Loss calculation method and device for power transformer

Abstract

The invention relates to a loss calculation method and device for a power transformer. The method comprises the following steps: obtaining a current deviation ratio corresponding to each coil wire branch by introducing a test current into the power transformer, and respectively obtaining a theoretical current value and an actual current value flowing through the coil wire branches according to the corresponding number of the coil wire branches and the current deviation ratio when introducing a rated current into the power transformer, obtaining a target temperature difference corresponding to the coil wire branch based on the actual current value, the theoretical current value and a structure parameter corresponding to the power transformer, and obtaining a loss increment corresponding to the coil wire branch according to the target temperature difference, the actual current value and the structure parameter; by adopting the method, the accuracy of loss calculation of the power transformer can be improved.

Description

Technical Field

[0001] The present application relates to the field of electric power technology, and in particular to a method and device for calculating the loss of a power transformer. Background Art

[0002] Power transformers are important equipment in power grids. Their principle is to achieve changes in voltage and current through electromagnetic induction to achieve power transmission. When the power transformer is in operation, there is a complex magnetic leakage distribution in the winding area, which will generate eddy current loss in the conductor, leading to overheating failure. It is necessary to calculate the loss of the power transformer for subsequent reasonable planning, so as to avoid excessive eddy current loss leading to power transformer failure; however, the existing calculation of power transformer loss has the problem of low accuracy. Summary of the invention

[0003] Based on this, it is necessary to provide a method and device for calculating the loss of a power transformer, which can improve the accuracy of the loss calculation of the power transformer, in order to solve the above technical problems.

[0004] In a first aspect, the present application provides a method for calculating the loss of a power transformer, the method comprising:

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

[0006] According to the number of coil wire branches corresponding to the current, the theoretical current value flowing through the coil wire branches under the rated current is obtained, and according to 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;

[0007] Based on the actual current value, the theoretical current value and the structural parameters corresponding to the power transformer, a 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 coil conductor branch when the current distribution is unbalanced;

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

[0009] In one embodiment, obtaining a theoretical current value flowing through the coil wire branch under a rated current according to the number of coil wire branches includes:

[0010] Obtaining a second total current value corresponding to the power transformer at rated current, and obtaining a theoretical current value based on the second total current value and the number of coil conductor branches;

[0011] According to the current deviation rate and the theoretical current value, the actual current value flowing through the coil wire branch under the rated current is determined, including:

[0012] The product of the current deviation rate and the theoretical current value is taken as the actual current value.

[0013] In one embodiment, 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, including:

[0014] A first temperature rise value is obtained according to the actual current value and the structural parameters, and the first temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is unbalanced;

[0015] A second temperature rise value is obtained according to the theoretical current value and the structural parameters, and the second temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is balanced;

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

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

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

[0019] Obtaining a first load loss of the coil wire branch according to a preset temperature coefficient and an actual current value, obtaining first load information of a surface of a winding in the coil wire branch according to the first load loss and structural information of the winding in the coil wire branch, and determining a first temperature rise value based on the first load information, structural information of the winding in the coil wire branch, and a size of an oil passage in the power transformer;

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

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

[0022] In one embodiment, the structural parameters include a resistance change rate corresponding to the wire in the coil wire branch, a length corresponding to the wire in the coil wire branch, and a cross-sectional area corresponding to the wire in the coil wire branch, and the resistance change rate is used to characterize the relationship between the resistivity of the wire in the coil wire 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 wire branch is obtained, including:

[0024] Determine the target resistivity based on the resistance change rate and the target temperature difference;

[0025] According to the target resistivity, the actual current value, the corresponding length of the wire in the coil wire branch and the corresponding cross-sectional area of ​​the wire in the coil wire branch, the loss increment corresponding to the coil wire branch is obtained.

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

[0027]

[0028] Among them, I' expi is the actual current value; Δρ is the target resistivity; L i S is the length of the wire in the coil wire branch; i It is the cross-sectional area corresponding to the wire inside the coil wire 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 is the current test value; I avr is the average current value.

[0032] In a second aspect, the present application also provides a loss calculation device for a power transformer, the device comprising:

[0033] The deviation acquisition module is used to obtain a first total current value corresponding to the power transformer under the test current, and a current test value flowing through each coil wire branch in the power transformer; based on the first total current value and the number of coil wire branches corresponding to the first total current value, an average current value is obtained, and a current deviation rate is determined according to the average current value and the current test value;

[0034] A current determination module, used to obtain a theoretical current value flowing through the coil wire branch under a rated current according to the number of coil wire branches corresponding thereto, and determine an actual current value flowing through the coil wire branch under a rated current according to a 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 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 coil conductor branch when the current distribution is unbalanced;

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

[0037] In a third aspect, the present application further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0038] In a fourth aspect, the present application also provides a computer-readable storage medium having a computer program stored thereon, which implements the steps of the above method when the computer program is executed by a processor.

[0039] The above-mentioned loss calculation method and device of the power transformer obtain the current deviation rate corresponding to each coil wire branch by passing a test current into the power transformer, and when the rated current is passed into the power transformer, the theoretical current value and the actual current value flowing through the coil wire branch are respectively obtained according to the number and current deviation rate corresponding to the coil wire branch, and the target temperature difference corresponding to the coil wire branch is obtained based on the actual current value, the theoretical current value and the structural parameters corresponding to the power transformer, and the loss increment corresponding to the coil wire branch is obtained according to the target temperature difference, the actual current value and the structural parameters; the present application tests the power transformer to obtain the current deviation rate of each coil wire branch in the power transformer, and then determines the temperature change value caused by each coil wire branch when the current distribution is unbalanced according to the current deviation rate and the structural parameters corresponding to the power transformer, and realizes the quantitative calculation of the loss increment corresponding to the coil wire branch based on the temperature change value, thereby improving the accuracy of the loss calculation of the power transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the drawings required for use in the embodiments of the present application or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0041] FIG1 is a schematic diagram of the structure of a power transformer in one embodiment;

[0042] FIG2 is a schematic flow chart of a method for calculating the loss of a power transformer in one embodiment;

[0043] FIG3 is a schematic flow chart of a method for calculating the loss of a power transformer in another embodiment;

[0044] FIG4 is a block diagram of a loss calculation device for a power transformer in one embodiment;

[0045] FIG. 5 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0046] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this 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 a first element from another element. For example, without departing from the scope of this application, a first adapter board may be referred to as a second adapter board, and similarly, a second adapter board may be referred to as a first adapter board. Both the first adapter board and the second adapter board are adapter boards, but they are not the same adapter board.

[0049] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0050] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0051] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0052] At present, when designing power transformers, it is usually necessary to use wires with smaller radial thickness and axial height in parallel, so as to control the amount of eddy current loss of the wires while controlling the current density, so as to avoid transformer failure caused by excessive eddy current loss, for example: using flat wires, combined wires or continuously transposed wires and other types of wires in parallel.

[0053] Since the magnetic flux leakage distribution along the upper and lower parts of the winding is different and the number of transpositions of the conductor is limited, transposition cannot completely solve the problem of unbalanced current distribution. It is necessary to conduct tests during the manufacturing process of the power transformer to evaluate the incremental loss value caused by the unbalanced current distribution problem, provide a basis for the operation and power planning of the power transformer, and avoid the resulting overheating, excessive short-circuit force of some conductors and other problems that lead to power transformer failures. However, the existing calculation of the loss of the power transformer has the problem of low accuracy.

[0054] The loss calculation method of the power transformer provided in the embodiment of the present application can be applied to computer equipment. For example, FIG1 provides a schematic diagram of the structure of a power transformer. As shown in FIG1, the primary side of the power transformer includes N wire branches and a current source connected in parallel (N is an arbitrary integer greater than 1), and the secondary side of the power transformer includes n wire branches connected in parallel (n is an arbitrary integer greater than 1). A current sensor is connected in series on each wire branch to measure the current value corresponding to each wire branch. In the embodiment of the present application, each wire branch in the primary side of the power transformer and each wire branch in the secondary side of the power transformer are collectively referred to as coil wire branches; wherein, the calculation The machine equipment can be connected to each current sensor and the current source respectively, so as to obtain the first total current value corresponding to the power transformer under the test current, and the current test value flowing through each coil wire branch in the power transformer, and then obtain the current deviation rate of each coil wire branch in the power transformer, and according to the corresponding number and current deviation rate of the coil wire branches, respectively obtain the theoretical current value and the actual current value flowing through the coil wire branch, based on the actual current value, the theoretical current value and the corresponding structural parameters of the power transformer, obtain the target temperature difference corresponding to the coil wire branch, and according to the target temperature difference, the actual current value and the structural parameters, obtain the loss increment corresponding to the coil wire branch.

[0055] It should be noted that the power transformer core shown in FIG1 has been fully assembled, the coil of the power transformer has been wound and assembled to the core, the coil conductor branches to be tested and evaluated have been separated at both ends of the coil, and each coil conductor branch has a winding and is wound around the conductor branch.

[0056] In an exemplary embodiment, as shown in FIG2 , a method for calculating the loss of a power transformer is provided, and the method is described by taking the application of the method to a computer device as an example. The method includes:

[0057] S202, obtaining a first total current value corresponding to the power transformer under the test current, and a current test value flowing through each coil conductor branch in the power transformer; obtaining an average current value based on the first total current value and the number of coil conductor branches corresponding to the first total current value, and determining a current deviation rate based on the average current value and the current test value.

[0058] Among them, the test current can be set according to actual conditions. In the embodiment of the present application, the test current is an alternating current of not less than 10% of the rated current as an example for explanation. It should be noted that the rated current can be set according to the operating parameters of the power transformer, which is not limited in the embodiment of the present application.

[0059] It should be noted that in the embodiments of the present 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 device can apply a test current on the primary side as a current source and record the current test value I of each wire branch on the primary side respectively. expi (i represents the i-th wire branch of the primary side), the current test value of each wire branch of the secondary side is I expk (k represents the kth wire branch of the secondary side), the current value of the primary current source I s , the total current value of the secondary side is I 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 and the total current value of the secondary side I sum The current test value flowing through each coil wire branch in the power transformer includes the current test value I flowing through each wire branch of the primary side. expi And the current test value I flowing through each wire branch of the secondary side expk .

[0062] Computer equipment based on the primary current source current value I s , the total current value of the secondary side I sum , the number N corresponding to the primary wire branches and the number n corresponding to the secondary wire branches, and calculate the theoretical average current value I of each wire branch on the primary side respectively avr1, the theoretical average current value of each wire branch on the secondary side is I avr2 , as shown in the following equations (1) and (2):

[0063] (1)

[0064] (2)

[0065] The computer equipment obtains the theoretical average current value I of each wire branch on the primary side. avr1 , the theoretical average current value of each wire branch on the secondary side I avr2 , the current test value of each wire branch on the primary side I expi And the current test value I of each wire branch on the secondary side expk , calculate the current deviation rate corresponding to each coil wire branch respectively.

[0066] S204, obtaining the theoretical current value flowing through the coil wire branch under the rated current according to the corresponding number of coil wire branches, and determining the actual current value flowing through the coil wire branch under the rated current according to 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 device 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 wire branch of the primary side under the condition of balanced current distribution according to the number N corresponding to the primary wire branch and the number n corresponding to the secondary wire branch. avr1 and the theoretical current value I' flowing through each wire branch of the secondary side avr2 The computer equipment determines the actual current value I' of each branch conductor on the primary side according to the current deviation rate and the theoretical current value. expi and 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 corresponding to the power transformer, obtain 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 coil conductor branch when the current distribution is unbalanced.

[0069] Specifically, since the surface temperature of each coil wire branch will increase when current flows through the coil wire branches, the computer equipment obtains the surface temperature rise (target temperature difference) of each coil wire branch when the current distribution is uneven based on 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, the actual current value and the structural parameters, the loss increment corresponding to the coil conductor branch is obtained.

[0071] Specifically, when the power transformer is in operation, current passes through the winding, generating load losses, including DC resistance losses of the conductors, eddy current losses of the conductors and structural parts caused by the leakage magnetic field, additional losses caused by the leakage magnetic field in the core sheets, and unbalanced current losses caused by the leakage magnetic field in the parallel conductors. Among them, the DC resistance losses of the windings and leads are the main part of the load losses. The computer equipment determines the resistivity change value corresponding to the corresponding coil conductor branch based on the target temperature difference, and obtains the loss increment corresponding to the coil conductor branch based on the resistivity change value, the corresponding actual current value and the structural parameters, so as to provide a basis for the subsequent operation and power planning of the power transformer.

[0072] In the above-mentioned method for calculating the loss of the power transformer, the current deviation rate of each coil conductor branch in the power transformer is obtained by testing the power transformer, and then the temperature change value of each coil conductor branch caused by the unbalanced current distribution is determined based on the current deviation rate and the corresponding structural parameters of the power transformer. Based on the 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 is the current test value; I avr is the average current value.

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

[0077] In one embodiment, obtaining a theoretical current value flowing through the coil wire branch under a rated current according to the number of coil wire branches includes:

[0078] Obtaining a second total current value corresponding to the power transformer at rated current, and obtaining a theoretical current value based on the second total current value and the number of coil conductor branches;

[0079] According to the current deviation rate and the theoretical current value, the actual current value flowing through the coil wire branch under the rated current is determined, including:

[0080] The product of the current deviation rate and the theoretical current value is taken as the actual current value.

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

[0082] Specifically, the computer equipment is based on the primary rated total current value I rated1 , rated total secondary current value I rated2 , the number N corresponding to the primary wire branches and the number n corresponding to the secondary wire branches, and the theoretical current value I' of the primary wire branches is obtained avr1 and the theoretical current value I' of the secondary conductor branch avr2 , the specific calculation method is shown in the following formulas (4) and (5):

[0083] (4)

[0084] (5)

[0085] The deviation rate α of each branch of the primary wire i The theoretical current value I' of the primary conductor branch avr1 The product of is taken as the actual current value I' of the primary conductor branch expk ; Set the deviation rate α of each branch of the secondary wire k and the theoretical current value I' of the secondary conductor branch avr2 Theoretical current value I' as the secondary conductor branch avr2 .

[0086] In an embodiment of the present application, the theoretical current value is obtained based on the second total current value and the corresponding number of coil wire branches, and the actual current value flowing through the coil wire branch under the rated current is determined based on the current deviation rate and the theoretical current value, so as to facilitate the subsequent acquisition of the temperature change value of the coil wire branch caused by the uneven current distribution.

[0087] In one embodiment, 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, including:

[0088] A first temperature rise value is obtained according to the actual current value and the structural parameters, and the first temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is unbalanced;

[0089] A second temperature rise value is obtained according to the theoretical current value and the structural parameters, and the second temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is balanced;

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

[0091] Specifically, an oil body is provided in the power transformer, and the computer device can obtain the temperature of the oil body (oil temperature) through a temperature sensor. The computer device obtains the first temperature rise value and the second temperature rise value respectively according to the following formula (6):

[0092] (6)

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

[0094] Exemplarily, the temperature rise value of the layer winding (inner and outer windings) can be obtained by the following equations (7) and (8), wherein the power transformer corresponding to equation (7) has interlayer longitudinal oil passages, and the power transformer corresponding to equation (8) has no interlayer longitudinal oil passages:

[0095] (7)

[0096] (8)

[0097] The method for obtaining the temperature rise values ​​corresponding to other types of windings will not be described in detail in the embodiments of the present application.

[0098] The computer device uses the difference between the acquired first temperature rise value and the second temperature rise value as the target temperature difference.

[0099] In the embodiment of the present application, by obtaining a first temperature rise value corresponding to the oil temperature in the power transformer when the conductor temperature of the coil conductor branch exceeds the first temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is uneven, and a second temperature rise value corresponding to the oil temperature in 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 conductor branch, thereby improving the accuracy of the loss calculation of the power transformer.

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

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

[0102] Obtaining a first load loss of the coil wire branch according to a preset temperature coefficient and an actual current value, obtaining first load information of a surface of a winding in the coil wire branch according to the first load loss and structural information of the winding in the coil wire branch, and determining a first temperature rise value based on the first load information, structural information of the winding in the coil wire branch, and a size of an oil passage in the power transformer;

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

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

[0105] Among them, the preset temperature coefficient can be set according to actual conditions, and is not limited in the embodiments of the present application. The preset temperature coefficient of the same wire is the same at the same temperature.

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

[0107] (9)

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

[0109] The structural information of the winding in the coil wire branch includes the effective heat dissipation area S of the winding (set according to actual conditions). The computer device obtains the first load information q1 (unit heat load on the winding surface) of the winding surface in the coil wire branch according to the first load loss and the effective heat dissipation area S of the winding in combination with the following formula (10):

[0110] (10)

[0111] The computer device determines a first temperature rise value τ based on the first load information, the structural information of the winding in the coil wire branch and the oil channel size in the power transformer. i ; By combining the above equations (6), (9) and (10), we can obtain the value of the temperature rise (first temperature rise value) τ corresponding to the oil temperature in the power transformer when the current distribution is unbalanced. i As shown in the following formula (11):

[0112] (11)

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

[0114] Similarly, the computer device determines the second temperature rise value τ based on the second load information, the structural information of the winding in the coil wire branch and the oil channel size in the power transformer. avr1 ; By combining the above equations (6), (9) and (10), we can obtain the value when the current distribution is balanced and the conductor temperature of the i-th coil conductor branch exceeds the temperature rise value (second temperature rise value) τ corresponding to the oil temperature in the power transformer avr1 As shown in the following formula (12):

[0115] (12)

[0116] Wherein, µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the surface condition to be cooled, the oil channel size and the oil flow rate, which are not limited in the present embodiment; S is the effective heat dissipation area of ​​the winding; I' avr1is the theoretical current value flowing through each wire branch of the primary side; it should be noted that the first temperature rise value corresponding to the wire branch of the secondary side can also be obtained according to the above formula (11), the difference is that the theoretical current value is switched to the theoretical current value I' flowing through each wire branch of the secondary side avr2 .

[0117] For example, by combining the above equations (11) and (12), the temperature rise (target temperature difference) Δτ of the primary side i-th coil branch wire caused by the unbalanced current distribution is obtained as shown in the following equation (13):

[0118] (13)

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

[0120] In one embodiment, the structural parameters include a resistance change rate corresponding to the wire in the coil wire branch, a length corresponding to the wire in the coil wire branch, and a cross-sectional area corresponding to the wire in the coil wire branch, and the resistance change rate is used to characterize the relationship between the resistivity of the wire in the coil wire 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 wire branch is obtained, including:

[0122] Determine the target resistivity based on the resistance change rate and the target temperature difference;

[0123] According to the target resistivity, the actual current value, the corresponding length of the wire in the coil wire branch and the corresponding cross-sectional area of ​​the wire in the coil wire branch, the loss increment corresponding to the coil wire branch is obtained.

[0124] It should be noted that the relationship between the resistivity of copper wire and temperature ρ(T) is as shown in the following formula (14):

[0125] (14)

[0126] Among them, T 0 is the reference temperature, taking 20℃ as an example; ρ 0 is the wire resistivity at the reference temperature; β is the physical quantity describing the rate of change of resistivity with temperature, and the temperature coefficient is 0.0039℃ -1 ; T is the ambient temperature of the copper wire.

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

[0128] (15)

[0129] The computer device obtains the loss increment corresponding to the coil wire branch according to the target resistivity, the actual current value, the corresponding length of the wire in the coil wire branch and the corresponding 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 is the actual current value; Δρ is the target resistivity; L i S is the length of the wire in the coil wire branch; i It is the cross-sectional area corresponding to the wire inside the coil wire branch.

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

[0134] (17)

[0135] Wherein, µ is the absolute viscosity of the oil, in cP; K and a are empirical coefficients related to the winding structure, the surface condition to be cooled, the oil channel size and the oil flow rate, which are not limited in the present embodiment; S is the effective heat dissipation area of ​​the winding; I' avr1 is the theoretical current value (flowing through each branch of the primary wire); β is the resistance change rate; m is the preset temperature coefficient; I' expi is the actual current value (flowing through each branch conductor of the primary side); L i S is the length of the wire in the coil wire branch; i It is the cross-sectional area corresponding to the wire inside the coil wire branch.

[0136] In order to facilitate the understanding of those skilled in the art, the loss calculation method of the power transformer is described below with reference to a specific example, as shown in FIG3 , where the power transformer is referred to as a transformer for short:

[0137] Make sure that the transformer product is in the state to be tested before the test, that is, the transformer core has been fully assembled, the coil of the power transformer has been wound and assembled to the core, the coil wire branches to be tested and evaluated have been separated at both ends of the coil, and each coil wire branch has a winding and is wound around the wire branch.

[0138] The computer equipment applies a small current (test current) to the primary side of the transformer, tests the current test values ​​of each wire branch on the primary and secondary sides, the current value of the primary current source, and the total current value of the secondary side, and calculates the theoretical average current value of each wire branch under small current through the current value of the primary current source and the total current value of the secondary side.

[0139] Compared with the measured current (current test value), the current deviation rate of each branch on the primary side and the secondary side is calculated respectively.

[0140] The current distribution value (actual current value, theoretical current value) of each branch of the winding at 100% rated current is calculated through the current deviation rate.

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

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

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

[0144] It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

[0145] Based on the same inventive concept, the embodiment of the present application also provides a power transformer loss calculation device for implementing the power transformer loss calculation method involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the embodiments of one or more power transformer loss calculation devices provided below can refer to the limitations of the power transformer loss calculation method above, and will not be repeated here.

[0146] In an exemplary embodiment, as shown in FIG4 , a loss calculation device 400 for a power transformer is provided, and the device 400 includes:

[0147] The deviation acquisition module 401 is used to obtain a first total current value corresponding to the power transformer under the test current, and a current test value flowing through each coil wire branch in the power transformer; based on the first total current value and the number of coil wire branches, an average current value is obtained, and a current deviation rate is determined according to 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 corresponding to the current deviation rate and the theoretical current value, and determine the actual current value flowing through the coil wire branch under the rated current; 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 coil conductor branch when the current distribution is unbalanced;

[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, the actual current value and the structural parameters.

[0151] In one embodiment, the current determination module 402 is further used to obtain a second total current value corresponding to the power transformer at the rated current, and obtain a theoretical current value based on the second total current value and the number of coil conductor branches;

[0152] The current determination module 402 is further configured 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 used to obtain a first temperature rise value according to the actual current value and the structural parameters, and the first temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is unbalanced;

[0154] A second temperature rise value is obtained according to the theoretical current value and the structural parameters, and the second temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is balanced;

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

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

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

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

[0159] In one embodiment, the structural parameters include a resistance change rate corresponding to the wire in the coil wire branch, a length corresponding to the wire in the coil wire branch, and a cross-sectional area corresponding to the wire in the coil wire branch, and the resistance change rate is used to characterize the relationship between the resistivity of the wire in the coil wire branch and the ambient temperature;

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

[0161] According to the target resistivity, the actual current value, the corresponding length of the wire in the coil wire branch and the corresponding cross-sectional area of ​​the wire in the coil wire branch, the loss increment corresponding to the coil wire branch is obtained.

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

[0163]

[0164] Among them, I' expi is the actual current value; Δρ is the target resistivity; L i S is the length of the wire in the coil wire branch; i It is the cross-sectional area corresponding to the wire inside the coil wire 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 is the current test value; I avr is the average current value.

[0168] Each module in the above-mentioned power transformer loss calculation device can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each of the above modules.

[0169] In an exemplary embodiment, a computer device is provided, which may be a server or a terminal. The server is used as an example for explanation, and its internal structure diagram may be shown in FIG5. The computer device includes a processor, a memory, an input / output interface (Input / Output, referred to as I / O) and a communication interface. The processor, the memory and the input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store current data (current test value, current deviation rate, etc.). The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a method for calculating the loss of a power transformer is implemented.

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

[0171] In an exemplary embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the above-mentioned method for calculating the loss of the power transformer when executing the computer program.

[0172] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the above-mentioned method for calculating the loss of the power transformer is implemented.

[0173] In one embodiment, a computer program product is provided, comprising a computer program, which implements the above-mentioned method for calculating the loss of a power transformer when executed by a processor.

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

[0175] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in the present 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. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, an artificial intelligence (AI) processor, etc., but are not limited to this.

[0176] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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 above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for calculating the loss of a power transformer, characterized in that: The method comprises: Obtaining a first total current value corresponding to the power transformer under the test current, and a current test value flowing through each coil conductor branch in the power transformer; obtaining an average current value based on the first total current value and the number of coil conductor branches, and determining a current deviation rate based on the average current value and the current test value; According to the number of coil wire branches corresponding to the coil wire branches, a theoretical current value flowing through the coil wire branches under a rated current is obtained, and according to the current deviation rate and the theoretical current value, an 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, a target temperature difference corresponding to the coil conductor branch is obtained; wherein the target temperature difference is used to characterize the temperature change value of the coil conductor branch caused by unbalanced current distribution; Based on the target temperature difference, the actual current value and the structural parameters, a loss increment corresponding to the coil conductor branch is obtained.

2. The method according to claim 1, characterized in that The step of obtaining a theoretical current value flowing through the coil wire branch under a rated current according to the number of the coil wire branches includes: Obtaining a second total current value corresponding to the power transformer under the rated current, and obtaining the theoretical current value based on the second total current value and the number of coil conductor branches; The step of determining the actual current value flowing through the coil conductor branch at the rated current based on the current deviation rate and the theoretical current value includes: The product of the current deviation rate and the theoretical current value is taken as the actual current value.

3. The method according to claim 1, characterized in that The step of obtaining a 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: Obtaining a first temperature rise value according to the actual current value and the structural parameter, wherein the first temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is unbalanced; A second temperature rise value is obtained according to the theoretical current value and the structural parameter, wherein the second temperature rise value is used to indicate that the wire temperature of the coil wire branch exceeds the temperature rise value corresponding to the oil temperature in the power transformer when the current distribution is balanced; The difference between the first temperature rise value and the second temperature rise value is used as the target temperature difference.

4. The method according to claim 3, characterized in that The structural parameters include structural information of windings in the coil conductor branches and dimensions of oil passages in the power transformer; The obtaining of the first temperature rise value according to the actual current value and the structural parameter comprises: According to the preset temperature coefficient and the actual current value, a first load loss of the coil wire branch is obtained, according to the first load loss and the structural information of the winding in the coil wire branch, a first load information of the surface of the winding in the coil wire branch is obtained, and based on the first load information, the structural information of the winding in the coil wire branch and the size of the oil channel in the power transformer, the first temperature rise value is determined; The obtaining of the second temperature rise value according to the theoretical current value and the structural parameter comprises: According to the preset temperature coefficient and the theoretical current value, the second load loss of the coil wire branch is obtained, and according to the second load loss and the structural information of the winding in the coil wire branch, the second load information of the surface of the winding in the coil wire branch is obtained, and based on the second load information, the structural information of the winding in the coil wire branch and the oil channel size in the power transformer, the second temperature rise value is determined.

5. The method according to claim 1, characterized in that The structural parameters include the resistance change rate corresponding to the wire in the coil wire branch, the length of the wire in the coil wire branch and the cross-sectional area of ​​the wire in the coil wire branch, and the resistance change rate is used to characterize the relationship between the resistivity of the wire in the coil wire branch and the ambient temperature; The step of obtaining the loss increment corresponding to the coil wire branch based on the target temperature difference, the actual current value and the structural parameter includes: Determining a target resistivity according to the resistance change rate and the target temperature difference; The loss increment corresponding to the coil wire branch is obtained according to the target resistivity, the actual current value, the corresponding length of the wire in the coil wire branch, and the corresponding cross-sectional area of ​​the wire in the coil wire branch.

6. The method according to claim 1, characterized in that The loss increment ΔP is obtained based on the following formula: Among them, the I' expi is the actual current value; Δρ is the target resistivity; L i is the length of the wire in the coil wire branch; i is the cross-sectional area corresponding to the wire inside the coil wire branch.

7. 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% Among them, the I exp is the current test value; the I avr is the average current value.

8. A loss calculation device for a power transformer, characterized in that: The device comprises: A deviation acquisition module is used to obtain a first total current value corresponding to the power transformer under a test current, and a current test value flowing through each coil wire branch in the power transformer; based on the first total current value and the number corresponding to the coil wire branch, an average current value is obtained, and a current deviation rate is determined according to the average current value and the current test value; a current determination module, configured to obtain a theoretical current value flowing through the coil wire branch under a rated current according to the number of coil wire branches corresponding thereto, and determine an actual current value flowing through the coil wire branch under the rated current according to the current deviation rate and the theoretical current value; wherein the rated current is greater than or equal to the test current; A temperature difference acquisition module, used to obtain a 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 of the coil conductor branch caused by unbalanced current distribution; The loss acquisition module is used to obtain the loss increment corresponding to the coil wire branch based on the target temperature difference, the actual current value and the structural parameter.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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