CN111273199A - Intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification - Google Patents

Abstract

测试系统中的采样电阻R_C1和R_C2的阻抗值一般为50Ω，因此流过非短路侧的电流。本发明根据元件参数值的变化情况进行变压器绕组变形的智能检测，避免了过于依赖于经验丰富的专业人员，统一了分析结论，给检修决策带来了很大的方便。The invention discloses an intelligent detection method for transformer winding deformation based on the identification of frequency sweep impedance curve. Combined with a short-circuit impedance method and a frequency response analysis method, an equivalent circuit model of the transformer winding is established to obtain the frequency sweep impedance curve of the transformer winding, comprising the following steps: When the sampling resistance R and its voltage U are known, the current I flowing through the winding can be obtained by the formula I=U/R, and the swept-frequency impedance method connection method that effectively combines the short-circuit impedance method and the frequency response analysis method can be obtained. ; During the test, one side of the transformer winding is short-circuited with a wire, and the head end of the other side of the winding is injected with a sine frequency sweep signal with a frequency of 10Hz to 1MHz.

The resistance values of the sampling resistors R _C1 and R _C2 in the test system are generally 50Ω, so the current flows through the non-short-circuit side. The invention performs intelligent detection of transformer winding deformation according to changes in component parameter values, avoids over-reliance on experienced professionals, unifies analysis conclusions, and brings great convenience to maintenance decision-making.

Description

Intelligent detection method of transformer winding deformation based on swept frequency impedance curve identification

technical field

The invention relates to the technical field of transformer winding detection, in particular to an intelligent detection method for transformer winding deformation based on frequency sweep impedance curve identification.

Background technique

Transformer is one of the important electrical equipment in the power system, and its safe operation is of great significance to ensure the security of the power grid. According to relevant statistics, the transformer winding is the main part of transformer accident damage. The poor short-circuit resistance of transformer windings is the main cause of transformer damage. With the continuous increase of power grid capacity, the gradual establishment of ultra-high voltage and ultra-high voltage power systems, and the imminent formation of complex systems such as large-capacity, large-area interconnection, and west-to-east power transmission, both the safe operation of the power system and the reliability of power supply are proposed. higher requirements. Especially with the national networking of ultra-high voltage transmission systems, the completion of compact transmission lines, and the adoption of AC flexible ultra-high voltage transmission systems with static compensation or series compensation, the short-circuit current of the transmission system will reach a higher level, such as 63kA. This requires that each transformer product can withstand the large electric power and mechanical force generated by the high short-circuit current. With the increasing capacity of the power grid, the short-circuit capacity also increases, and the transformer damage accidents caused by short-circuit faults are on the rise. The deformation of transformer windings caused by external short circuit is a common fault during the operation of the transformer, which seriously threatens the safe operation of the system. When the transformer is impacted by short-circuit fault current during operation, a large short-circuit current will flow in the transformer winding, and the short-circuit current will generate a large electromotive force under the interaction with the leakage magnetic field. Will withstand huge, non-uniform radial and axial electrodynamic forces. In addition, the transformer may also be subjected to accidental impact, bumps and vibrations during transportation and installation. Under the action of these forces (electric power or mechanical force), the winding may produce mechanical displacement and deformation, and may cause serious transformer accidents such as insulation damage, winding short circuit and burnout. In addition, the existence of dead zone or failure of the protection system will cause the transformer to withstand the action of short-circuit current for a long time, which is also one of the reasons for the deformation of the winding. Therefore, in-depth research on the detection and diagnosis methods of transformer winding deformation has positive significance for improving the production level of transformers and ensuring the safe operation of power grids.

Sweep Frequency Impedance (Sweep Frequency Impedance) is the main experimental method for winding deformation research in recent years. It combines the advantages of the frequency response method and the short-circuit impedance method. It can not only effectively monitor the transformer winding deformation, reduce the false detection rate, and effectively ensure the operation of the power grid, but also has a higher signal-to-noise ratio, better repeatability and reproducibility, and a simpler wiring method.

The domestic use of swept-frequency impedance analysis to diagnose transformer winding deformation is mainly based on the comparison of swept-frequency curves through experience, and there are few data analysis methods. Among them, the empirical analysis method is a method for transformer professionals to judge whether the winding is deformed according to the change of frequency and amplitude at the extreme point of the sweep frequency curve based on past experience. For experienced professionals, it can more accurately judge whether the winding is deformed. However, this purely empirical method has obvious shortcomings: 1) The experience requirements of analysts are relatively high, and it is difficult to perform without experience or lack of experience; 2) Due to the dispersion and uncertainty of experience, it is difficult to standardize and promote, and different The analysts may come to different analysis conclusions, which brings certain difficulties to the maintenance decision. The feasibility of this method is not high. The main reasons are: 1) The judgment accuracy is low; 2) The specific changes of the frequency and amplitude of the extreme point of the sweep frequency curve cannot be accurately reflected.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide an intelligent detection method for transformer winding deformation based on the identification of the frequency sweep impedance curve. Intelligent detection of transformer winding deformation based on changing conditions avoids over-reliance on experienced professionals, unifies analysis conclusions, and brings great convenience to maintenance decision-making, so as to solve the problems raised in the above background technology.

To achieve the above object, the present invention provides the following technical solutions:

The intelligent detection method of transformer winding deformation based on swept-frequency impedance curve identification, combined with short-circuit impedance method and frequency response analysis method, establishes the equivalent circuit model of transformer winding, and obtains the swept-frequency impedance curve of transformer winding. The detection method includes the following steps:

S1: When the sampling resistance R and its voltage U are known, the current I flowing through the winding can be obtained by the formula I=U/R, and the frequency sweep impedance effectively combining the short-circuit impedance method and the frequency response analysis method can be obtained. method of wiring;

并利用采样电阻R_C1和R_C2分别得到该绕组的激励信号

和响应信号

通过以上参数可得变压器的阻抗

S2: During the test, one side of the transformer winding is short-circuited with a wire, and a sinusoidal sweep frequency signal with a frequency of 10Hz to 1MHz is injected into the head end of the other side of the winding.

And use the sampling resistors R _C1 and R _C2 to get the excitation signal of the winding respectively

and response signal

Through the above parameters, the impedance of the transformer can be obtained

S3: Considering that most of the connecting lines in the test are coaxial cables with an impedance of 50Ω, in order to meet the impedance matching factor and reduce the test wave process, the impedance values of the sampling resistors R _C1 and R _C2 in the test system are generally 50Ω, so flow through Current on the non-shorted side.

Further, the steps for establishing the equivalent circuit model of the transformer winding are as follows:

The first step: establish a suitable ANSYS simulation model, and calculate the mutual capacitance between the high and low voltage windings in the same phase, the capacitance between the adjacent high voltage windings, the winding-to-ground capacitance and the longitudinal capacitance inductance under the fault-free state;

Step 2: First, establish a three-dimensional simulation model of the transformer, establish high and low voltage winding models for A and B phases, and only establish a high voltage winding model for C phase;

Step 3: After the modeling is completed, electrostatic analysis needs to be performed, and the CMATRIX command in the ANSYS software is called to obtain the corresponding capacitance value;

Step 4: Calculate the capacitance and inductance, and simplify the model to a single-phase two-dimensional axisymmetric situation for calculation;

Step 5: Calculate the capacitance and inductance parameters when the winding condition changes. Based on the three-dimensional model of the transformer, create corresponding defects for simulation;

Step 6: The ATP model of the winding equivalent circuit is established, and the model should be compared horizontally with the common model;

Step 7: Simulation analysis of swept frequency impedance method. According to the simulation model established above, carry out winding deformation analysis, discuss the factors and winding deformation forms that cause transformer winding deformation, and study the characteristics of swept frequency impedance test methods, so as to establish and Improve the equivalent model of transformer winding suitable for swept frequency impedance simulation.

Further, the steps of acquiring the frequency sweep impedance curve of the transformer winding are as follows:

Step 1: Make a transformer model, use a three-phase core structure to make a model transformer, and simulate various types, different degrees and different positions of faults by connecting capacitors, inductors or short-circuit windings in parallel or in series;

Step 2: Build the frequency sweep impedance test system, build a hardware test platform for the frequency sweep impedance method according to the implementation method of the frequency sweep impedance method;

Step 3: Manufacture winding displacement, unequal height, inter-turn short circuit, bulging, warping faults of various types, degrees and positions on the model transformer, and use the established sweep impedance method to test the system and the corresponding software platform , test the model transformer, compare and analyze the changes of the frequency sweep impedance test data before and after deformation, study the stability and accuracy of the sweep frequency impedance method, and obtain the sweep frequency characteristic curves according to different types and degrees of faults and the deduced The short-circuit reactance value establishes the criterion for diagnosing the type and degree of winding deformation;

Step 4: Study the relationship between the change of winding system parameters and the factors of fault type, deformation position and degree of deformation, obtain the intelligent detection method of winding deformation based on the winding parameter identification technology and the influence law of winding parameters, summarize the law, summarize and improve, and use the simulation test With the results of laboratory simulation tests, a winding deformation criterion based on swept-frequency impedance is proposed, and further verification is carried out with the help of simulation tools, so that the criterion is continuously improved, and the improved swept-frequency short-circuit impedance method is applied to the field. Power transformer, in-depth study of measurement repeatability, the impact of electromagnetic interference on the test site, measurement sensitivity and accuracy, and further improve the sweep impedance method according to the measurement results.

Further, it also includes two kinds of equivalent circuits: low-frequency equivalent test circuit and medium-high frequency equivalent test circuit. For the low-frequency equivalent test circuit, when the voltage frequency applied to the winding head is low, the transformer can be regarded as composed of resistance and inductance. For the medium and high frequency equivalent test circuit, when the applied voltage frequency is >1kHz, the excitation effect of the transformer core is weakened, and the winding can be regarded as a linear two-port network composed of a series of inductance, capacitance and resistance distribution parameters.

Further, the middle part of the three-dimensional simulation model of the transformer is the iron core and the three-phase winding, and the iron core and the shell are grounded.

Further, the model transformer has a capacity of 50kVA and a transformation ratio of 10kV/380V. The first and last ends of the high and low voltage windings are drawn out through bushings respectively. The high voltage windings of the transformer evenly take out 50 taps in the axial direction, and the low voltage windings take out 10 taps.

Further, the design elements for building a swept-frequency impedance method hardware test platform include a high-power swept-frequency signal source, a broadband power amplifier, a signal conversion unit, a data acquisition unit, and a data transmission module, and a software platform for the swept-frequency impedance method is established.

Further, the software platform includes a sweep frequency curve drawing module, a low frequency band fitting module, a short-circuit reactance calculation module and a fault diagnosis module.

Further, the experimental steps of step 3 are as follows:

(1) Apply sweep frequency signals to the three-phase windings respectively, and obtain sweep frequency charts corresponding to different defects;

(2) Perform Δ/Y switching on the high-voltage side of the transformer winding, and apply sweep frequency signals to the three-phase low-voltage sides respectively, and measure the sweep spectrum diagram;

(3) Apply the sweep frequency signal on the high-voltage side of the winding, and repeat steps 1 and 2.

Compared with the prior art, the beneficial effects of the present invention are as follows: the intelligent detection method of transformer winding deformation based on the identification of the frequency sweep impedance curve proposed by the present invention can carry out the winding deformation test based on the frequency sweep impedance by means of the established simulation circuit model. Simulation, to obtain the typical sweep impedance test results of different forms of transformer models and different deformation forms. At the same time, during the simulation research, the typical parameters of the laboratory model can be obtained, and the simulation research can be carried out to verify the correctness of the simulation model by using the comparative analysis results. The swept-frequency impedance method can effectively detect the deformation defects of transformer windings. Since the swept-frequency impedance curve is obtained from the above equivalent circuit, the swept-frequency impedance curve can be identified, and the circuit elements in the equivalent circuit can be deduced accordingly. Parameter value, and intelligently detect transformer winding deformation according to the change of component parameter value, avoid relying too much on experienced professionals, unify analysis conclusions, and bring great convenience to maintenance decision-making.

Description of drawings

Fig. 1 is the test principle diagram of frequency sweep impedance method of the present invention;

Fig. 2 is the low frequency equivalent test circuit diagram of the frequency sweep impedance method of the present invention;

Fig. 3 is the high frequency equivalent test circuit diagram of the frequency sweep impedance method of the present invention;

4 is a three-dimensional ANSYS simulation diagram of a transformer of the present invention;

Fig. 5 is the transformer capacitance parameter calculation model diagram of the present invention;

Fig. 6 is the transformer inductance parameter calculation model diagram of the present invention;

Fig. 7 is the variation trend diagram of the transformer capacitance of the present invention with displacement;

Fig. 8 is the winding model diagram under the lower frequency of the present invention;

Fig. 9 is the winding model diagram under the high frequency of the present invention;

Fig. 10 is the winding model diagram after considering electrostatic coupling according to the present invention;

Fig. 11 is the model transformer design drawing a of the present invention;

Fig. 12 is the model transformer design drawing b of the present invention;

FIG. 13 is a schematic diagram of the test wiring of the frequency sweep impedance method of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

An intelligent detection method for transformer winding deformation based on swept-frequency impedance curve identification, combined with short-circuit impedance method and frequency response analysis method. , and both collect the voltage signal. The difference is that the short-circuit impedance method needs to obtain the current flowing through the test winding, and the frequency response analysis method needs to obtain the voltage on the sampling resistor at the end of the winding. The detection method includes the following steps:

Step 1: It can be seen from the circuit principle that when the sampling resistance R and its voltage U are known, the current I flowing through the winding can be obtained by the formula I=U/R, and the short-circuit impedance method and the frequency response analysis method can be obtained. The effective combination of swept-frequency impedance method wiring method is shown in Figure 1;

并利用采样电阻R_C1和R_C2分别得到该绕组的激励信号

和响应信号

通过以上参数可得变压器的阻抗

Step 2: As can be seen from Figure 1, during the test, one side of the transformer winding (generally the low-voltage winding) is short-circuited with a wire, and a sinusoidal frequency sweep signal with a frequency of 10Hz to 1MHz is injected into the head end of the winding on the other side.

And use the sampling resistors R _C1 and R _C2 to get the excitation signal of the winding respectively

and response signal

Through the above parameters, the impedance of the transformer can be obtained

为变压器的阻抗值/Ω，j为虚数单位，ω为加载信号的角频率/rad/s，

和

分别为被测绕组的首端电压及末端电压/V，

为被测绕组的电流/A，R为被测变压器的电阻/Ω，X为被测变压器的电抗/Ω。In the formula,

is the impedance value of the transformer/Ω, j is the imaginary unit, ω is the angular frequency of the loading signal/rad/s,

and

are the head-end voltage and end-end voltage/V of the winding under test, respectively.

is the current/A of the winding under test, R is the resistance/Ω of the transformer under test, and X is the reactance/Ω of the transformer under test.

Step 3: Considering that most of the connecting lines in the test are coaxial cables with an impedance of 50Ω, in order to meet the impedance matching factor and reduce the test wave process, the impedance values of the sampling resistors R _C1 and R _C2 in the test system are generally 50Ω (as shown in the figure). 1), so the current flowing through the non-shorted side is:

Substitute equation (2) into equation (1) to get:

Equation (3) can be further transformed into:

The mode of formula (4) is the frequency sweep impedance of the transformer

At the same time, the sweep resistance R and sweep reactance X of the transformer can be further obtained by using the formula (4):

和响应电压

的相位。根据图1可知，该测试方法包含2种等效电路，一种为低频等效测试电路，另一种为中高频等效测试电路，具体如下：In the formula, the phase difference θ=(θ _i -θ _o ), where θ _i and θ _o are the excitation voltages, respectively

and response voltage

phase. According to Figure 1, the test method includes two equivalent circuits, one is a low-frequency equivalent test circuit, and the other is a medium-high-frequency equivalent test circuit, as follows:

(1) Low frequency equivalent circuit

和

分别为加载于绕组的激励电压和响应电压，R₁、X₁和Z₁分别为被测绕组的电阻、电抗及阻抗，R′₂、X′₂和Z′₂分别为短路侧绕组变比到被测绕组的电阻、电抗及阻抗，R₃、X₃和Z₃分别为变压器的励磁电阻、励磁电抗及励磁阻抗，R_C1和R_C2分别为绕组首、末端的采样电阻，

为流过被测绕组的电流，Z为变压器的阻抗。When the frequency of the applied voltage at the head end of the winding is low, the transformer can be regarded as a T-shaped circuit composed of resistance and inductance, as shown in Figure 2. in,

and

are the excitation voltage and response voltage applied to the winding, respectively, R ₁ , X ₁ and Z ₁ are the resistance, reactance and impedance of the winding to be measured, respectively, R' ₂ , X' ₂ and Z' ₂ are the short-circuit side winding transformation ratios, respectively The resistance, reactance and impedance of the winding to be measured, R ₃ , X ₃ and Z ₃ are the excitation resistance, excitation reactance and excitation impedance of the transformer respectively, R _C1 and R _C2 are the sampling resistances at the beginning and end of the winding, respectively,

is the current flowing through the winding under test, and Z is the impedance of the transformer.

It can be seen from Figure 2 that at low frequency, the test circuit of the sweep impedance method is completely equivalent to the short-circuit impedance method, so the value at 50Hz of the sweep impedance curve can be used as the short-circuit impedance value to determine the transformer winding state. For comparison with the transformer nameplate value, the swept impedance value at 50Hz needs to be normalized. For a single-phase transformer, the short-circuit impedance percentage Z _ke is:

In the formula, Z _k is the frequency sweep impedance value/Ω at 50Hz, I _e and U _e are the rated current/A and voltage/V of the transformer, respectively. conversion of:

(2) Medium and high frequency equivalent circuit

和

分别为加载于变压器绕组的激励电压和响应电压，L、R和C_k分别为被测变压器绕组的电感、电阻及饼间电容，C_d为被测变压器的对地电容，

为流过被测绕组的电流，R_C1和R_C2分别为绕组首、末端的采样电阻。When the applied voltage frequency is greater than 1kHz, the excitation effect of the transformer core is weakened, and the winding can be regarded as a linear two-port network composed of a series of distributed parameters such as inductance, capacitance and resistance. The frequency sweep impedance test circuit is shown in Figure 3. in,

and

are the excitation voltage and response voltage applied to the transformer windings, respectively, L, R and C _k are the inductance, resistance and inter-cake capacitance of the transformer winding under test, respectively, C _d is the ground capacitance of the transformer under test,

For the current flowing through the winding under test, R _C1 and R _C2 are the sampling resistors at the beginning and end of the winding, respectively.

It can be seen from Figure 3 that if the distribution parameters of the transformer in the circuit change, the sweep impedance value in equation (5) will inevitably change. Therefore, the sweep impedance curve is similar to the frequency response curve and can describe the transformer winding state.

The steps for establishing the equivalent circuit model of the transformer winding are as follows:

The first step: According to the actual size and material properties of the transformer provided by the transformer manufacturer, establish a suitable ANSYS simulation model, and calculate the mutual capacitance between the high and low voltage windings in the same phase, the capacitance between the adjacent high voltage windings, and the winding to ground under the fault-free state. parameters such as capacitance and longitudinal capacitance and inductance, and further study the change of winding distribution parameters under fault conditions such as inter-turn short circuit, displacement, bending and warpage;

Step 2: In order to determine the specific capacitance parameters between the windings and to the ground, it is necessary to establish a three-dimensional simulation model of the transformer. A and B phases establish high and low voltage winding models, and C phase only establishes a high voltage winding model to solve the mutual capacitance between windings and The capacitance to ground, the ANSYS simulation is shown in Figure 4;

Step 3: The rectangular parallelepiped in the model is the simplified transformer shell, the middle part is the iron core and the three-phase winding, and the iron core and the shell are grounded. After the modeling is completed, electrostatic analysis needs to be performed, and the CMATRIX command in the ANSYS software is called to obtain the corresponding Capacitance value;

Step 4: Calculate the capacitance and inductance;

(1) Capacitance calculation: The longitudinal capacitance of a single winding is only determined by the geometric size of the winding itself and related material properties. In this case, the model can be simplified to a single-phase two-dimensional axisymmetric situation for calculation. Taking the high-voltage winding as an example (the calculation method of the low-voltage winding is similar, and will not be repeated here), the high-voltage winding of the physical transformer has a total of 50 cakes, which can be divided into three parts along the axis of the upper, middle and lower parts, and each calculation The five cakes of one part are built in detail, and the mutual capacitance between the cakes is obtained by calling the CMATRIX macro in the ANSYS electrostatic analysis, and then the total capacitance is obtained from the series relationship as the average capacitance of each part. The simulation graph is shown in Figure 5. In Figure 5, A1 represents the low-voltage winding, A8 represents the transformer oil, and A2 and A3-A7 are the high-voltage segmented windings; the iron core part and the transformer shell are grounded, so they have been deducted and simplified;

(2) Inductance calculation: The calculation of winding inductance is relatively simple. It is only necessary to build the required winding in the three-dimensional model. The specific current, number of turns and size parameters can be controlled according to the actual situation. The real constants of the unit can be controlled. The simulation graph is shown in Figure 6.

Step 5: Calculate the capacitance and inductance parameters when the winding condition changes. The form of winding deformation is mainly considered: plum blossom deformation, local bulge, winding displacement, collapse and tilt of the wire cake, short circuit between turns, warping, etc. In order to study the changes of the winding distribution parameters (inductance and capacitance) under the above conditions, the corresponding defects were simulated based on the three-dimensional model of the transformer. The purpose is to deeply understand the variation of winding distribution parameters under different defect types and degrees, summarize its laws, and lay the foundation for ATP modeling analysis and experiments. Figure 7 shows the change of the capacitance to ground after the lateral displacement of different parts of the A-phase high-voltage winding;

Step 6: The ATP model of the winding equivalent circuit is established, the frequency involved is 0.5kHz-1MHz, and the frequency range span is large. When constructing the transformer winding model, the role of the core and the winding should be considered mainly. The role of the iron core includes the magnetizing inductance, the parasitic capacitance generated by the magnetizing inductance and the core loss; the role of the winding includes copper loss, leakage inductance and stray loss. When the model is constructed, it should be compared with common models, such as classic model, improved model, RLC circuit model, multi-conductor transmission line model, etc. Taking into account the difference in the role of the iron core under different frequency values, the two winding models are shown in Figure 8 and Figure 9;

The above two models take out the voltage value U(f) at the head end, ground the end and obtain the current value I(f) through a small resistance, then the transfer impedance response function U(f)/I(f) can be obtained; The electrostatic coupling effect of , the winding model at high frequency is corrected to the form shown in Figure 10, so that by adjusting the capacitance and inductance parameters in the circuit, the 0.5kHz-1MHz swept frequency power supply and the 50Hz power frequency power supply can be calculated and analyzed respectively. Under the action, the quantitative change of the transfer impedance response function U(f)/I(f) and the short-circuit reactance, and the value at 50Hz was deduced by linearly fitting the low-frequency curve of the transfer impedance response function, and compared with the short-circuit reactance value. , through the above work, the theoretical system of the sweep impedance method is established.

Step 7: Simulation analysis of swept frequency impedance method. According to the simulation model established above, carry out winding deformation analysis, discuss the factors and winding deformation forms that cause transformer winding deformation, and study the characteristics of swept frequency impedance test methods, so as to establish and To improve the equivalent model of transformer winding suitable for swept frequency impedance simulation, the following factors are mainly considered during simulation analysis:

The influence of typical parameters of transformers with different voltage levels (110kV and above), different winding forms (three-turn transformer, two-turn transformer, auto-coupling transformer) and different number of phases (single-phase, three-phase) on the simulation model.

Consider the influence of transformer-related accessories such as bushings, tap-changers, and other related factors on the simulation model.

In addition, based on the normal transformer model, various typical winding deformation forms are simulated, and the corresponding relationship between the winding deformation and the equivalent resistance, inductance, and capacitance parameter changes is discussed.

With the help of the established simulation circuit model, the winding deformation test simulation based on swept-frequency impedance is carried out, and the influence of various factors on the swept-frequency impedance test results is considered, such as the influence of the test lead arrangement on the swept-frequency impedance test results. Obtain the typical swept impedance test results of different transformer models and different deformation forms, which provides a basis for the research of swept impedance diagnostic technology. The analysis results verify the correctness of the simulation model.

The steps to obtain the swept frequency impedance curve of the transformer winding are as follows:

1. The production of the transformer model, the three-phase core structure is used to make the model transformer, the capacity is 50kVA, the transformation ratio is 10kV/380V, and the first and last ends of the high and low voltage windings are respectively drawn out through the bushing (a total of 12 high and low voltage outlet ends, which can be used for Δ/ Y-type switching); 50 taps are uniformly drawn from the high-voltage winding of the transformer along the axial direction, and 10 taps are drawn from the low-voltage winding, so as to obtain the changes of capacitance and inductance under different deformation forms according to the simulation research results, through parallel connection (series connection) The faults of various types, degrees and positions are simulated by means of capacitance, inductance or winding between short-circuit cakes. The preliminary design diagram of the transformer is shown in Figure 11 and Figure 12;

2. Construction of the frequency sweep impedance test system. According to the implementation method of the frequency sweep impedance method, a hardware test platform of the frequency sweep impedance method is built. The preliminary design plan mainly includes: a high-power frequency sweep signal source, a broadband power amplifier, and a signal conversion unit. , data acquisition unit and data transmission module, etc.; and establish a software platform for sweep frequency impedance method, including: sweep frequency curve drawing module, low frequency band fitting module, short-circuit reactance calculation module and fault diagnosis module, etc. The specific implementation scheme is shown in the figure. 13 shown;

3. Manufacture winding displacement, unequal height, inter-turn short circuit, bulge, warpage and other types of faults, different degrees and different positions on the model transformer, and use the established sweep impedance method test system and corresponding software platform , test the model transformer, compare and analyze the changes of the frequency sweep impedance test data before and after deformation, study the stability and accuracy of the sweep frequency impedance method, and obtain the sweep frequency characteristic curves according to different types and degrees of faults and the deduced The short-circuit reactance value establishes a criterion for diagnosing the type and degree of winding deformation, and provides a basis for the research of swept-frequency impedance diagnosis. The preliminary experimental steps are as follows:

1) Apply sweep frequency signals to the three-phase windings respectively, and obtain sweep frequency charts corresponding to different defects. (The single-phase experiment requires all the other two-phase windings to be suspended, and the defect is designed on the high-voltage side of the tested winding)

2) Perform Δ/Y switching on the high-voltage side of the transformer winding, and apply sweep frequency signals to the three-phase low-voltage sides respectively, and measure the sweep spectrum diagram. (In each test, each defect is designed on the three-phase high-voltage side of A, B, and C in turn)

3) Apply the sweep frequency signal on the high voltage side of the winding, and repeat steps 1 and 2.

It should be noted that the frequency sweep spectrum curve under defect-free conditions needs to be measured and recorded before the experiment as a reference comparison. Of course, the above experimental steps can also be continuously adjusted according to the actual situation during the experiment to achieve the best effect.

4. Study the relationship between the change of winding system parameters and factors such as fault type, deformation position and degree of deformation, obtain the intelligent detection method of winding deformation based on the winding parameter identification technology and the influence law of winding parameters, summarize the law, and summarize and improve, which is based on simulation Based on the results of the test and laboratory simulation test, a winding deformation criterion based on swept frequency impedance is proposed, and further verification is carried out with the help of simulation tools, so that the criterion is continuously improved, and the improved swept frequency short-circuit impedance method is applied to the field. The measurement repeatability, the influence of electromagnetic interference on the test site, the sensitivity and accuracy of the measurement, etc. are further studied, and the sweep impedance method is further improved according to the measurement results, so that the method can be practically applied to the deformation of power transformer windings. Testing and Diagnosis.

To sum up, the intelligent detection method of transformer winding deformation based on swept-frequency impedance curve identification proposed by the present invention, with the help of the established simulation circuit model, carries out winding deformation test simulation based on swept-frequency impedance, and obtains different forms of transformer models and different models. The typical swept-frequency impedance test results of the deformed form, at the same time, during the simulation research, the typical parameters of the laboratory model can be obtained, the simulation research can be carried out, and the correctness of the simulation model can be verified by the comparative analysis results. The swept-frequency impedance method can effectively detect transformers Winding deformation defects, and since the frequency sweep impedance curve is obtained from the above equivalent circuit, the sweep frequency impedance curve can be identified, and the circuit element parameter values in the equivalent circuit can be deduced accordingly. The intelligent detection of transformer winding deformation in the changing situation avoids over-reliance on experienced professionals, unifies the analysis conclusions, and brings great convenience to maintenance decision-making.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (9)

1. An intelligent detection method for transformer winding deformation based on swept-frequency impedance curve identification, combined with short-circuit impedance method and frequency response analysis method, establishes an equivalent circuit model of transformer winding, and obtains transformer winding swept-frequency impedance curve, characterized in that the detection method includes: Follow the steps below: S1: When the sampling resistance R and its voltage U are known, the current I flowing through the winding can be obtained by the formula I=U/R, and the frequency sweep impedance effectively combining the short-circuit impedance method and the frequency response analysis method can be obtained. method of wiring; S2: During the test, one side of the transformer winding is short-circuited with a wire, and a sinusoidal sweep frequency signal with a frequency of 10Hz to 1MHz is injected into the head end of the other side of the winding.

And use the sampling resistors R _C1 and R _C2 to get the excitation signal of the winding respectively

and response signal

Through the above parameters, the impedance of the transformer can be obtained

S3: Considering that most of the connecting lines in the test are coaxial cables with an impedance of 50Ω, in order to meet the impedance matching factor and reduce the test wave process, the impedance values of the sampling resistors R _C1 and R _C2 in the test system are generally 50Ω, so flow through Current on the non-shorted side. 2. the transformer winding deformation intelligent detection method based on frequency sweep impedance curve identification according to claim 1, is characterized in that, the establishment step of transformer winding equivalent circuit model is as follows: The first step: establish a suitable ANSYS simulation model, and calculate the mutual capacitance between the high and low voltage windings in the same phase, the capacitance between the adjacent high voltage windings, the winding-to-ground capacitance and the longitudinal capacitance inductance under the fault-free state; Step 2: First, establish a three-dimensional simulation model of the transformer, establish high and low voltage winding models for A and B phases, and only establish a high voltage winding model for C phase; Step 3: After the modeling is completed, electrostatic analysis needs to be performed, and the CMATRIX command in the ANSYS software is called to obtain the corresponding capacitance value; Step 4: Calculate the capacitance and inductance, and simplify the model to a single-phase two-dimensional axisymmetric situation for calculation; Step 5: Calculate the capacitance and inductance parameters when the winding condition changes. Based on the three-dimensional model of the transformer, create corresponding defects for simulation; Step 6: The ATP model of the winding equivalent circuit is established, and the model should be compared horizontally with the common model; Step 7: Simulation analysis of swept frequency impedance method. According to the simulation model established above, carry out winding deformation analysis, discuss the factors and winding deformation forms that cause transformer winding deformation, and study the characteristics of swept frequency impedance test methods, so as to establish and Improve the equivalent model of transformer winding suitable for swept frequency impedance simulation. 3. the transformer winding deformation intelligent detection method based on frequency sweep impedance curve identification according to claim 1, is characterized in that, the step that transformer winding sweep frequency impedance curve obtains is as follows: Step 1: Make a transformer model, use a three-phase core structure to make a model transformer, and simulate various types, different degrees and different positions of faults by connecting capacitors, inductors or short-circuit windings in parallel or in series; Step 2: Build the frequency sweep impedance test system, build a hardware test platform for the frequency sweep impedance method according to the implementation method of the frequency sweep impedance method; Step 3: Manufacture winding displacement, unequal height, inter-turn short circuit, bulging, warping faults of various types, degrees and positions on the model transformer, and use the established sweep impedance method to test the system and the corresponding software platform , test the model transformer, compare and analyze the changes of the frequency sweep impedance test data before and after deformation, study the stability and accuracy of the sweep frequency impedance method, and obtain the sweep frequency characteristic curves according to different types and degrees of faults and the deduced The short-circuit reactance value establishes the criterion for diagnosing the type and degree of winding deformation; Step 4: Study the relationship between the change of winding system parameters and the factors of fault type, deformation position and degree of deformation, obtain the intelligent detection method of winding deformation based on the winding parameter identification technology and the influence law of winding parameters, summarize the law, summarize and improve, and use the simulation test With the results of laboratory simulation tests, a winding deformation criterion based on swept-frequency impedance is proposed, and further verification is carried out with the help of simulation tools, so that the criterion is continuously improved, and the improved swept-frequency short-circuit impedance method is applied to the field. Power transformer, in-depth study of measurement repeatability, the impact of electromagnetic interference on the test site, measurement sensitivity and accuracy, and further improve the sweep impedance method according to the measurement results. 4. The intelligent detection method for transformer winding deformation based on frequency sweep impedance curve identification according to claim 1, is characterized in that, also comprises 2 kinds of equivalent circuits of low frequency equivalent test circuit and medium and high frequency equivalent test circuit, for low frequency etc. When the applied voltage frequency at the winding head is low, the transformer can be regarded as a T-type circuit composed of resistance and inductance. For the medium and high frequency equivalent test circuit, when the applied voltage frequency is >1kHz, the excitation effect of the transformer core Attenuated, the winding can be viewed as a linear two-port network consisting of a series of inductive, capacitive, and resistive distribution parameters. 5 . The intelligent detection method for transformer winding deformation based on frequency sweep impedance curve identification according to claim 2 , wherein the middle part of the three-dimensional simulation model of the transformer is an iron core and a three-phase winding, and the iron core and the casing are grounded. 6 . 6. The intelligent detection method for transformer winding deformation based on frequency sweep impedance curve identification according to claim 3, characterized in that, the model transformer capacity is 50kVA, the transformation ratio is 10kV/380V, and the head and end of the high and low voltage windings are drawn out through bushings, respectively, The high-voltage winding of the transformer evenly draws 50 taps in the axial direction, and the low-voltage winding draws 10 taps. 7. The transformer winding deformation intelligent detection method based on the identification of frequency sweep impedance curve according to claim 3, is characterized in that, the design element that builds frequency sweep impedance method hardware test platform comprises high-power frequency sweep signal source, broadband power amplifier, Signal conversion unit, data acquisition unit and data transmission module, and establish a software platform for sweep impedance method. 8. The transformer winding deformation intelligent detection method based on frequency sweep impedance curve identification according to claim 3, is characterized in that, the software platform comprises the drawing module of sweep frequency curve, low frequency band fitting module, short circuit reactance calculation module and fault diagnosis module. 9. The intelligent detection method of transformer winding deformation based on frequency sweep impedance curve identification according to claim 3, is characterized in that, the experimental procedure of step 3 is as follows: (1) Apply sweep frequency signals to the three-phase windings respectively, and obtain sweep frequency charts corresponding to different defects; (2) Perform Δ/Y switching on the high-voltage side of the transformer winding, and apply sweep frequency signals to the three-phase low-voltage sides respectively, and measure the sweep spectrum diagram; (3) Apply the sweep frequency signal on the high-voltage side of the winding, and repeat steps 1 and 2.

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