Methods and apparatus for calculating losses in power transformers

Abstract

This application relates to a method and apparatus for calculating the losses of a power transformer. The method includes: obtaining the current deviation rate corresponding to each coil conductor branch by passing a test current through the power transformer; and obtaining the theoretical current value and actual current value flowing through the coil conductor branch according to the number of coil conductor branches and the current deviation rate when the rated current is passed through the power transformer; obtaining the target temperature difference corresponding to the coil conductor branch based on the actual current value, the theoretical current value and the corresponding structural parameters of the power transformer; and obtaining the loss increment corresponding to the coil conductor branch according to the target temperature difference, the actual current value and the structural parameters. This method can improve the accuracy of power transformer loss calculation.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a method and apparatus for calculating the losses of a power transformer. Background Technology

[0002] Power transformers are crucial equipment in power grids. They transmit electricity by changing voltage and current through electromagnetic induction. During operation, power transformers exhibit complex leakage flux distribution in their windings. This leakage flux generates eddy current losses in the conductors, potentially leading to overheating faults. Therefore, calculating power transformer losses is necessary for proper planning and to prevent excessive eddy current losses from causing malfunctions. However, current methods for calculating power transformer losses suffer from inaccuracies. Summary of the Invention

[0003] Therefore, it is necessary to provide a method and apparatus for calculating the losses of power transformers that can improve the accuracy of loss calculation for power transformers, in order to address the above-mentioned technical problems.

[0004] Firstly, this application provides a method for calculating the losses of a power transformer, the method comprising:

[0005] Obtain the first total current value corresponding to the power transformer under the test current, as well as the current test value of each coil conductor branch in the power transformer; based on the first total current value and the number of coil conductor branches, obtain the average current value, and determine the current deviation rate based on the average current value and the current test value.

[0006] Based on the number of coil wire branches, obtain the theoretical current value flowing through the coil wire branches under the rated current, and determine the actual current value flowing through the coil wire branches under the rated current based on the current deviation rate and the theoretical current value; wherein, the rated current is greater than or equal to the test current.

[0007] Based on the actual current value, the theoretical current value, and the structural parameters of the power transformer, the target temperature difference corresponding to the coil conductor branch is obtained; whereby the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch.

[0008] Based on the target temperature difference, actual current value, and structural parameters, the loss increment corresponding to the coil conductor branch is obtained.

[0009] In one embodiment, the theoretical current value flowing through the coil wire branches under rated current is obtained based on the number of branches corresponding to the coil wire branches, including:

[0010] Obtain the second total current value corresponding to the power transformer under the rated current, and obtain the theoretical current value based on the second total current value and the number of coil wire branches;

[0011] Based on the current deviation rate and the theoretical current value, the actual current value flowing through the coil conductor branch under the rated current is determined, including:

[0012] The actual current value is obtained by multiplying the current deviation rate and the theoretical current value.

[0013] In one embodiment, the target temperature difference corresponding to the coil conductor branch is obtained based on the actual current value, the theoretical current value, and the structural parameters corresponding to the power transformer, including:

[0014] The first temperature rise value is obtained based on the actual current value and structural parameters. The first temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven.

[0015] The second temperature rise value is obtained based on the theoretical current value and structural parameters. The second temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced.

[0016] The difference between the first temperature rise and the second temperature rise is taken as the target temperature difference.

[0017] In one embodiment, the structural parameters include structural information of the windings within the coil conductor branches and the dimensions of the oil passages within the power transformer;

[0018] The first temperature rise value is obtained based on the actual current value and structural parameters, including:

[0019] Based on the preset temperature coefficient and the actual current value, the first load loss of the coil conductor branch is obtained. Based on the first load loss and the structural information of the winding inside the coil conductor branch, the first load information of the surface of the winding inside the coil conductor branch is obtained. Based on the first load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer, the first temperature rise value is determined.

[0020] The second temperature rise value is obtained based on the theoretical current value and structural parameters, including:

[0021] Based on the preset temperature coefficient and theoretical current value, the second load loss of the coil conductor branch is obtained. Based on the second load loss and the structural information of the winding inside the coil conductor branch, the second load information of the surface of the winding inside the coil conductor branch is obtained. Based on the second load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer, the second temperature rise value is determined.

[0022] In one embodiment, the structural parameters include the resistance change rate of the conductors within the coil conductor branch, the length of the conductors within the coil conductor branch, and the cross-sectional area of ​​the conductors within the coil conductor branch. The resistance change rate is used to characterize the relationship between the resistivity of the conductors within the coil conductor branch and the ambient temperature.

[0023] Based on the target temperature difference, actual current value, and structural parameters, the loss increment corresponding to the coil conductor branch is obtained, including:

[0024] The target resistivity is determined based on the rate of change of resistance and the target temperature difference;

[0025] Based on the target resistivity, the actual current value, the length of the conductor within the coil conductor branch, and the cross-sectional area of ​​the conductor within the coil conductor branch, the loss increment corresponding to the coil conductor branch is obtained.

[0026] In one embodiment, the loss increment ΔP is obtained based on the following formula:

[0027]

[0028] Among them, I' expi The actual current value is Δρ; the target resistivity is L. i S represents the length of the conductor within the coil conductor branch; i This represents the cross-sectional area of ​​the conductor within the coil conductor branch.

[0029] In one embodiment, the current deviation rate α is obtained based on the following formula:

[0030] α = (I exp / I avr )*100%

[0031] Among them, I exp This is the current test value; I avr This represents the average current value.

[0032] Secondly, this application also provides a power transformer loss calculation device, the device comprising:

[0033] The deviation acquisition module is used to acquire the first total current value of the power transformer under the test current, as well as the current test value of each coil conductor branch flowing through the power transformer; based on the first total current value and the number of coil conductor branches, the average current value is obtained, and the current deviation rate is determined based on the average current value and the current test value.

[0034] The current determination module is used to obtain the theoretical current value flowing through the coil wire branches under the rated current based on the number of corresponding coil wire branches, and to determine the actual current value flowing through the coil wire branches under the rated current based on the current deviation rate and the theoretical current value; wherein, the rated current is greater than or equal to the test current;

[0035] The temperature difference acquisition module is used to obtain the target temperature difference of the coil conductor branch based on the actual current value, the theoretical current value, and the structural parameters of the power transformer; wherein, the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch;

[0036] The loss acquisition module is used to obtain the loss increment corresponding to the coil wire branch based on the target temperature difference, actual current value and structural parameters.

[0037] Thirdly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the above-described method.

[0038] Fourthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0039] The aforementioned method and apparatus for calculating the losses of a power transformer obtains the current deviation rate corresponding to each coil conductor branch by passing a test current through the power transformer. When the rated current is passed through the power transformer, the theoretical and actual current values ​​flowing through each coil conductor branch are obtained based on the number of coil conductor branches and the current deviation rate. Based on the actual current value, the theoretical current value, and the structural parameters of the power transformer, the target temperature difference corresponding to each coil conductor branch is obtained. Based on the target temperature difference, the actual current value, and the structural parameters, the loss increment corresponding to each coil conductor branch is obtained. This application obtains the current deviation rate of each coil conductor branch by testing the power transformer, and then determines the temperature change value caused by uneven current distribution in each coil conductor branch based on the current deviation rate and the structural parameters of the power transformer. Based on this temperature change value, the quantitative calculation of the loss increment corresponding to each coil conductor branch is achieved, improving the accuracy of the power transformer loss calculation. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the structure of a power transformer in one embodiment;

[0042] Figure 2 This is a flowchart illustrating a method for calculating the losses of a power transformer in one embodiment.

[0043] Figure 3 This is a flowchart illustrating the loss calculation method for a power transformer in another embodiment;

[0044] Figure 4 This is a structural block diagram of a power transformer loss calculation device in one embodiment;

[0045] Figure 5 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0046] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0048] It is understood that the terms "first," "second," etc., used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first adapter plate may be referred to as a second adapter plate, and similarly, a second adapter plate may be referred to as a first adapter plate. Both the first adapter plate and the second adapter plate are adapter plates, but they are not the same adapter plate.

[0049] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0050] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0051] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0052] Currently, when designing power transformers, it is usually necessary to use conductors with smaller radial thickness and axial height in parallel. This is to control the amount of eddy current loss in the conductors while controlling the current density, so as to avoid transformer failure caused by excessive eddy current loss. For example, flat conductors, composite conductors, or continuously transposed conductors are used in parallel.

[0053] Because the leakage flux distribution along the winding is different and the number of transpositions of the conductors is limited, transposition cannot completely solve the problem of uneven current distribution. It is necessary to test during the manufacturing process of power transformers to evaluate the loss increment caused by uneven current distribution, so as to provide a basis for the operation of power transformers and power planning, and avoid power transformer failures caused by overheating, excessive short-circuit force in some conductors, etc. However, the existing calculation of power transformer losses has the problem of low accuracy.

[0054] The power transformer loss calculation method provided in this application embodiment can be applied to computer equipment. For example, Figure 1 A schematic diagram of the structure of a power transformer is provided, such as... Figure 1 The primary side of the power transformer shown includes N parallel conductor branches and current sources (N is any integer greater than 1), and the secondary side of the power transformer includes n parallel conductor branches (n is any integer greater than 1). Each conductor branch is connected in series with a current sensor to measure the current value corresponding to each conductor branch. In this embodiment, each conductor branch in the primary side and each conductor branch in the secondary side of the power transformer are collectively referred to as a coil conductor branch. A computer device can be connected to each current sensor and current source to obtain the first total current value of the power transformer under the test current, as well as the current test value flowing through each coil conductor branch within the power transformer. This allows for the acquisition of the current deviation rate of each coil conductor branch within the power transformer. Based on the number of coil conductor branches and the current deviation rate, the theoretical current value and the actual current value flowing through each coil conductor branch are obtained. Based on the actual current value, the theoretical current value, and the structural parameters of the power transformer, the target temperature difference corresponding to the coil conductor branch is obtained. Finally, based on the target temperature difference, the actual current value, and the structural parameters, the loss increment corresponding to the coil conductor branch is obtained.

[0055] It should be noted that, Figure 1 The power transformer core shown is fully assembled. The power transformer coils have been wound and assembled to the core. The coil conductor branches that need to be tested and evaluated have been separated at both ends of the coil, and each coil conductor branch has taken the winding and wound the conductor branch.

[0056] In one exemplary embodiment, such as Figure 2 As shown, a method for calculating the losses of a power transformer is provided. Taking the application of this method to computer equipment as an example, the method includes:

[0057] S202, obtain the first total current value corresponding to the power transformer under the test current, and the current test value of each coil wire branch flowing through the power transformer; based on the first total current value and the number of coil wire branches, obtain the average current value, and determine the current deviation rate based on the average current value and the current test value.

[0058] The test current can be set according to the actual situation. In this embodiment, the test current is an AC current of not less than 10% of the rated current. It should be noted that the rated current can be set according to the operating parameters of the power transformer, and is not limited in this embodiment.

[0059] It should be noted that in this embodiment of the application, the primary side of the power transformer is hereinafter referred to as the primary side, and the secondary side of the power transformer is hereinafter referred to as the secondary side.

[0060] Specifically, the computer equipment can apply a test current as a current source to the primary side and record the current test value I of each conductor branch on the primary side. expi (i represents the i-th wire branch on the primary side), the measured current value I of each wire branch on the secondary side. expk (k represents the kth branch of the secondary conductor), primary current source current value I s The total current value I on the secondary side sum .

[0061] It should be noted that the first total current value corresponding to the power transformer includes the primary current source current value I. s The total current value I on the secondary side sum The measured current values ​​flowing through each coil conductor branch within the power transformer include the measured current values ​​I flowing through each conductor branch on the primary side. expi and the measured current I flowing through each branch of the secondary conductor. expk .

[0062] Computer equipment based on the primary current source current value I s The total current value I on the secondary side sumCalculate the theoretical average current value I for each primary side conductor branch, given the number N of primary side conductor branches and the number n of secondary side conductor branches. avr1 The theoretical average current value I of each conductor branch on the secondary side avr2 As shown in equations (1) and (2) below:

[0063] (1)

[0064] (2)

[0065] The computer equipment uses the theoretical average current value I of each conductor branch on the primary side as a basis. avr1 The theoretical average current value I of each conductor branch on the secondary side avr2 The measured current value I of each branch of the primary conductor. expi The measured current value I of each conductor branch on the secondary side expk Calculate the current deviation rate for each coil conductor branch.

[0066] S204. Based on the number of coil wire branches, obtain the theoretical current value flowing through the coil wire branches under the rated current, and determine the actual current value flowing through the coil wire branches under the rated current based on the current deviation rate and the theoretical current value; wherein, the rated current is greater than or equal to the test current.

[0067] Specifically, the computer equipment obtains the rated total current of the primary side and the rated total current of the secondary side under the rated current, and determines the theoretical current value I' flowing through each branch of the primary side conductor under the condition of balanced current distribution based on the number N of the primary side conductor branches and the number n of the secondary side conductor branches. avr1 and the theoretical current value I' flowing through each branch of the secondary conductor. avr2 The computer equipment determines the actual current value I' of each branch conductor on the primary side based on the current deviation rate and the theoretical current value. expi The actual current value I' of each branch conductor on the secondary side expk .

[0068] S206, based on the actual current value, the theoretical current value and the structural parameters of the power transformer, obtains the target temperature difference corresponding to the coil conductor branch; wherein, the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch.

[0069] Specifically, since the current flowing through the coil wire branches will cause the surface temperature of each coil wire branch to rise, the computer equipment obtains the surface temperature rise (target temperature difference) of each coil wire branch when the current distribution is uneven by using the actual current value, theoretical current value and structural parameters of the power transformer corresponding to each coil wire branch.

[0070] S208, based on the target temperature difference, actual current value and structural parameters, obtains the loss increment corresponding to the coil conductor branch.

[0071] Specifically, during operation, current flows through the windings of a power transformer, generating load losses, including DC resistance losses of the conductors, eddy current losses in the conductors and structural components caused by leakage magnetic fields, additional losses caused by leakage magnetic fields in the core laminations, and unbalanced current losses in parallel conductors caused by leakage magnetic fields. Among these, DC resistance losses of the windings and leads constitute the main part of the load losses. The computer equipment determines the resistivity change value corresponding to the coil conductor branch based on the target temperature difference, and obtains the loss increment corresponding to that coil conductor branch based on the resistivity change value, the corresponding actual current value, and structural parameters, so as to provide a basis for the operation of the power transformer and power planning.

[0072] In the above-mentioned method for calculating the loss of a power transformer, the current deviation rate of each coil conductor branch within the power transformer is obtained by testing the power transformer. Then, based on the current deviation rate and the corresponding structural parameters of the power transformer, the temperature change value caused by the uneven current distribution of each coil conductor branch is determined. Based on this temperature change value, the quantitative calculation of the loss increment corresponding to the coil conductor branch is realized, thereby improving the accuracy of the loss calculation of the power transformer.

[0073] In one embodiment, the current deviation rate α is obtained based on the following equation (3):

[0074] α = (I exp / I avr )*100% (3)

[0075] Among them, I exp This is the current test value; I avr This represents the average current value.

[0076] Specifically, the current test values ​​include the current test values ​​I of each conductor branch on the primary side. expi The measured current value I of each conductor branch on the secondary side expk The average current value includes the theoretical average current value I of each conductor branch on the primary side. avr1 The theoretical average current value I of each conductor branch on the secondary side avr2 Based on the above formula (3), the deviation rate α of each conductor branch on the primary side is obtained respectively. i And the deviation rate α of each conductor branch on the secondary side. k , where i represents the i-th wire branch of the primary side, and k represents the k-th wire branch of the secondary side.

[0077] In one embodiment, the theoretical current value flowing through the coil wire branches under rated current is obtained based on the number of branches corresponding to the coil wire branches, including:

[0078] Obtain the second total current value corresponding to the power transformer under the rated current, and obtain the theoretical current value based on the second total current value and the number of coil wire branches;

[0079] Based on the current deviation rate and the theoretical current value, the actual current value flowing through the coil conductor branch under the rated current is determined, including:

[0080] The actual current value is obtained by multiplying the current deviation rate and the theoretical current value.

[0081] It should be noted that the second total current value corresponding to the power transformer includes the primary side rated total current value I. rated1 and secondary side rated total current value I rated2 The theoretical current value includes the theoretical current value I' of the primary conductor branch. avr1 The theoretical current value I' of the secondary conductor branch avr2 The actual current value includes the actual current value I' of the primary conductor branch. expk The actual current value I' of the secondary conductor branch expi .

[0082] Specifically, computer equipment is based on the primary side rated total current value I rated1 Secondary side rated total current value I rated2 The theoretical current value I' of the primary side conductor branches is obtained by calculating the number N of primary side conductor branches and the number n of secondary side conductor branches. avr1 The theoretical current value I' of the secondary conductor branch avr2 The specific calculation methods are shown in equations (4) and (5) below:

[0083] (4)

[0084] (5)

[0085] The deviation rate α of each wire branch on the primary side i The theoretical current value I' of the primary side conductor branch avr1 The product of these two values ​​is used as the actual current value I' of the primary side conductor branch. expk The deviation rate α of each conductor branch on the secondary side k The theoretical current value I' of the secondary conductor branch avr2 The theoretical current value I' as a branch of the secondary conductor avr2 .

[0086] In this embodiment, the theoretical current value is obtained based on the second total current value and the number of coil wire branches, and the actual current value flowing through the coil wire branches under the rated current is determined based on the current deviation rate and the theoretical current value, which facilitates the subsequent acquisition of the temperature change value of the coil wire branches caused by uneven current distribution.

[0087] In one embodiment, the target temperature difference corresponding to the coil conductor branch is obtained based on the actual current value, the theoretical current value, and the structural parameters corresponding to the power transformer, including:

[0088] The first temperature rise value is obtained based on the actual current value and structural parameters. The first temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven.

[0089] The second temperature rise value is obtained based on the theoretical current value and structural parameters. The second temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced.

[0090] The difference between the first temperature rise and the second temperature rise is taken as the target temperature difference.

[0091] Specifically, the power transformer contains oil, and the computer equipment can obtain the temperature of the oil through a temperature sensor. The computer equipment obtains the first temperature rise value and the second temperature rise value according to the following formula (6):

[0092] (6)

[0093] Where τ can represent the first temperature rise or the second temperature rise; µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the condition of the cooled surface, the size of the oil passage, and the oil flow rate, respectively, and are not limited in the embodiments of this application; q is the unit heat load on the winding surface, in W / m 2 .

[0094] For example, the temperature rise of the layered winding (inner and outer windings) can be obtained from the following equations (7) and (8), wherein the power transformer corresponding to equation (7) has interlayer longitudinal oil channels, and the power transformer corresponding to equation (8) does not have interlayer longitudinal oil channels:

[0095] (7)

[0096] (8)

[0097] The methods for obtaining the temperature rise values ​​for other types of windings are not described in the embodiments of this application.

[0098] The computer equipment uses the difference between the first and second temperature rise values ​​as the target temperature difference.

[0099] In this embodiment, by obtaining the first temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven, and the second temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced, the target temperature difference is determined, which facilitates the subsequent quantitative calculation of the loss increment corresponding to the coil wire branch and improves the accuracy of the loss calculation of the power transformer.

[0100] In one embodiment, the structural parameters include structural information of the windings within the coil conductor branches and the dimensions of the oil passages within the power transformer;

[0101] The first temperature rise value is obtained based on the actual current value and structural parameters, including:

[0102] Based on the preset temperature coefficient and the actual current value, the first load loss of the coil conductor branch is obtained. Based on the first load loss and the structural information of the winding inside the coil conductor branch, the first load information of the surface of the winding inside the coil conductor branch is obtained. Based on the first load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer, the first temperature rise value is determined.

[0103] The second temperature rise value is obtained based on the theoretical current value and structural parameters, including:

[0104] Based on the preset temperature coefficient and theoretical current value, the second load loss of the coil conductor branch is obtained. Based on the second load loss and the structural information of the winding inside the coil conductor branch, the second load information of the surface of the winding inside the coil conductor branch is obtained. Based on the second load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer, the second temperature rise value is determined.

[0105] The preset temperature coefficient can be set according to the actual situation, and is not limited in this embodiment. The preset temperature coefficient is the same for the same conductor at the same temperature.

[0106] Specifically, the corresponding preset temperature coefficient is selected based on the current temperature. Taking a current temperature of 75℃ as an example, the first load loss / second load loss corresponding to the primary / secondary conductor branch is obtained according to the following formula (9):

[0107] (9)

[0108] Where m is the preset temperature coefficient; when P fz Let P represent the first load loss, and I' represent the actual current value; when P fz Let I' represent the second load loss, and let I' represent the theoretical current value.

[0109] The structural information of the winding inside the coil conductor branch includes the effective heat dissipation area S of the winding (set according to the actual situation). The computer equipment obtains the first load information q1 (unit heat load on the surface of the winding) of the winding inside the coil conductor branch based on the first load loss and the effective heat dissipation area S of the winding and the following formula (10):

[0110] (10)

[0111] Based on the first load information, the structural information of the windings within the coil conductor branches, and the oil passage dimensions within the power transformer, the computer equipment determines the first temperature rise value τ. i By combining equations (6), (9), and (10) above, we can obtain the temperature rise value (first temperature rise value) τ corresponding to the temperature of the i-th coil conductor branch exceeding the oil temperature inside the power transformer when the current distribution is uneven. i As shown in equation (11):

[0112] (11)

[0113] Where µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the condition of the cooled surface, the size of the oil passage, and the oil flow rate, respectively, and are not limited in the embodiments of this application; S is the effective heat dissipation area of ​​the winding; I' expi The actual current value flowing through each branch conductor of the primary side is given. It should be noted that the first temperature rise value corresponding to the branch conductor of the secondary side can also be obtained according to the above formula (11), the difference being that the actual current value is switched to the actual current value I' flowing through each branch conductor of the secondary side. expk .

[0114] Similarly, based on the second load information, the structural information of the windings within the coil conductor branches, and the oil passage dimensions within the power transformer, the computer equipment determines the second temperature rise value τ. avr1 By combining equations (6), (9), and (10) above, we can obtain the temperature rise value (second temperature rise value) τ corresponding to the temperature of the i-th coil conductor branch exceeding the oil temperature inside the power transformer when the current distribution is balanced. avr1 As shown in equation (12):

[0115] (12)

[0116] Where µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the condition of the cooled surface, the size of the oil passage, and the oil flow rate, respectively, and are not limited in the embodiments of this application; S is the effective heat dissipation area of ​​the winding; I' avr1This represents the theoretical current value flowing through each branch of the primary conductor; it should be noted that the first temperature rise value corresponding to the branch of the secondary conductor can also be obtained according to the above formula (11), the difference being that the theoretical current value is switched to the theoretical current value I' flowing through each branch of the secondary conductor. avr2 .

[0117] For example, by referring to equations (11) and (12) above, the temperature rise (target temperature difference) Δτ of the i-th coil branch conductor on the primary side caused by uneven current distribution is obtained by equation (13) below:

[0118] (13)

[0119] It should be noted that the meanings of each letter in equation (13) are the same as those in equations (11) and (12), and will not be repeated here.

[0120] In one embodiment, the structural parameters include the resistance change rate of the conductors within the coil conductor branch, the length of the conductors within the coil conductor branch, and the cross-sectional area of ​​the conductors within the coil conductor branch. The resistance change rate is used to characterize the relationship between the resistivity of the conductors within the coil conductor branch and the ambient temperature.

[0121] Based on the target temperature difference, actual current value, and structural parameters, the loss increment corresponding to the coil conductor branch is obtained, including:

[0122] The target resistivity is determined based on the rate of change of resistance and the target temperature difference;

[0123] Based on the target resistivity, the actual current value, the length of the conductor within the coil conductor branch, and the cross-sectional area of ​​the conductor within the coil conductor branch, the loss increment corresponding to the coil conductor branch is obtained.

[0124] It should be noted that the resistivity of the copper conductor changes with temperature, ρ(T), as shown in equation (14):

[0125] (14)

[0126] Where T0 is the reference temperature, taken as 20℃ for example; ρ0 is the resistivity of the conductor at the reference temperature; β is a physical quantity describing the rate of change of resistivity with temperature, with a temperature coefficient of 0.0039℃. -1 T represents the ambient temperature of the copper conductor.

[0127] Specifically, the computer equipment determines the target resistivity Δρ based on the resistance change rate β and the target temperature difference Δτ, as shown in the following formula (15):

[0128] (15)

[0129] The computer equipment obtains the loss increment corresponding to the coil wire branch based on the target resistivity, the actual current value, the length of the wire in the coil wire branch, and the cross-sectional area of ​​the wire in the coil wire branch.

[0130] In one embodiment, the loss increment ΔP is obtained based on the following equation (16):

[0131] (16)

[0132] Among them, I' expi The actual current value is Δρ; the target resistivity is L. i S represents the length of the conductor within the coil conductor branch; i This represents the cross-sectional area of ​​the conductor within the coil conductor branch.

[0133] Specifically, in connection with the above equations (13), (15) and (16), the loss increment ΔP corresponding to each coil wire branch is shown in equation (17) below:

[0134] (17)

[0135] Where µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the condition of the cooled surface, the size of the oil passage, and the oil flow rate, respectively, and are not limited in the embodiments of this application; S is the effective heat dissipation area of ​​the winding; I' avr1 β is the theoretical current value (flowing through each branch of the primary conductor); m is the rate of change of resistance; I' is the preset temperature coefficient; expi L represents the actual current value (flowing through each branch conductor of the primary side); i S represents the length of the conductor within the coil conductor branch; i This represents the cross-sectional area of ​​the conductor within the coil conductor branch.

[0136] To facilitate understanding by those skilled in the art, the following example illustrates the method for calculating the losses of power transformers. Figure 3 As shown, the power transformer is simply referred to as a transformer:

[0137] Before testing, the transformer product is in a state of readiness for testing. That is, the transformer core has been fully assembled, the coils of the power transformer have been wound and assembled into the core, and the coil conductor branches that need to be tested and evaluated have been separated at both ends of the coil, and each coil conductor branch has taken the winding and wound the conductor branch.

[0138] The computer equipment applies a small current (test current) to the primary side of the transformer and measures the current values ​​of each conductor branch on the primary and secondary sides, the current value of the primary current source, and the total current value on the secondary side. Based on the current values ​​of the primary current source and the total current value on the secondary side, the theoretical average current value of each conductor branch under the small current is calculated.

[0139] Compare the measured current (current test value) with the actual current and calculate the current deviation rate of each branch on the primary and secondary sides respectively.

[0140] Calculate the current distribution values ​​(actual current value and theoretical current value) of each branch of the winding under 100% rated current by the current deviation rate.

[0141] Calculate the surface temperature rise (target temperature difference) of the winding caused by current imbalance in each branch of the winding.

[0142] Calculate the resistivity change (target resistivity) caused by the temperature rise of each branch conductor of the winding.

[0143] Calculate the change in DC resistance loss of the conductor caused by the change in resistivity, and obtain the incremental value of the load loss of each parallel branch (the loss increment corresponding to the coil conductor branch).

[0144] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0145] Based on the same inventive concept, this application also provides a power transformer loss calculation device for implementing the power transformer loss calculation method described above. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations of one or more power transformer loss calculation device embodiments provided below can be found in the limitations of the power transformer loss calculation method described above, and will not be repeated here.

[0146] In one exemplary embodiment, such as Figure 4 As shown, a power transformer loss calculation device 400 is provided. The device 400 includes:

[0147] The deviation acquisition module 401 is used to acquire the first total current value corresponding to the power transformer under the test current, and the current test value of each coil conductor branch flowing through the power transformer; based on the first total current value and the number of coil conductor branches, the average current value is obtained, and the current deviation rate is determined based on the average current value and the current test value.

[0148] The current determination module 402 is used to obtain the theoretical current value flowing through the coil wire branch under the rated current according to the number of coil wire branches, and to determine the actual current value flowing through the coil wire branch under the rated current based on the current deviation rate and the theoretical current value; wherein the rated current is greater than or equal to the test current.

[0149] The temperature difference acquisition module 403 is used to obtain the target temperature difference corresponding to the coil conductor branch based on the actual current value, the theoretical current value and the structural parameters corresponding to the power transformer; wherein, the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch;

[0150] The loss acquisition module 404 is used to obtain the loss increment corresponding to the coil wire branch based on the target temperature difference, actual current value and structural parameters.

[0151] In one embodiment, the current determination module 402 is further configured to obtain the second total current value corresponding to the power transformer under the rated current, and obtain the theoretical current value based on the second total current value and the number of coil wire branches.

[0152] The current determination module 402 is also used to take the product of the current deviation rate and the theoretical current value as the actual current value.

[0153] In one embodiment, the temperature difference acquisition module 403 is further configured to obtain a first temperature rise value based on the actual current value and structural parameters. The first temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven.

[0154] The second temperature rise value is obtained based on the theoretical current value and structural parameters. The second temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced.

[0155] The difference between the first temperature rise and the second temperature rise is taken as the target temperature difference.

[0156] In one embodiment, the structural parameters include structural information of the windings within the coil conductor branches and the dimensions of the oil passages within the power transformer;

[0157] The temperature difference acquisition module 403 is also used to obtain the first load loss of the coil conductor branch according to the preset temperature coefficient and the actual current value, obtain the first load information of the surface of the winding inside the coil conductor branch according to the first load loss and the structural information of the winding inside the coil conductor branch, and determine the first temperature rise value based on the first load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer.

[0158] The temperature difference acquisition module 403 is also used to obtain the second load loss of the coil conductor branch according to the preset temperature coefficient and theoretical current value, obtain the second load information of the surface of the winding inside the coil conductor branch according to the second load loss and the structural information of the winding inside the coil conductor branch, and determine the second temperature rise value based on the second load information, the structural information of the winding inside the coil conductor branch and the oil passage size in the power transformer.

[0159] In one embodiment, the structural parameters include the resistance change rate of the conductors within the coil conductor branch, the length of the conductors within the coil conductor branch, and the cross-sectional area of ​​the conductors within the coil conductor branch. The resistance change rate is used to characterize the relationship between the resistivity of the conductors within the coil conductor branch and the ambient temperature.

[0160] The loss acquisition module 404 is also used to determine the target resistivity based on the resistance change rate and the target temperature difference;

[0161] Based on the target resistivity, the actual current value, the length of the conductor within the coil conductor branch, and the cross-sectional area of ​​the conductor within the coil conductor branch, the loss increment corresponding to the coil conductor branch is obtained.

[0162] In one embodiment, the loss increment ΔP is obtained based on the following formula:

[0163]

[0164] Among them, I' expi The actual current value is Δρ; the target resistivity is L. i S represents the length of the conductor within the coil conductor branch; i This represents the cross-sectional area of ​​the conductor within the coil conductor branch.

[0165] In one embodiment, the current deviation rate α is obtained based on the following formula:

[0166] α = (I exp / I avr )*100%

[0167] Among them, I exp This is the current test value; I avr This represents the average current value.

[0168] Each module in the aforementioned power transformer loss calculation device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the computer device's memory as software, so that the processor can call and execute the corresponding operations of each module.

[0169] In one exemplary embodiment, a computer device is provided, which may be a server or a terminal. Taking a server as an example, its internal structure diagram can be as follows: Figure 5 As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operating system and computer programs stored in the non-volatile storage media. The database stores current data (current test values, current deviation rates, etc.). The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements a method for calculating the losses of a power transformer.

[0170] Those skilled in the art will understand that Figure 5 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0171] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the above-described method for calculating the losses of a power transformer.

[0172] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the above-described method for calculating the losses of a power transformer.

[0173] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the above-described method for calculating the losses of a power transformer.

[0174] It should be noted that the data involved in this application (including but not limited to data used for analysis, data stored, data displayed, etc.) are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0175] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0176] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0177] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for calculating the losses of a power transformer, characterized in that, The method includes: Obtain the first total current value corresponding to the power transformer under the test current, and the current test value of each coil conductor branch in the power transformer; based on the first total current value and the number of coil conductor branches, obtain the average current value, and determine the current deviation rate based on the average current value and the current test value; Based on the number of coil wire branches, the theoretical current value flowing through the coil wire branches under the rated current is obtained, and based on the current deviation rate and the theoretical current value, the actual current value flowing through the coil wire branches under the rated current is determined; wherein, the rated current is greater than or equal to the test current; Based on the actual current value, the theoretical current value, and the structural parameters corresponding to the power transformer, the target temperature difference corresponding to the coil conductor branch is obtained; wherein, the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch; Based on the target temperature difference, the actual current value, and the structural parameters, the loss increment corresponding to the coil conductor branch is obtained; The process of obtaining the target temperature difference corresponding to the coil conductor branch based on the actual current value, the theoretical current value, and the structural parameters corresponding to the power transformer includes: A first temperature rise value is obtained based on the actual current value and the structural parameters. The first temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven. A second temperature rise value is obtained based on the theoretical current value and the structural parameters. The second temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced. The difference between the first temperature rise and the second temperature rise is taken as the target temperature difference; The structural parameters include the resistance change rate of the conductors within the coil conductor branch, the length of the conductors within the coil conductor branch, and the cross-sectional area of ​​the conductors within the coil conductor branch. The resistance change rate is used to characterize the relationship between the resistivity of the conductors within the coil conductor branch and the ambient temperature. The step of obtaining the loss increment corresponding to the coil conductor branch based on the target temperature difference, the actual current value, and the structural parameters includes: The target resistivity is determined based on the resistance change rate and the target temperature difference; The loss increment corresponding to the coil wire branch is obtained based on the target resistivity, the actual current value, the length of the wire in the coil wire branch, and the cross-sectional area of ​​the wire in the coil wire branch.

2. The method according to claim 1, characterized in that, The step of obtaining the theoretical current value flowing through the coil wire branches under rated current based on the number of branches corresponding to the coil wire branches includes: Obtain the second total current value corresponding to the power transformer under the rated current, and obtain the theoretical current value based on the second total current value and the number of coil conductor branches; The determination of the actual current value flowing through the coil conductor branch under the rated current, based on the current deviation rate and the theoretical current value, includes: The actual current value is obtained by multiplying the current deviation rate and the theoretical current value.

3. The method according to claim 1, characterized in that, The structural parameters include the structural information of the windings within the coil conductor branches and the dimensions of the oil passages within the power transformer; The process of obtaining the first temperature rise value based on the actual current value and the structural parameters includes: Based on the preset temperature coefficient and the actual current value, the first load loss of the coil conductor branch is obtained. Based on the first load loss and the structural information of the winding inside the coil conductor branch, the first load information of the surface of the winding inside the coil conductor branch is obtained. Based on the first load information, the structural information of the winding inside the coil conductor branch, and the oil passage size inside the power transformer, the first temperature rise value is determined. The process of obtaining the second temperature rise value based on the theoretical current value and the structural parameters includes: Based on the preset temperature coefficient and the theoretical current value, the second load loss of the coil conductor branch is obtained. Based on the second load loss and the structural information of the winding inside the coil conductor branch, the second load information of the surface of the winding inside the coil conductor branch is obtained. Based on the second load information, the structural information of the winding inside the coil conductor branch, and the oil passage size inside the power transformer, the second temperature rise value is determined.

4. The method according to claim 1, characterized in that, The loss increment ΔP is obtained based on the following formula: Wherein, the I' expi The actual current value; Δρ is the target resistivity; L i The length of the conductor within the branch of the coil conductor; the S i This refers to the cross-sectional area of ​​the conductor within the branch of the coil conductor.

5. The method according to claim 1, characterized in that, The current deviation rate α is obtained based on the following formula: α = (I exp / I avr )*100% Wherein, the I exp The current test value; the I avr The average current value is given.

6. A loss calculation device for a power transformer, characterized in that, The device includes: The deviation acquisition module is used to acquire the first total current value corresponding to the power transformer under the test current, and the current test value of each coil conductor branch flowing through the power transformer; based on the first total current value and the number of coil conductor branches, the average current value is obtained, and the current deviation rate is determined according to the average current value and the current test value. The current determination module is used to obtain the theoretical current value flowing through the coil wire branch under the rated current according to the number of the coil wire branches, and to determine the actual current value flowing through the coil wire branch under the rated current based on the current deviation rate and the theoretical current value; wherein the rated current is greater than or equal to the test current; The temperature difference acquisition module is used to obtain the target temperature difference corresponding to the coil conductor branch based on the actual current value, the theoretical current value, and the structural parameters corresponding to the power transformer; wherein, the target temperature difference is used to characterize the temperature change value caused by the uneven current distribution of the coil conductor branch; The loss acquisition module is used to obtain the loss increment corresponding to the coil conductor branch based on the target temperature difference, the actual current value, and the structural parameters. The temperature difference acquisition module is further configured to obtain a first temperature rise value based on the actual current value and the structural parameters, wherein the first temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is uneven; obtain a second temperature rise value based on the theoretical current value and the structural parameters, wherein the second temperature rise value is used to characterize the temperature rise value corresponding to the wire temperature of the coil wire branch exceeding the oil temperature inside the power transformer when the current distribution is balanced; and use the difference between the first temperature rise value and the second temperature rise value as the target temperature difference; The structural parameters include the resistance change rate of the conductors within the coil conductor branch, the length of the conductors within the coil conductor branch, and the cross-sectional area of ​​the conductors within the coil conductor branch. The resistance change rate is used to characterize the relationship between the resistivity of the conductors within the coil conductor branch and the ambient temperature. The loss acquisition module is also used to determine the target resistivity based on the resistance change rate and the target temperature difference; The loss increment corresponding to the coil wire branch is obtained based on the target resistivity, the actual current value, the length of the wire in the coil wire branch, and the cross-sectional area of ​​the wire in the coil wire branch.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 5.

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