2}will result in a more significant increase in the PDIV value of the mixed gas at higher pressure.

In summary, when the pressure is more than 0.16 MPa and the mixing ratio is more than 2%, the PDIV value of the mixed gas is increased by 50% or more compared to pure N_{2}.

### PDEV

In this experiment, the measurement results of the partial discharge extinction voltage according to the experimental procedure are shown in Figs. 7 and 8. The figures show the change of PDEV value with pressure under different mixing ratios and the change of PDEV value with mixing ratio under different pressures.

In Figs. 7 and 8, similar to the change of the PDIV value of the gas, as the mixing ratio and the pressure increase, the PDEV value of the gas gradually increases. For pure N_{2}, its PDEV value is 5.8 kV at 0.1 MPa and its PDEV value is 6.9 kV at 0.2 MPa, an increase of 1.1 kV. For 2%C_{6}F_{12}O, its PDEV value is 6.2 kV at 0.1 MPa and its PDEV value is 9.2 kV at 0.2 MPa, an increase of 3 kV. When the mixing ratio is 4%, the PDEV value of the 0.1 MPa mixed gas is 6.4 kV, which is not significantly improved compared to the 2% mixed gas. When it reaches 0.2 MPa, it changes to 10.3 kV and increases by 3.9 kV. When the mixing ratio reaches 6%, the PDEV value of the mixed gas is 7 kV at 0.1 MPa, which is a relatively large increase from the ratio of 2% and 4%. At 0.2 MPa, the PDEV value of the mixed gas is 10.6 kV, which increases by 3.6 kV. Therefore, adding C_{6}F_{12}O increases the PDEV value by N_{2}while pressure sensitivity increases slightly.

According to formula (2), linearly fit each curve in Fig. 7 to investigate the linear relationship between the PDEV value of various mixed gases and pressure.

$$ U_{PDEV} = A^{prime}P + B^{prime}, $$

(2)

or *you*_{PDEV} is the value of the partial discharge quenching discharge voltage, and *A*′ is the slope. The values of *A*′ calculated for each curve are: *A*′_{0%}= 11, *A*′_{2%}= 30.71, *A*′_{4%} = 36.71, *A*′_{6%} = 37.71. The values of the four curves *A*′ are all positive values, i.e. the voltage value PDEV of each gas group is positively correlated with pressure. After adding C_{6}F_{12} O, the influence of pressure on the PDEV value of the mixed gas increases sharply, and the higher the mixing ratio of the mixed gas, the more the PDEV value is affected by the pressure. The PDEV value of mixed gas with a mixing ratio of 4% and 6% is approximately the same under the influence of pressure.

From Fig. 8, adding 2% C_{6} F_{12}O will increase the PDEV value by N_{2}, and as the pressure increases, the magnitude of the increase also increases accordingly. However, the PDEV value of the mixed gas with a mixing ratio of 4% compared to the mixed gas of 2% did not increase much. At 0.14 MPa and 0.18 MPa, the PDEV values of the two mixed gases are almost equal. That is, as the mixing ratio continues to increase, the upward trend of the PDEV value of the mixed gas gradually slows down.

Table 3 lists the ratio of the PDEV value of each group of mixed gases to the PDEV value of pure N_{2} , further showing the partial discharge quenching voltage characteristics of the mixed gas. In the case where the mixing ratio is constant, the ratio of the PDEV value of the mixed gas to the PDEV value of N_{2}gradually increases as the pressure increases. When the mixing ratio is 2% and the pressure is 0.1 to 0.2 MPa, the ratio of the PDEV value of the mixed gas to the PDEV value of N_{2}goes from 1.07 to 1.33; At a mix ratio of 6%, this value increased from 1.21 to 1.54. Thus, the higher the mixing ratio, the higher the ratio of the PDEV value of the mixed gas to the PDEV value of N._{2}. At fixed pressure, increasing the mixing ratio for increasing N_{2}^{‘}s The PDEV value is as follows. At 0.1 MPa, the ratio of the PDEV value of the mixed gas to the PDEV value of N_{2}goes from 1.07 to 1.21 when the mixing ratio increases. At 0.2 MPa, the ratio of the PDEV value of the mixed gas to the PDEV value of N_{2} increases from 1.33 to 1.54 as the mixing ratio increases. It can be concluded that the higher the pressure, the higher the ratio between the PDEV value of the mixed gas and the PDEV value of pure N._{2}and the greater the increase in PDEV of the mixed gas compared to pure N_{2}. The PDEV value of 6% of the mixed gas at 0.18 MPa and above can reach more than 1.5 times N_{2}under the same conditions.

### Comparison of Partial Discharge Voltage and Mixed Gas Breakdown Voltage

This section compares partial discharge characteristics and gas breakdown characteristics. Tables 4 and 5 list the ratio of partial discharge initiation voltage and partial discharge extinction voltage to the breakdown voltage of the mixed gas under different mixing ratios and pressure conditions, respectively.

Table 4 shows that the ratio of pure N_{2}The PDIV value of the breakdown voltage value is concentrated around 0.6-0.1-0.2MPa, when the mixing ratio is 2%, the ratio of the PDIV value of the mixed gas to the voltage breakdown voltage is about 0.4–0.1–0.2 MPa, so the partial discharge voltage of the mixed gas is already lower than the breakdown voltage value under the same conditions. When the mixing ratio is 4% and 6%, the ratio of the PDIV value of the mixed gas to the breakdown voltage value is about 0.34 at 0.1-0.2 MPa. It shows that under this mixing ratio condition, the partial discharge starting voltage is much lower than the breakdown voltage. It can be concluded that when the pure N_{2}is partially discharged, the voltage value may be relatively close to the breakdown value. After adding C_{6}F_{12}O, the difference between the partial discharge voltage and the gas breakdown voltage increases significantly.

It can be seen in Table 5 that the ratio of pure N_{2}The PDEV value of the corresponding breakdown voltage value is 0.59 at 0.1-0.2 MPa, which is relatively close to the PDIV value mentioned above. When the mixing ratio is 2%, the ratio of the PDEV value of the mixed gas to the breakdown voltage value under the corresponding conditions is about 0.35 to 0.1-0.2 MPa. When the mixing ratio is 4% and 6%, this value is 0.31 and 0.32 respectively. Adding C_{6}F_{12}Mixed gas O can reduce the ratio of pure N_{2}the extinction voltage of partial discharges to the breakdown voltage under the corresponding conditions.