Large-scale single-phase autotransformer induction voltage withstand test modeling and parameter calculation method

Abstract

The invention discloses a large-scale single-phase autotransformer induction withstand voltage test modeling and parameter calculation method, and the modeling comprises a variable-frequency power supply, an excitation transformer, an autotransformer and a partial discharge instrument, and a compensation reactance assembly is connected in parallel between the high-voltage side of the excitation transformer and the low-voltage winding of the autotransformer. The high-voltage winding is provided with zero potential and is connected with the sensor and the partial discharge instrument. According to the parameter calculation method, total reactive power and active loss are obtained by collecting no-load data and calculating capacitance, voltage distribution, capacitive and inductive reactive power and active loss. Test verification shows that the deviation between calculated values and measured values of parameters such as resonant frequency and variable-frequency power supply input current is within 10%, test equipment model selection and scheme making can be accurately guided, test efficiency is improved, and equipment safety is guaranteed.

Description

Technical Field

[0001] This application belongs to the field of transformer simulation calculation, and specifically relates to a modeling method for induced withstand voltage test of a large single-phase autotransformer and its parameter calculation method. Background Technology

[0002] Inductive withstand voltage testing is a key component of power transformer commissioning tests for verifying insulation performance. It simulates insulation stress during operation by applying an alternating voltage higher than the rated voltage, thereby detecting insulation defects between winding layers, turns, and to ground. For large single-phase autotransformers (such as those at 750kV and above), due to their unique structure (e.g., high / medium voltage winding autocoupling, independent low-voltage winding), large rated capacity (typically exceeding 500MVA), and high insulation level (LI1950kV / AC 900kV and above), induced withstand voltage testing faces the following technical challenges:

[0003] 1. Lack of targeted modeling methods

[0004] Existing technologies primarily focus on modeling and parameter calculation for induced withstand voltage tests of three-phase transformers. However, the winding coupling relationships (such as the high-voltage and medium-voltage windings sharing a common core and the neutral grounding method) and voltage distribution characteristics (such as the potential gradient difference between the high-voltage and medium-voltage sides) of single-phase autotransformers differ significantly from those of three-phase transformers. Traditional three-phase models cannot accurately describe the capacitive coupling effects (such as winding-to-ground capacitance and inter-winding longitudinal capacitance) and voltage distribution patterns of single-phase autotransformers, leading to significant deviations in the calculation of test parameters.

[0005] 2. The calculation of experimental parameters relies on experience and lacks accuracy.

[0006] Before testing large single-phase autotransformers, key parameters (such as resonant frequency, reactive power, and excitation current) need to be determined to guide the selection of frequency converters, the configuration of compensation reactance, and test safety control. Existing methods largely rely on empirical formulas for estimation, neglecting the following crucial factors:

[0007] Stray capacitance effect: Stray capacitance generated by live equipment in the field test environment will change the equivalent capacitance value of the test circuit, resulting in a shift in the resonant frequency;

[0008] Longitudinal capacitance loss: The high-voltage / medium-voltage windings of the autotransformer adopt a tangled structure with a large longitudinal capacitance. Its reactive power loss accounts for a significant proportion of the total reactive power loss. This component is not included in the traditional model.

[0009] Nonlinearity of core loss: The magnetic flux density of the core may deviate from the rated value under the test voltage, resulting in errors in the calculation of active power loss and affecting the selection of power supply capacity. Summary of the Invention

[0010] This application provides a precise modeling and parameter calculation method for the induced withstand voltage test of a large single-phase autotransformer. By constructing an electromagnetic coupling model including high-voltage, medium-voltage, and low-voltage windings, an equivalent network of distributed parameters for the longitudinal capacitance between windings and the capacitance to ground is introduced. Combined with the field stray capacitance correction coefficient, the total capacitance and resonant frequency of the test circuit are accurately calculated. Based on the core flux density distribution characteristics under frequency converter excitation, the active power loss under non-rated magnetic flux density is corrected, and the additional reactive power loss caused by the longitudinal capacitance of the entangled winding is taken into account, thereby improving the calculation accuracy of the excitation current and the required reactive power.

[0011] To achieve the above objectives, this application provides a modeling method for a large single-phase autotransformer induced withstand voltage test, including a frequency converter, an excitation transformer T, an autotransformer, and a partial discharge instrument. The characteristic feature is that the input terminal of the frequency converter is connected to a three-phase 380V alternating test power supply, and the output terminal is connected to the low-voltage side of the excitation transformer T. The high-voltage side of the excitation transformer T is connected to the ax terminal of the low-voltage winding of the autotransformer, and a zero potential A is set on the ax terminal side of the high-voltage winding of the autotransformer. m A first sensor and a second sensor are respectively connected to the A end of the AX end of the high voltage winding and the zero point Am. The first sensor and the second sensor are connected to the partial discharge instrument.

[0012] A compensating reactor assembly is connected in parallel on the connection line between the high-voltage side of the excitation transformer T and the low-voltage winding ax terminal of the autotransformer.

[0013] In one embodiment, the compensation reactor assembly includes two compensation reactors L connected in series, and a first grounding terminal is provided on the connection line between the two compensation reactors L;

[0014] The excitation transformer T, the high-voltage winding AX end X, and the first sensor and second sensor are respectively provided with a second grounding terminal, a third wiring terminal, a fourth grounding terminal, and a fifth grounding terminal.

[0015] A method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers includes the following steps:

[0016] S1. Collect no-load data of the autotransformer and excitation transformer T under rated voltage, and preprocess the no-load data to obtain various voltage values ​​of the autotransformer and excitation transformer T.

[0017] S2. Collect the capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground during the routine test of the autotransformer in the acceptance test. HM-LE The capacitance C of the low-voltage winding to the high-voltage and medium-voltage windings and ground. L-HME The capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground.HML-E C was calculated H0 C HM-L , C L0 ;

[0018] S3. Based on the various voltage values ​​of the autotransformer, calculate the relationship between the high-voltage winding, medium-voltage winding, and low-voltage winding of the autotransformer and the winding height h during the test.

[0019] S4. Take a small element with height dh between the high-voltage winding and the medium-voltage winding, calculate the capacitor current di, integrate the capacitor current di to obtain the capacitive current i, and substitute the voltage distribution of the high-voltage winding, medium-voltage winding, and low-voltage winding with the winding height h into the capacitive current i to obtain the reactive power Q of the high-voltage winding and medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E and the capacitive reactive power Q between the high-voltage winding, the medium-voltage winding and the low-voltage winding. AAm-a ;

[0020] S5. Collect the capacitance C between the high-voltage winding and the medium-voltage winding and the low-voltage winding and ground. HM-LE Calculate the longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding. HM ;

[0021] S6. During the experiment, the total loss S0 of the autotransformer under rated operating conditions and the no-load loss P0 of the autotransformer under rated operating conditions were collected to obtain the inductive reactive power Q. L ;

[0022] S7. Extract the reactive power Q from the high-voltage winding and the medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a The longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding HM and inductive reactive power Q L The total reactive power Q consumed by the autotransformer during the induced withstand voltage test was calculated.

[0023] S8. Collect the magnetic flux density B of the autotransformer under test conditions and the magnetic flux density B under rated conditions. N Based on the coefficients m and n of the cold-rolled silicon steel sheet, the active power loss P of the autotransformer described in the experiment was obtained.

[0024] In one embodiment, according to step S1, the values ​​of the autotransformer include the high-voltage winding-to-ground voltage and the high-voltage winding phase voltage. and low-voltage winding phase voltage ;

[0025] The voltage values ​​of the excitation transformer T include the phase voltage of the low-voltage winding, the input voltage, and the turns ratio k1 during the test.

[0026] In one embodiment, according to step S2, the test measurements and the capacitances of each winding to ground and between windings satisfy the following equations:

[0027] (1);

[0028] The capacitance C between the high-voltage winding and ground is obtained by substituting into formula (1). H0 The capacitance C between the high-voltage winding and the low-voltage winding HM-L The capacitance C between the low-voltage winding and ground L0 .

[0029] In one embodiment, according to step S3, the relationship between the high-voltage winding, medium-voltage winding, and low-voltage winding of the autotransformer and the winding height h during the test is as follows:

[0030] (2);

[0031] In formula (2), U AAm It is the voltage between the high-voltage winding and the medium-voltage winding; U AAm-a It is the voltage between the high-voltage winding and the medium-voltage winding and the low-voltage winding; H is the total height of the winding.

[0032] In one embodiment, according to step S4, the expression for the capacitor current di is:

[0033] (3);

[0034] In formula (3), ω represents capacitance; ω represents the angular frequency during the test. This represents the substitution expression in formula (2);

[0035] Integrating equation (3) and substituting it into equation (2), we obtain the capacitive current i of the high-voltage winding and the medium-voltage winding. AAM-E The capacitive current i of the low-voltage winding a-E The capacitive current i between the high-voltage winding and the medium-voltage winding and the low-voltage winding AAm-a ;

[0036] Integrating formula (3), substituting it into formula (2), and multiplying by U respectively AAm U a U AAm-a The reactive power Q of the high-voltage winding and the medium-voltage winding to ground is obtained. AAM-EReactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a .

[0037] In one embodiment, according to step S5, the longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding... HM The calculation formula is as follows:

[0038] (4);

[0039] In formula (4), α is the longitudinal capacitance value; α is the square root of the ratio of the sum of the capacitance to ground and the capacitance to adjacent windings per unit length to the longitudinal capacitance per unit length; the value of αH ranges from 1.5 to 3.0. Indicates voltage; C HM-LE This refers to the capacitance of the high-voltage and medium-voltage windings to the low-voltage winding and ground.

[0040] In one embodiment, according to step S6, the rated reactive power loss Q0 is calculated using the total loss S0 and the no-load loss P0;

[0041] (5);

[0042] The inductive reactive power Q L The expression is:

[0043] (6);

[0044] Substituting formula (5) into formula (6), the inductive reactive power Q is calculated. L In formula (6), f N f is the rated frequency; f is the test frequency; U N U is the rated voltage; U is the test voltage, and ; This represents the total magnetic flux in the iron core.

[0045] According to step S7, the formula for calculating the total reactive power Q consumed by the autotransformer during the induced withstand voltage test is as follows:

[0046] (7).

[0047] In one embodiment, according to step S8, the active power loss P of the autotransformer is calculated as follows:

[0048] (8);

[0049] In formula (8), P is the active power loss under test conditions; P0 is the active power loss under rated operating conditions;

[0050] If the core of the autotransformer described in the experiment operates in the unsaturated region, the calculation method is as follows: (9).

[0051] Compared with the prior art, the beneficial effects of this application are:

[0052] By constructing a large-scale single-phase autotransformer induced withstand voltage test model and verifying it with field test parameter measurements, a solid theoretical foundation and technical guidance are provided for similar testing work. Simultaneously, calculation methods for key test parameters such as winding potential distribution, inlet capacitance, capacitive reactive power, and active power loss are proposed. These methods facilitate the rational selection of test equipment and the precise selection of test power sources during handover testing, significantly improving work efficiency and effectively avoiding waste of human and material resources. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 The wiring diagram for the induced withstand voltage test modeling of the large single-phase autotransformer provided in this application;

[0055] Figure 2 The method for calculating modeling parameters for the induced withstand voltage test of a large single-phase autotransformer provided in this application includes a phasor diagram of the potential at each end of the winding during the test.

[0056] Figure 3 The diagram shows the capacitance of each winding that needs to be calculated during the induced withstand voltage test modeling parameter calculation method for the large single-phase autotransformer provided in this application. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0058] See Figures 1 to 3As shown, the large single-phase autotransformer induced withstand voltage test modeling provided in this application includes a frequency converter, an excitation transformer T, an autotransformer, and a partial discharge instrument. Its features include: the input terminal of the frequency converter is connected to a three-phase 380V alternating test power supply, and the output terminal is connected to the low-voltage side of the excitation transformer T; the high-voltage side of the excitation transformer T is connected to the low-voltage winding ax terminal of the autotransformer; and a zero potential A is set on the high-voltage winding ax terminal side of the autotransformer. m A first sensor and a second sensor are respectively connected to the A end of the AX end of the high voltage winding and the zero point Am. The first sensor and the second sensor are connected to the partial discharge instrument.

[0059] A compensating reactor assembly is connected in parallel on the connection line between the high-voltage side of the excitation transformer T and the low-voltage winding ax terminal of the autotransformer.

[0060] Optionally, the compensation reactor assembly includes two compensation reactors L connected in series, and a first grounding terminal is provided on the connection line between the two compensation reactors L;

[0061] The excitation transformer T, the high-voltage winding AX end X, and the first sensor and second sensor are respectively provided with a second grounding terminal, a third wiring terminal, a fourth grounding terminal, and a fifth grounding terminal.

[0062] Example 1

[0063] In this experiment, a single-phase autotransformer from a 750 kV substation was used. Its main parameters are shown in Table 1.

[0064] Table 1 Parameters of the Test Transformer

[0065] A method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers includes the following steps:

[0066] S1. Collect no-load data of the autotransformer and excitation transformer T under rated voltage, and preprocess the no-load data to obtain various voltage values ​​of the autotransformer and excitation transformer T.

[0067] During the test, the rated voltage of the autotransformer's medium-voltage side was 597.56 kV, the high-voltage to low-voltage side variation ratio k was 7.01, and the high-voltage side winding insulation level was 900 kV. According to the "750 kV Power Equipment Acceptance Test Procedure" (Q / GDW1157—2013), the test voltage should be calculated based on the highest operating voltage Um=800 kV, corresponding to the high-voltage winding phase voltage. =665.13 kV, low-voltage winding phase voltage =94.88 kV.

[0068] The calculation shows that the phase voltage of the low-voltage winding of the excitation transformer T during the test is 102.71 kV, and its output voltage is 132.00 kV, which is formed by two 66.00 kV windings connected in series. The input voltage is 0.38 kV, and the corresponding excitation transformer turns ratio k1 is 347.37.

[0069] S2. Collect the capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground during the routine test of the autotransformer in the acceptance test. HM-LE The capacitance C of the low-voltage winding to the high-voltage and medium-voltage windings and ground. L-HME The capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground. HML-E C was calculated H0 C HM-L , C L0 .

[0070] like Figure 2 As shown in the figure, H, M, and L represent the high-voltage winding, medium-voltage winding, and low-voltage winding, respectively. Let C... HM-LE C L-HME C HML-E The capacitance C of the high-voltage winding and the medium-voltage winding to the low-voltage winding and ground are respectively. HM-LE The capacitance C of the low-voltage winding to the high-voltage winding and ground. L-HME The capacitance C of the high-voltage winding and low-voltage winding to ground HML-E These three values ​​are the experimental values ​​obtained during the dielectric loss measurement test, and are also measured in the routine test of the acceptance test. HM-LE It is 12.11 nF, C L-HME It is 23.46 nF, C HML-E It is 24.27 nF.

[0071] Meanwhile, the experimental measurements and the capacitance of each winding to ground and between windings satisfy the following equations:

[0072] (1);

[0073] C is obtained by substituting into formula (1). H0 It is 6.46 nF, C HM-L It is 5.65 nF, C L0 It is 17.81 nF.

[0074] S3. Based on the various voltage values ​​of the autotransformer, calculate the relationship between the high-voltage winding, medium-voltage winding, and low-voltage winding of the autotransformer and the winding height h during the test.

[0075] Let the total height of the winding be H. As shown in Figure (3), the voltage distribution between the high-voltage winding, the medium-voltage winding, and the low-voltage winding is linearly related to the winding height h, as shown below:

[0076] (2);

[0077] In formula (2), U AAm It is the voltage between the high-voltage winding and the medium-voltage winding; U AAm-a It is the voltage between the high-voltage winding and the medium-voltage winding and the low-voltage winding; H is the total height of the winding.

[0078] S4. Take a small element with height dh between the high-voltage winding and the medium-voltage winding, calculate the capacitor current di, integrate the capacitor current di to obtain the capacitive current i, and substitute the voltage distribution of the high-voltage winding, medium-voltage winding, and low-voltage winding with the winding height h into the capacitive current i to obtain the reactive power Q of the high-voltage winding and medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E and the capacitive reactive power Q between the high-voltage winding, the medium-voltage winding and the low-voltage winding. AAm-a .

[0079] Calculate the capacitive current di within a infinitesimal segment of height dh:

[0080] (3);

[0081] In formula (3), ω represents capacitance; ω represents the angular frequency during the test. The expression in formula (2) is the substitution expression.

[0082] Substituting equation (2) into equation (3) and performing integration, we obtain: the capacitance current i of the high-voltage winding and the medium-voltage winding under distributed capacitance conditions. AAM-E The low-voltage winding's capacitive current i a-E The capacitive current i between the high-voltage winding and the medium-voltage winding and the low-voltage winding AAm-a .in:

[0083] ;

[0084] ;

[0085] The capacitive current i of the low-voltage winding a-E .

[0086] ;

[0087] In the above formula, C HM-L This represents the capacitance value between the high-voltage winding and the medium-voltage winding and the low-voltage winding.

[0088] Integrate equation (3), substitute it into the relationship between voltage distribution and height h in equation (2), and multiply by U. AAm U a U AAm-a， Thus, the reactive power Q of the high-voltage winding and the medium-voltage winding relative to ground is obtained. AAM-E Reactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a .in:

[0089] ;

[0090] ;

[0091] ;

[0092] In the above formula, C L0 This is the capacitance value between the low-voltage winding and ground.

[0093] S5. Collect the capacitance C between the high-voltage winding and the medium-voltage winding and the low-voltage winding and ground. HM-LE Calculate the longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding. HM .

[0094] During the test, the high-voltage and medium-voltage windings of the autotransformer adopted an intertwined structure, resulting in a large longitudinal capacitance, which necessitates accounting for reactive power losses. The low-voltage winding, due to its lower applied voltage and smaller longitudinal capacitance, had a negligible impact.

[0095] For a winding element of length dh, the longitudinal capacitance component Q of the reactive power of the high-voltage and medium-voltage windings is... HM The calculation formula is as follows:

[0096] (4);

[0097] In formula (4), α is the longitudinal capacitance value; α is the square root of the ratio of the sum of the capacitance to ground and the capacitance to adjacent windings per unit length to the longitudinal capacitance per unit length; the value of αH ranges from 1.5 to 3.0. C represents voltage. HM-LE This refers to the capacitance of the high-voltage and medium-voltage windings to the low-voltage winding and ground.

[0098] In this embodiment, the value of αH is 2.

[0099] S6. During the experiment, the total loss S0 of the autotransformer under rated operating conditions and the no-load loss P0 of the autotransformer under rated operating conditions were collected to obtain the inductive reactive power Q. L .

[0100] The rated reactive power loss Q0 is calculated using the total loss S0 and the no-load loss P0. Here, P0 is the no-load loss of the transformer under test under rated operating conditions, which is 91.56 kW. .

[0101] In the formula, S N I represents the apparent power of the transformer under rated operating conditions. 0% This represents the percentage of the no-load current. According to the formula... Therefore, the corresponding rated reactive power loss Q0 is 243.35 kVar.

[0102] Therefore, it can be further concluded that the silicon steel sheets for the core of the autotransformer used in the experiment were Baosteel B23P095 grade. During the experiment, the autotransformer core operated in the unsaturated region under both rated and test conditions, combined with the test voltage. The inductive reactive power Q generated by the no-load current can be obtained. L .

[0103] (6);

[0104] In formula (6), f N f is the rated frequency; f is the test frequency; U N This is the rated voltage.

[0105] S7. Extract the reactive power Q from the high-voltage winding and the medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a The longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding HM and inductive reactive power Q L The total reactive power Q consumed by the autotransformer during the induced withstand voltage test was calculated.

[0106] Through the formula: (7);

[0107] Among them, the low-voltage side input capacitor C of the autotransformer L As shown below:

[0108] ;

[0109] According to the resonance condition, the resonant angular frequency ω of the experiment satisfies the following formula:

[0110]

[0111] Capacitor C L Substituting the resonant angular frequency ω into formula (7), the capacitance C can be obtained. L The capacitance is 237.63 nF, and the resonant frequency f is 112.65 Hz.

[0112] Substituting the above results into formula (7), the total reactive power Q consumed by the autotransformer under test conditions is calculated to be 1514.12 kVar.

[0113] S8. Collect the magnetic flux density B of the autotransformer under test conditions and the magnetic flux density B under rated conditions. N Based on the coefficients m and n of the cold-rolled silicon steel sheet, the active power loss P of the autotransformer described in the experiment was obtained.

[0114] During the experiment, the active power loss P depends on the magnetic flux density B and the frequency, as shown in the following expression:

[0115] (8);

[0116] In formula (8), P is the active power loss under test conditions, P0 is the active power loss under rated operating conditions, and B is the magnetic flux density under test conditions. N ρ represents the magnetic flux density under rated conditions. m and n are the coefficients of cold-rolled silicon steel sheets, with m set to 1.6 and n to 1.9.

[0117] Furthermore, since the core of the autotransformer operates in the unsaturated region, formula (8) can be expressed as:

[0118] (9);

[0119] The actual voltage on the low-voltage side of the transformer under test passes through The obtained value is U = 142.41 kV, and the rated voltage U on the low-voltage side is... N It is 94.88 kV, with a rated frequency f. N The actual frequency f is 112.65 Hz, and substituting it into formula (9), we get P = 156.16 kW. Meanwhile, since the compensating reactor and autotransformer are in resonance under experimental conditions, the low-voltage side current is approximately equal to the active current, which can be expressed as follows:

[0120] .

[0121] It should be noted that the test plan was formulated based on the experimental parameters calculated above, and the on-site test was carried out. The on-site measured data and calculated values ​​of the transformer under test are compared in Table 2.

[0122] Table 2 Comparison of calculated and measured values

[0123] As can be seen from the data in Table 2, there is a deviation between the calculated and measured values ​​of the parameters. This is because the presence of live equipment and stray capacitance in the surrounding area during the field test affects the test parameters, and the influence of transformer bushing capacitance is ignored. According to relevant literature, a deviation of less than 10% between the calculated and measured values ​​is considered acceptable for this method.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A modeling method for induced withstand voltage test of a large single-phase autotransformer, comprising a frequency converter, an excitation transformer T, an autotransformer, and a partial discharge instrument, characterized in that: The input terminal of the frequency converter is connected to a three-phase 380V alternating test power supply, and the output terminal is connected to the low-voltage side of the excitation transformer T. The high-voltage side of the excitation transformer T is connected to the low-voltage winding ax terminal of the autotransformer. A zero potential A is set on the high-voltage winding AX terminal side of the autotransformer. m A first sensor and a second sensor are respectively connected to the A end of the AX end of the high voltage winding and the zero point Am. The first sensor and the second sensor are connected to the partial discharge instrument. A compensating reactor assembly is connected in parallel on the connection line between the high-voltage side of the excitation transformer T and the low-voltage winding ax terminal of the autotransformer.

2. The modeling of the induced withstand voltage test for a large single-phase autotransformer according to claim 1, characterized in that: The compensation reactor assembly includes two compensation reactors L connected in series, and a first grounding terminal is provided on the connection line between the two compensation reactors L. The excitation transformer T, the high-voltage winding AX end X, and the first sensor and second sensor are respectively provided with a second grounding terminal, a third wiring terminal, a fourth grounding terminal, and a fifth grounding terminal.

3. A method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers, employing the induced withstand voltage test modeling for large single-phase autotransformers as described in claims 1-2, characterized in that: Includes the following steps: S1. Collect no-load data of the autotransformer and excitation transformer T under rated voltage, and preprocess the no-load data to obtain various voltage values ​​of the autotransformer and excitation transformer T. S2. Collect the capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground during the routine test of the autotransformer in the acceptance test. HM-LE The capacitance C of the low-voltage winding to the high-voltage and medium-voltage windings and ground. L-HME The capacitance C of the high-voltage and medium-voltage windings to the low-voltage winding and ground. HML-E C was calculated H0 C HM-L C L0 ; S3. Based on the various voltage values ​​of the autotransformer, calculate the relationship between the high-voltage winding, medium-voltage winding, and low-voltage winding of the autotransformer and the winding height h during the test. S4. Take a small element with height dh between the high-voltage winding and the medium-voltage winding, calculate the capacitor current di, integrate the capacitor current di to obtain the capacitive current i, and substitute the voltage distribution of the high-voltage winding, medium-voltage winding, and low-voltage winding with the winding height h into the capacitive current i to obtain the reactive power Q of the high-voltage winding and medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E and the capacitive reactive power Q between the high-voltage winding, the medium-voltage winding and the low-voltage winding. AAm-a ; S5. Collect the capacitance C between the high-voltage winding and the medium-voltage winding and the low-voltage winding and ground. HM-LE Calculate the longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding. HM ; S6. During the experiment, the total loss S0 of the autotransformer under rated operating conditions and the no-load loss P0 of the autotransformer under rated operating conditions were collected to obtain the inductive reactive power Q. L ; S7. Extract the reactive power Q from the high-voltage winding and the medium-voltage winding to ground. AAM-E Reactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a The longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding HM and inductive reactive power Q L The total reactive power Q consumed by the autotransformer during the induced withstand voltage test was calculated. S8. Collect the magnetic flux density B of the autotransformer under test conditions and the magnetic flux density B under rated conditions. N Based on the coefficients m and n of the cold-rolled silicon steel sheet, the active power loss P of the autotransformer described in the experiment was obtained.

4. The method for calculating modeling parameters for the induced withstand voltage test of a large single-phase autotransformer according to claim 3, characterized in that: According to step S1, the values ​​of the autotransformer include the voltage of the high-voltage winding to ground and the phase voltage of the high-voltage winding. and low-voltage winding phase voltage ; The voltage values ​​of the excitation transformer T include the phase voltage of the low-voltage winding, the input voltage, and the turns ratio k1 during the test.

5. The method for calculating modeling parameters for the induced withstand voltage test of a large single-phase autotransformer according to claim 3, characterized in that: According to step S2, the test measurements and the capacitances of each winding to ground and between windings satisfy the following equations: （1）； The capacitance C between the high-voltage winding and ground is obtained by substituting into formula (1). H0 The capacitance C between the high-voltage winding and the low-voltage winding HM-L The capacitance C between the low-voltage winding and ground L0 .

6. The method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers according to claim 3, characterized in that: According to step S3, the relationship between the high-voltage winding, medium-voltage winding and low-voltage winding of the autotransformer and the winding height h during the test is as follows: （2）； In formula (2), U AAm It is the voltage between the high-voltage winding and the medium-voltage winding; U AAm-a It is the voltage between the high-voltage winding and the medium-voltage winding and the low-voltage winding; H is the total height of the winding.

7. The method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers according to claim 6, characterized in that: According to step S4, the expression for the capacitor current di is: （3）； In formula (3), ω represents capacitance; ω represents the angular frequency during the test. This represents the substitution expression in formula (2); Integrating equation (3) and substituting it into equation (2), we obtain the capacitive current i of the high-voltage winding and the medium-voltage winding. AAM-E The capacitive current i of the low-voltage winding a-E The capacitive current i between the high-voltage winding and the medium-voltage winding and the low-voltage winding AAm-a ; Integrating formula (3), substituting it into formula (2), and multiplying by U respectively AAm U a U AAm-a The reactive power Q of the high-voltage winding and the medium-voltage winding to ground is obtained. AAM-E Reactive power Q of low-voltage winding to ground a-E The capacitive reactive power Q between the high-voltage and medium-voltage windings and the low-voltage winding. AAm-a .

8. The method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers according to claim 3, characterized in that: According to step S5, the longitudinal capacitance component Q of the reactive power of the high-voltage winding and the medium-voltage winding HM The calculation formula is as follows: （4）； In formula (4), α is the longitudinal capacitance value; α is the square root of the ratio of the sum of the capacitance to ground and the capacitance to adjacent windings per unit length to the longitudinal capacitance per unit length; the value of αH ranges from 1.5 to 3.

0. Indicates voltage; C HM-LE This refers to the capacitance of the high-voltage and medium-voltage windings to the low-voltage winding and ground.

9. The method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers according to claim 3, characterized in that: According to step S6, the rated reactive power loss Q0 is calculated using the total loss S0 and the no-load loss P0. （5）； The inductive reactive power Q L The expression is: （6）； Substituting formula (5) into formula (6), the inductive reactive power Q is calculated. L In formula (6), f N f is the rated frequency; f is the test frequency; U N U is the rated voltage; U is the test voltage, and ; This represents the total magnetic flux in the iron core. According to step S7, the formula for calculating the total reactive power Q consumed by the autotransformer during the induced withstand voltage test is as follows: （7）。 10. The method for calculating modeling parameters for induced withstand voltage tests of large single-phase autotransformers according to claim 3, characterized in that: According to step S8, the active power loss P of the autotransformer is calculated as follows: （8）； In formula (8), P is the active power loss under test conditions; P0 is the active power loss under rated operating conditions; If the core of the autotransformer described in the experiment operates in the unsaturated region, the calculation method is as follows: (9).

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