A mixed insulating gas containing perfluoromethane thioether and its use

Abstract

This invention relates to gas insulation technology for power systems, specifically to a mixed insulating gas containing perfluoromethyl sulfide and its applications. The insulating mixed gas consists of component 1 and component 2, where component 1 is perfluoromethyl sulfide; and component 2 is 1,1,2,2-tetrafluoroethane, 2,3,3,3-tetrafluoropropylene, and 1,1-difluoroethane. The insulating mixed gas of this invention possesses insulating properties comparable to or even superior to sulfur hexafluoride, and has a lower gas-to-water (GWP) value, making it particularly suitable for gas-insulated electrical transformers, gas-insulated wires for transmitting or distributing power, or connectors / disconnectors in medium- and high-voltage applications. The mixed gas of this invention exhibits properties similar to a single gas, and the liquefaction temperature of the insulating mixed gas is lower than that of each component; furthermore, the mixed gas also has a synergistic insulating effect, offering advantages such as low GWP, low toxicity, low boiling point, and high insulating strength.

Description

Technical Field

[0001] This invention relates to the field of electrical insulation technology, and in particular to an environmentally friendly insulating gas and its application in insulating or arc-extinguishing electrical equipment. Background Technology

[0002] Perfluoromethyl sulfide (CF3SCF3, CAS: 371-78-8) is a novel, environmentally friendly insulating gas. Its insulating strength is approximately 1.7 times that of sulfur hexafluoride, and its estimated global energy cost (GWP) is only 2.8 times that of carbon dioxide. Furthermore, it has low toxicity, does not deplete the ozone layer, and is stable in the atmosphere. The boiling point of perfluoromethyl sulfide gas is -22°C, significantly better than most existing sulfur hexafluoride alternatives.

[0003] However, compared to sulfur hexafluoride (relative insulation strength of 1, liquefaction temperature of -56°C, and GWP of 23900), perfluoromethyl sulfide (PFMS) has a lower GWP and higher insulation strength, but its liquefaction temperature is still relatively high. Patent CN 118352919 A ​​discloses that a mixture of PFMS and background gas can be used as an alternative insulating gas to sulfur hexafluoride. However, while mixing PFMS with background gas can lower the liquefaction temperature of the mixed gas, the introduction of background gas will reduce the insulation strength of PFMS. The mixing ratio of background gas will affect both the liquefaction temperature and insulation strength, and the alternative gas still needs further optimization. Summary of the Invention

[0004] In view of the defects or deficiencies of the prior art, the present invention provides a mixed insulating gas containing perfluoromethyl sulfide.

[0005] The mixed insulating gas provided by the present invention includes component 1 and component 2, wherein component 1 is perfluoromethyl sulfide; and component 2 is 1,1,2,2-tetrafluoroethane, 2,3,3,3-tetrafluoropropylene or 1,1-difluoroethane.

[0006] Furthermore, the insulation strength Er_ of the mixed gas 混合气体 Satisfy the relationship shown in equation (a):

[0007] Er_ 混合气体 >Er_ 组元1 ×x1+Er_ 组元2 ×x2 (a)

[0008] In the formula, Er_ 组元1 The insulation strength of gas component 1 relative to SF6; Er_ 组元2 x1 represents the insulation strength of gas component 2 relative to SF6; x2 represents the mass percentage of component 1 in the gas mixture; and x3 represents the mass percentage of component 2 in the gas mixture.

[0009] Optionally, the mass percentage of component 1 is 9.4% to 75.5%, and the mass percentage of component 2 is 24.5% to 90.6%.

[0010] Optionally, the insulating gas includes component 3, which is at least one of nitrogen, oxygen, air, and carbon dioxide. Optionally, based on a mass percentage of 100%, the insulating mixture comprises components 1, 2, and 3 in the following mass percentages: 9.3%–43.4% : 46%–89.9% : 0%–28%, respectively, with component 3 having a mass percentage greater than 0.

[0011] The mixed insulating gas of the present invention can be used in gas-insulated electrical transformers, gas-insulated wires for transmitting or distributing electricity, connectors, or cut-off devices. The operating voltage of the mixed insulating gas is 3kV to 35kV, 35kV to 330kV, or 330kV to 1200kV.

[0012] The components 1 and 2 used in this invention are both substances with low global warming potential (GWP). Component 1, perfluoromethyl sulfide, has an insulation strength 1.7 times that of SF6, a short atmospheric lifetime, low toxicity, a GWP of only 8, and a liquefaction temperature of -20°C. Component 2 is one of 1,1,2,2-tetrafluoroethane, cis-1,3,3,3-tetrafluoropropene, and 3,3,3-trifluoropropene.

[0013] When the gas combination formed by component 1 and component 2 in the mixed gas of the present invention meets the screening conditions S1 to S3, it can form an insulating gas with macroscopic properties similar to a single substance, and has a lower liquefaction temperature than component 1 and component 2 alone. Detailed Implementation

[0014] Unless otherwise specified, the scientific and technical terms used herein are for the understanding of those skilled in the art. Based on component 1 and component 2 described in this invention, specific solutions can be derived by comprehensively considering the insulating properties, liquefaction temperature, and greenhouse effect of these gases to obtain a mixed gas with specific components and proportions.

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Example 1:

[0017] This embodiment describes the screening process for gas component 2 of the present invention. The specific screening method includes:

[0018] In the following screening method, component i is perfluoromethyl sulfide, and component j is component 2. Component j is determined by the following steps:

[0019] S1, select an insulating gas with a liquefaction temperature range of -40 to 20°C under standard atmospheric pressure as the initial component j;

[0020] S2, Under a given equilibrium pressure P, determine at least one set of T and x values ​​that satisfy the following formulas (1) to (16) for the gas-liquid equilibrium state of the mixture of component i and initial component j. i y i x j and y j Where: the given equilibrium pressure P is the working pressure of SF6 gas, and the unit of P is MPa; T is the gas-liquid equilibrium temperature, and the unit is °C; x i y represents the molar percentage of gaseous component i in the liquid phase of the gas mixture; i x represents the molar percentage of gaseous component i in the gas phase of the gas mixture; j y represents the molar percentage of gaseous component j in the liquid phase of the gas mixture; j x is the molar percentage of gaseous component j in the gas phase of the gas mixture; -40℃≤T≤20℃, 0<x i <1, 0<y i <1, 0<x j <1, 0<y j <1, and x i +x j =1, y i +y j =1;

[0021]

[0022]

[0023] α(T ri )=[1+(β2+β3ω i -β4ω i 2 (1-T) ri 1 / 2 )] 2 ,

[0024] 0.30000≤β2≤0.40000

[0025] 1.50000≤β3≤1.60000,

[0026] 0.20000≤β4≤0.30000 (12)

[0027]

[0028] 0.40000≤β6≤0.50000

[0029] 0.30000≤β7≤0.40000

[0030] 1.50000≤β8≤1.60000,

[0031] 0.20000≤β9≤0.30000

[0032] In equations (1)-(16):

[0033] Let i be the gas phase fugacity of gas component i in the gas mixture. Let be the liquid phase fugacity of gas component i in the gas mixture. Let be the gas phase fugacity of gas component j in the gas mixture;

[0034] Let be the liquid phase fugacity of gas component j in the gas mixture;

[0035] R is the gas constant;

[0036] Z L The gas-phase compressibility factor of the gas mixture. Z V The liquid-phase compressibility factor of the gas mixture. V L The liquid molar volume of the gas mixture under P and T conditions, in m³. 3 / mol;V V The molar volume of the gas phase of the gas mixture under P and T conditions, in m³. 3 / mol; V is the volume of the gas mixture under P and T conditions, in m³. 3 ;

[0037] N i The molar amount of gas component i in the gas mixture, expressed in mol;

[0038] N j The molar amount of gaseous component j in the gas mixture, expressed in mol.

[0039] N is the total molar amount of the gas mixture, expressed in mol.

[0040] a and b are both parameters in the equation of state for the mixed gas;

[0041] a i Let b be the molecular energy constant of gas component i, with a value ranging from 12000 to 3845000;i is the volume correction constant for gas component i, with a value ranging from 12.85 to 140.68;

[0042] The free energy of the gas mixture;

[0043] k ij For binary interaction parameters, 0 < k ij <5;

[0044] C is a constant, with a value ranging from 24.68500 to 24.68600;

[0045] ω i is the eccentricity factor for gas component i, which is set to 0.335;

[0046] ω j , is the eccentricity factor of gas component j;

[0047] T ri The relative state temperature of gas component i; its value ranges from 0.5 to 1.

[0048] T ci Here is the critical temperature of gas component i; the unit is K, and it is taken as 376.75 K.

[0049] T cj Here is the critical temperature of gaseous component j; the unit is K.

[0050] p ci Let be the critical pressure of gas component i, in MPa; take 3.843 MPa.

[0051] p cj Here is the critical pressure of gas component j, in MPa.

[0052] P i sat Let be the saturated vapor pressure of gaseous component i at temperature T, in MPa.

[0053] Let be the saturated vapor pressure of gaseous component j at temperature T, in MPa.

[0054] V i L The liquid phase volume of gaseous component i under P and T conditions is expressed in m³. 3 ;

[0055] The liquid phase volume of gaseous component j under P and T conditions is expressed in cubic meters (m³). 3 ;

[0056] T / K is the equilibrium temperature T converted to Kelvin;

[0057] N gi All groups separated from the molecule of gaseous component i, with CF3SCF3 as the entire group; N gi The value is 1.

[0058] N gj All groups separated from the molecule of gaseous component j;

[0059] k represents the molecular group CF3SCF3 of gaseous component i;

[0060] l represents any group among the groups split from the molecule of gas component j;

[0061] α ik The relative mole fraction of the CF3SCF3 group is the number of CF3SCF3 groups divided by the total number of groups in gaseous component i molecule, and the value is 1.

[0062] α jk The relative mole fraction of the CF3SCF3 group in gaseous component j is taken as the number of CF3SCF3 groups divided by the total number of groups in the gaseous component j molecule.

[0063] α il The relative mole fraction of group l in gaseous component i is taken as the number of group l divided by the total number of groups in the gaseous component i molecule;

[0064] α jl The relative mole fraction of group l in gaseous component j is taken as the number of group l divided by the total number of groups in the gaseous component j molecule;

[0065] A kl With B kl All are group parameters of groups CF3SCF3 and l;

[0066]

[0067] In the formula, A wk _CH2 represents the interaction parameter between the ethylene group and group l; A wk _CH2 represents the interaction parameter between the ethylene group and group l; N l The number of positively valence atoms in group l;

[0068] S3, based on the screening results of S2, further screening is performed to determine whether, under a given equilibrium pressure P, there exists x. i =y i Under the condition that the equilibrium temperature T is the minimum equilibrium temperature, and the minimum equilibrium temperature is less than the liquefaction temperature of each gas component j in the gas mixture.

[0069] The screening range of component j in this embodiment is shown in Table 1, which includes eight gases: perfluoromethyl sulfide (A), trifluoroiodomethyl (B), cis-1,3,3,3-tetrafluoropropene (C), 1,1-difluoroethane (D), 3,3,3-trifluoropropene (E), 1,1,2,2-tetrafluoroethane (F), 2,3,3,3-tetrafluoropropene (G), and heptafluoroisobutyronitrile (H).

[0070] Table 1 Results of Gas Combination Screening in Step S1

[0071] gas serial number Liquefaction temperature / °C Perfluoromethyl sulfide A -22 Trifluoroiodomethane B -25 cis-1,3,3,3-tetrafluoropropylene C 9 1,1-Difluoroethane D -52 3,3,3-Trifluoropropylene E -28 1,1,2,2-Tetrafluoroethane F -23 2,3,3,3-Tetrafluoropropylene G 9 Heptafluoroisobutyronitrile H -7

[0072] Based on the conditions in S1, seven gases were used as initial component j. Further, using MATLAB software, the methods in steps S2 and S3 were used for screening calculations. During this process, P was set to p = 0.1 MPa (in other specific schemes, P can be determined based on the working pressure of the insulating gas; 0.1 MPa is used here as an example to explain this invention in detail; the common working pressure of the insulating mixed gas described in this invention is 0.1 MPa to 0.5 MPa). The screening results are shown in Table 2.

[0073] The results obtained after screening under conditions S2 and S3 are: perfluoromethyl sulfide + 1,1-difluoroethane, perfluoromethyl sulfide + 1,1,2,2-tetrafluoroethane, and perfluoromethyl sulfide + 2,3,3,3-tetrafluoropropylene, a total of 3 mixed gases.

[0074] During the screening process, C took the value 24.68544; Take 1.1001; Take 1.3741; a i Take 1645070; b i Take 40.78; T ri Take 0.8; β1=-0.62323, β2=0.37464, β3=1.54226, β4=0.26992, β5=0.07780, β6=0.45724, β7=0.37464, β8=1.54226, β9=0.26992;

[0075] Table 2 shows the calculation results of the gas combinations screened in steps S2 and S3 at 0.1 MPa.

[0076]

[0077] To meet the requirements of applications with higher insulation strength, a further optimized approach is to use formula (a) to screen mixed gases that exhibit a synergistic effect in insulation strength.

[0078] The following examples illustrate the preparation of mixed gases with different ratios of perfluoromethyl sulfide + 1,1,2,2-tetrafluoroethane, perfluoromethyl sulfide + 2,3,3,3-tetrafluoropropylene, and perfluoromethyl sulfide + 1,1-difluoroethane, and the insulation strength was measured in experiments.

[0079] Example 2:

[0080] At a temperature of -40℃, 45.5% by mass of perfluoromethyl sulfide and 54.5% by mass of 1,1-difluoroethane were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0081] Example 3:

[0082] At a temperature of -40℃, 45.5% by mass of perfluoromethyl sulfide and 54.5% by mass of perfluoromethyl sulfide + 1,1,2,2-tetrafluoroethane were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0083] Example 4:

[0084] At a temperature of -40℃, 48.5% by mass of perfluoromethyl sulfide and 61.9% by mass of perfluoromethyl sulfide + 1,1,2,2-tetrafluoroethane were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0085] Example 5:

[0086] At a temperature of -40℃, 55.5% by mass of perfluoromethyl sulfide and 44.5% by mass of 2,3,3,3-tetrafluoropropylene were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0087] Example 6:

[0088] At a temperature of -40℃, 63.5% by mass of perfluoromethyl sulfide and 36.5% by mass of 2,3,3,3-tetrafluoropropylene were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0089] Example 7:

[0090] At a temperature of -40℃, 70.5% by mass of perfluoromethyl sulfide and 29.5% by mass of 2,3,3,3-tetrafluoropropylene were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0091] Example 8:

[0092] At a temperature of -40℃, 75.5% by mass of perfluoromethyl sulfide and 24.5% by mass of 2,3,3,3-tetrafluoropropylene were physically mixed in the liquid phase and completely vaporized to obtain a mixed insulating gas.

[0093] Comparative Example 1:

[0094] Perfluoromethyl sulfide, with a mass percentage of 100%, is used as the insulating gas.

[0095] Comparative Example 2:

[0096] 1,1-Difluoroethane, with a mass percentage of 100%, was used as the insulating gas.

[0097] Comparative Example 3:

[0098] 1,1,2,2-Tetrafluoroethane, with a mass percentage of 100%, was used as the insulating gas.

[0099] Comparative Example 4:

[0100] 100% by mass of 2,3,3,3-tetrafluoropropylene was used as the insulating gas.

[0101] After the liquid mixture in the above embodiments was heated to room temperature and completely vaporized, the insulation strength of the gas relative to SF6 gas in the above embodiments and each comparative example was tested under the condition of an electrode spacing of 0.1 inches. The results are shown in Table 3. Among them, the GWP value is based on CO2 as the reference value of 1.0 (100 years), and the insulation strength is based on sulfur hexafluoride as the reference value.

[0102] A flammability testing apparatus was constructed according to the European standard EN14756 [European standard. Determination of the limiting oxygen concentration (LOC) for gases and vapors: EN 14756-2007[S]. Berlin: European committee for standardization, 2006.], and the results are shown in Table 1;

[0103] The liquefaction temperature of the examples and comparative examples was measured by observation, and the results are shown in Table 3. As can be seen from Table 3, the present invention has a lower liquefaction temperature.

[0104] Table 3 Comparison of Environmental Performance and Insulation Strength

[0105]

[0106]

[0107] As can be seen from Table 3, the Greenhouse Potential (GWP) values ​​of the above embodiments are also much lower than those of sulfur hexafluoride, which is more in line with the current environmental protection requirements for reducing the effects of global warming; in terms of liquefaction temperature, the liquefaction temperature range of the mixed gas is -55 to -25°C, which is much lower than that of perfluoroisoamyl ketone (C5F). 10 O), perfluoroisobutyronitrile (PFO), and other G3 gases are suitable for high-voltage switchgear and other insulating equipment, but they are not suitable for liquefaction in cold northern regions. In terms of flammability, the mixed gas suppresses the combustion performance of the flammable components in the single gas, making its macroscopic properties similar to the non-flammability of a single substance.

Claims

1. A mixed insulating gas comprising perfluoromethyl sulfide, characterized in that, The mixed insulating gas includes component 1, component 2, and component 3. Component 1 is perfluoromethyl sulfide; component 2 is 1,1,2,2-tetrafluoroethane, 2,3,3,3-tetrafluoropropylene, or 1,1-difluoroethane; and component 3 is at least one of nitrogen, oxygen, air, and carbon dioxide. The mass percentages of component 1, component 2, and component 3 in the mixed insulating gas are 9.3%~43.4%, 46%~89.9%, and 0%~28%, respectively, and the mass percentage of component 3 is greater than 0.

2. The application of the mixed insulating gas of claim 1 in gas-insulated electrical transformers, gas-insulated wires for transmitting or distributing electricity, connectors or cut-off devices.

3. The application according to claim 2, characterized in that: The operating voltage of the mixed insulating gas is 3kV to 35kV.

4. The application according to claim 2, characterized in that: The operating voltage of the mixed insulating gas is 35kV to 330kV.

5. The application according to claim 2, characterized in that: The operating voltage of the mixed insulating gas is 330kV to 1200kV.

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