A calculation model of noise of dry capacitor with round element structure at different temperature

Abstract

The application discloses a calculation model of noise of a dry capacitor with a circular element structure at different temperatures and belongs to the technical field of dry high-voltage capacitor noise calculation. The calculation model comprises the following steps: S1, establishing a model of the influence of temperature on element and core noise; and S2, establishing a model of the influence of temperature on capacitor noise. The model of the influence of temperature on capacitor noise is further obtained by the model of the influence of temperature on element and core noise.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of different temperature under the calculation model of round element structure dry capacitor noise, belong to dry high-voltage capacitor noise calculation technical field. BACKGROUND

[0002] Noise in UHVDC transmission capacitor, for a long time, position outstanding, always pay close attention.Especially in recent years, with the demand of people for a better life improves, noise problem is more important.For the noise problem of UHVDC transmission capacitor, the past researches are only for oil-immersed capacitor.

[0003] With the progress of dry self-healing capacitor technology, in recent years, researchers begin to pay attention to some problems of dry self-healing metallized film capacitor used for UHV capacitor, which inevitably involves the noise problem of dry capacitor.Through the unremitting research on dry capacitor noise, it is found that temperature has a greater impact on dry capacitor noise, but there is no public literature on the influence of different temperatures on dry capacitor noise. SUMMARY

[0004] The purpose of the present application is to provide a calculation model for the noise of dry capacitor with round element structure at different temperatures, to solve the problem of not having a calculation model for the noise of dry capacitor with round element structure at different temperatures.

[0005] To achieve the above purpose, the present application provides the following technical solution: a calculation model for the noise of dry capacitor with round element structure at different temperatures, comprising the following steps,

[0006] S1, establish the influence model of temperature on element and core noise;

[0007] The noise of the element is mainly determined by the change of material elastic modulus with temperature, so the vibration deformation variable generated by the plate pressure of round element is calculated by the following formula:

[0008]

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

[0010] L w =20 log (ε) (2)

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

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

[0013] In formula (1)-(3): ε - the deformation of the metallized polypropylene film under the action of electric field force; Y = E r (T) - the modulus of elasticity of the polypropylene film, MPa; L w - the calculated value of the noise of the element, dB; L wx - the calculated value of the noise of the capacitor unit, dB; n - a constant related to the arrangement of the element; M - the number of elements in the capacitor core.

[0014] According to the noise synthesis rule, for the sound pressure level, generally n = 10, considering that the arrangement of the elements in the core is relatively close, a parameter n is first set. 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, which is transmitted to the capacitor shell through the gel, assuming that the damping coefficient of the polyurethane elastomer is X, the equivalent deformation of the elastomer caused by the vibration of the capacitor core is calculated by the following formula:

[0017]

[0018] In order to simplify the formula, the modulus of elasticity E r (T) of the polypropylene material is replaced by Y, and formula (4) is substituted into formula (5) to obtain:

[0019]

[0020] Thus, the noise of the capacitor unit is calculated by the following formula:

[0021] L wd = 10 log (ε w ) + log (B) (7)

[0022] In formula (4)-(7): P x - the equivalent vibration pressure of the core, MPa; X - the deformation index of the polyurethane elastomer; ε w - the equivalent deformation of the capacitor core; L wd - the noise of the capacitor unit, dB; B - a constant determined according to the performance of the gel of the capacitor unit, and the rest are the same as before.

[0023] S2, establish a model of the influence of temperature on the noise of the capacitor;

[0024] Substitute formula (6) into formula (7), the following formula (8) can be obtained:

[0025]

[0026] In formula (8), X represents the damping coefficient of the polyurethane elastomer; Y represents the elastic modulus of the polypropylene, MPa; L represents a constant irrelevant to temperature; L wd L represents the noise value of the capacitor unit, dB, in order to simplify the formula, L

[0027] Decompose formula (8) into two parts, one part is related to temperature, and the other part is irrelevant to temperature, in order to simplify the formula, L wd is replaced by L. That is:

[0028]

[0029] Suppose there are i points, so the difference between adjacent two noise values can be obtained as follows:

[0030]

[0031] Let L i+1 -L i = α i , formula (10) can be obtained as follows:

[0032]

[0033] It can be seen from formula (11) that the noise difference between two temperature points is irrelevant to the non-temperature change parameter. The non-temperature change parameter only has an influence on the first measurement value of the noise, and the noise of other temperature points can be obtained by calculation. According to the definition of the material loss factor in standard GB / T 16406, the heat loss factor tan δ x of the polyurethane elastomer is defined as follows:

[0034]

[0035] In formula (12), tan δ xi represents the heat loss factor of the i-th temperature point; X i and X i+1 respectively represent the thermal deformation of the i-th temperature point and the i+1-th temperature point; ΔT represents the temperature difference between the two temperature points, K, and the rest are the same as above.

[0036] Considering the conversion between the common logarithm and the natural logarithm, that is, log(a)=ln(a) / ln(10), formula (12) is substituted into formula (11), and the following formula (13) can be obtained:

[0037]

[0038] According to the problem, there should be That is:

[0039]

[0040] Substitute a1=1.7dB, Y1=1706MPa, Y2=1335MPa into formula (14) to obtain: n<2.6. Substitute n=2.5 into formula (13) to obtain:

[0041]

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

[0043] According to the above analysis, n=12.3 is taken, and formula (15) is substituted into formula (11) to obtain a calculation formula of noise corresponding to different temperatures:

[0044]

[0045] According to formula (16), in combination with the tan delta Figure 1 -temperature curve, a noise value is measured at a certain temperature point, and the noise values at other temperature points can be obtained by calculation. x L is the measured value of the capacitor at a certain temperature, and L i is the calculated value of the capacitor at a certain temperature. i+1

[0046] Formula (16) obtains the difference of noise corresponding to two temperatures, so that if the noise at a certain temperature is measured, the noise at other temperatures can be obtained by calculation according to formula 16 without actual measurement.

[0047] The present application has the beneficial effects that:

[0048] The present application further obtains the influence model of temperature on capacitor noise by establishing the influence model of temperature on element and core noise, thereby obtaining a calculation model of dry capacitor noise of circular element structure at different temperatures, so as to solve the problem of no calculation model of dry capacitor noise of circular element structure at different temperatures. BRIEF DESCRIPTION OF DRAWINGS

[0049] ​In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0050] Figure 1 is a schematic diagram of the relationship between the loss factor of the polyurethane elastomer and the temperature in the embodiments of the present application, wherein the abscissa is the temperature T, the unit is ℃, the ordinate is the heat loss factor of the polyurethane elastomer, the red represents the direct current, and the blue represents the alternating current;

[0051] Figure 2 is a schematic diagram of the calculated value and the measured value of the noise of the dry capacitor at different temperatures in the embodiments of the present application; DETAILED DESCRIPTION

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

[0053] Embodiment one:

[0054] The present embodiment provides a calculation model of the noise of the dry capacitor with a round element structure at different temperatures,

[0055] S1, establishing a model of the influence of temperature on the noise of the element and the core;

[0056] The capacitor has a box shell, the box shell has a core inside, the gap between the core and the box shell is filled with glue, and the core is composed of a plurality of cylindrical elements.

[0057] The noise of the element is mainly determined by the change of the elastic modulus of the material with temperature. Thus, the vibration deformation variable generated by the plate pressure of the round element can be calculated according to the following formula:

[0058]

[0059] The sound pressure level noise of the round element can be calculated according to the following formula:

[0060] L w =20log(ε) (2)

[0061] The capacitor core is composed of M elements, and according to the noise superposition rule, the noise of the core can be calculated according to the following formula:

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

[0063] In formula (1)-(3): ε - the deformation of the metallized polypropylene film under the action of electric field force; Y = E r (T) - the modulus of elasticity of the polypropylene film, MPa; L w - the calculated value of the noise of the element, dB; L wx - the calculated value of the noise of the capacitor unit, dB; n - a constant related to the arrangement of the element; M - the number of elements in the capacitor core.

[0064] According to the noise synthesis rule, for the sound pressure level, generally n = 10, considering that the arrangement of the elements in the core is relatively close, a parameter n is first set. 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, which is transmitted to the capacitor shell through the gel, assuming that the damping coefficient of the polyurethane elastomer is X, then the equivalent deformation of the elastomer caused by the vibration of the capacitor core is:

[0067]

[0068] In order to simplify the formula, the modulus of elasticity E r (T) of the polypropylene material is replaced by Y, and formula (4) is substituted into formula (5) to obtain:

[0069]

[0070] In this way, the noise of the capacitor unit can be calculated according to the following formula:

[0071] L wd = 10 log(ε w ) + log(B) (7)

[0072] In formula (4)-(7): P x - the equivalent vibration pressure of the core, MPa; X - the deformation index of the polyurethane elastomer; ε w - the equivalent deformation of the capacitor core; L wd - the noise of the capacitor unit, dB; B - a constant determined according to the performance of the gel of the capacitor unit, and the rest are the same as before.

[0073] S2, establish a model of the influence of temperature on the noise of the capacitor;

[0074] Substitute equation (6) into equation (7), we can get:

[0075]

[0076] In equation (8), X—damping coefficient of polyurethane elastomer; Y—elastic modulus of polypropylene, MPa; —constant independent of temperature; L wd —noise value of capacitor unit, dB, L is used instead of it in the following for simplifying equation, 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 independent of temperature, L is used instead of it for simplifying equation. That is: wd

[0078]

[0079] Assume there are i points, so the difference between adjacent two noise values can be obtained:

[0080]

[0081] Let L i+1 -L i = α i , equation (10) can be obtained:

[0082]

[0083] From equation (11), the noise difference between two temperature points is independent of non-temperature variable parameter. The non-temperature variable parameter only has influence on the first measurement of noise, and the noise of other temperature points can be obtained by calculation. According to the definition of material loss factor tanδ x in standard GB / T 16406, the thermal loss factor tanδ of polyurethane elastomer is defined as:

[0084]

[0085] In equation (12), tanδ xi —thermal loss factor of i-th temperature point; X i and X i+1 —thermal deformation of i-th temperature point and i+1-th temperature point, respectively; 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), equation (12) is substituted into equation (11), we can get:

[0087]

[0088] According to the problem, there should be That is:

[0089]

[0090] Substitute a1 = 1.7 dB, Y1 = 1706 MPa, Y2 = 1335 MPa into equation (14) to obtain: n < 2.6. Substitute n = 2.5 into equation (13) to obtain:

[0091]

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

[0093] The calculation result of equation (15) is shown in Table 1 and Figure 1 .

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

[0095]

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

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

[0098]

[0099] According to equation (16), if tan δ x - temperature curve, a noise value is measured at a certain temperature point, and the noise values at other temperature points can be obtained by calculation.

[0100] The calculation result of equation (16) is shown in Table 2 and Figure 2 . Among them, the value at -25°C is the corresponding measured value, and the noise values at 25°C, 55°C, and 80°C are the calculated values obtained by adjusting the loss factors of AC and DC.

[0101] A certain type of dry self-healing capacitor was tested at -25°C, 25°C, 55°C, and 80°C, and the results are shown in Table 2.

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

[0103]

[0104]

[0105] The curves plotted based on the data in Table 2 are as follows: Figure 2 As shown in Table 2 and Figure 2 It can be seen that the calculated values ​​of the noise 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] This invention is designed for dry capacitors with round element structures and may not be suitable for flat elements. The research in this invention primarily provides a noise analysis approach or method and cannot cover the diverse range of polyurethane materials and other filler materials. Furthermore, the change in elastic modulus with temperature is based on polypropylene materials and may differ from that of polypropylene films; the polyurethane elastomer filling the space between the core and the shell is not universally applicable, and its vibration damping and the change in elastic modulus with temperature need to be determined based on specific circumstances.

[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 principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A computational model for noise in dry tantalum capacitors of round element construction at different temperatures, characterized by, The computing model comprises: S1, establishing a model of influence of temperature on noise of the circular element and the capacitor core; The noise of the circular element is mainly determined by the change of the elastic modulus of the material with temperature, so the vibration deformation variable of the circular element 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 = 20 log(ε) (2) The capacitor core is composed of M circular elements, according to the noise superposition rule, the noise of the core is calculated by the following formula: L wx = n log(ε) + log(M) = log(ε n M)(3) In the formulas (1) to (3): ε - the deformation of the metallized polypropylene film under the action of the electric field force; Y = E r (T) - the modulus of elasticity of the polypropylene film, MPa; L w N - the calculated value of the noise of the circular element, dB; L wx N - the calculated value of the noise of the capacitor unit, dB; n - a constant related to the arrangement of the circular elements; M - the number of circular elements in the capacitor core; According to the noise synthesis rule, for the sound pressure level, generally n = 10, considering the arrangement of the elements in the center of the core is relatively close, first set a parameter n, 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: P x = ε d E r (T) = ε n ME r (T) (4) Considering the vibration of the core, the vibration is transmitted to the capacitor shell through the colloid, assuming that the damping coefficient of the polyurethane elastomer is X, then the equivalent deformation variable of the elastomer caused by the vibration of the capacitor core is calculated by the following formula: For simplicity of the formula, the elastic modulus E of the polypropylene material r (T) substituting Y for Y, and substituting equation (4) into equation (5), to obtain: So the noise of the capacitor unit is calculated by the following formula: L wd = 10 log(ε w ) + log(B) (7) In formulas (4) to (7): P x — equivalent vibration pressure of the core, MPa; ε w — equivalent deformation of the capacitor core; L wd — noise of the capacitor unit, dB; B — constant determined according to the properties of the gel of the capacitor unit, the rest as before. S2, establishing a model of influence of temperature on noise of the capacitor; Substitute formula (6) into formula (7) to obtain: In formula (8): Y - the modulus of elasticity of polypropylene, MPa; - a constant independent of temperature; L wd - the noise value of the capacitor unit, dB, in the following replaced by L for the sake of simplicity of the formula, the rest being as before. Splitting equation (8) into two parts, one of which is temperature dependent and the other of which is temperature independent, L wd replaced by L; i.e.: Suppose there are i points, so the difference between the adjacent two noise values is obtained: Let L i+1 -L i = a i From equation (10), we get: From equation (11), it can be seen that the noise difference between two temperature points is independent of the non-temperature-dependent parameter; the non-temperature-dependent parameter only affects the first measurement of noise, and the noise at other temperature points is obtained by calculation; according to the definition of the material loss factor tan δ in standard GB / T 16406, the thermal loss factor tan δ of the polyurethane elastomer is defined as: x ​ tan δ in formula (12) xi — thermal loss factor at the i-th temperature point; X i and X i+1 — thermal deformation at the i-th temperature point and the i+1-th temperature point, respectively; ΔT — temperature difference between the two temperature points, K, and the rest are the same as before; Considering the conversion of common logarithm and natural logarithm, that is, log(a)=ln(a) / ln(10), substitute formula (12) into formula (11) to obtain: According to the problem setting, there should be That is: Substitute α1=1.7dB, Y1=1706MPa, Y2=1335MPa into formula (14) to obtain: n<2.6; take n=2.5 and substitute it into formula (13) to obtain: From the calculation result of formula (14), n=2.5, x=n / 10=25%; That is, in the noise synthesis of the capacitor core, the vibration synthesis of the circular element 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, take n=12.3, and substitute formula (15) into formula (11) to obtain the calculation formula of noise corresponding to different temperatures: According to equation (16), tan δ x — temperature curve, at a certain temperature point, a noise value is measured, and the noise values at other temperature points are calculated; L i is the measured value of the capacitor at a certain temperature, L i+1 is the calculated value of the capacitor at other temperatures.

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