CN111273199A - Intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification - Google Patents
Intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification Download PDFInfo
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Abstract
The invention discloses a transformer winding deformation intelligent detection method based on sweep frequency impedance curve identification, which combines a short-circuit impedance method and a frequency response analysis method to establish a transformer winding equivalent circuit model and acquire a transformer winding sweep frequency impedance curve, and comprises the following steps: under the condition that the sampling resistor R and the voltage U thereof are known, the current I flowing through the winding can be obtained through a formula I which is U/R, and a frequency sweep impedance method wiring mode which effectively combines a short circuit impedance method and a frequency response analysis method can be obtained; during testing, one side of the transformer winding is short-circuited by a lead, and a sine frequency sweeping signal with the frequency of 10 Hz-1MHz is injected into the head end of the winding on the other side
Sampling in a test systemResistance RC1And RC2Is generally 50 Ω, and therefore a current on the non-short-circuited side flows. According to the invention, the intelligent detection of the transformer winding deformation is carried out according to the change condition of the element parameter value, the condition that the transformer winding deformation excessively depends on experienced professionals is avoided, the analysis conclusion is unified, and great convenience is brought to maintenance decision.
Description
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 sweep frequency impedance curve identification.
Background
The transformer is one of important electrical equipment in a power system, and the safe operation of the transformer has great significance for ensuring the safety of a power grid. According to the statistics, the transformer winding is the main part of the accident damage of the transformer. The poor short-circuit resistance of the transformer winding is a main cause of the operational damage of the transformer. With the continuous increase of the capacity of a power grid, the gradual establishment of an extra-high voltage and extra-high voltage power system and the formation of complex systems such as high capacity, large area interconnection, west-east power transmission and the like are about to occur, and higher requirements are put forward on the safe operation and the power supply reliability of the power system. Particularly, with national networking of an ultrahigh voltage power transmission system, establishment of compact power transmission lines and adoption of an alternating-current flexible ultrahigh voltage power transmission system with static compensation or series compensation, the short-circuit current of the power transmission system reaches a high level, such as 63 kA. This requires that each transformer product be able to withstand the large electrodynamic and mechanical forces generated by the high short-circuit currents. With the increasing capacity of the power grid, the short-circuit capacity also increases, and the damage accidents of the transformer caused by short-circuit faults are on the rise. The deformation of the transformer winding caused by external short circuit is a common fault in the running process of the transformer, and the safe running of the system is seriously threatened. When the transformer is impacted by short-circuit fault current in the operation process, large short-circuit current flows in the windings of the transformer, the short-circuit current generates large electrodynamic force under the interaction with a leakage magnetic field, and each winding bears large and uneven radial electrodynamic force and axial electrodynamic force. In addition, the transformer may also be subjected to accidental impact, jolt, vibration, etc. during transportation, installation, etc. Under the action of these forces (electrodynamic or mechanical), the windings may be displaced and deformed mechanically, and serious transformer accidents such as insulation damage, winding short circuit and burnout may be caused. In addition, the dead zone or the action failure of the protection system can cause the transformer to bear the short-circuit current for a long time, which is also one of the reasons for the deformation of the winding. Therefore, the method for detecting and diagnosing the deformation of the transformer winding is deeply researched, and has positive significance for improving the production level of the transformer and ensuring the safe operation of a power grid.
The swept Frequency Impedance method (Sweep Frequency Impedance) is the main experimental method for the winding deformation research in recent years. It combines the advantages of the frequency response method and the short-circuit impedance method. The transformer winding deformation monitoring device can effectively monitor transformer winding deformation, reduce false detection rate, effectively guarantee operation of a power grid, and has the advantages of higher signal-to-noise ratio, better repeatability and reproducibility, and simpler wiring mode.
The method for diagnosing the transformer winding deformation by using the sweep frequency impedance analysis method is mainly established on the basis of comparing sweep frequency curves through experience, and has fewer data analysis means. The empirical analysis method is a method for judging whether the winding is deformed or not by transformer professionals according to previous experiences and changes of frequency and amplitude values of extreme points of a sweep frequency curve. And for professionals with abundant experience, whether the winding is deformed or not can be judged more accurately. However, this purely empirical approach has significant disadvantages: 1) the requirement on the experience of an analyst is high, and the analyst is difficult to be qualified without experience or with insufficient experience; 2) due to the dispersion and uncertainty of experience, the method is difficult to standardize and popularize, different analysts can obtain different analysis conclusions, and certain difficulty is brought to maintenance decision. This method is not highly feasible. The main reasons are: 1) the judgment accuracy is low; 2) the specific changes of the frequency and the amplitude of the extreme point of the sweep frequency curve cannot be accurately reflected.
Disclosure of Invention
The invention aims to provide an intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification, which can identify a sweep frequency impedance curve, reversely deduce the circuit element parameter value in an equivalent circuit according to the sweep frequency impedance curve, and intelligently detect the transformer winding deformation according to the change condition of the element parameter value, thereby avoiding excessively relying on experienced professionals, unifying the analysis conclusion, bringing great convenience to maintenance decision and solving the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
the intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification is combined with a short-circuit impedance method and a frequency response analysis method to establish a transformer winding equivalent circuit model and obtain a transformer winding sweep frequency impedance curve, and the detection method comprises the following steps:
s1: under the condition that the sampling resistor R and the voltage U thereof are known, the current I flowing through the winding can be obtained through a formula I which is U/R, and a frequency sweep impedance method wiring mode which effectively combines a short circuit impedance method and a frequency response analysis method can be obtained;
s2: during testing, one side of the transformer winding is short-circuited by a lead, and a sine frequency sweeping signal with the frequency of 10 Hz-1MHz is injected into the head end of the winding on the other side
And using a sampling resistor RC1And RC2Respectively obtaining excitation signals of the windings
And a response signal
The impedance of the transformer can be obtained by the above parameters
S3: considering that the connecting line in the test is mostly a coaxial line with 50 omega impedance, in order to meet the requirement of impedance matching factor and reduce the test wave process, the sampling resistor R in the test systemC1And RC2Is generally 50 Ω, and therefore a current on the non-short-circuited side flows.
Further, the transformer winding equivalent circuit model is established by the following steps:
the first step is as follows: establishing a proper ANSYS simulation model, and respectively calculating mutual capacitance between in-phase high-voltage and low-voltage windings, capacitance between adjacent-phase high-voltage windings, winding ground capacitance and longitudinal capacitance inductance in a fault-free state;
the second step is that: firstly, establishing a three-dimensional simulation model of the transformer, establishing a high-low voltage winding model for A, B phases, and only establishing a high-voltage winding model for C phase;
the third step: after modeling is completed, electrostatic analysis is required, and a CMATRIX command in ANSYS software is called to obtain a corresponding capacitance value;
the fourth step: calculating capacitance and inductance, and simplifying the model into a single-phase two-dimensional axisymmetric condition for calculation;
the fifth step: calculating the parameters of capacitance and inductance when the winding condition changes, and manufacturing corresponding defects for simulation on the basis of a three-dimensional model of the transformer;
and a sixth step: establishing an ATP model of the winding equivalent circuit, and transversely comparing the model with a common model during model establishment;
the seventh step: and (3) carrying out simulation analysis of the frequency sweep impedance method, developing winding deformation analysis according to the established simulation model, discussing factors causing transformer winding deformation and winding deformation forms, and researching the characteristics of a frequency sweep impedance test means, thereby establishing and perfecting a transformer winding equivalent model suitable for frequency sweep impedance simulation.
Further, the steps of obtaining the frequency sweep impedance curve of the transformer winding are as follows:
step 1: manufacturing a transformer model, namely manufacturing a model transformer by adopting a three-phase core type structure, and simulating various types, different degrees and different positions of faults by parallelly connecting or serially connecting a capacitor, an inductor or a short-circuit inter-cake winding wire;
step 2: building a frequency sweep impedance test system, namely building a frequency sweep impedance method hardware test platform according to an implementation method of a frequency sweep impedance method;
and step 3: manufacturing faults of winding displacement, unequal height, turn-to-turn short circuit, bulging, warping in various types, different degrees and different positions on a model transformer, testing the model transformer by utilizing the established sweep frequency impedance method testing system and a corresponding software platform, comparing and analyzing the change of sweep frequency impedance testing data before and after deformation, researching the stability and accuracy of the sweep frequency impedance method, and establishing a criterion for diagnosing the winding deformation type and degree according to sweep frequency characteristic curves obtained by faults in different types and different degrees and the deduced short circuit reactance value;
and 4, step 4: the method comprises the steps of researching the relation between the winding system parameter change and fault type, deformation position and deformation degree factors, obtaining a winding deformation intelligent detection mode based on a winding parameter identification technology and a winding parameter influence rule, summarizing the rule, concluding and perfecting, providing a winding deformation criterion based on sweep frequency impedance by means of results of simulation test and laboratory simulation test, and carrying out further verification by means of a simulation tool, so that the criterion is continuously perfected, applying the improved sweep frequency short-circuit impedance method to a field power transformer, deeply researching measurement repeatability, the influence of electromagnetic interference on a test field, and the sensitivity and accuracy of measurement, and further perfecting the sweep frequency impedance method according to the measurement result.
The transformer can be regarded as a T-shaped circuit consisting of a resistor and an inductor for the low-frequency equivalent test circuit when the frequency of voltage loaded at the head end of the winding is lower, and the excitation function of the iron core of the transformer is weakened for the medium-high frequency equivalent test circuit when the frequency of the loaded voltage is more than 1kHz, and the winding can be regarded as a linear dual-port network consisting of a series of distributed parameters of the inductor, the capacitor and the resistor.
Furthermore, the middle part of the three-dimensional simulation model of the transformer comprises an iron core and a three-phase winding, and the iron core and the shell are grounded.
Furthermore, the capacity of the model transformer is 50kVA, the transformation ratio is 10kV/380V, the head end and the tail end of the high-low voltage winding are respectively led out through the sleeve, 50 taps are uniformly drawn out from the high-voltage winding of the transformer along the axial direction, and 10 taps are drawn out from the low-voltage winding.
Furthermore, the design elements for constructing the hardware test platform of the frequency sweep impedance method comprise a high-power frequency sweep signal source, a broadband power amplifier, a signal conversion unit, a data acquisition unit and a data transmission module, and a software platform of the frequency sweep impedance method is established.
Furthermore, the software platform comprises a sweep frequency curve drawing module, a low-frequency band simulation module, a short-circuit reactance calculation module and a fault diagnosis module.
Further, the experimental procedure of step 3 is as follows:
(1) respectively applying frequency sweep signals to the three-phase winding to obtain frequency sweep spectrograms corresponding to different defects;
(2) carrying out delta/Y switching on the high-voltage side of the transformer winding, respectively applying frequency sweep signals on the three-phase low-voltage side, and measuring a frequency sweep spectrogram;
(3) applying a frequency sweep signal on the high voltage side of the winding, and repeating 1 and 2 steps.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a transformer winding deformation intelligent detection method based on sweep frequency impedance curve identification, which is characterized in that winding deformation test simulation based on sweep frequency impedance is carried out by means of an established simulation circuit model, typical sweep frequency impedance test results of different forms of transformer models and different deformation forms are obtained, meanwhile, typical parameters of a laboratory model can be obtained when simulation research is carried out, the correctness of the simulation model is verified by using a comparative analysis result, the sweep frequency impedance method can effectively detect the deformation defect of the transformer winding, and because the sweep frequency impedance curve is obtained according to the equivalent circuit, the sweep frequency impedance curve can be identified, circuit element parameter values in an equivalent circuit are reversely deduced, the intelligent detection of transformer winding deformation is carried out according to the change condition of the element parameter values, and the condition that the intelligent detection is too dependent on experienced professionals is avoided, the analysis conclusion is unified, and great convenience is brought to the maintenance decision.
Drawings
FIG. 1 is a schematic diagram of a test by a frequency sweep impedance method according to the present invention;
FIG. 2 is a circuit diagram of the low frequency equivalent test by the swept frequency impedance method of the present invention;
FIG. 3 is a circuit diagram of the middle-high frequency equivalent test by the swept-frequency impedance method of the present invention;
FIG. 4 is a three-dimensional ANSYS simulation of the transformer of the present invention;
FIG. 5 is a diagram of a model for calculating capacitance parameters of a transformer according to the present invention;
FIG. 6 is a model diagram of the transformer inductance parameter calculation according to the present invention;
FIG. 7 is a graph showing the variation of the capacitance of the transformer with displacement according to the present invention;
FIG. 8 is a diagram of a winding model for a lower frequency of the present invention;
FIG. 9 is a diagram of a winding model of the present invention at high frequency;
FIG. 10 is a diagram of a winding model of the present invention with electrostatic coupling taken into account;
FIG. 11 is a model transformer layout of the present invention a;
FIG. 12 is a model transformer layout b of the present invention;
fig. 13 is a test wiring schematic diagram of the swept frequency impedance method of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification combines a short-circuit impedance method and a frequency response analysis method, the short-circuit impedance method and the frequency response analysis method have certain similarity, voltage signals are injected into a transformer through a winding head end, the voltage signals are collected by the short-circuit impedance method and the frequency response analysis method, the difference is that the short-circuit impedance method needs to obtain current flowing through a test winding, the frequency response analysis method needs to obtain voltage on a winding tail end sampling resistor, and the detection method comprises the following steps:
step 1: according to the circuit principle, under the condition that the sampling resistor R and the voltage U thereof are known, the current I flowing through the winding can be obtained through the formula I which is U/R, and the connection mode of the frequency sweep impedance method which effectively combines the short circuit impedance method and the frequency response analysis method can be obtained, as shown in fig. 1;
step 2: as shown in FIG. 1, during the test, a wire is used to short-circuit one side of the transformer winding (generally, the low-voltage winding), and the head end of the winding at the other side is injected with a sinusoidal sweep frequency signal with a frequency of 10 Hz-1MHz
And using a sampling resistor RC1And RC2Respectively obtaining excitation signals of the windings
And a response signal
The impedance of the transformer can be obtained by the above parameters
In the formula (I), the compound is shown in the specification,
is the impedance value/omega of the transformer, j is an imaginary number unit, omega is the angular frequency/rad/s of the loading signal,
and
respectively the head end voltage and the tail end voltage/V of the winding to be tested,
the current/A of the winding to be tested, R is the resistance/omega of the transformer to be tested, and X is the reactance/omega of the transformer to be tested.
And step 3: considering that the connecting line in the test is mostly a coaxial line with 50 omega impedance, in order to meet the requirement of impedance matching factor and reduce the test wave process, the sampling resistor R in the test systemC1And RC2Is typically 50 Ω (as in fig. 1), so the current flowing through the non-shorted side is:
substituting formula (2) into formula (1) to obtain:
formula (3) can be converted further into:
the mode of the formula (4) is the frequency-sweeping impedance of the transformer
Meanwhile, the sweep frequency resistance R and the sweep frequency reactance X of the transformer can be further obtained by using the formula (4):
wherein the phase difference θ is (θ)i-θo) Wherein thetaiAnd thetaoRespectively an excitation voltage
And response voltage
The phase of (c). As can be seen from fig. 1, the test method includes 2 kinds of equivalent circuits, one is a low-frequency equivalent test circuit, and the other is a medium-high frequency equivalent test circuit, which is as follows:
(1) low frequency equivalent circuit
When the frequency of the voltage loaded at the head end of the winding is lower, the transformer can be regarded as a T-shaped circuit consisting of a resistor and an inductor, as shown in fig. 2. Wherein the content of the first and second substances,
and
respectively excitation voltage and response voltage, R, applied to the winding1、X1And Z1Respectively the resistance, reactance and impedance, R 'of the winding to be tested'2、X′2And Z'2Respectively, the short-circuit side winding transformation ratio to the resistance, reactance and impedance, R, of the winding to be tested3、X3And Z3Respectively the excitation resistance, excitation reactance and excitation impedance, R, of the transformerC1And RC2Respectively are sampling resistors at the head end and the tail end of the winding,
z is the impedance of the transformer for the current flowing through the winding under test.
As can be seen from FIG. 2, in the low frequency band, the test circuit of the frequency sweep impedance method is completely equivalent to the short circuit impedance method, so that the value at 50Hz of the frequency sweep impedance curve can be used as the short circuit impedance value to the winding state of the transformerAnd (6) judging. If the frequency sweep impedance value at 50Hz is compared with the nameplate value of the transformer, normalization is also needed to be carried out on the frequency sweep impedance value, and for a single-phase transformer, the short-circuit impedance percentage Z iskeComprises the following steps:
in the formula, ZkIs the frequency sweep impedance value/omega, I at 50HzeAnd UeRated current/a and voltage/V of the transformer, respectively, and for three-phase transformers, the conversion between phase voltage and line voltage must also be considered:
(2) middle-high frequency equivalent circuit
When loaded with voltage frequency>At 1kHz, the excitation of the transformer core is reduced, the winding can be regarded as a linear two-port network consisting of a series of distributed parameters such as inductance, capacitance and resistance, and the swept-frequency impedance test circuit is shown in fig. 3. Wherein the content of the first and second substances,
and
the excitation voltage and the response voltage applied to the transformer winding, L, R and C, respectivelykRespectively, the inductance, the resistance and the inter-cake capacitance of the winding of the tested transformer, CdIn order to measure the capacitance to ground of the transformer,
for the current flowing through the winding under test, RC1And RC2The sampling resistors are respectively the head end and the tail end of the winding.
As can be seen from fig. 3, if the distribution parameters of the transformer in the circuit change, the swept-frequency impedance value in equation (5) inevitably changes, so that the swept-frequency impedance curve is similar to the frequency response curve, and the winding state of the transformer can be described.
The method for establishing the equivalent circuit model of the transformer winding comprises the following steps:
the first step is as follows: establishing a proper ANSYS simulation model according to parameters such as the actual size and material properties of the transformer provided by a transformer manufacturer, respectively calculating parameters such as mutual capacitance between in-phase high-voltage and low-voltage windings, capacitance between adjacent-phase high-voltage windings, capacitance to ground of the windings, longitudinal capacitance inductance and the like in a fault-free state, and further researching the change conditions of winding distribution parameters under fault conditions such as turn-to-turn short circuit, displacement, bending, warping and the like;
the second step is that: in order to determine the specific capacitance parameters between windings and to the ground, a three-dimensional simulation model of the transformer needs to be established, a high-voltage winding model and a low-voltage winding model are established for the A, B phase, only a high-voltage winding model is established for the C phase, so that the mutual capacitance and the ground capacitance between the windings are solved, and ANSYS simulation is shown in FIG. 4;
the third step: the cuboid in the model is a simplified transformer shell, the middle part of the model is an iron core and a three-phase winding, the iron core and the shell are grounded, after modeling is completed, electrostatic analysis is needed, and a CMATRIX command in ANSYS software is called to obtain a corresponding capacitance value;
the fourth step: calculating capacitance and inductance;
(1) and (3) capacitance calculation: the longitudinal capacitance of a single winding is only determined by the geometric dimension of the winding and the related material properties, and the model can be simplified into a single-phase two-dimensional axial symmetry condition for calculation. Taking a high-voltage winding as an example (calculation methods of low-voltage windings are similar and are not described herein again), the high-voltage winding of the physical transformer has 50 cakes in total, the high-voltage winding can be divided into an upper part, a middle part and a lower part along the axial direction during simulation, five cakes of one part are established in detail during each calculation, the mutual capacitance between the cakes is obtained through calling of CMATRIX macro in ANSYS electrostatic analysis, and then the total capacitance is obtained through the series connection relation and is used as the average capacitance of each part. The simulation graph is as shown in FIG. 5. In FIG. 5, A1 represents a low-voltage winding, A8 represents transformer oil, and A2 and A3-A7 are high-voltage segment windings; the grounding of the iron core part and the transformer shell is reduced and simplified;
(2) and (3) inductance calculation: the calculation of the winding inductance is simple, the required winding is only needed to be built in the three-dimensional model, the specific current, the number of turns, the size parameters and the like can be controlled according to the real constants of the control unit under the actual condition, and the simulation graph is as shown in figure 6.
The fifth step: when the winding condition changes, the calculation of capacitance and inductance parameters and the form of winding deformation mainly consider: quincunx deformation, local bulging, winding displacement, line cake collapse and inclination, turn-to-turn short circuit, warping and the like. In order to research the change condition of the winding distribution parameters (inductance and capacitance) under the above conditions, the corresponding defects are manufactured and simulated on the basis of the three-dimensional model of the transformer. The method aims to deeply understand the change condition of winding distribution parameters under different defect types and degrees, summarize the rule of the change condition and lay a foundation for ATP modeling analysis and experiments. Fig. 7 illustrates the capacitance change to ground after the lateral displacement of different parts of the a-phase high-voltage winding;
and a sixth step: and establishing an ATP model of the winding equivalent circuit, wherein the related frequency is 0.5kHz-1MHz, and the span of the frequency range is large. In the construction of the transformer winding model, the core and winding functions are mainly considered. The function of the iron core comprises magnetization inductance, parasitic capacitance generated by the magnetization inductance and iron core loss; the effects of the windings include copper losses, leakage inductance and stray losses. The model is constructed by performing a transverse comparison with a common model, such as a classical model, an improved model, an RLC circuit model, a multi-conductor transmission line model, and the like. Two winding models are shown in fig. 8 and 9, taking into account the difference in core action at different frequency values;
the two models respectively take out a voltage value U (f) at the head end, the tail end is grounded, and a current value I (f) is obtained through a small resistor, so that a transfer impedance response function U (f)/I (f) can be obtained; considering the electrostatic coupling effect between windings, the winding model under high frequency is corrected to the form shown in fig. 10, so that the quantitative change conditions of the transfer impedance response function U (f)/I (f) and the short-circuit reactance under the action of a 0.5kHz-1MHz frequency sweep power supply and a 50Hz power frequency power supply can be respectively calculated and analyzed by adjusting the capacitance and inductance parameters in the circuit, the value under 50Hz is deduced by linearly fitting the transfer impedance response function low-frequency curve, the comparison and analysis are carried out on the value and the short-circuit reactance, and the theoretical system of the frequency sweep impedance method is established through the work.
The seventh step: the simulation analysis of the frequency sweep impedance method is carried out, winding deformation analysis is carried out according to the established simulation model, factors causing transformer winding deformation and winding deformation forms are discussed, and the characteristics of a frequency sweep impedance testing means are researched, so that a transformer winding equivalent model suitable for frequency sweep impedance simulation is established and perfected, and the following factors are mainly considered during the simulation analysis:
influence of typical parameters of transformers with different voltage grades (110kV and above), different winding forms (three-turn-to-two-turn-to-self-coupling-to-three-turn-to-three-phase) and different phase numbers (single-phase and three-phase) on the simulation model.
The influence of transformer-related accessories, such as bushings, tap changers and other related factors, on the simulation model is considered.
In addition, on the basis of a normal transformer model, various typical winding deformation forms are simulated, and the corresponding relation between the winding deformation and the parameter changes of equivalent resistance, inductance and capacitance is discussed.
And developing the winding deformation test simulation based on the frequency sweep impedance by means of the established simulation circuit model, and considering the influence of various factors on the frequency sweep impedance test result, such as the influence of test lead arrangement on the frequency sweep impedance test result. The method comprises the steps of obtaining typical frequency sweep impedance test results of different forms of transformer models and different deformation forms, providing a foundation for research of frequency sweep impedance diagnosis technology, obtaining typical parameters of a laboratory model during simulation research, developing simulation research, and verifying the correctness of the simulation model by using comparison analysis results.
The steps of obtaining the frequency sweep impedance curve of the transformer winding are as follows:
1. manufacturing a transformer model, namely manufacturing a model transformer by adopting a three-phase core type structure, wherein the capacity is 50kVA, the transformation ratio is 10kV/380V, and the head and tail ends of a high-voltage winding and a low-voltage winding are respectively led out by virtue of sleeves (the high-voltage winding and the low-voltage winding have 12 outlet ends in total and can be subjected to delta/Y type switching); the transformer high-voltage winding is uniformly provided with 50 taps in the axial direction, the low-voltage winding is provided with 10 taps in the axial direction, so that the faults of various types, different degrees and different positions can be simulated in the modes of winding among capacitors, inductors or short circuit cakes in parallel (in series) according to the change of the capacitors and the inductors in different deformation modes obtained according to simulation research results, and the primary design drawing of the transformer is shown in fig. 11 and 12;
2. the method comprises the following steps of establishing a frequency sweep impedance test system, establishing a frequency sweep impedance method hardware test platform according to an implementation method of a frequency sweep impedance method, and mainly adopting a preliminary design scheme that: the device comprises a high-power frequency-sweeping signal source, a broadband power amplifier, a signal conversion unit, a data acquisition unit, a data transmission module and the like; and a software platform for the frequency sweep impedance method is established, which comprises the following steps: a sweep frequency curve drawing module, a low-frequency band simulation module, a short-circuit reactance calculation module, a fault diagnosis module and the like, wherein the specific implementation scheme is shown in fig. 13;
3. the method comprises the following steps of manufacturing various types, different degrees and different positions of faults such as winding displacement, unequal height, turn-to-turn short circuit, bulging, warping and the like on a model transformer, testing the model transformer by utilizing an established sweep frequency impedance method testing system and a corresponding software platform, comparing and analyzing the change of sweep frequency impedance testing data before and after deformation, researching the stability and the accuracy of the sweep frequency impedance method, establishing a criterion for diagnosing the winding deformation type and degree according to sweep frequency characteristic curves obtained by faults of different types and different degrees and an estimated short circuit reactance value, providing a basis for the research of the sweep frequency impedance diagnosis, and primarily simulating the experiment steps as follows:
1) and respectively applying frequency sweep signals to the three-phase winding to obtain frequency sweep spectrograms corresponding to different defects. (Single phase experiment requires the other two phase winding outlet terminals to be all suspended, the defect is designed on the high voltage side of the tested winding)
2) And carrying out delta/Y switching on the high-voltage side of the transformer winding, respectively applying frequency sweep signals on the three-phase low-voltage side, and measuring a frequency sweep spectrogram. (each defect is designed on the A, B and C three-phase high-voltage side in sequence in each test)
3) Applying a frequency sweep signal on the high voltage side of the winding, and repeating 1 and 2 steps.
It should be noted that before the experiment, the sweep frequency spectrum curve under the defect-free condition needs to be measured and recorded as the reference contrast, and of course, the above experimental steps can be continuously adjusted according to the actual situation in the experimental process to achieve the best effect.
4. The method is characterized in that a winding deformation criterion based on sweep frequency impedance is provided by means of results of simulation test and laboratory simulation test, and further verification is carried out by means of a simulation tool, so that the criterion is continuously perfected, the improved short-circuit sweep frequency impedance method is applied to a field power transformer, the measurement repeatability, the influence of electromagnetic interference on a test field, the measurement sensitivity and accuracy and the like are deeply researched, the sweep frequency impedance method is further perfected according to the measurement result, and the method can be practically applied to the test and diagnosis of the winding deformation of the power transformer.
In summary, the intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification provided by the invention develops the winding deformation test simulation based on sweep frequency impedance by means of the established simulation circuit model, obtains the typical sweep frequency impedance test results of different forms of transformer models and different deformation forms, simultaneously, when carrying out the simulation research, can obtain the typical parameters of a laboratory model, develop the simulation research, verify the correctness of the simulation model by using the comparative analysis result, the sweep frequency impedance method can effectively detect the transformer winding deformation defect, and because the sweep frequency impedance curve is obtained according to the equivalent circuit, the sweep frequency impedance curve can be identified, thereby the circuit element parameter value in the equivalent circuit is reversely deduced, and the intelligent detection of the transformer winding deformation is carried out according to the change condition of the element parameter value, the method avoids the excessive dependence on experienced professionals, unifies the analysis conclusion and brings great convenience to maintenance decision.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to cover the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (9)
1. The intelligent detection method for transformer winding deformation based on sweep frequency impedance curve identification is characterized in that the detection method comprises the following steps of:
s1: under the condition that the sampling resistor R and the voltage U thereof are known, the current I flowing through the winding can be obtained through a formula I which is U/R, and a frequency sweep impedance method wiring mode which effectively combines a short circuit impedance method and a frequency response analysis method can be obtained;
s2: during testing, one side of the transformer winding is short-circuited by a lead, and a sine frequency sweeping signal with the frequency of 10 Hz-1MHz is injected into the head end of the winding on the other side
And using a sampling resistor RC1And RC2Respectively obtaining excitation signals of the windings
And a response signal
The impedance of the transformer can be obtained by the above parameters
S3: considering that the connecting line in the test is mostly a coaxial line with 50 omega impedance, in order to meet the requirement of impedance matching factor and reduce the test wave process, the sampling resistor R in the test systemC1And RC2Is generally 50 Ω, and therefore a current on the non-short-circuited side flows.
2. A sweep-frequency impedance curve identification-based transformer winding deformation intelligent detection method as claimed in claim 1, characterized in that the transformer winding equivalent circuit model is established by the following steps:
the first step is as follows: establishing a proper ANSYS simulation model, and respectively calculating mutual capacitance between in-phase high-voltage and low-voltage windings, capacitance between adjacent-phase high-voltage windings, winding ground capacitance and longitudinal capacitance inductance in a fault-free state;
the second step is that: firstly, establishing a three-dimensional simulation model of the transformer, establishing a high-low voltage winding model for A, B phases, and only establishing a high-voltage winding model for C phase;
the third step: after modeling is completed, electrostatic analysis is required, and a CMATRIX command in ANSYS software is called to obtain a corresponding capacitance value;
the fourth step: calculating capacitance and inductance, and simplifying the model into a single-phase two-dimensional axisymmetric condition for calculation;
the fifth step: calculating the parameters of capacitance and inductance when the winding condition changes, and manufacturing corresponding defects for simulation on the basis of a three-dimensional model of the transformer;
and a sixth step: establishing an ATP model of the winding equivalent circuit, and transversely comparing the model with a common model during model establishment;
the seventh step: and (3) carrying out simulation analysis of the frequency sweep impedance method, developing winding deformation analysis according to the established simulation model, discussing factors causing transformer winding deformation and winding deformation forms, and researching the characteristics of a frequency sweep impedance test means, thereby establishing and perfecting a transformer winding equivalent model suitable for frequency sweep impedance simulation.
3. A method for intelligently detecting transformer winding deformation based on swept-impedance curve identification as claimed in claim 1, wherein the steps of obtaining the swept-impedance curve of the transformer winding are as follows:
step 1: manufacturing a transformer model, namely manufacturing a model transformer by adopting a three-phase core type structure, and simulating various types, different degrees and different positions of faults by parallelly connecting or serially connecting a capacitor, an inductor or a short-circuit inter-cake winding wire;
step 2: building a frequency sweep impedance test system, namely building a frequency sweep impedance method hardware test platform according to an implementation method of a frequency sweep impedance method;
and step 3: manufacturing faults of winding displacement, unequal height, turn-to-turn short circuit, bulging, warping in various types, different degrees and different positions on a model transformer, testing the model transformer by utilizing the established sweep frequency impedance method testing system and a corresponding software platform, comparing and analyzing the change of sweep frequency impedance testing data before and after deformation, researching the stability and accuracy of the sweep frequency impedance method, and establishing a criterion for diagnosing the winding deformation type and degree according to sweep frequency characteristic curves obtained by faults in different types and different degrees and the deduced short circuit reactance value;
and 4, step 4: the method comprises the steps of researching the relation between the winding system parameter change and fault type, deformation position and deformation degree factors, obtaining a winding deformation intelligent detection mode based on a winding parameter identification technology and a winding parameter influence rule, summarizing the rule, concluding and perfecting, providing a winding deformation criterion based on sweep frequency impedance by means of results of simulation test and laboratory simulation test, and carrying out further verification by means of a simulation tool, so that the criterion is continuously perfected, applying the improved sweep frequency short-circuit impedance method to a field power transformer, deeply researching measurement repeatability, the influence of electromagnetic interference on a test field, and the sensitivity and accuracy of measurement, and further perfecting the sweep frequency impedance method according to the measurement result.
4. A method for intelligently detecting the deformation of a transformer winding based on the identification of a swept-frequency impedance curve as claimed in claim 1, further comprising 2 equivalent circuits of a low-frequency equivalent test circuit and a medium-high frequency equivalent test circuit, wherein for the low-frequency equivalent test circuit, when the frequency of the voltage loaded at the head end of the winding is lower, the transformer can be regarded as a T-shaped circuit consisting of a resistor and an inductor, for the medium-high frequency equivalent test circuit, when the frequency of the voltage loaded is more than 1kHz, the excitation of the iron core of the transformer is weakened, and the winding can be regarded as a linear dual-port network consisting of a series of distributed parameters of the inductor, the capacitor and the resistor.
5. A swept-frequency impedance curve identification-based transformer winding deformation intelligent detection method as claimed in claim 2, wherein the middle part of the three-dimensional simulation model of the transformer is provided with an iron core and a three-phase winding, and the iron core and a shell are grounded.
6. A sweep-frequency impedance curve identification-based transformer winding deformation intelligent detection method as claimed in claim 3, wherein the model transformer has a capacity of 50kVA and a transformation ratio of 10kV/380V, the head and tail ends of the high-voltage and low-voltage windings are respectively led out through bushings, 50 taps are uniformly drawn out from the high-voltage winding of the transformer along the axial direction, and 10 taps are drawn out from the low-voltage winding.
7. A swept-frequency impedance curve identification-based intelligent detection method for transformer winding deformation according to claim 3, wherein design elements for building a swept-frequency impedance method hardware test platform comprise 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 of a swept-frequency impedance method is built.
8. A method for intelligently detecting transformer winding deformation based on sweep frequency impedance curve identification as claimed in claim 3, wherein the software platform comprises a sweep frequency curve drawing module, a low frequency band simulation module, a short circuit reactance calculation module and a fault diagnosis module.
9. A sweep-frequency impedance curve identification-based intelligent detection method for transformer winding deformation according to claim 3, characterized in that the experimental steps of step 3 are as follows:
(1) respectively applying frequency sweep signals to the three-phase winding to obtain frequency sweep spectrograms corresponding to different defects;
(2) carrying out delta/Y switching on the high-voltage side of the transformer winding, respectively applying frequency sweep signals on the three-phase low-voltage side, and measuring a frequency sweep spectrogram;
(3) applying a frequency sweep signal on the high voltage side of the winding, and repeating 1 and 2 steps.
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| CN116679236A (en) * | 2023-06-01 | 2023-09-01 | 中铁一局集团电务工程有限公司 | LSM-based subway contact network short-circuit impedance and short-circuit simulation test method and system |
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