Oil-immersed transformer electromagnetic force calculation system and method

Abstract

The application provides an oil-immersed transformer electromagnetic force calculation system and belongs to the field of transformer electromagnetic field analysis. The system comprises a calculation model establishment module, a calculation module, and an actual measurement data acquisition module. The calculation model establishment module is used for establishing a calculation model of electromagnetic force in a transformer. The calculation model is a corresponding relationship between the electromagnetic force F1 and the surface vibration speed V(x) of the transformer shell. The calculation module is used for calculating parameters in the calculation model according to product parameters of the transformer. The actual measurement data acquisition module is used for collecting vibration signals at the x point and position data of the x point. The calculation module is further used for acquiring the vibration speed V(x) of the transformer shell at the x point according to the vibration signals. The calculation module is further used for calculating the Y 1x and the Y 2x according to the position data of the x point. The calculation module is further used for calculating the electromagnetic force F1 according to the calculation model. The application further provides an oil-immersed transformer electromagnetic force calculation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transformer electromagnetic field analysis, and particularly relates to an oil-immersed transformer electromagnetic force calculation system and method. BACKGROUND

[0002] The transformer is the main noise source of the transformer substation. Excessive transformer noise can cause the transformer core to be loose, the winding to be deformed, and the temperature to be excessively high. These conditions can reduce the ability of the transformer to resist short-circuit current impact, seriously affect the normal operation of the transformer, reduce the operation life of the transformer, and also affect the normal operation of the power grid. The transformer noise is caused by the electromagnetic force generated by the transient short-circuit current acting on the transformer shell, and the transformer shell is vibrated under stress. The transformer noise of main transformers of different voltage levels and different heat dissipation modes is different. The noise of a common 110kV oil-immersed self-cooled main transformer is about 65dB(A), the noise of a 330kV forced oil circulation air-cooled main transformer is about 70dB(A), and the noise of a 750kV forced oil circulation air-cooled main transformer is about 75dB(A). The electromagnetic force acting on the transformer shell is one of the main parameters for analyzing the vibration noise of the transformer. The electromagnetic force cannot be directly measured, and reference electromagnetic force data needs to be calculated. SUMMARY

[0003] Therefore, the present application provides an oil-immersed transformer electromagnetic force calculation system and method. The correspondence between the electromagnetic force acting on the transformer and the vibration speed of the transformer shell surface is established based on the admittance power flow theory, which has strong applicability and can be widely applied to various transformers above 110kV.

[0004] The technical solution adopted by the embodiment of the present application to solve the technical problems is:

[0005] An oil-immersed transformer electromagnetic force calculation system comprises:

[0006] A calculation model establishment module is configured to establish a calculation model of electromagnetic force in a transformer. The calculation model is a correspondence between the electromagnetic force F1 and the vibration speed V(x) of the transformer shell surface.

[0007]

[0008] Y 12 is the transfer admittance from a first position to a second position on the transformer shell, Y 22 is the input point admittance of the transformer shell at the second position, Y 1x is the transfer admittance from the first position to the x point, and Y 2xY2 is an effective line inductance of the reinforcing rib in the transformer, the first position is a force point of the transformer shell under the electromagnetic force F1, and the second position is a connection between the transformer shell and the reinforcing rib;

[0009] The calculation module is configured to calculate the Y 12 , the Y 22 , and the Y2 in the calculation model according to product parameters of the transformer.

[0010] The actual measurement data acquisition module is configured to collect a vibration signal at the x point and position data of the x point.

[0011] The calculation module is further configured to acquire the vibration velocity V(x) of the transformer shell at the x point according to the vibration signal, to calculate the Y 1x and the Y 2x according to the position data of the x point, and to calculate the electromagnetic force F1 according to the calculation model.

[0012] Preferably, the calculation model establishment module is further configured to derive the calculation model as follows:

[0013] The vibration velocity of the transformer shell at the second position is V2,

[0014] V2 = F1Y 12 + F2Y 22

[0015] F2 is a reaction force of the reinforcing rib on the transformer shell, F1Y 12 is a vibration response under the action of F1, and F2Y 22 is a vibration response at the second position under the action of F2.

[0016] At the second position, the vibration velocity of the reinforcing rib is V2′,

[0017] V2′ = F2′Y2

[0018] F2′ is a force of the transformer shell on the reinforcing rib.

[0019] F2′ and F2 are equal in size and opposite in direction, and V2′ and V2 are equal,

[0020] F2 = -F2′

[0021] V2 = V2′

[0022] The equation relationship between F2 and F1 is derived,

[0023]

[0024] The vibration velocity formula of the x point on the transformer shell is,

[0025] V(x) = F1Y 1x +F2Y 2x

[0026] The equation relationship of F2 and F1 is brought into the vibration velocity formula of the x point, and the equation relationship of V(x) and F1 is derived,

[0027]

[0028] Thus, the calculation model of the electromagnetic force F1 is derived,

[0029]

[0030] Preferably, the calculation module is further used for,

[0031] calculating the Y 12 ,

[0032]

[0033] calculating the Y 22 ,

[0034]

[0035] calculating the Y2,

[0036]

[0037] The L is the height of the transformer shell, the a is the length and width of the transformer shell, the h is the thickness of the transformer shell, the p is the density of the transformer shell material, the w mn is the natural frequency of the transformer, the h m is the frequency function, the e n is the elastic modulus, the B is the stiffness of the transformer, the l 12 is the horizontal distance between the first position and the second position, the horizontal distance is the coordinate difference of two end points in the X-axis direction, the B B is the bending stiffness of the reinforcing rib, the k B is the radial stiffness of the reinforcing rib, and the coefficient l mn is,

[0038]

[0039] The k m is,

[0040] k m = mπ / a

[0041] the k n = nπ / a

[0042] k n = nπ / a

[0043] the ω mn = nπ / a

[0044]

[0045] Preferably, the calculation module is further configured to,

[0046] calculate the Y 1x ,

[0047]

[0048] calculate the Y 2x ,

[0049]

[0050] the l 1x is the horizontal distance between the first position and the x point, and the l 2x is the horizontal distance between the second position and the x point.

[0051] The application further provides an oil-immersed transformer electromagnetic force calculation method, comprising:

[0052] establishing a transformer electromagnetic force calculation model, wherein the calculation model is a corresponding relationship between the electromagnetic force F1 and the transformer shell surface vibration speed V(x):

[0053]

[0054] the Y 12 is the transfer admittance of a first position to a second position on the transformer shell, the Y 22 is the input point admittance of the transformer shell at the second position, the Y 1x is the transfer admittance of the first position to an x point, the Y 2x is the transfer admittance of the second position to the x point, and the Y2 is the effective line admittance of a reinforcing rib in the transformer, the first position is a force point of the transformer shell subjected to the electromagnetic force F1, and the second position is a connection between the transformer shell and the reinforcing rib.

[0055] According to the product parameters of the transformer, the Y 12 , the Y22 and the Y2;

[0056] collecting vibration signals at the x point and position data of the x point;

[0057] obtaining the vibration velocity V(x) of the transformer shell at the x point according to the vibration signals;

[0058] calculating the Y according to the position data of the x point 1x and the Y 2x ;

[0059] calculating the electromagnetic force F1 according to the calculation model.

[0060] Preferably, the calculation model of the electromagnetic force in the transformer comprises:

[0061] at the second position, the vibration velocity of the transformer shell is V2,

[0062] V2=F1Y 12 +F2Y 22

[0063] the F2 is the reaction force of the reinforcing rib to the transformer shell, the F1Y 12 is the vibration response under the action of F1, and the F2Y 22 is the vibration response at the second position under the action of F2;

[0064] at the second position, the vibration velocity of the reinforcing rib is V2',

[0065] V2'=F2'Y2

[0066] the F2' is the force of the transformer shell acting on the reinforcing rib;

[0067] the F2' is equal in size and opposite in direction to the F2, and the V2' is equal to the V2,

[0068] F2=-F2'

[0069] V2=V2'

[0070] deduce the equation relationship between the F2 and the F1,

[0071]

[0072] the vibration velocity formula of the x point on the transformer shell is,

[0073] V(x)=F1Y 1x +F2Y 2x

[0074] The equation relationship of the F2 and the F1 is brought into the vibration velocity formula of the x point, and the equation relationship of the V(x) and the F1 is derived,

[0075]

[0076] Thus, the calculation model of the electromagnetic force F1 is derived,

[0077]

[0078] Preferably, the Y in the calculation model is calculated according to product parameters of the transformer, 12 , the Y 22 and the Y2 include:

[0079] The Y 12 is calculated,

[0080]

[0081] The Y 22 is calculated,

[0082]

[0083] The Y2 is calculated,

[0084]

[0085] The L is the height of the transformer shell, the a is the length and width of the transformer shell, the h is the thickness of the transformer shell, the p is the density of the transformer shell material, the w mn is the natural frequency of the transformer, the h m is a frequency function, the e n is the elastic modulus, the B is the stiffness, the l 12 is the horizontal distance between the first position and the second position, the B B is the bending stiffness of the reinforcing rib, the k B is the radial stiffness of the reinforcing rib, the coefficient l mn is,

[0086]

[0087] The k m is,

[0088] k m = m p / a

[0089] The k n is,

[0090] kn = nπ / a

[0091] The ω mn is,

[0092]

[0093] Preferably, the Y 1x is calculated according to the position data of the x point. 2x

[0094] The Y 1x is calculated according to the position data of the x point.

[0095]

[0096] The Y 2x is calculated according to the position data of the x point.

[0097]

[0098] The l 1x is the horizontal distance between the first position and the x point. 2x The l 1x is the horizontal distance between the first position and the x point.

[0099] From the above technical solution, the oil-immersed transformer electromagnetic force calculation system and method provided by the embodiment of the present application establishes the corresponding relationship between the electromagnetic force borne by the transformer shell and the vibration speed of the transformer shell surface based on the admittance power flow theory, calculates the electromagnetic force borne by the transformer according to the measured vibration signal and vibration position data, fully considers the influence of the reinforcing rib and other factors in the transformer on the vibration of the transformer shell, and has a convenient, high-precision and less environment-affected data measurement scheme, so that the data obtained by measurement has high accuracy and provides electromagnetic force data with higher reference value for transformer noise research. BRIEF DESCRIPTION OF DRAWINGS

[0100] Figure 1 The flowchart of the oil-immersed transformer electromagnetic force calculation method of the embodiment of the present application.

[0101] Figure 2 The structural composition schematic diagram of the oil-immersed transformer electromagnetic force calculation system of the embodiment of the present application.

[0102] Figure 3 The stress analysis diagram of the transformer shell and the reinforcing rib combination of the embodiment of the present application.

[0103] Figure 4 The stress analysis diagram of the transformer shell of the embodiment of the present application.

[0104] Figure 5 The stress analysis diagram of the reinforcing rib of the embodiment of the present application.

[0105] Fig. The transformer shell 1, reinforcing rib 2, the first position a, the second position b, position x. DETAILED DESCRIPTION

[0106] The technical solutions and technical effects of the present application are further described in detail below in combination with the drawings of the present application.

[0107] The embodiment of the present application establishes the corresponding relationship between the electromagnetic force borne by the transformer shell and the vibration speed of the transformer shell surface based on the admittance power flow theory, inversely deduces the electromagnetic force borne by the transformer according to the measured vibration signal and vibration position data, and fully considers the influence of the reinforcing rib and other factors in the transformer on the vibration of the transformer shell.

[0108] In the algorithm of the present application, the transformer foundation is regarded as an approximate rigid body, and the transformer is rigidly connected to the foundation; inside the transformer, the transformer shell and the reinforcing rib are rigidly connected; when calculating the vibration of the transformer shell, since the transformer contains the reinforcing rib, it cannot be simply simplified as the transformer shell calculation, and the vibration of the reinforcing rib due to the force of the transformer shell also needs to be considered. According to the admittance power flow theory, the factors affecting the electromagnetic force and the surface vibration speed of the transformer are extracted, including the input point admittance, the transfer admittance, and the effective line admittance (beam admittance) of the reinforcing rib; a calculation model is established, which embodies the relationship between the vibration response speed of each point in the x-axis direction of the transformer shell and the electromagnetic force borne by the transformer shell.

[0109] As shown in Figure 1 , the embodiment of the present application provides an oil-immersed transformer electromagnetic force calculation method, the implementation main body of which is an oil-immersed transformer electromagnetic force calculation system as shown in Figure 2 , and the specific steps include:

[0110] Step S1, a calculation model of the electromagnetic force in the transformer is established, which is the corresponding relationship between the electromagnetic force F1 and the vibration speed V(x) of the transformer shell surface:

[0111]

[0112] Step S2, Y 12 , Y 22 and Y2 in the calculation model formula (1) are calculated according to the product parameters of the transformer;

[0113] Step S3, the vibration signal of the x point on the transformer shell surface and the position data of the x point are collected;

[0114] Step S4, the vibration speed V(x) of the transformer shell at the x point is obtained according to the vibration signal;

[0115] Step S5, calculating Y according to the position data of x point 1x and Y 2x ;

[0116] Step S6, calculating electromagnetic force F1 according to the calculation model (1).

[0117] Wherein, Y 12 is the transfer admittance from the first position to the second position of the transformer shell, Y 22 is the input point admittance of the transformer shell at the second position, Y 1x is the transfer admittance from the first position to x point, Y 2x is the transfer admittance from the second position to x point, Y2 is the effective line admittance of the reinforcing rib in the transformer, and the first position mentioned is the force point of the transformer shell under the electromagnetic force F1, and the second position is the connection between the transformer shell and the reinforcing rib.

[0118] The transformer contains reinforcing ribs, which are rigidly connected with the transformer shell. When the transformer shell is subjected to the magnetic field force F1, the transformer shell and the reinforcing rib are actually subjected to the magnetic field force F1 at the same time, as shown in Figure 3 , Figure 3 The transformer shell 1 and the reinforcing rib 2 are rigidly connected, and when the transformer shell 1 is subjected to the magnetic field force F1, the transformer shell 1 and the reinforcing rib 2 are subjected to the electromagnetic force F1 at the same time. In the figure, l 12 is the horizontal distance between the first position a and the second position b, l 1x is the horizontal distance between the first position a and the position x, and l 2x is the horizontal distance between the second position b and the position x, wherein the horizontal distance refers to the coordinate difference of the two end points in the X-axis direction. Figure 4 is the force condition of the transformer shell 1. When the transformer shell 1 vibrates under the magnetic field force F1, the transformer shell 1 will apply a force to the reinforcing rib 2, and at the same time, the reinforcing rib 2 will apply a reaction force F2 to the transformer shell 1, Figure 5 is the force condition of the reinforcing rib 2. The reinforcing rib 2 will be subjected to the magnetic field force F1 and the force F2′ applied by the transformer shell 1 at the same time.

[0119] Step S3 collects the vibration signal at x point, which can be achieved by setting a vibration sensor at x point to directly measure the vibration speed of x point. The position data of x point uses its coordinate value in the X-axis direction when calculating and applying;

[0120] The specific derivation process of step S1 for establishing the calculation model of electromagnetic force in the transformer is as follows:

[0121] At the second position, the vibration speed of the transformer shell is V2,

[0122] V2=F1Y 12 +F2Y22 (2)

[0123] Where F2 is the reaction force of the stiffener to the transformer tank, F1Y 12 is the vibration response under the action of F1, F2Y 22 is the vibration response at the second position under the action of F2;

[0124] At the second position, the vibration velocity of the stiffener is V2', and F2' is the force of the stiffener to the transformer tank;

[0125] V2' = F2'Y2 (3)

[0126] Since the stiffener and the tank are considered to be rigidly connected, F2' and F2 are equal in size and opposite in direction, and V2' and V2 are equal,

[0127] F2 = -F2' (4)

[0128] V2 = V2' (5)

[0129] From the above formulas (1)-(5), the equation relationship (6) between F2 and F1 can be derived,

[0130]

[0131] According to the admittance power flow theory, the vibration velocity formula of point x on the transformer tank is,

[0132] V(x) = F1Y 1x +F2Y 2x (7)

[0133] The equation relationship between V(x) and F1 is derived by bringing the equation relationship between F2 and F1 into the vibration velocity formula (7) of point x as follows:

[0134]

[0135] Through formula (8), the calculation model of electromagnetic force F1 can be deduced,

[0136]

[0137] According to the product parameters of the transformer, the parameters in the calculation model formula (1) are calculated, and the calculation formula is as follows:

[0138]

[0139]

[0140] Wherein, L is the height of the transformer shell (m), a is the length and width of the transformer shell (m), h is the thickness of the transformer shell (m), p is the density of the transformer shell material (kg·m -3 ),ω mn is the natural frequency of the transformer (Hz), η is the frequency function, e n is the elastic modulus, B is the stiffness, B B is the bending stiffness of the reinforcing rib (N / M), k B is the radial stiffness of the reinforcing rib (N / M), l 12 is the horizontal distance between the first position and the second position, l 1x is the horizontal distance between the first position and the point x, l 2x is the horizontal distance between the second position and the point x, the coefficient λ mn ,

[0141]

[0142] k m =mπ / a (15)

[0143] k n =nπ / a (16)

[0144] Wherein, the empirical formula of the frequency function is:

[0145]

[0146] The empirical formula of the natural frequency of the transformer is:

[0147]

[0148] The empirical formula of the coefficient G mn is:

[0149]

[0150] Taking a 110kV main transformer in the northwest as an example, the electromagnetic force applied by the core winding thereof is estimated by the method of the present application. Wherein, the main transformer shell is 5.125m long, 2.6m wide, 3.35m high, and 30mm thick, the reinforcing rib in the main transformer is 15mm thick and 45mm wide, and is located on both sides of the shell. The elastic modulus of the structural steel of the main transformer is E=1.96×10 11 N / m 2 , the density p=7.85×10 3 kg / m 3 , and the Poisson's ratio is 0.5. When the vibration velocity v=0.000142m / s is measured by the vibration sensor, the electromagnetic force applied by the core winding can be obtained by the calculation of the present application, which is F1=1.12×10 4 N.

[0151] As Figure 2 shown, the embodiment of the present application also provides an oil-immersed transformer electromagnetic force calculation system for implementing the method shown in the embodiment of the present application, and specifically comprises a calculation model establishing module 21, a calculation module 22 and a measured data acquisition module 23. Figure 1

[0152] The calculation model establishing module 21 is used to implement step S1, and establish a calculation model (1) of electromagnetic force in the transformer.

[0153] The calculation module 22 is used to implement steps S2, S4 and S5, and calculate each parameter in the calculation model according to product parameters of the transformer.

[0154] The measured data acquisition module 23 is used to implement step S3, and specifically comprises signal acquisition and position data acquisition.

[0155] The calculation module is also used to implement step S6, and calculate electromagnetic force F1 according to the calculation model (1).

[0156] The oil-immersed transformer electromagnetic force calculation system and method provided by the embodiment of the present application establish the corresponding relationship between electromagnetic force borne by the transformer shell and vibration speed of the transformer shell surface based on the admittance power flow theory, calculate the electromagnetic force borne by the transformer according to the measured vibration signal and vibration position data, fully consider the influence of factors such as reinforcing ribs in the transformer on the vibration of the transformer shell, and have the advantages of convenient data measurement scheme, high precision, small environmental influence and high accuracy of the calculated data, thereby providing electromagnetic force data with higher reference value for the research on the noise of the transformer.

[0157] The above only discloses the preferred embodiments of the present application, and of course cannot limit the scope of the rights of the present application, and those skilled in the art can understand that all or part of the above-mentioned embodiments are implemented, and equivalent changes are made according to the claims of the present application, which still belong to the scope covered by the present application.​

Claims

1. An electromagnetic force calculation system for oil-immersed transformers, characterized by comprising: The method comprises the following steps: The computing model of the electromagnetic force in the transformer is established, and the computing model is a corresponding relationship between the electromagnetic force F1 and the vibration velocity V(x) of the transformer shell surface: The Y 12 is the transfer admittance from a first position to a second position of the transformer housing, the Y 22 is the input point admittance of the transformer housing at the second position, the Y 1x is the transfer admittance from the first position to a point x, the Y 2x is the transfer admittance from the second position to the point x, the Y2 is the effective line admittance of the reinforcing rib in the transformer, the first position is the force point of the transformer housing subjected to the electromagnetic force F1, and the second position is the connection between the transformer housing and the reinforcing rib. a computing module for calculating said Y 12 , said Y 22 and said Y2in said calculation model according to product parameters of said transformer. The measured data acquisition module is used for collecting the vibration signal at the x point and the position data of the x point; the calculation module is further used for obtaining the vibration velocity V(x) of the transformer shell surface at the x point according to the vibration signal; and is further used for calculating the Y 1x and the Y 2x ; and is further used for calculating the electromagnetic force F1 according to the calculation model.

2. The oil-immersed transformer electromagnetic force calculation system according to claim 1, characterized by, The computing model is derived by the computing model establishing module: The vibration velocity of the transformer shell at the second position is V2, V2 = F1Y 12 + F2Y 22 F2 is the reaction force of the reinforcing rib to the transformer shell, F1Y 12 is the vibration response under the action of F1, F2Y 22 is the vibration response at the second position under the action of F2; The vibration velocity of the reinforcing rib at the second position is V2', V2'=F2'Y2 The F2' is the force that the reinforcing rib is subjected to by the transformer shell; The F2' is equal in size and opposite in direction to the F2, and the V2' is equal to the V2, F2=-F2' V2=V2' The equation relationship between the F2 and the F1 is derived, The vibration velocity formula of the x point on the transformer shell is, V(x) = F1Y 1x +F2Y 2x The equation relationship between the V(x) and the F1 is derived by bringing the equation relationship between the F2 and the F1 into the vibration velocity formula of the x point, Thus, the computing model of the electromagnetic force F1 is derived, 3. The electromagnetic force calculation system of the oil immersed transformer according to claim 1, wherein, The computing module is further used to, The Y is calculated 12 , The Y is calculated 22 , Calculate the Y2, L is the height of the transformer housing, a is the length width of the transformer housing, h is the thickness of the transformer housing, p is the density of the transformer housing material, w mn is the natural frequency of the transformer, e m is a frequency function, s n is the elastic modulus, l 12 is the horizontal distance between the first position and the second position, the horizontal distance being the coordinate difference of two end points in the X-axis direction, B B is the bending stiffness of the reinforcing rib, k B is the radial stiffness of the reinforcing rib, B is the stiffness of the transformer, the coefficient l mn is, The k m is, k m = mπ / a The k n is, k n = nπ / a The omega mn is, 4. The electromagnetic force calculation system of the oil immersed transformer according to claim 3, wherein, The computing module is further used to, The Y is calculated 1x , The Y is calculated 2x , The l 1x is the horizontal distance between the first position and the x point, the l 2x is the horizontal distance between the second position and the x point.

5. A method of calculating electromagnetic force of an oil-immersed transformer, characterized by, The method comprises the following steps: The computing model of the electromagnetic force in the transformer is established, and the computing model is a corresponding relationship between the electromagnetic force F1 and the vibration velocity V(x) of the transformer shell surface: Y1 12 Y1 22 Y1 1x Y1 2x Y1 calculating the Y1, the Y2 and the Y3 in the calculation model according to the product parameters of the transformer 12 , the Y1 22 and the Y2; collecting the vibration signal at the x point and the position data of the x point; The vibration velocity V(x) of the transformer shell surface at the x point is obtained according to the vibration signal; According to the position data of the x point, the Y 1x and the Y 2x ; The electromagnetic force F1 is calculated according to the computing model.

6. The electromagnetic force calculation method of an oil-immersed transformer according to claim 5, characterized by, The computing model of the electromagnetic force in the transformer comprises the following steps: The vibration velocity of the transformer shell at the second position is V2, V2 = F1Y 12 + F2Y 22 F2 is the reaction force of the reinforcing rib to the transformer shell, F1Y 12 is the vibration response under the action of F1, F2Y 22 is the vibration response at the second position under the action of F2; The vibration velocity of the reinforcing rib at the second position is V2', V2'=F2'Y2 The F2' is the force that the reinforcing rib is subjected to by the transformer shell; The F2' is equal in size and opposite in direction to the F2, and the V2' is equal to the V2, F2=-F2' V2=V2' The equation relationship between the F2 and the F1 is derived, The vibration velocity formula of the x point on the transformer shell is, V(x) = F1Y 1x +F2Y 2x The equation relationship between the V(x) and the F1 is derived by bringing the equation relationship between the F2 and the F1 into the vibration velocity formula of the x point, Thus, the computing model of the electromagnetic force F1 is derived, 7. The electromagnetic force calculation method of an oil-immersed transformer according to claim 6, characterized by, calculating the Y 12 , the Y 22 , and the Y2 in the calculation model according to the product parameters of the transformer include: calculating the Y 12 , The Y is calculated 22 , Calculate the Y2, L is the height of the transformer housing, a is the length width of the transformer housing, h is the thickness of the transformer housing, p is the density of the transformer housing material, w mn is the natural frequency of the transformer, η m is a frequency function, e n is the elastic modulus, l 12 is the horizontal distance between the first position and the second position, the horizontal distance being the coordinate difference of two end points in the X-axis direction, B B is the bending stiffness of the reinforcing rib, k B is the radial stiffness of the reinforcing rib, B is the stiffness of the transformer, the coefficient l mn is, The k m is, k m = mπ / a The k n is, k n = nπ / a The omega mn is, 8. The electromagnetic force calculation method of an oil-immersed transformer according to claim 7, characterized by, calculating the Y 1x and the Y 2x comprising: The Y is calculated 1x , The Y is calculated 2x , The l 1x is the horizontal distance between the first position and the x point, the l 2x is the horizontal distance between the second position and the x point.

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