Calculation model for noise of dry-type capacitor with circular element structure at different temperatures

Abstract

The invention discloses a calculation model for noise of a dry-type capacitor with a circular element structure at different temperatures, and belongs to the technical field of noise calculation of dry-type high-voltage capacitors. The calculation model comprises the following steps: S1, establishing an influence model of temperature on element and core noise; s2, establishing an influence model of temperature on capacitor noise; the influence model of the temperature on the capacitor noise is further obtained by establishing the influence model of the temperature on the element and core noise.

Description

Technical Field

[0001] The invention relates to a calculation model for noise of a circular element structure dry capacitor at different temperatures, belonging to the technical field of dry high-voltage capacitor noise calculation. Background Art

[0002] Noise has long been a prominent issue in capacitors used in UHV DC transmission and has always attracted much attention. In recent years, as people's demand for a better life increases, the noise problem has become more important. Previous studies on the noise problem of capacitors used in UHV DC transmission have only focused on oil-immersed capacitors.

[0003] With the advancement of dry self-healing capacitor technology, researchers have begun to pay attention to some issues of using dry self-healing metallized film capacitors for UHV capacitors in recent years, which inevitably involves the noise problem of dry capacitors. Through unremitting research on dry capacitor noise, it is found that temperature has a great influence on dry capacitor noise, but there has been no public literature focusing on the influence of different temperatures on dry capacitor noise. Summary of the invention

[0004] The object of the present invention is to provide a calculation model for the noise of a circular element structure dry-type capacitor at different temperatures, so as to solve the above-mentioned problem that there is no calculation model for the noise of a circular element structure dry-type capacitor at different temperatures.

[0005] To achieve the above object, the present invention provides the following technical solution: a calculation model of the noise of a circular element structure dry capacitor at different temperatures, comprising the following steps:

[0006] S1. Establish a model for the effect of temperature on components and core noise;

[0007] The noise of the element is mainly determined by the change of the elastic modulus of the material with temperature. The vibration deformation caused by the plate pressure of the circular element is calculated by the following formula:

[0008]

[0009] The sound pressure level noise of the circular element is calculated by the following formula:

[0010] L w =20 log(ε) (2)

[0011] The core of the capacitor is composed of M components. According to the noise superposition law, the noise of the core is calculated by the following formula:

[0012] L wx =nlog(ε)+log(M)=log(ε n M)(3)

[0013] In formulas (1) to (3): ε is the deformation of the metallized polypropylene film under the action of the electric field; Y = E r (T)——Elastic modulus of polypropylene film, MPa; L w ——component noise calculation value, dB; L wx ——Calculated noise value of the capacitor unit, dB; n——Constant related to the arrangement of components; M——Number of components in the capacitor core.

[0014] According to the noise synthesis rule, for the sound pressure level, n = 10 in general. Considering that the components in the core are arranged closely, a parameter n is set first. Let ε d =ε n M, which is the equivalent deformation of the core. According to the generalized Hooke's law, the equivalent vibration pressure of the core is:

[0015] P x =ε d E r (T) = ε n ME r (T) (4)

[0016] Considering the vibration of the core, it is transmitted to the capacitor housing through the colloid. Assuming that the damping coefficient of the polyurethane elastomer is X, the equivalent deformation of the elastic body caused by the vibration of the capacitor core is calculated by the following formula:

[0017]

[0018] To simplify the formula, the elastic modulus E of polypropylene material r Substituting (T) with Y and substituting equation (4) into equation (5), we can obtain:

[0019]

[0020] The noise of the capacitor unit is calculated as follows:

[0021] L wd =10log(ε w )+log(B) (7)

[0022] In formulas (4) to (7): P x ——Equivalent vibration pressure of the core, MPa; X——Deformation index of polyurethane elastomer; ε w ——Equivalent deformation of capacitor core; L wd ——Noise of capacitor unit, dB; B——constant, determined according to the performance of capacitor unit colloid, the rest is the same as before.

[0023] S2. Establish a model for the effect of temperature on capacitor noise;

[0024] Substituting formula (6) into formula (7), we can obtain:

[0025]

[0026] In formula (8): X is the damping coefficient of polyurethane elastomer; Y is the elastic modulus of polypropylene, MPa; ——constant independent of temperature; L wd ——Noise value of capacitor unit, dB. In order to simplify the formula, L is used instead below, and the rest is the same as before.

[0027] Decompose equation (8) into two parts, one part is related to temperature, and the other part is not related to temperature. In order to simplify the formula, L wd Replace it with L. That is:

[0028]

[0029] Assuming there are i points, subtracting two adjacent noise values ​​can yield:

[0030]

[0031] Let L i+1 -L i =α i , from formula (10) we can get:

[0032]

[0033] It can be seen from formula (11) that the noise difference between two temperature points is independent of the non-temperature-dependent parameters. The non-temperature-dependent parameters only affect the first measured value of the noise, and the noise at other temperature points can be calculated. According to the definition of material loss factors in standard GB / T 16406, the present invention uses the heat loss factor tanδ of polyurethane elastomer as x Defined as:

[0034]

[0035] In formula (12): tanδ xi ——heat loss factor of the ith temperature point; X i and X i+1 ——The thermal deformation at the i-th temperature point and the i+1-th temperature point respectively; ΔT——The temperature difference between two temperature points, K, and the rest are the same as before.

[0036] Considering the conversion between common logarithm and natural logarithm, that is, log(a)=ln(a) / ln(10), substituting equation (12) into equation (11) yields:

[0037]

[0038] According to the question, there should be Right now:

[0039]

[0040] Substituting α1=1.7dB, Y1=1706MPa, Y2=1335MPa into equation (14), we can get: n<2.6. Substituting n=2.5 into equation (13), we can get:

[0041]

[0042] From the calculation result of formula (14), we can see that n = 2.5, x = n / 10 = 25%. That is to say, in the noise synthesis of the capacitor core, the vibration synthesis of the component is only about 25%, which does not reach 100% of the capacitor unit. n = 2.5 is basically applicable to dry capacitors.

[0043] According to the above analysis, taking n = 12.3, and substituting equation (15) into equation (11), we can get the calculation formula for the noise corresponding to different temperatures:

[0044]

[0045] According to formula (16), combined with Figure 1 tanδ x -Temperature curve, if a noise value is measured at a certain temperature point, the noise value at other temperature points can be calculated. i is the measured value of the capacitor at a certain temperature, L i+1 It is the calculated value of the capacitor at a certain temperature.

[0046] Formula (16) obtains the difference between the noises corresponding to the two temperatures. Thus, if the noise at a certain temperature is measured, the noise at other temperatures can be directly calculated based on Formula 16 without actual measurement.

[0047] The beneficial effects of the present invention are:

[0048] The present invention further obtains a model of the influence of temperature on capacitor noise by establishing a model of the influence of temperature on component and core noise, thereby obtaining a calculation model of the noise of a dry-type capacitor with a circular element structure at different temperatures, so as to solve the problem of the lack of a calculation model of the noise of a dry-type capacitor with a circular element structure at different temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0050] Figure 1 Schematic diagram of the relationship between the loss factor and temperature of the polyurethane elastomer in an embodiment of the present invention, wherein the abscissa is the temperature T in ° C., the ordinate is the heat loss factor of the polyurethane elastomer, red represents direct current, and blue represents alternating current;

[0051] Figure 2 Schematic diagram of calculated and measured values ​​of dry capacitor noise at different temperatures in an embodiment of the present invention; DETAILED DESCRIPTION

[0052] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0053] Embodiment 1:

[0054] This embodiment provides a calculation model for the noise of a circular element structure dry capacitor at different temperatures.

[0055] S1. Establish a model for the effect of temperature on components and core noise;

[0056] The capacitor has a case with a core inside the case. The gap between the core and the case is filled with colloid, and the core is composed of several cylindrical components.

[0057] The noise of the component is mainly determined by the change of the elastic modulus of the material with temperature. The vibration deformation caused by the plate pressure of the circular component can be calculated as follows:

[0058]

[0059] The sound pressure level noise of the circular element can be calculated as follows:

[0060] L w =20log(ε) (2)

[0061] The core of the capacitor is composed of M components. According to the noise superposition law, the noise of the core can be calculated as follows:

[0062] L wx =nlog(ε)+log(M)=log(ε n M) (3)

[0063] In formulas (1) to (3): ε is the deformation of the metallized polypropylene film under the action of the electric field; Y = E r (T)——Elastic modulus of polypropylene film, MPa; L w ——component noise calculation value, dB; L wx ——Calculated noise value of the capacitor unit, dB; n——Constant related to the arrangement of components; M——Number of components in the capacitor core.

[0064] According to the noise synthesis rule, for the sound pressure level, n = 10 in general. Considering that the components in the core are arranged closely, a parameter n is set first. Let ε d =ε n M, which is the equivalent deformation of the core. According to the generalized Hooke's law, the equivalent vibration pressure of the core is:

[0065] P x =ε d E r (T) = ε n ME r (T) (4)

[0066] Considering the vibration of the core, it is transmitted to the capacitor housing through the colloid. Assuming that the damping coefficient of the polyurethane elastomer is X, the equivalent deformation of the elastic body caused by the vibration of the capacitor core is:

[0067]

[0068] To simplify the formula, the elastic modulus E of polypropylene material r Substituting (T) with Y and substituting equation (4) into equation (5), we can obtain:

[0069]

[0070] The noise of the capacitor unit can be calculated as follows:

[0071] L wd =10 log(ε w )+log(B) (7)

[0072] In formulas (4) to (7): P x ——Equivalent vibration pressure of the core, MPa; X——Deformation index of polyurethane elastomer; ε w ——Equivalent deformation of capacitor core; L wd ——Noise of capacitor unit, dB; B——constant, determined according to the performance of capacitor unit colloid, the rest is the same as before.

[0073] S2. Establish a model for the effect of temperature on capacitor noise;

[0074] Substituting formula (6) into formula (7), we can obtain:

[0075]

[0076] In formula (8): X is the damping coefficient of polyurethane elastomer; Y is the elastic modulus of polypropylene, MPa; ——constant independent of temperature; L wd ——Noise value of capacitor unit, dB. In order to simplify the formula, L is used instead below, and the rest is the same as before.

[0077] Decompose equation (8) into two parts, one part is related to temperature, and the other part is not related to temperature. In order to simplify the formula, L wd Replace it with L. That is:

[0078]

[0079] Assuming there are i points, subtracting two adjacent noise values ​​can yield:

[0080]

[0081] Let L i+1 -L i =α i , from formula (10) we can get:

[0082]

[0083] It can be seen from formula (11) that the noise difference between two temperature points is independent of the non-temperature-dependent parameters. The non-temperature-dependent parameters only affect the first measured value of the noise, and the noise at other temperature points can be calculated. According to the definition of material loss factors in standard GB / T 16406, this paper defines the heat loss factor tanδ of polyurethane elastomer as x Defined as:

[0084]

[0085] In formula (12): tanδ xi ——heat loss factor of the ith temperature point; X i and X i+1 ——respectively thermal deformation at the ith temperature point and the i+1th temperature point; ΔT——temperature difference between two temperature points, K. The rest is the same as before.

[0086] Considering the conversion between common logarithm and natural logarithm, that is, log(a)=ln(a) / ln(10), substituting equation (12) into equation (11) yields:

[0087]

[0088] According to the question, there should be Right now:

[0089]

[0090] Substituting α1=1.7dB, Y1=1706MPa, Y2=1335MPa into equation (14), we can get: n<2.6. Substituting n=2.5 into equation (13), we can get:

[0091]

[0092] From the calculation result of formula (14), we can see that n = 2.5, x = n / 10 = 25%. That is to say, in the noise synthesis of the capacitor core, the vibration synthesis of the component is only about 25%, which does not reach 100% of the capacitor unit. n = 2.5 is basically applicable to dry capacitors.

[0093] The calculation results of formula (15) are shown in Table 1 and Figure 1 shown.

[0094] Table 1 Relationship between the loss factor of polyurethane elastomer and temperature

[0095]

[0096] From Table 1 and Figure 1 It can be seen that the change trend of loss factor and temperature of polyurethane elastomer under DC superimposed harmonics and AC superimposed harmonics is the same, the main difference is that the maximum value is different.

[0097] According to the previous analysis, we take n = 12.3 and substitute equation (15) into equation (11) to obtain:

[0098]

[0099] According to formula (16), if tanδ x -Temperature curve: if a noise value is measured at a certain temperature point, the noise value at other temperature points can be calculated.

[0100] The calculation results of formula (16) are shown in Table 2 and Figure 2 The value at -25°C corresponds to the measured value, and the noise values ​​at the three temperature points of 25°C, 55°C, and 80°C are calculated values ​​by swapping the loss factors of AC and DC.

[0101] The noise test of a certain type of dry self-healing capacitor was carried out at four temperature points: -25℃, 25℃, 55℃ and 80℃. The results are shown in Table 2.

[0102] Table 2 Calculated and measured values ​​of dry capacitor noise at different temperatures

[0103]

[0104]

[0105] The curve drawn according to the data in Table 2 is as follows Figure 2 As shown in Table 2 and Figure 2 It can be seen that the noise calculation values ​​of the calculation model of the circular element structure dry capacitor at different temperatures are basically consistent with the laboratory measured values, which can guide the estimation of noise in product design.

[0106] The present invention is aimed at dry capacitors with round components, and may not be suitable for flat components; the research of the present invention is more about providing a noise analysis idea or method, and cannot cover the ever-changing polyurethane materials and other filling materials. In addition, the change of elastic modulus with temperature is made of polypropylene material, which may be different from polypropylene film; the polyurethane elastomer filled between the core and the shell is not universal, and its vibration damping and elastic modulus change with temperature need to be determined according to actual conditions.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A calculation model for the noise of a circular element structure dry capacitor at different temperatures, characterized in that: The calculation model includes: S1. Establish a model for the effect of temperature on components and core noise; The noise of the element is mainly determined by the change of the elastic modulus of the material with temperature. The vibration deformation caused by the plate pressure of the circular element is calculated by the following formula: The sound pressure level noise of the circular element is calculated by the following formula: L w =20log(ε) (2) The core of the capacitor is composed of M components. According to the noise superposition law, the noise of the core is calculated by the following formula: L wx =nlog(ε)+log(M)=log(ε n M) (3) In formulas (1) to (3): ε is the deformation of the metallized polypropylene film under the action of the electric field; Y = E r (T)——Elastic modulus of polypropylene film, MPa; L w ——component noise calculation value, dB; L wx ——Calculated noise value of the capacitor unit, dB; n——Constant related to the arrangement of components; M——Number of components in the capacitor core. According to the noise synthesis rule, for the sound pressure level, n = 10 in general. Considering that the components in the core are arranged closely, a parameter n is set first. Let ε d =ε n M, this is the equivalent shape variable of the heart. According to the generalized Hooke's law, the equivalent vibration pressure of the core is: P x =ε d E r (T)=ε n ME r (T) (4) Considering the vibration of the core, it is transmitted to the capacitor housing through the colloid. Assuming that the damping coefficient of the polyurethane elastomer is X, the equivalent deformation of the elastic body caused by the vibration of the capacitor core is calculated by the following formula: To simplify the formula, the elastic modulus E of polypropylene material r Substituting (T) with Y and substituting equation (4) into equation (5), we can obtain: The noise of the capacitor unit is calculated as follows: L wd =10 log(ε w )+log(B) (7) In formulas (4) to (7): P x ——Equivalent vibration pressure of the core, MPa; X——Deformation index of polyurethane elastomer; ε w ——Equivalent deformation of capacitor core; L wd ——Noise of capacitor unit, dB; B——constant, determined according to the performance of capacitor unit colloid, the rest is the same as before. S2. Establish a model for the effect of temperature on capacitor noise; Substituting formula (6) into formula (7), we can obtain: In formula (8): X is the damping coefficient of polyurethane elastomer; Y is the elastic modulus of polypropylene, MPa; ——constant independent of temperature; L wd ——Noise value of capacitor unit, dB. In order to simplify the formula, L is used instead below, and the rest is the same as before. Decompose equation (8) into two parts, one part is related to temperature, and the other part is not related to temperature. In order to simplify the formula, L wd Replace it with L. That is: Assuming there are i points, subtracting two adjacent noise values ​​can yield: Let L i+1 -L i =α i , from formula (10) we can get: It can be seen from formula (11) that the noise difference between two temperature points is independent of the non-temperature-dependent parameters. The non-temperature-dependent parameters only affect the first measured value of the noise, and the noise at other temperature points can be calculated. According to the definition of material loss factors in standard GB / T 16406, the present invention uses the heat loss factor tanδ of polyurethane elastomer as x Defined as: In formula (12): tanδ xi ——heat loss factor of the ith temperature point; X i and X i+1 ——The thermal deformation at the i-th temperature point and the i+1-th temperature point respectively; ΔT——The temperature difference between two temperature points, K, and the rest are the same as before. Considering the conversion between common logarithm and natural logarithm, that is, log(a)=ln(a) / ln(10), substituting equation (12) into equation (11) yields: According to the question, there should be Right now: Substituting α1=1.7dB, Y1=1706MPa, Y2=1335MPa into equation (14), we can get: n<2.

6. Substituting n=2.5 into equation (13), we can get: From the calculation result of formula (14), we can see that n = 2.5, x = n / 10 = 25%. That is to say, in the noise synthesis of the capacitor core, the vibration synthesis of the component is only about 25%, which does not reach 100% of the capacitor unit. n = 2.5 is basically applicable to dry capacitors. According to the above analysis, taking n = 12.3, and substituting equation (15) into equation (11), we can get the calculation formula for the noise corresponding to different temperatures: According to formula (16), combined with Figure 1 Temperature curve, if a noise value is measured at a certain temperature point, the noise value at other temperature points can be calculated. i is the measured value of the capacitor at a certain temperature, L i+1 It is the calculated value of the capacitor at a certain temperature.

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