Construction method of main insulation reverse connection method test equivalent model

Abstract

The invention discloses a construction method of a main insulation reverse connection method test equivalent model, which belongs to the technical field of power equipment operation and maintenance, and is characterized in that an existing XY model is expanded by determining a proportion coefficient alpha of the thickness of the XY model in an overall model and a proportion coefficient beta of the perimeter of the XY model in the overall model during reverse connection method test; obtaining an equivalent dielectric model, an equivalent conductivity model and an equivalent dielectric relaxation activation energy model of the main insulation of the oil-immersed transformer in a reverse connection method test according to the determined alpha and beta in combination with the structural characteristics of the main insulation; and performing temperature translation reduction on the effective dielectric constant and the equivalent conductivity of the main insulation of the oil-immersed transformer by using the equivalent dielectric relaxation activation energy to obtain a dielectric loss factor curve and equivalent insulation resistance of the main insulation of the oil-immersed transformer. The insulation state of the on-site oil-immersed transformer when the grounding points of the high and low windings cannot be disassembled is effectively evaluated, and the construction cost is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of power equipment operation and maintenance, and in particular relates to a method for constructing an equivalent model for main insulation reverse connection method testing. Background Art

[0002] As an important part of energy transmission security, the stable and safe operation of the power system is of great significance to maintaining people's production and life. As a key component of the power system, the safe and reliable operation of the oil-immersed transformer directly affects the stability of the power system, so the study of its performance and insulation status is crucial.

[0003] At present, there are two main methods for testing the dielectric parameters of oil-immersed transformers, namely the positive connection method and the reverse connection method. The distinction between the positive connection method and the reverse connection method is mainly based on whether the sample to be tested is grounded. When conducting dielectric parameter tests on oil-immersed transformers on site, due to the limitations of the test instrument and the transformer structure, or due to long-term corrosion, the grounding points of the high and low windings of the transformer cannot be disassembled, and only the reverse connection method can be used for dielectric parameter testing. However, when using the frequency domain dielectric response instrument to test the main insulation equivalent model of the oil-immersed transformer, the positive connection method is often used for testing. Therefore, at this stage, the research on the main insulation equivalent model of the oil-immersed transformer is carried out around the positive connection method, and the research on the reverse connection method for testing the main insulation equivalent model is still in a blank stage. Due to the differences in the theoretical model and the field test method, the insulation status evaluation of the oil-immersed transformer on site is prone to misjudgment, affecting its safety and stability. Even if the grounding points of the high and low windings of the transformer can be disassembled, it also increases the construction cost.

[0004] Therefore, a new technical solution is urgently needed in the prior art to solve this problem. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a method for constructing an equivalent model for testing the main insulation reverse connection method, which is used to solve the problem that when the grounding points of the high and low windings of the transformer cannot be disassembled, there are differences in methods between the theoretical model and the on-site test, which easily leads to misjudgment of the insulation status evaluation of the on-site oil-immersed transformer.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for constructing an equivalent model for main insulation reverse connection method test, comprising the following steps:

[0007] S1. Construct the laboratory model of the main insulation of the oil-immersed transformer and the corresponding XY model;

[0008] S2. Determine the proportion coefficient α of the thickness of the XY model in the overall model and the proportion coefficient β of the circumference of the XY model in the overall model during the reverse connection method test according to the parameters of the laboratory model of the main insulation of the oil-immersed transformer constructed in S1;

[0009] S3, according to α and β determined by S2, use the calculation formula of complex capacitance to obtain the equivalent complex capacitance C1 of the high voltage winding to the shell or the low voltage winding to the iron core * (ω,T) and the equivalent complex capacitance C2 of the main insulation between the high and low voltage windings * The expression of (ω,T);

[0010] S4, according to C1 * (ω,T) and C2 * The capacitance value of (ω,T) is connected in parallel and equivalent, and the equivalent dielectric model of the main insulation of the oil-immersed transformer in the reverse connection method test is obtained by using the capacitance and dielectric constant expression;

[0011] S5. Based on α and β determined in S2, the relationship between resistance and conductivity is used to obtain the expression of the equivalent resistance R1(T) of the high-voltage winding to the casing or the low-voltage winding to the iron core and the equivalent resistance R2(T) of the main insulation between the high-voltage and low-voltage windings;

[0012] S6. Based on the parallel equivalent of the resistance values ​​of R1(T) and R2(T), the equivalent conductivity model of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained by using the relationship between resistance and conductivity;

[0013] S7. According to α and β determined in S2, determine the area proportion k of transformer oil in the equivalent model of the main insulation of the oil-immersed transformer o The area ratio k of oil-immersed paperboard in the equivalent model of main insulation of oil-immersed transformer p Expression of

[0014] S8, using the dielectric relaxation activation energy of oil-immersed paperboard and transformer oil and k obtained in S7 o and k p , the equivalent dielectric relaxation activation energy model of the main insulation of the oil-immersed transformer in the reverse connection test is obtained;

[0015] S9, using the equivalent dielectric relaxation activation energy obtained in S8, to perform temperature translation calculation on the equivalent dielectric constant of the main insulation of the oil-immersed transformer in S4 and the equivalent conductivity of the main insulation of the oil-immersed transformer in S6;

[0016] S10, using the equivalent conductivity of the main insulation of the oil-immersed transformer after temperature translation obtained in S9 to obtain the equivalent insulation resistance of the main insulation of the oil-immersed transformer during the reverse connection method test;

[0017] S11. Using the equivalent dielectric constant of the main insulation of the oil-immersed transformer after temperature translation obtained in S9, a dielectric loss factor curve of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained.

[0018] Through the above design scheme, the present invention can bring the following beneficial effects:

[0019] 1. By determining the proportional coefficient α of the thickness of the XY model in the overall model and the proportional coefficient β of the circumference of the XY model in the overall model during the reverse connection method test, the existing XY model is expanded to make it more consistent with the equivalent model of the reverse connection method;

[0020] 2. According to the determined α and β, combined with the structural characteristics of the main insulation between the high-voltage winding and the shell or the low-voltage winding and the iron core, and between the high-voltage and low-voltage windings, the equivalent dielectric model, equivalent conductivity model and equivalent dielectric relaxation activation energy model of the main insulation of the oil-immersed transformer during the reverse connection test are obtained, laying the foundation for the construction of an equivalent model for the reverse connection test of the main insulation of the oil-immersed transformer;

[0021] 3. Use the equivalent dielectric relaxation activation energy to perform temperature translation calculation on the equivalent dielectric constant and equivalent conductivity of the main insulation of the oil-immersed transformer, and obtain the dielectric loss factor curve and equivalent insulation resistance of the main insulation of the oil-immersed transformer during the reverse connection test. This can effectively evaluate the insulation status of the high and low windings of the oil-immersed transformer on site when the grounding points cannot be disassembled;

[0022] 4. There is no need to dismantle the grounding points of the high and low windings of the oil-immersed transformer on site, saving construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a method for constructing an equivalent model for main insulation reverse connection method testing.

[0024] Figure 2 The present invention is a schematic diagram of a laboratory model structure of a method for constructing an equivalent model for main insulation reverse connection method testing.

[0025] Figure 3 The present invention is an XY model schematic diagram of a method for constructing an equivalent model for main insulation reverse connection method testing.

[0026] Figure 4 The test curve and calculation curve diagram of the loss factor of a 10kV oil-immersed transformer in an embodiment of a method for constructing an equivalent model for testing a main insulation reverse connection method of the present invention.

[0027] In the figure, 1-housing, 2-oil channel, 3-high voltage winding, 4-low voltage winding, 5-iron core, 6-support bar. DETAILED DESCRIPTION

[0028] The following is a detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings.

[0029] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with the preferred embodiments. It should be understood by those skilled in the art. The content described in detail below is illustrative rather than restrictive, and the user may make various changes to the following parameters without departing from the inventive mechanism and scope set forth in the claims. In order to avoid confusing the essence of the present invention, known methods and processes are not described in detail.

[0030] By the attached Figures 1 to 4 As shown: A method for constructing an equivalent model for main insulation reverse connection test includes the following steps:

[0031] S1. Construct the laboratory model of the main insulation of the oil-immersed transformer and the corresponding XY model;

[0032] S2. Determine the proportion coefficient α of the thickness of the XY model in the overall model and the proportion coefficient β of the circumference of the XY model in the overall model during the reverse connection method test according to the parameters of the laboratory model of the main insulation of the oil-immersed transformer constructed in S1;

[0033] S3, according to α and β determined by S2, use the calculation formula of complex capacitance to obtain the equivalent complex capacitance C1 of the high voltage winding to the shell or the low voltage winding to the iron core * (ω,T) and the equivalent complex capacitance C2 of the main insulation between the high and low voltage windings * The expression of (ω,T);

[0034] S4, according to C1 * (ω,T) and C2 * The capacitance value of (ω,T) is connected in parallel and equivalent, and the equivalent dielectric model of the main insulation of the oil-immersed transformer in the reverse connection method test is obtained by using the capacitance and dielectric constant expression;

[0035] S5. Based on α and β determined in S2, the relationship between resistance and conductivity is used to obtain the expression of the equivalent resistance R1(T) of the high-voltage winding to the casing or the low-voltage winding to the iron core and the equivalent resistance R2(T) of the main insulation between the high-voltage and low-voltage windings;

[0036] S6. Based on the parallel equivalent of the resistance values ​​of R1(T) and R2(T), the equivalent conductivity model of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained by using the relationship between resistance and conductivity;

[0037] S7. According to α and β determined in S2, determine the area proportion k of transformer oil in the equivalent model of the main insulation of the oil-immersed transformer o The area ratio k of oil-immersed paperboard in the equivalent model of main insulation of oil-immersed transformer p Expression of

[0038] S8, using the dielectric relaxation activation energy of oil-immersed paperboard and transformer oil and k obtained in S7 o and k p , the equivalent dielectric relaxation activation energy model of the main insulation of the oil-immersed transformer in the reverse connection test is obtained;

[0039] S9, using the equivalent dielectric relaxation activation energy obtained in S8, to perform temperature translation calculation on the equivalent dielectric constant of the main insulation of the oil-immersed transformer in S4 and the equivalent conductivity of the main insulation of the oil-immersed transformer in S6;

[0040] S10, using the equivalent conductivity of the main insulation of the oil-immersed transformer after temperature translation obtained in S9 to obtain the equivalent insulation resistance of the main insulation of the oil-immersed transformer during the reverse connection method test;

[0041] S11. Using the equivalent dielectric constant of the main insulation of the oil-immersed transformer after temperature translation obtained in S9, a dielectric loss factor curve of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained.

[0042] Further, the laboratory model of the main insulation of the oil-immersed transformer described in S1 includes a casing 1, an oil channel 2, a high-voltage winding 3, a low-voltage winding 4, an iron core 5 and a support bar 6.

[0043] Further, the parameters of the laboratory model of the main insulation of the oil-immersed transformer described in S2 include the inner radius r of the high-voltage winding 3 hi , the outer radius r of the low voltage winding 4 lo , the distance d from the inner wall of the shell 1 to the center of the iron core 5 o , the outer radius r of the high voltage winding 3 ho , the inner radius r of the low voltage winding 4 li and the radius r of the core 5 F .

[0044] Further, the dielectric constant in S4 includes the complex dielectric constant of the oil-immersed paperboard and the complex dielectric constant of the transformer oil; the complex dielectric constant of the oil-immersed paperboard and the complex dielectric constant of the transformer oil are obtained by performing frequency domain dielectric response testing on oil-immersed paperboard samples and transformer oil samples with different aging degrees at different temperatures using a frequency domain dielectric response tester.

[0045] Further, the electrical conductivity in S6 includes the electrical conductivity of the oil-immersed cardboard and the electrical conductivity of the transformer oil; the electrical conductivity of the oil-immersed cardboard and the electrical conductivity of the transformer oil are obtained by performing insulation resistance tests on oil-immersed cardboard samples and transformer oil samples with different degrees of aging at different temperatures using a high resistance meter and calculating the DC conductivity.

[0046] The equivalent dielectric model described in S4 is derived as follows:

[0047] Using the laboratory model of the main insulation of the oil-immersed transformer and the corresponding extended XY model as shown in Figure 1 , 2 As shown, when the reverse connection method test selects the high voltage to ground + high and low voltage winding mode, the equivalent circumference of the oil channel is greater than the equivalent circumference of the insulation between the high and low voltage windings. When the reverse connection method test selects the low voltage to ground + high and low voltage winding mode, the equivalent circumference of the oil channel is less than the equivalent circumference of the insulation between the high and low voltage windings. In order to ensure that the radial proportions in the two test modes are represented by the same parameter, this patent believes that the sum of the radial proportions is 2. When the reverse connection method test selects the high voltage to ground + high and low voltage winding mode, β is less than 1 and greater than 0, and the radial proportion of the oil channel is greater than the insulation between the high and low voltage windings. When the reverse connection method test selects the low voltage to ground + high and low voltage winding mode, β is greater than 1, and the radial proportion of the oil channel is less than the insulation between the high and low voltage windings.

[0048] When calculating the equivalent capacitance, the capacitance values ​​of the two parts can be connected in parallel and calculated according to the calculation formula of the flat electrode:

[0049]

[0050] Among them, C1 * (ω,T) is the equivalent complex capacitance of the high voltage winding to the casing or the low voltage winding to the core, C2 * (ω,T) is the equivalent complex capacitance of the main insulation between the high and low voltage windings of the transformer, ω is the angular frequency of the test power supply, unit: radian / second, T is the temperature, unit: Kelvin.

[0051]

[0052] Where S1 is the equivalent lateral area of ​​the high-voltage winding to the casing or the low-voltage winding to the core insulation, unit: square meters, d1 is the equivalent thickness of the high-voltage winding to the casing or the low-voltage winding to the core insulation,

[0053] S1=2πl1h

[0054] Where, l1 is the equivalent circumference of the insulation between the high-voltage winding and the casing or the low-voltage winding and the core, in meters, and h is the insulation height of the transformer, in meters.

[0055]

[0056] Among them, l2 is the equivalent perimeter of the main insulation between the high and low voltage windings of the transformer, unit: meter, thus we can get

[0057]

[0058] Among them, S is the equivalent side area of ​​the main insulation between the high and low voltage windings of the transformer, unit: square meters

[0059] d1=(1-α)d

[0060] Where d is the total insulation thickness, unit: meter

[0061] Combined, we get C1 * The expression of (ω,T) is:

[0062]

[0063] Among them, ε oil * (ω,T) is the complex dielectric constant of transformer oil; ε0 is the dielectric constant of vacuum, unit Farad / meter, 8.854×10 -12 Farad / meter; S is the equivalent area of ​​the main insulation between the high and low voltage windings of the transformer, unit: square meters, d is the total insulation thickness, unit: meter; α is the proportion coefficient of the thickness of the XY model in the overall model; β is the proportion coefficient of the circumference of the XY model in the overall model. The calculation formula is as follows:

[0064] When the reverse connection method is used for testing, high voltage to ground + high and low voltage winding mode:

[0065]

[0066] Among them, r hi is the inner radius of the high voltage winding, unit: meter, r lo is the outer radius of the low voltage winding, unit: meter, d o is the distance from the inner wall of the shell to the center of the core, unit: meter, r ho is the outer radius of the high voltage winding, unit: meter

[0067]

[0068] Among them, r hi is the inner radius of the high voltage winding, unit: meter, r lo is the outer radius of the low voltage winding, unit: meter, d o is the distance from the inner wall of the shell to the center of the core, unit: meter, r ho is the outer radius of the high voltage winding, unit: meter

[0069] When the reverse connection method is used for testing, the low voltage to ground + high and low voltage winding mode is selected.

[0070]

[0071] Among them, r hi is the inner radius of the high voltage winding, unit: meter, r lo is the outer radius of the low voltage winding, unit: meter, r li is the inner radius of the low voltage winding, unit: meter, r F is the core radius, unit: meter

[0072]

[0073] Among them, r hi is the inner radius of the high voltage winding, unit: meter, r lo is the outer radius of the low voltage winding, unit: meter, r li is the inner radius of the low voltage winding, unit: meter, r F is the core radius, unit: meter

[0074]

[0075] Among them, C 21 * (ω,T) is the total series capacitance of the left support bar and the partition in the XY model; since the materials of the support bar and the paperboard are both oil-impregnated paperboard, this patent regards this part as a whole composed of oil-impregnated paperboard, C 22 * (ω,T) is the total series capacitance of the right oil gap and the partition in the XY model

[0076]

[0077] Among them, S 21 is the equivalent side area of ​​the left brace and partition in the XY model, unit: square meters, d2 is the total thickness of the XY model, unit: meter

[0078] S 21 =2πl 21 h

[0079] Among them, l 21 is the equivalent perimeter of the left support and partition in the XY model, unit: meter,

[0080] l 21 =Yl2

[0081] S 21 =Y·2πhl2=YS

[0082] d2=αd

[0083] Combined to get C 21 * (ω,T) is:

[0084]

[0085]

[0086] Among them, C 22o * (ω,T) is the capacitance of the right oil gap in the XY model, C 22p * (ω,T) is the capacitance of the right partition in the XY model,

[0087]

[0088]

[0089] Among them, S 22 is the equivalent lateral area of ​​the right part of the XY model, d 2o is the equivalent thickness of the right oil gap in the XY model, d 2p is the equivalent thickness of the right oil gap in the XY model

[0090] S 22 =2πl 22 h

[0091] l 22 =(1-Y)l2

[0092] S 22 =(1-Y)·2πhl2=(1-Y)S

[0093] d 2o =α(1-X)d

[0094] d 2p =αXd

[0095] Bring in:

[0096]

[0097]

[0098]

[0099] Therefore, C2 * The expression of (ω,T) is:

[0100]

[0101] In the formula, ε p * (ω,T) is the complex dielectric constant of the oil-impregnated paperboard; X is the ratio of the sum of the thickness of all partitions to the thickness of the main insulation, Y is the ratio of the sum of the thickness of all stays to the average perimeter of the main insulation, ε oil * (ω,T) is the complex dielectric constant of transformer oil; ε0 is the dielectric constant of vacuum, unit Farad / meter, 8.854×10 -12 Farad / meter; S is the equivalent area of ​​main insulation between high and low voltage windings of transformer, unit: square meter, d is the total insulation thickness, unit: meter;

[0102] When the reverse connection method is used for testing, the oil channel 2 and the main insulation between the high and low voltage windings of the transformer form a parallel circuit. At this time, the insulation complex capacitance C* (ω,T) can be expressed as:

[0103]

[0104] From the above formula, the equivalent complex dielectric constant of the insulating medium can be obtained as:

[0105]

[0106] The equivalent conductivity model described in S6 is derived as follows:

[0107] When calculating the equivalent resistance, the two resistance values ​​can be connected in parallel for equivalent calculation:

[0108]

[0109] In the formula, R1(T) is the equivalent resistance of the high-voltage winding to the casing or the low-voltage winding to the iron core; R2(T) is the equivalent resistance of the main insulation between the high-voltage and low-voltage windings.

[0110]

[0111] Substituting the expressions of the capacitor S1 and d1, we can get the expression of R1(T):

[0112]

[0113] Where γ1(T) is the equivalent conductivity of the high voltage winding to the casing or the low voltage winding to the iron core.

[0114]

[0115] Substituting the expression of the capacitance part d2, the expression of R2(T) is:

[0116]

[0117] Where γ2(T) is the equivalent conductivity of the main insulation between the high and low voltage windings.

[0118] Combining the above three equations, we can get:

[0119]

[0120] From the above formula, the equivalent conductivity of the insulating medium is:

[0121]

[0122] Since the insulating medium between the high voltage winding and the casing or the low voltage winding and the core is transformer oil, γ1(T) = γ oil (T), γ2(T) is the equivalent conductivity of the transformer XY model,

[0123]

[0124] Among them, R 21 (T) is the total series resistance of the left support bar and the partition in the XY model. Since the materials of the support bar and the paperboard are both oil-impregnated paperboard, this patent regards this part as a whole composed of oil-impregnated paperboard, R 22 (T) is the total series resistance of the right oil gap and the partition in the XY model

[0125]

[0126] Substituting the parameters of the capacitor part into the equation, we can get:

[0127]

[0128] R 22 (T) = R 22o (T)+R 22p (T)

[0129] Among them, R 22o (T) is the resistance of the right oil gap in the XY model, R 22p (T) is the resistance of the right partition in the XY model,

[0130]

[0131]

[0132] Substituting the parameters of the capacitor into

[0133]

[0134] Combined, the expression of γ2(T) is:

[0135]

[0136] In the formula, γ p (T) is the conductivity of the oil-impregnated paperboard. From this we can get:

[0137]

[0138] The equivalent dielectric relaxation activation energy model described in S8 is derived as follows:

[0139] The dielectric relaxation activation energy of the equivalent model of the reverse connection method can be calculated based on the area ratio of transformer oil and oil-immersed paperboard in the equivalent model, as shown below:

[0140] ΔE(τ)=k o ΔE o (τ)+k p ΔE p(τ)

[0141] Where ΔE(τ) is the dielectric relaxation activation energy of the equivalent model of the reverse connection method, ΔE o (τ) is the dielectric relaxation activation energy of transformer oil, unit: electron volt; ΔE p (τ) is the dielectric relaxation activation energy of the oil-impregnated paperboard, in electron volts, τ is the relaxation time, in seconds, k o is the area ratio of transformer oil in the equivalent model, k p is the area ratio of the oil-impregnated paperboard in the equivalent model, and the expression is as follows:

[0142]

[0143] Among them, S oil is the equivalent area of ​​transformer oil in the equivalent model, unit: square meter, S sum is the total area of ​​the equivalent model, unit: square meters,

[0144] S oil =S oil1 +S oil2

[0145] Among them, S oil1 It is the equivalent area of ​​insulation between high voltage winding and shell or low voltage winding and core, unit: square meter, S oil2 is the equivalent area of ​​the oil gap in the XY model, unit: square meters

[0146] S oil1 =d1l oil1

[0147] Among them, l oil1 It is the equivalent length of the insulation between the high voltage winding and the shell or the low voltage winding and the core, in meters, and its expression is:

[0148]

[0149] Where l is the total length of the model, in meters. Since the sum of the radial proportions of the two insulation parts is 2, the formula is calculated as 1 / 2.

[0150] Combined with:

[0151]

[0152] S oil2 =d 2o l oil2

[0153] Among them l oil2 is the equivalent length of the oil gap in the XY model, unit: meter, and its expression is

[0154]

[0155] Combined with:

[0156]

[0157] but

[0158]

[0159] S sum =S oil +S p

[0160] Among them, S p is the equivalent area of ​​the oil-impregnated cardboard in the equivalent model, unit: square meters, and its expression is:

[0161] S p =S p1 +S p2

[0162] Among them, S p1 is the equivalent area of ​​the left support and partition in the XY model, unit: square meters, S p2 is the equivalent area of ​​the right partition in the XY model, unit: square meters,

[0163] S p1 =d2l p1

[0164] Among them, l p1 is the equivalent length of the left support and partition in the XY model, unit: meter,

[0165]

[0166] Bring in

[0167]

[0168] S p2 =d 2p l oil2

[0169] Bring in

[0170]

[0171] but

[0172]

[0173]

[0174]

[0175]

[0176] Bring in

[0177]

[0178] Bring in

[0179]

[0180] Among them, ΔE o (τ) is the dielectric relaxation activation energy of transformer oil, unit: electron volt; ΔE p (τ) is the dielectric relaxation activation energy of the oil-impregnated paperboard, unit: electron volt.

[0181] The temperature shift calculation of the dielectric constant in S9 is carried out, and the corresponding frequency points are calculated to obtain the frequency points corresponding to each loss factor at the target temperature:

[0182]

[0183] Among them, f T is the frequency required to be translated to the temperature T, in Hertz; f0 is the test frequency, in Hertz; T is the target temperature of the translation, in Kelvin; T0 is the test temperature, in Kelvin, and k is the Boltzmann constant, which is 1.38×10 -23 Joule / Kelvin.

[0184] The conductivity temperature is converted to obtain the DC conductivity at the target temperature:

[0185]

[0186] Among them, γ T is the DC conductivity at the target temperature, unit: Siemens / meter; γ0 is the DC conductivity at the test temperature, unit: Siemens / meter; T is the target temperature of the translation, unit: Kelvin; T0 is the test temperature, unit: Kelvin.

[0187] The calculation formula of the equivalent insulation resistance described in S10 is as follows:

[0188]

[0189] Among them, R t is the equivalent insulation resistance of the oil-immersed transformer when the main insulation is tested by reverse connection method, unit: ohm, M is the volume coefficient of the oil-immersed transformer when the main insulation is tested by reverse connection method, γ r (T) is the equivalent DC conductivity of the main insulation of the oil-immersed transformer when tested by the reverse connection method, unit: Siemens / meter, T is the test temperature, unit: Kelvin.

[0190] The calculation formula of dielectric loss factor in S11 is:

[0191]

[0192] Among them, tanδ is the dielectric loss factor, ε r ” (ω,T) is the imaginary part of the equivalent complex dielectric constant of the oil-immersed transformer when the main insulation is tested by reverse connection method, ε r '(ω,T) is the real part of the equivalent complex dielectric constant of the oil-immersed transformer when the main insulation is tested by the reverse connection method.

[0193] In the specific implementation, the reverse connection method is used to test the newly-made 10kV oil-immersed transformer to obtain the dielectric loss factor curve and insulation resistance, and calculate its DC conductivity. In the main insulation structure of the transformer, X is 0.5, Y is 0.3, α is 0.4, and β is 0.6. The on-site test temperature is 27°C, the test voltage is 1000 volts, and the test curve is as follows: Figure 4 As shown in the measured curve, the DC conductivity calculation result is 1.11×10 -13 Siemens / meter, the insulation resistance is calculated to be 7.93×10 12 ohm.

[0194] According to the oil-immersed transformer main insulation reverse connection method test equivalent model of the present invention, the dielectric loss factor calculation curve is as follows Figure 4 As shown in the figure, the fitting degree with the measured curve is 98.3%, and the DC conductivity calculation result is 1.17×10 -13 Siemens / meter, the insulation resistance calculated by reverse connection method is 7.53×10 12 Ohms. The error with the actual measurement result is 5%.

[0195] If the positive connection method is performed on the main insulation of the oil-immersed transformer, the test insulation is the main insulation between the high and low voltage windings, and the model structure is the traditional XY model. Therefore, the DC conductivity of the oil-immersed cardboard and transformer oil can be brought into the XY conductivity model to obtain the positive connection method equivalent conductivity. The XY conductivity model is

[0196]

[0197] The conductivity of oil-impregnated paperboard is 6.65×10 -14 Siemens / meter, the conductivity of transformer oil is 6×10 -15 Siemens / Mietz method complex dielectric constant calculation model

[0198]

[0199] The calculated result of DC conductivity by positive connection method is 2.77×10 -14 Siemens / meter, insulation resistance calculation result is 3.18×1013 Ohm, the error with the measured result is 75%, the dielectric loss factor curve is as follows Figure 4 As shown in the figure, the fitting degree with the measured curve is 84.7%. It can be seen that when the positive connection method is performed on the main insulation of the oil-immersed transformer, the calculated result deviates greatly from the actual result.

[0200] Obviously, the above described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0201] The above mainly introduces the solution of the embodiment of the present application from the perspective of the execution process of the method side. It can be understood that in order to implement the above functions, the network device includes a hardware structure and / or software module corresponding to each function. Those skilled in the art should easily realize that, in combination with the units and algorithm steps of each example described in the embodiment provided in this article,

[0202] The present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is performed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present application.

[0203] If the above-mentioned integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a memory, including a number of instructions to enable a computer device to perform all or part of the steps of each embodiment method of the present application for a personal computer, server or TRP. The aforementioned memory includes: U disk, read-only memory ROM, Read-Only Memory, random access memory RAM, RandomAccess Memory, mobile hard disk, disk or optical disk and other media that can store program codes.

Claims

1. A method for constructing an equivalent model for main insulation reverse connection test, characterized in that: The steps include: S1. Construct the laboratory model of the main insulation of the oil-immersed transformer and the corresponding XY model; S2. Determine the proportion coefficient α of the thickness of the XY model in the overall model and the proportion coefficient β of the circumference of the XY model in the overall model during the reverse connection method test according to the parameters of the laboratory model of the main insulation of the oil-immersed transformer constructed in S1; S3, according to α and β determined by S2, use the calculation formula of complex capacitance to obtain the equivalent complex capacitance C1 of the high voltage winding to the shell or the low voltage winding to the iron core * (ω,T) and the equivalent complex capacitance C2 of the main insulation between the high and low voltage windings * The expression of (ω,T); S4, according to C1 * (ω,T) and C2 * The capacitance value of (ω,T) is connected in parallel and equivalent, and the equivalent dielectric model of the main insulation of the oil-immersed transformer in the reverse connection method test is obtained by using the capacitance and dielectric constant expression; S5. Based on α and β determined in S2, the relationship between resistance and conductivity is used to obtain the expression of the equivalent resistance R1(T) of the high-voltage winding to the casing or the low-voltage winding to the iron core and the equivalent resistance R2(T) of the main insulation between the high-voltage and low-voltage windings; S6. Based on the parallel equivalent of the resistance values ​​of R1(T) and R2(T), the equivalent conductivity model of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained by using the relationship between resistance and conductivity; S7. According to α and β determined in S2, determine the area proportion k of transformer oil in the equivalent model of the main insulation of the oil-immersed transformer o The area ratio k of oil-immersed paperboard in the equivalent model of the main insulation of oil-immersed transformer p Expression of S8, using the dielectric relaxation activation energy of oil-impregnated paperboard and transformer oil and k obtained in S7 o and k p , the equivalent dielectric relaxation activation energy model of the main insulation of the oil-immersed transformer in the reverse connection test is obtained; S9, using the equivalent dielectric relaxation activation energy obtained in S8, to perform temperature translation calculation on the equivalent dielectric constant of the main insulation of the oil-immersed transformer in S4 and the equivalent conductivity of the main insulation of the oil-immersed transformer in S6; S10, using the equivalent conductivity of the main insulation of the oil-immersed transformer after temperature translation obtained in S9 to obtain the equivalent insulation resistance of the main insulation of the oil-immersed transformer during the reverse connection method test; S11. Using the equivalent dielectric constant of the main insulation of the oil-immersed transformer after temperature translation obtained in S9, a dielectric loss factor curve of the main insulation of the oil-immersed transformer during the reverse connection method test is obtained.

2. The method for constructing an equivalent model for main insulation reverse connection test according to claim 1, characterized in that: The laboratory model of the main insulation of the oil-immersed transformer S1 comprises a casing (1), an oil channel (2), a high-voltage winding (3), a low-voltage winding (4), an iron core (5) and a stay (6).

3. The method for constructing an equivalent model for main insulation reverse connection test according to claim 2, characterized in that: The parameters of the laboratory model of the main insulation of the oil-immersed transformer S2 include the inner radius r of the high-voltage winding (3) hi , the outer radius r of the low voltage winding (4) lo , the distance d from the inner wall of the housing (1) to the center of the iron core (5) o , the outer radius r of the high voltage winding (3) ho , the inner radius r of the low voltage winding (4) li and the radius r of the core (5) F .

4. The method for constructing an equivalent model for main insulation reverse connection test according to claim 2, characterized in that: S4 The dielectric constant includes the complex dielectric constant of the oil-immersed paperboard and the complex dielectric constant of the transformer oil; the complex dielectric constant of the oil-immersed paperboard and the complex dielectric constant of the transformer oil are obtained by performing frequency domain dielectric response testing on oil-immersed paperboard samples and transformer oil samples with different aging degrees at different temperatures using a frequency domain dielectric response tester.

5. The method for constructing an equivalent model for main insulation reverse connection test according to claim 2, characterized in that: S6 The conductivity includes the conductivity of the oil-immersed cardboard and the conductivity of the transformer oil; the conductivity of the oil-immersed cardboard and the conductivity of the transformer oil are obtained by performing insulation resistance tests on oil-immersed cardboard samples and transformer oil samples with different aging degrees at different temperatures using a high resistance meter and calculating the DC conductivity.

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