The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF3I

Many researches of trifluoroiodomethane (CF3I) have shown that CF3I has many excellent properties that make it one of the possible alternatives of SF6. This paper reveals the effect laws of CF3I gas content, gap distance, gas pressure, polarity, and electric field nonuniform coefficient on the insulation performance of CF3I gas mixtures. In general, CF3I-N2 gas mixtures present a superior dielectric strength than CF3I-CO2 under different electric field sets. The experimental results indicate that 20 and 30% content CF3I-N2 gas mixtures can achieve nearly 50 and 55% insulation strength of pure SF6. In addition, to evaluate the arc interruption performance of environmentally friendly gas CF3I, we set up a CF3I transient nozzle arc model to study its thermodynamic and transport property. The analysis shows that CF3I gas has a good arc interruption capability, which mainly functions thermodynamic and transport properties approach that of SF6, and some are even better than SF6. The decomposition process is also aggravated by impurities including metal and water. The main by-products are greenhouse gases with GWP below that of SF6 and are lowly toxic and incombustible.


Comparison of CF 3 I and its mixtures with SF 6 and its mixtures on insulation property
In order to assess the insulation strength of CF 3 I and its mixtures, power frequency breakdown voltages of SF 6 and 20%SF 6 -80%N 2 mixture are measured in the same experimental condition [1].The result is shown in Tables 1 and 2.
Seen from Table 1, when P = 0.1 MPa and d = 10 mm, breakdown voltage of SF 6 in slightly nonuniform electric field is 82.9 kV, approximate to the standard value of breakdown voltage in uniform electric field, 89 kV/(mm•MPa).Moreover, breakdown voltage of 20%SF 6 -80%N 2 mixture is 57.7 kV, roughly 70% of the value of SF 6 , which is in agreement with data of other researchers.
Figure 1 compares the insulation property of CF 3 I-N 2 gas mixtures [2] with SF 6 and SF 6 -N 2 gas mixtures in slightly nonuniform electric field.It is obvious that the breakdown voltage of CF 3 I-N 2 mixture is lower than SF 6 and SF 6 -N 2 in the whole pressure range and distance range but higher than N 2 in the same condition.Table 3 shows the insulation strength of CF 3 I-N 2 mixture relative to pure SF6 and 20%SF 6 -80%N 2 mixture in different distances and pressures.It can be known from Table 3 that the insulation strength of 20%CF 3 I-80%N 2 in slightly nonuniform electric field is as high as 50% of SF 6 and 70% of 20%CF 3 I-80%N 2 .If the mixing ratio of CF 3 I increases to 30%, the insulation strength of CF 3 I-N 2 mixture becomes 55% of SF6 and 78% of 20%SF 6 -80%N 2 .In this paper, CF 3 I-CO 2 mixture, whose insulation strength is 97% of CF 3 I-N 2 in the same condition if the mixing ratio is 30%, is researched [3].With this proportion relationship, insulation property of CF 3 I-CO 2 mixture relative to SF 6 and 20%SF 6 -80%N 2 can be calculated [4].About the situation in highly nonuniform electric field, breakdown voltage of CF 3 I-N 2 mixture with the distances of 10 mm and 20 mm as examples is compared with SF 6 and 20%SF 6 -80%N 2 , as shown in Figure 2. Because of the strong electronegativity of SF 6 and CF 3 I, the mixtures present drastic changing breakdown property.It is useless to define the relative insulation strength in highly nonuniform electric field generally, and analysis according to specific pressure condition is necessary [5].Seen from Figure 2, power frequency breakdown voltage of SF 6 has obvious "hump effect" as a function of pressure with the distance of 10 and 20 mm.Similarly, the increase of breakdown voltage of 20%-mixed SF 6 -N 2 mixture with pressure also tends to saturate.It is discovered by comparison that 30%CF 3 I-70%N 2 possesses comparative insulation property to 20%SF 6 -80%N 2 , which is around 60% of SF 6 .When P = 0.2 MPa, the insulation property of 30%CF 3 I-70%N 2 mixture is as high as 80% of 20%SF 6 -80%N 2 mixture and more than 55% of pure SF 6 [6].

Gas
When the pressure increases to 0.3 MPa, breakdown voltage of SF 6 declines rapidly because of the "hump effect."In this way, the breakdown voltage of 30%CF 3 I-70%N 2 gas mixtures even exceeds pure SF 6 , becoming 1.17 times higher than the latter.Because the power frequency breakdown voltage of 20%SF 6 -80%N 2 always increases with the pressure, insulation strength   [7].It can be indicated that the insulation strength of CF 3 I-N 2 gas mixtures relative to SF 6 -N 2 declines gradually with the increase of pressure, but the breakdown level is always more than 55% of SF 6 .It is partly because the "hump effect" of SF 6 in the pressure is 0.1-0.3MPa and also because interfusing buffer gas N 2 improves the abnormal breakdown phenomenon in highly nonuniform electric field [8].
Table 4 shows the insulation strength of CF 3 I gas mixtures relative to SF 6 and 20%SF 6 -80%N 2 in the same condition.It can be seen that the insulation property of 20%CF 3 I-80%N 2 in highly nonuniform electric field is more than 49% of SF 6 and 69% of 20%SF 6 -80%N 2 in the same condition.
CF 3 I-CO 2 gas mixtures, also affected by "hump effect," present obvious decline in high pressure.Under the pressure 0.1 and 0.15 MPa, the breakdown voltage of 30%-mixed CF 3 I-CO 2 gas mixtures is 60% of pure SF 6 and 1.05 times of 20%SF 6 -80%N 2 gas mixtures [9].However when the pressure rises to 0.3 MPa, the insulation property of CF 3 I-CO 2 gas mixtures is only around 40% of 20%SF 6 -80%N 2 mixture [10].Relative insulation strength of different pressures is shown in Table 4 in detail.
The insulation properties of CF 3 I-N 2 and CF 3 I-CO 2 gas mixtures can be concluded with the analysis above.
In uniform electric field, the insulation strength of 30%-mixed CF 3 I-N 2 gas mixtures can approach 72% of pure SF 6 theoretically and in slightly nonuniform electric field more than 55% of pure SF 6 [11].In highly nonuniform electric field, the relative insulation strength of CF 3 I-N 2 gas mixtures is influenced by the pressure seriously, which ranges from 55 to 117% in the researched pressure range [12].
The insulation strength of 30%-mixed CF 3 I-CO 2 gas mixtures can approach 68% of pure SF 6 theoretically in uniform electric field, and in slightly nonuniform electric field, it can be more than 53% [13].In highly nonuniform electric field, the relative insulation strength is also influenced by the pressure.The insulation strength of 30%-mixed CF 3 I-CO 2 gas mixtures is 0.42-0.62times of pure SF 6 .
Detailed comparative data and the insulation strength of 20%SF 6 -80%N 2 gas mixtures are listed in Table 5. Seen from the table, whether in slightly nonuniform electric field or highly nonuniform electric field, the insulation strength of CF 3 I-N 2 is better than CF 3 I-CO 2 in the same condition.Therefore, in actual equipment application, CF 3 I-N 2 gas mixtures with the mixing ratio of 20-30% should be considered preferentially.
Then, principles of applying CF 3 I mixture in actual electrical equipment are discussed with the example of 40.5 kV cubicle-type gas-insulated switchgear (C-GIS).
C-GIS, vulgarly named "gas-filled cabinet," is suitable for situations that have high requirement on reliability and limited space and floor area such as rail transit, high buildings, and industrial enterprises.40. of products on the market, the most popular practice currently is employing SF 6 with the pressure 0.12-0.15MPa (abs) as the main insulation medium of primary loop.For example, the SF 6 charge pressures of XGN46-40.5 model C-GIS developed by Xi'an High Voltage Apparatus Research Institute and ZX2 model C-GIS produced by ABB are, respectively, 0.15 and 0.13 MPa.Meanwhile, some companies employ higher pressure, e.g., 8DA10 model C-GIS produced by Siemens, whose SF 6 charge pressure is 0.26 MPa.C-GIS is complicated on structure and different on shape, containing function units such as breakers, disconnectors, current/voltage transformers, etc., and forming both slightly nonuniform electric field and highly nonuniform electric field.In accordance to relative insulation strength shown in Table 5, replacing SF 6 in C-GIS with CF 3 I-N 2 with the mixing ratio of 20-30% as insulation medium without changing the gap distance and pressure, insulation strength is not strong enough, so it is necessary to adjust the charge pressure or structure properly.
Through analysis, we can know that increasing pressure or increasing gap distance can effectively improve the insulation level of CF 3 I gas mixtures.If the gap distance is kept constant, the CF 3 I-N 2 gas mixtures of 20-30% mixing ratio at 0.25-0.3MPa will reach the insulation level of SF 6 at 0.15 MPa.In this case, there is no need to change the existing C-GIS internal structure; only a thickened metal enclosure is needed to ensure the operation pressure and the leakage level meet the requirements.At the same time, the liquefaction temperature of CF 3 I-N 2 gas mixtures around this pressure can be maintained below −25°C, which is in accordance with the requirements of GB/T 11022-2011 on the operating temperature of the switch equipment.
If the operating pressure is kept constant, the data in Figure 1 and Table 1 show that to achieve the same insulation strength as SF 6 , the gap distance of 30%CF 3 I-70%N 2 gas mixtures needs to be increased by about twice as much.
Therefore, although the insulation strength of the CF 3 I gas mixtures is weaker than pure SF 6 , CF 3 I gas mixtures can not only achieve the same insulation level as the SF 6 , but also the liquefaction temperature can meet the operation requirement of the switch equipment by adjusting the operating condition or structure parameters properly.More importantly, CF 3 I-N 2 gas mixtures will not affect global warming.It can solve the unfriendly environmental problems of SF 6 and realize the green upgrading of electrical equipment.Therefore, it is suggested that CF 3 I-N 2 gas mixtures with the mixing ratio of 20-30% can be used as alternative medium for SF 6 in low-and medium-voltage electrical equipment.

New Trends in High Voltage Engineering
Based on the results of power frequency and lightning impulse tests, it is shown that the insulation strength of CF 3 I-N 2 gas mixtures increases with the increase of CF 3 I mixing ratio in slightly nonuniform electric field or in highly nonuniform electric field.For CF 3 I-CO 2 gas mixtures, the breakdown voltage varies with the mixing ratio in slightly nonuniform electric field, similar to CF 3 I-N 2 .However, in highly nonuniform electric field, the breakdown voltage of 10%-mixed CF 3 I-CO 2 gas mixtures is higher than mixtures with mixing ratio of 20 and 30%, due to the abnormal breakdown of the high pressure.It can be seen that higher mixing ratio of electronegative gas in the CF 3 I gas mixtures does not always cause better insulation performance, and it will also be influenced by many factors such as the gap distance, the pressure, and the unevenness of the electric field.
From the change of the breakdown voltage with the gap distance, the breakdown voltage of CF 3 I-N 2 and CF 3 I-CO 2 gas mixtures increases linearly with the increase of the gap, and the increase speed is proportional to the pressure in slightly nonuniform electric field.In highly nonuniform electric field, the breakdown voltage of CF 3 I-N 2 gas mixtures shows a tendency to saturate with the gap distance, while the CF 3 I-CO 2 combination has obvious nonlinear characteristics.
From the change of the breakdown voltage with the pressure, the insulation strength of the CF 3 I-N 2 and CF 3 I-CO 2 gas mixtures in the slightly nonuniform field increases linearly with the increase of the pressure and even shows a certain degree of negative synergy.However, under the highly nonuniform electric field environment, there is a clear "hump" in the power frequency breakdown voltage of CF 3 I-CO 2 gas mixtures with the change of pressure, and the positive lightning impulse coefficient in the "hump" section is always less than 1.
From the effect of polarity on discharge, the breakdown voltage of CF 3 I gas mixtures under positive polarity is higher than that of negative polarity in slightly nonuniform electric field.But in highly nonuniform electric field, the opposite is true.In addition, the uniformity of electric field will also affect the insulation performance of CF 3 I gas mixtures.Therefore, in the actual product application, the uniformity of the electric field should be improved as much as possible for the purpose to ensure that the insulation strength of the CF 3 I gas mixtures can be maintained at a high level.
Finally, by comparing with the SF 6 and 20%SF 6 -80%N 2 , it is found that the 20%CF 3 I-80%N 2 gas mixtures can reach the insulation level of 50% of pure SF 6 gas and about 65% of 20%SF 6 -80%N 2 gas mixtures.When the mixing ratio of CF 3 I is increased to 30%, insulation strength of CF 3 I-N 2 gas mixtures can reach about 55% and 75% of SF 6 and 20%SF 6 -80%N 2 gas mixtures, respectively.For the combination of CF 3 I-CO 2 , 30%-mixed CF 3 I-CO 2 gas mixtures can reach the insulation level of more than 53% of pure SF 6 in slightly nonuniform electric field, but in highly nonuniform electric field, relative insulation strength depends on the pressure and can only reach 42-67% of the latter.

The radial temperature distribution characteristics and leading energy transport process of CF 3 I nozzle arc
The transient temperature distribution of arc is decided by the mutual equilibrium among the energy input of arc, different energy transport processes, and changing rate of energy storage, The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968which determines the characteristics of arc in turn.We analyze the arc extinction characteristics of CF 3 I through the thermodynamic characteristics of CF 3 I arc.
The temperature of arc plasma changes with the changes of time and position, and that's decided by the interactions of the produce of the joule heat of arc and different energy transport processes in itself.The following are the calculation and analysis of the energy balance of the core area (in the radius with 83.3% highest temperature) and conducting regions (in the radius with 4000K temperature) of arc in the conditions with 900 A large current, 50 A small current, and current-zero period.
By the radial temperature analysis of arc, during the process that the head of the moving contact moves from the nozzle upstream to the throat, because the space of the throat is small, and the moving contact and thermal plasma of arc will block the flow of the fluid to the catchment area through the nozzle, and the slow speed of the fluid causes a bigger radius of arc so that the core area is not obvious and the temperature is relatively lower.We choose the time of 900 A current to analyze in Table 6.In the time of large current, the sinusoidal current waveform changes relatively slowly with the change of time, and the changing rate of energy storage of the core area of arc can almost be negligible, and as the slow decline of arc, global energy of arc also goes down, so the change of energy storage in the radius of arc reaches more than 20%.As the interior of the thicker arc cannot be influenced by the cold fluid, the electric power produced in the core area of arc is lost more than 90% by the radiation process, and beyond the core area of arc, the interactions of arc and fluid are more drastic, and the energy loss of radiation lowers obviously.As a whole, the axial convection process of arc does positive work, and the core area does less work.Although the radial convection of arc is small, it takes the joule heat away, and that's because the cold fluid in upstream moves from the entrance to the lower right and contacts with the thermal plasma with a bigger oblique angle to form convection, especially the cold fluid which flows along the slope of fixed contact even forms eddy in the interior of arc.Therefore, the radial convection in the arc boundary has a good cooling effect, especially in the reabsorption area of the radiation energy.
When the current lowers to 50 A, the moving contact moves to the catchment of nozzle, and the distance of contact reaches more than 18 mm.The throat of the nozzle opens completely, and the thermal characteristics of the nozzle arc are decided by the energy distribution and transport process in New Trends in High Voltage Engineering characteristics of arc and the effect of high-speed cold fluid, the loss ratio of radiation energy decreases sharply.After the reabsorption process of radiation in the arc boundary, the loss ratio of radiation energy approaches zero.Around arc, the high-speed movement of the cold fluid in the nozzle makes arc form an obvious high-temperature core area.The fast change of radial temperature makes the radial thermal conduction become strong, and the energy transport ratio in the core area and arc area is both 70%.In comparison, the convection effect works little to the change of energy.Because the moving contact pulls to the right and arc plasma strengths in axial, the axial convection does positive works in the core area of arc, but in the arc boundary, the highspeed cold fluid around arc effectively takes the energy away, and it has an obvious cooling effect to arc.The radial convection in the core area begins to do negative works, and that's because the temperature gradient in the core area of arc is very big, and the gas with relatively lower temperature in the radiation reabsorption region begins to enter into the core area to maintain the conservation of mass in the interior of arc; however, out of the core area of arc, the decline of the radial temperature becomes slow, and the radial convection effect still does positive works.
In the current-zero area, shown in Table 8, the joule heat of arc is zero, and the temperature of plasma lowers to less than 10,000 K, and the radiation effect is almost 0. The radius of arc Note: Because the current input in the current-zero area is zero, the change of arc's energy storage is the changing power of energy, and it is regarded as the energy input to measure the strength of every energy transport process.
Table 8.Percentage of electrical power input associated with various energy transport processes for the whole CF 3 I arc length at core and arc boundary at current zero.
The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968 is very small, and the thermal conduction is relatively weaker.Convection mainly consumes arc's energy, whether in the core area or within the arc boundary, and the radial thermal convection takes more than 30% energy away as the axial reaches about one half of the change of arc's energy.

The arc's characteristics near the arc-zero area
The thermal interruption of nozzle arc is decided by the arc's temperature around the current-zero area.Through the discussion of the above section, when it's close to the currentzero area (25 A and lower), the arc's temperature and radius decrease rapidly and become a key time of arc interruption, and this process is worth being researched more.When the current is very small, a strong radial thermal conduction makes arc form a relatively bigger radial temperature gradient in the radiation reabsorption area, which takes the energy in the arc's interior away effectively.And this promotes more entrance of cold fluid of outside into the high-temperature plasma of arc (to maintain the conversation of mass), so that the radial convection heat dissipation becomes the main form of energy transport when the current approaches zero.The superposition of two effects explains the sharp declines of the arc's temperature and radius in dozens of microseconds before current zero-crossing in New Trends in High Voltage Engineering time of arc (see Table 9), at 10 μs before current zero-crossing (arc current is about 5 A), the characteristic time about arc's radius and temperature is 24.75 and 40.64 μs which are equivalent to SF 6 arc's values in the same time.In the last 10 μs, the characteristic time of CF 3 I arc in the current-zero area lowers to about 3 μs which is much smaller than air and CO 2 arc and approaches SF 6 arc.The comparison shows that the declines of CF 3 I arc's temperature and radius near current-zero area are equivalent to SF 6 and much bigger than air and CO 2 arc.

Analysis of the by-product after CF 3 I interrupts arc
There are three reasons to cause gas decomposition, and they are decomposition caused by electron collision, thermal decomposition, and photodecomposition.There are mainly first two types in the high-voltage electrical equipment.The main discharge forms in switching arc or equipment such as GIS are high-power arc discharge, spark discharge, and partial discharge.Among them, high-power discharge has large current and a long time of duration, and energy can accumulate in a short time, and temperature can reach more than 20,000 K, and it's the most serious discharge form of decomposition reaction.According to conservation of elements, it will separate out a little iodine.When the arcing interruption fails, more than 95% CF 3 I becomes CF 4 and separates out iodine at the same time.This shows that the ratio of by-product after successful arcing interruption of CF 3 I is very low and the main by-products are CF 4 and C 2 F 6 .However, when arc interruption fails and arc continues to burn, a mass of CF 3 I will decompose and produce much CF 4 so that it cannot be used as arc-quenching medium.By examining the switch cabinet after the failure of arc quenching, we can find that there are much black solid attached on the surface of insulator and contact and this solid is carbon and iodine.The production of elementary substance shows that during the drastic burning of arc-restrike gas, many organic compounds decompose into elementary substance due to the lack of oxidizer (such as oxygen).Therefore, when CF 3 I is applied in interrupting arc, we should reserve enough margin for interrupting current, and at the same time, we can use some absorbents or make air-blast-arc method to eliminate produced iodine.

Characteristic analysis of CF 3 I decomposing products
Based on environmentally friendly purpose and toxicity, we analyze the composition of arclater gases, and the results are listed in Table 11.It shows that compared with SF 6 , the global warming potential (GWP) of decomposing gases of CF 3 I under conditions of large current decreases at different levels.Except CF 4 , the existence time in the atmosphere of other gases drastically reduces.As for toxicity, the arc-later decompositions of CF 3 I belong to perfluorocarbon and partial fluorocarbon, which both have low toxicity, so it will cause headache, nausea, or dizziness under conditions of long-time or high-density inhalation.While doing experiment, we should note ventilation and appropriate self-protection.
In a word, after CF 3 I arc discharges under conditions of high voltage and large current, main by-products are perfluorocarbons, CF 4 and C 2 F 6 ; in the event of mixing trace amounts of water, it will produce a little hydrofluorocarbons such as CHF 3 and C 2 HF 5 .Perfluorocarbon and hydrofluorocarbon with few carbon atoms both have low toxicity; the consequences of inhalation are connected with the density.Only in closed environment, when human inhales higher-density gas, it will damage the cardiovascular system to a certain degree.During experiment and use, we should note ventilation and appropriate self-protection to ensure a safe process.The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968

Figure 1 .
Figure 1.Comparison of the insulation property of CF 3 I-N 2 mixture with SF 6 and SF 6 -N 2 mixture in slightly nonuniform electric field.

Figure 2 .
Figure 2. Comparison of the insulation property of CF 3 I-N 2 gas mixtures with SF 6 and SF 6 -N 2 mixture in highly nonuniform electric field.

Figures 3 and 4 .Figure 3 .
Figures3 and 4.The changes of nozzle throat arc's temperature and radius with time near current-zero area are shown in Figures3 and 4. They show that in 30 s before arc-zero area, CF 3 I arc's temperature shows a trend of faster decrease without obvious phenomenon that the declines of temperature about time decrease.And the arc's radius decreases with time.From the characteristic

Figure 4 .
Figure 4. Arc radius varied with time at nozzle throat near current zero.

Table 2 .
Power frequency breakdown voltages of SF 6 and 20%SF 6 -80%N 2 gas mixtures in highly nonuniform electric field.

Table 1 .
Power frequency breakdown voltages of SF 6 and 20%SF 6 -80%N 2 gas mixtures in slightly nonuniform electric field.

Table 3 .
Insulation strength of CF 3 I mixture relative to SF 6 and 20%SF 6 -80%N 2 in slightly nonuniform electric field.

Table 4 .
Insulation strength of CF 3 I gas mixtures relative to SF 6 and 20%SF 6 -80%N 2 gas mixtures in highly nonuniform electric field.The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968 5 kV C-GIS is the most popularly employed.Known from the survey

Table 5 .
Insulation strength of CF 3 I gas mixtures relative to SF 6 and 20%SF 6 -80%N 2 gas mixtures.

Table 7 .
Differing from large current, because of the temperature distribution

Table 6 .
Percentage of electrical power input associated with various energy transport processes for the whole CF 3 I arc length at core and arc boundary at 900 A.

Table 7 .
Percentage of electrical power input associated with various energy transport processes for the whole CF 3 I arc length at core and arc boundary at 50 A.

Table 9 .
Characteristic time of CF 3 I arc near current zero.The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968experiment under 630 A current is just done for one time, and we obtain the gas after unsuccessful interruption as testing sample.In the results, except the main composition CF 3 I, other impurities or gas decompositions are N 2 , CF 4 , CO 2 , C 2 F 6 , CHF 3 , H 2 O, and C 4 F 8 .N 2 and H 2 O are impurities because of mixture of air.CO 2 , CHF 3, and C 4 F 8 exist in the original gas, so they are the impurities in the producing process of gas.Therefore, CF 4 and C 2 F 6 are the products of the high-voltage and large-current arcing experiment of CF 3 I.The comparisons of the response values of CF 3 I, CF 4 , C 2 F 6 , C 4 F 8 , and CHF 3 in original gas after different times' arcing experiment are shown in Figure 5. From the spectrum data of CF 3 I, CF 3 I decomposes little after five times' successful interruption of 400 A arc, and CF3I is 97.0% of original gas; the decomposition can be ignored.But after the unsuccessful interruption of 630 A current, CF 3 I is only 3.4% of original gas.Other gases' spectrum data shows that under conditions of successful interruption, only 3% CF 3 I produces CF 4 and C 2 F 6 and little C 4 F 8 and CHF 3 as the gas reaches room temperature from arc's high temperature.

Gas Dielectric strength compared with SF 6 Liquefaction temperature (°C) GWP Existence time in the atmosphere (year)
The Performance of Insulation and Arc Interruption of the Environmentally Friendly Gas CF 3 I http://dx.doi.org/10.5772/intechopen.79968

Table 11 .
Environmental and toxic analysis of CF 3 I gas composition after arc.