CN111999381A - A method for analyzing synergistic effect of electronegative gas mixture - Google Patents

Abstract

The invention discloses a method for analyzing the synergistic effect of an electronegative mixed gas. The method includes: under the same gas pressure, determining the breakdown voltage U _{1 of the electronegative gas, the breakdown voltage U 2 of} the buffer gas, and the electronegative mixing The breakdown voltage U _m of the gas, the volume fraction k of the electronegative gas in the electronegative mixed gas; the synergistic effect coefficient C is calculated by the improved synergistic effect coefficient formula, and the boundary synergistic effect coefficient C _lim is introduced at the same time, according to the synergistic effect coefficient The value of the effect coefficient C and the demarcation synergistic effect coefficient C _lim can accurately and clearly determine the type of synergistic effect after mixing the electronegative gas and the buffer gas. The invention solves the problem in the prior art that the synergistic effect type after the electronegative gas is mixed with the buffer gas cannot be accurately determined.

Description

A method for analyzing synergistic effect of electronegative gas mixture

technical field

The invention relates to the analysis of insulating substitute gas, in particular to a synergistic effect analysis method of an electronegative mixed gas, which is applied to tests such as the breakdown test of the insulating substitute gas, the insulation strength test of the insulating substitute gas and the like.

Background technique

SF ₆ gas has excellent insulation performance and arc extinguishing ability, and is widely used in various medium and high voltage equipment such as gas insulated switchgear, gas insulated transmission lines, gas circuit breakers, etc. The development of high voltage electrical equipment industry has led to the rapid growth of SF ₆ usage. . Under such a development trend, the leakage and emission of SF ₆ are becoming more and more serious, and the content of SF ₆ gas in the atmosphere is increasing, which has a great impact on the greenhouse effect. At the same time, SF ₆ and its decomposition products have great harm to human body. It also damages the metal insulation of the equipment, so it is urgent to find a new insulating gas to replace _SF6 gas.

The new type of electronegative gas has received extensive attention from scholars at home and abroad due to its strong insulating ability, low greenhouse effect and stable physicochemical properties. At present, there are more researches on CF ₃ I, cC ₄ F ₈ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₇ N, C ₅ F ₁₀ O and C ₆ F ₁₂ O and so on. However, because most of the pure electronegative gases have high liquefaction temperature (such as CF ₃ I, cC ₄ F ₈ and C ₃ F ₈ ), the practical value of engineering is low, so buffer gas should be added. Electronegative gases generally use N ₂ and CO ₂ gases as buffer gases, because these two gases have stable physical and chemical properties and low liquefaction temperature, which can better improve the liquefaction performance of electronegative gases after mixing.

When the electronegative gas is mixed with the buffer gas, it can be divided into linear relationship, synergistic effect, positive synergistic effect and negative synergistic effect according to the different relationship between its insulating properties. The above relationship types are defined as follows:

Linear relationship: After the electronegative gas is mixed with the buffer gas, the dielectric strength of the mixed gas is equal to the sum of the dielectric strengths of the two gases linearly weighted by the volume ratio.

Synergistic effect: After the electronegative gas is mixed with the buffer gas, the dielectric strength of the mixed gas changes non-linearly. The dielectric strength of the mixed gas is higher than the linear weighted value of the dielectric strength of the two gases, but there is a composition of gases (mostly electronegativity). The dielectric strength of the gas) is higher than that of the mixed gas, which is called the synergistic effect.

Positive synergistic effect: After the electronegative electronegative gas is mixed with the buffer gas, the dielectric strength of the mixed gas changes nonlinearly. If it is higher, it is called positive synergy.

Negative synergistic effect: When the dielectric strength of the mixed gas is lower than the linear weighted value of the dielectric strength of the two gases, the negative synergistic effect is obtained.

When using electronegative mixed gas as SF ₆ substitute gas, in order to improve the insulation performance of the mixed gas, it is necessary to avoid negative synergistic effect, so that the mixed gas has a synergistic effect or a positive synergistic effect, and the most ideal situation is a positive synergistic effect. Therefore, in the process of studying the insulating properties of the electronegative mixed gas, it is judged whether the buffer gas is suitable by analyzing the type of synergistic effect of the mixed gas.

A commonly used calculation formula for calculating the synergistic effect of electronegative mixed gas is as follows, but this formula cannot distinguish the positive synergistic effect from the negative synergistic effect by determining the C value:

In the formula: U ₁ is the power frequency breakdown voltage of the electronegative gas; U ₂ is the power frequency breakdown voltage of the buffer gas; U _m is the power frequency breakdown voltage of the electronegative mixed gas; k is the mixing ratio; C is the synergistic effect coefficient.

When calculated using this formula, the relationship between the type of gas relationship and the coefficient of synergy is as follows:

When the gas relationship satisfies the linear relationship, C=1.

When the gas relationship is a synergistic effect (that is, U ₁ >U _m > linear weighted value), 0<C<1 or C>1, where the linear weighted value refers to the impact of the mixed gas calculated on the basis of the volume fraction k as the weight. The breakdown voltage value is kU ₁ +(1-k)U ₂ .

When the gas relationship is a positive synergistic effect, U _m >U ₁ >U ₂ , and into the above formula, it can be obtained:

When the gas relationship is a negative synergistic effect, U _m <U ₂ <U ₁ , and into the above formula, it can be obtained:

If all cases of synergistic effect are considered, that is, positive synergistic effect, negative synergistic effect, and synergistic effect are considered at the same time, by judging the value range of the synergistic effect coefficient C, these types cannot be well distinguished. For example When C is negative, it may be a negative synergistic effect or a positive synergistic effect.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the deficiencies of the prior art, the present invention proposes a method for analyzing the synergistic effect of an electronegative mixed gas, which solves the problem that it is impossible to accurately and clearly determine the mixture of electronegative gas and buffer gas through the value range of the synergistic effect coefficient C. Post-synergy types of questions.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

A method for analyzing the synergistic effect of an electronegative mixed gas, comprising:

Step 1: Using the insulating gas breakdown voltage measuring device, under a certain pressure, measure the breakdown voltage of the electronegative gas, denoted as U ₁ ;

Step 2: Using an insulating gas breakdown voltage measuring device, under the same pressure as in Step 1, measure the breakdown voltage of the buffer gas, denoted as U ₂ , and the buffer gas refers to the gas mixed with the electronegative gas;

Step 3: mixing the electronegative gas described in step 1 with the buffer gas described in step 2 to form an electronegative mixed gas;

Step 4: According to the mixing operation in the step 3, determine the volume fraction k of the electronegative gas in the electronegative mixed gas;

Step 5: Using the insulating gas breakdown voltage measuring device, under the same gas pressure as in step 1, measure the breakdown voltage of the electronegative mixed gas described in step 3, and denote it as U _m ;

Step 6: Calculate the synergistic effect coefficient C of the electronegative mixed gas according to the following formula, and determine the synergistic effect type after mixing the electronegative gas and the buffer gas according to the value range of the synergistic effect coefficient C:

The types of synergistic effects include linear relationship, synergistic effect, positive synergistic effect, and negative synergistic effect, and the division relationship is as follows:

When C=0, the electronegative gas and the buffer gas are mixed to satisfy a linear relationship;

When 0< _C≤Clim , the electronegative gas and the buffer gas are mixed to satisfy the synergistic effect;

When C>C _lim , the electronegative gas and the buffer gas meet the positive synergistic effect after mixing;

When C<0, the negative synergistic effect is satisfied after the electronegative gas is mixed with the buffer gas;

where C _lim is the demarcation synergistic effect coefficient between synergistic effect and positive synergistic effect.

The calculation formula of the demarcation synergy coefficient is as follows:

Beneficial effect: The present invention proposes a method for analyzing the synergistic effect of electronegative mixed gas, using a new synergistic effect calculation formula, and introducing the synergistic effect coefficient that demarcates the synergistic effect and the positive synergistic effect, through the value interval of the synergistic effect coefficient C Accurately and clearly determine the type of synergistic effect after mixing electronegative gas and buffer gas. The method is simple and fast, and can be applied to tests such as insulation substitute gas breakdown test, insulation substitute gas insulation strength test and the like.

Description of drawings

Fig. 1 is a flow chart of the method for analyzing the synergistic effect of the electronegative mixed gas of the present invention.

Detailed ways

The technical solutions of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

The present invention provides a method for analyzing the synergistic effect of electronegative mixed gas, as shown in FIG. 1 , which is specifically implemented according to the following steps:

Step 1: Using an insulating gas breakdown voltage measuring device, under a certain pressure, measure the breakdown voltage of the electronegative gas, denoted as U ₁ . Electronegative gases are SF ₆ , CF ₃ I, cC ₄ F ₈ , C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₇ N, C ₅ F ₁₀ O, C ₆ F ₁₂ O and other electronegative gases.

Step 2: Using the insulating gas breakdown voltage measuring device, under the same pressure as step 1, measure the breakdown voltage of the buffer gas, denoted as U ₂ , the buffer gas refers to the gas mixed with the electronegative gas, specifically CO ₂ , N ₂ , CF ₄ , He, air and other gases.

Step 3: Mix any one of the electronegative gases described in Step 1 with any one of the buffer gases described in Step 2 to form an electronegative mixed gas.

Step 4: According to the mixing operation in the step 3, determine the volume fraction k of the electronegative gas in the electronegative mixed gas, and the volume fraction k of the electronegative gas in the electronegative mixed gas is taken as: Values range from 0 to 100.

Step 5: Using an insulating gas breakdown voltage measuring device, under the same gas pressure as that in Step 1, measure the breakdown voltage of the electronegative mixed gas described in Step 3, which is recorded as U _m .

Step 6: Calculate the synergistic effect coefficient according to the following formula, and determine the synergistic effect type according to the value range of the synergistic effect coefficient:

In the formula: U ₁ is the power frequency breakdown voltage of the electronegative gas; U ₂ is the power frequency breakdown voltage of the buffer gas; U _m is the power frequency breakdown voltage of the electronegative mixed gas; k is the mixing ratio, that is, The volume fraction of the electronegative gas in the mixed gas; C is the synergistic effect coefficient.

相比，避免考虑当C值为负时的取值范围的对应关系，能够更直观、本质地的反应混合气体的协同效应关系。In the above formula, the denominator is the weighted breakdown voltage of the mixed gas. According to the general expression of the linear weighted value kU ₁ +(1-k)U ₂ , U ₂ +k(U ₁ -U ₂ ) is obtained by expanding, and the numerator is The difference between the actual breakdown voltage of the mixed gas and the weighted breakdown voltage, and the synergistic effect coefficient is the ratio of the difference between the actual breakdown voltage and the weighted breakdown voltage to the weighted breakdown voltage. When the C value is negative, that is, the actual breakdown voltage of the mixed gas is less than the weighted breakdown voltage value, it can be known by definition that it is a negative synergistic effect. Computational formulas in the prior art

In contrast, avoiding considering the corresponding relationship of the value range when the C value is negative, the synergistic effect relationship of the reaction mixture gas can be more intuitively and intrinsically understood.

Specifically, when determining the type of synergistic effect (ie, linear relationship, synergistic effect, positive synergistic effect, and negative synergistic effect) after mixing the electronegative gas and the buffer gas according to the synergistic effect coefficient C, the present invention introduces a boundary synergistic effect coefficient to assist It is determined that the corresponding relationship is as follows:

(1) When C=0, the electronegative gas and the buffer gas are mixed to satisfy a linear relationship;

(2) When 0< _C≤Clim , the electronegative gas and the buffer gas meet the synergistic effect after mixing;

(3) When C>C _lim , the electronegative gas and the buffer gas are mixed to satisfy the positive synergistic effect;

(4) When C<0, the negative synergistic effect is satisfied after the electronegative gas is mixed with the buffer gas.

Among them, C _lim is the demarcation synergistic effect coefficient between synergistic effect and positive synergistic effect, which is calculated according to the following formula:

The principle of the above formula is as follows: from the definition of the type of synergistic effect relationship, it can be known that when U ₁ >U _m >U _{linear weighting value} , the mixed gas is a synergistic effect; U ₁ is the breakdown voltage value of the electronegative gas, and the electronegative gas The breakdown voltage value of the mixed gas is higher than the weighted breakdown voltage value of the mixed gas. When there is a _{linear weighted value} of U _m > U ₁ > U, the mixed gas has a positive synergistic effect. It can be known from the calculation formula of the synergistic effect coefficient of the mixed gas: U _m =(1+C)[U ₂ +k(U ₁ -U ₂ )], when it is in a critical state, that is, U ₁ =U _m , there are: (1+C )[U ₂ +k(U ₁ -U ₂ )=U ₁ , which is the demarcation synergistic effect coefficient in the above formula after simplification.

According to the method for analyzing the synergistic effect of the electronegative mixed gas proposed in the present invention, the synergistic effect coefficient C and the demarcation synergistic effect coefficient C _lim can be obtained by bringing U ₁ , U ₂ , U _m , and k into the corresponding formula. The C _lim value can accurately and clearly determine the type of synergistic effect after mixing the electronegative gas and the buffer gas, and provide more reliable analysis results for the insulation substitute gas breakdown test, the insulation substitute gas insulation strength test and other tests.

In order to verify the effectiveness of this method, the breakdown voltages of C ₄ F ₇ N/CO ₂ mixed gas under different conditions in an extremely inhomogeneous electric field are obtained through experiments as follows:

Table 1 Breakdown voltage of C ₄ F ₇ N/CO ₂ mixed gas

The synergistic effect coefficient and decomposition synergy effect coefficient under different mixing ratios and air pressures can be obtained through the calculation formula of the synergistic effect coefficient proposed in the present invention, and the details are as follows:

Table 2 Coefficient of synergistic effect C

Table 3 Demarcation synergy coefficient C _lim

The C ₄ F ₇ N/CO ₂ mixed gas synergistic effect value calculated by the prior art is as follows:

Table 4 Synergy coefficient C

By comparing the calculation results of the two synergistic effect coefficients, it can be seen that the mixed gas of C ₄ F ₇ N/CO ₂ has a negative synergistic effect when the mixing ratio is 2% and the gas pressure is 0.1 MPa. The calculation results of the synergistic relationship of the mixed gas under different conditions in the prior art are consistent.

Claims (6)

1. a synergistic effect analysis method of electronegative mixed gas, is characterized in that, comprises: Step 1: Using the insulating gas breakdown voltage measuring device, under a certain pressure, measure the breakdown voltage of the electronegative gas, denoted as U ₁ ; Step 2: Using an insulating gas breakdown voltage measuring device, under the same pressure as in Step 1, measure the breakdown voltage of the buffer gas, denoted as U ₂ , and the buffer gas refers to the gas mixed with the electronegative gas; Step 3: mixing the electronegative gas described in step 1 with the buffer gas described in step 2 to form an electronegative mixed gas; Step 4: According to the mixing operation in the step 3, determine the volume fraction k of the electronegative gas in the electronegative mixed gas; Step 5: Using the insulating gas breakdown voltage measuring device, under the same gas pressure as in step 1, measure the breakdown voltage of the electronegative mixed gas described in step 3, and denote it as U _m ; Step 6: Calculate the synergistic effect coefficient C of the electronegative mixed gas according to the following formula:

According to the value range of the synergistic effect coefficient C, the type of synergistic effect after mixing the electronegative gas and the buffer gas is determined. 2. The method for analyzing the synergistic effect of an electronegative mixed gas according to claim 1, wherein the electronegative gas in the step 1 is SF ₆ , CF ₃ I, cC ₄ F ₈ , C Any of ₂ F ₆ , C ₃ F ₈ , C ₄ F ₇ N, C ₅ F ₁₀ O, and C ₆ F ₁₂ O. 3 . The method for analyzing the synergistic effect of an electronegative mixed gas according to claim 1 , wherein a certain gas pressure in the step 1 refers to any gas pressure greater than or equal to 0 Mpa. 4 . 4. the synergistic effect analysis method of a kind of electronegativity mixed gas according to claim 1, is characterized in that, the buffer gas in described step 2 is CO ₂ , N ₂ , CF ₄ , He, any in air a gas. 5. The method for analyzing the synergistic effect of an electronegative mixed gas according to claim 1, wherein the synergistic effect type comprises a linear relationship, a synergistic effect, a positive synergistic effect, and a negative synergistic effect, and the division relationship is as follows: When C=0, the electronegative gas and the buffer gas are mixed to satisfy a linear relationship; When 0< _C≤Clim , the electronegative gas and the buffer gas are mixed to satisfy the synergistic effect; When C>C _lim , the electronegative gas and the buffer gas meet the positive synergistic effect after mixing; When C<0, the negative synergistic effect is satisfied after the electronegative gas is mixed with the buffer gas; where C _lim is the demarcation synergistic effect coefficient between synergistic effect and positive synergistic effect. 6. the synergistic effect analysis method of a kind of electronegativity mixed gas according to claim 5, is characterized in that, the calculation formula of described boundary synergistic effect coefficient is as follows:

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