Transformer frequency response analysis method based on digital signal filter

Abstract

The invention discloses a transformer frequency response analysis method based on a digital signal filter, and the method comprises the following steps: constructing a transformer winding two-port network model with an end screen, and the distribution parameters of the transformer winding two-port network model with the end screen comprise linear resistance, inductance, capacitance and end screen capacitance; an active compensation band-pass filter is connected to an end screen branch of the passive linear two-port network of the transformer winding; and the winding deformation tester is connected between the transformer winding two-port network model with the end screen and the filter for transformer frequency response analysis. A two-port network model structure with an end screen is constructed, the model is used as a design object, a set of active digital filtering equipment and a software digital filter are formed to eliminate the influence of the end screen on the two-port network model of the main transformer winding, and a pure transformer winding frequency response characteristic curve can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of transformers, and in particular relates to a transformer frequency response analysis method based on a digital signal filter. Background Art

[0002] Power transformers are classified into step-up, step-down or interconnecting transformers according to their uses. Their working principle is that they are a kind of static electrical appliance used to transform AC voltage and current to transmit AC power. Power transformers are important equipment in power systems and are of great significance to the safe operation of power systems. According to statistics, transformer windings are the main components damaged by transformer accidents. Therefore, it is very important to test and analyze the condition of transformer windings. Transformer windings are generally made of copper or aluminum wires made of enameled wires wound on iron cores.

[0003] The winding of the transformer will change due to the force: first, the transformer will break, shift, and twist when it is hit during transportation or installation; second, the transformer will be deformed when it is hit by short-circuit current or electromotive force during operation; in serious cases, it may cause the transformer to short-circuit or burn. The winding deformation of the power transformer is defined as: the axial or radial size change of the power transformer winding under the action of electromotive force or mechanical force when it is hit by short-circuit current or hit during transportation, which is usually manifested as local twisting, bulging or displacement of the winding. There are generally two methods for detecting the deformation of the transformer winding: one is the low voltage impedance method, which compares the deviation between the low voltage impedance of the three-phase winding of the transformer and the design value to determine the deformation of the winding; the other is the frequency response analysis method, which compares the response characteristic curve of the winding at different frequencies of 1kHz~1MHz with the factory characteristic curve and determines the degree of winding deformation by comparing their correlation coefficients.

[0004] Because the power transformers used in power plants, most of the main transformers use closed bushings on the high-voltage side to connect to the GIS part, oil-immersed closed bushings or sulfur hexafluoride gas insulated closed bushings. Generally, the test uses the bushing end screen connection instead of directly connecting the transformer winding, which causes the two-port network model of the winding to change. Traditional frequency response test equipment is based on the attached Figure 1The two-port network model of the main transformer shown in the figure is used for relevant calculations. The detection instrument needs to be directly connected to the transformer winding to obtain the frequency response characteristic curve reflecting the deformation of the winding. For transformers in the form of GIS equipment with high-voltage side windings connected to GIS equipment through closed bushings, the windings are generally connected through the end screen of the bushing. It is difficult to open the high-voltage side of some transformers to access the windings, or the test conditions for accessing the windings are not met due to the busbar being energized during the test, resulting in the inability to directly access the transformer windings during the field test. Although this method can also obtain the frequency characteristic response curve of the transformer winding, the deformation of the three-phase winding can be compared horizontally; however, this curve is difficult to make a vertical comparison with the frequency response characteristic curve delivered by the factory, which makes the comparability of the historical changes of the transformer windings insufficient, and it is difficult to reflect the degree of deviation of the transformer winding deformation during this period, which affects the judgment of the actual deformation of the transformer windings. The two-port network model used in the design of traditional test equipment only includes the transformer winding part, and does not take into account the actual use of the main transformer. The existing test method results in inaccurate test results of the transformer winding frequency response characteristic curve due to the limitations of on-site detection conditions. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that the test results of the transformer winding frequency response characteristic curve are inaccurate due to the limitation of on-site detection conditions in the existing test method, and propose a transformer frequency response analysis method based on a digital signal filter.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: A transformer frequency response analysis method based on a digital signal filter comprises the following steps: Constructing a two-port network model of a transformer winding with an end screen, wherein the distributed parameters of the two-port network model of the transformer winding with an end screen include linear resistance, inductance, capacitance and end screen capacitance; An active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding; The winding deformation tester is connected between the two-port network model of the transformer winding with the end screen and the filter to perform transformer frequency response analysis.

[0007] Furthermore, an active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding, specifically: A variable inductor is connected to the end screen branch of the passive linear two-port network of the transformer winding to form an LC series circuit, and a control unit is connected in parallel at both ends of the variable inductor to form an active compensation bandpass filter.

[0008] Furthermore, the control unit is composed of a final screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit and a variable reactor control unit.

[0009] Furthermore, the steps of obtaining the parameters of the active compensation bandpass filter are as follows: After the end-screen capacitance value is input into the end-screen parameter input unit, the test signal frequency is measured by the test signal frequency measurement unit, the end-screen capacitance value and the test signal frequency are input into the LC circuit calculation unit to calculate the reactance value under different test signal frequencies, and the filter parameters are obtained by adjusting the reactance value through the reactor control unit.

[0010] Furthermore, the LC circuit calculation unit establishes a reactance frequency function of the winding deformation according to a resonant frequency formula of the LC series circuit to obtain a continuously changing reactance value.

[0011] Furthermore, the resonant frequency formula of the LC series circuit is as follows:

[0012] in, is the resonant frequency of the LC series circuit, L is the inductance value, and C is the capacitance value.

[0013] Furthermore, the reactance frequency function of the winding deformation is shown as follows:

[0014] Where L(f) is the reactance frequency function of the winding deformation, is the resonant frequency of the LC series circuit, and C is the capacitance value.

[0015] An active compensation bandpass filter comprises a variable inductor, two ends of the variable inductor are connected in parallel to a control unit, and the control unit comprises an end screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit, and a variable reactor control unit.

[0016] Furthermore, the bandpass filter is provided with two ports. A transformer frequency response analysis device based on a digital signal filter is characterized in that it includes a winding deformation test device, one end of which is connected to the end screen of the transformer bushing, and the other end of which is connected to one end of an active compensation bandpass filter, and the other end of the active compensation bandpass filter is connected to the end screen of the transformer bushing.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a transformer frequency response analysis method based on a digital signal filter. Based on the filter design of the spectrum response characteristic curve of the transformer two-port network model including an end screen, a two-port network model structure with an end screen is constructed. This model is used as a design object to form a set of active digital filtering equipment and software digital filters to eliminate the influence of the end screen on the two-port network model of the main transformer winding, so that a simple transformer winding frequency response characteristic curve can be obtained, thereby overcoming the problem of inaccurate test results of the transformer winding frequency response characteristic curve due to limitations of on-site detection conditions.

[0018] Furthermore, since there is no need to remove the high-voltage side bushing connection, the transformer maintenance workload is greatly reduced, which reduces the risk of on-site work on the one hand and shortens the maintenance time on the other hand; since the frequency response characteristic curve of the transformer delivered from the factory is a curve that simply reflects the winding characteristics, this method can be used to obtain a comparable characteristic curve to compare the historical curve of the transformer; improve the performance of the transformer spectrum response test equipment, enhance the applicability of the spectrum response tester, and improve the detection capability; perform digital signal processing or hardware filtering on existing equipment without modifying the equipment itself, and only need to connect the hardware filter to the test loop to meet the performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are for explanation purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only for illustration purposes to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the components of the present invention. In the drawings: Figure 1 is the two-port network model of the transformer winding.

[0020] Figure 2 It is the equivalent two-port network model of the transformer winding plus the end screen element.

[0021] Figure 3 Equivalent two-port network model to eliminate the influence of transformer end screen.

[0022] Figure 4 This is the schematic diagram of the hardware filter structure.

[0023] Figure 5 This is the schematic diagram of testing the transformer winding deformation with hardware filter using the frequency response method.

[0024] Figure 6 The present invention is a wiring schematic diagram of a winding deformation tester for a transformer frequency response analysis method based on a digital signal filter. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] Embodiment 1 A transformer frequency response analysis method based on a digital signal filter comprises the following steps: Construct a two-port network model of a transformer winding with an end screen, wherein the distributed parameters of the two-port network model of the transformer winding with an end screen include linear resistance, inductance, capacitance and end screen capacitance; An active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding; The winding deformation tester is connected between the two-port network model of the transformer winding with the end screen and the filter to perform transformer frequency response analysis.

[0029] The present embodiment provides a transformer frequency response analysis method based on a digital signal filter. The two-port network model of the transformer winding with an end screen takes into account the distributed parameters such as the end screen capacitance, so that the model is closer to the electrical characteristics of the actual transformer. The refined model can more accurately reflect the actual working state of the transformer winding and improve the accuracy of fault detection. The transformer is subjected to frequency response analysis through a winding deformation tester to obtain the frequency response characteristic curve of the transformer winding, which can reflect the electrical performance of the transformer winding at different frequencies and further determine whether the winding has deformation, short circuit and other faults. The active compensation bandpass filter can compensate for signals within a specific frequency range, thereby improving the frequency response characteristics of the transformer winding, helping to reduce the degradation of electrical performance caused by faults such as winding deformation, and improving the operating stability and safety of the transformer.

[0030] An active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding, specifically: A variable inductor is connected to the end screen branch of the passive linear two-port network of the transformer winding to form an LC series circuit, and a control unit is connected in parallel at both ends of the variable inductor to form an active compensation bandpass filter.

[0031] The control unit consists of a terminal screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit and a variable reactor control unit.

[0032] The steps to obtain the parameters of the active compensation bandpass filter are as follows: After the end-screen capacitance value is input into the end-screen parameter input unit, the test signal frequency is measured by the test signal frequency measurement unit, the end-screen capacitance value and the test signal frequency are input into the LC circuit calculation unit to calculate the reactance value under different test signal frequencies, and the filter parameters are obtained by adjusting the reactance value through the reactor control unit.

[0033] The LC circuit calculation unit establishes a reactance frequency function of the winding deformation according to the resonant frequency formula of the LC series circuit to obtain a continuously changing reactance value.

[0034] The resonant frequency formula of the LC series circuit is shown below:

[0035] in, is the resonant frequency of the LC series circuit, L is the inductance value, and C is the capacitance value.

[0036] The reactance frequency function of the winding deformation is shown as follows:

[0037] Where L(f) is the reactance frequency function of the winding deformation, is the resonant frequency of the LC series circuit, and C is the capacitance value.

[0038] Embodiment 2 An active compensation bandpass filter includes a variable inductor, two ends of the variable inductor are connected in parallel to a control unit, and the control unit includes an end screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit, and a variable reactor control unit. The bandpass filter is provided with two ports.

[0039] Embodiment 3 A transformer frequency response analysis device based on a digital signal filter is characterized in that it includes a winding deformation test device, one end of the winding deformation test device is connected to the end screen of the transformer bushing, the other end of the winding deformation test device is connected to one end of an active compensation bandpass filter, and the other end of the active compensation bandpass filter is connected to the end screen of the transformer bushing.

[0040] Embodiment 4 This embodiment provides a transformer frequency response analysis method based on a digital signal filter, which optimizes a traditional transformer frequency response analysis test method.

[0041] The principle of frequency response method to test transformer winding deformation: Under the action of a high frequency (1kHz~1MHz) input signal, the transformer winding can be regarded as a passive linear two-port network consisting of distributed parameters such as linear resistance, inductance (mutual inductance), and capacitance. If the winding is deformed, the distributed inductance, capacitance and other parameters inside the winding will inevitably change, resulting in changes in the frequency response characteristics of the two-port network.

[0042] The wiring schematic diagram of the winding deformation test is as follows Figure 6 As shown, the winding deformation tester is actually a variable frequency waveform generator.

[0043] 1. Standard model of transformer two-port network Traditional frequency response test equipment is based on Figure 1 In order to perform relevant calculations using the two-port network model of the main transformer shown in the figure, it is necessary to connect the detection instrument directly to the transformer winding in order to obtain the frequency response characteristic curve reflecting the deformation of the winding.

[0044] 2. The high-voltage side is a two-port network model of a transformer in the form of a sealed bushing By analyzing the two-port network model of transformer winding with end screen, the test method is optimized to eliminate the influence of the end screen on the frequency response characteristic curve of the transformer.

[0045] The two-port network model of the transformer with the end screen is as follows: Figure 2 As shown, from Figure 2It can be found that the end screen behaves as a capacitor. In principle, if a variable inductor is connected in series to the branch where the end screen is located, an LC series resonance is formed to eliminate the influence of the end screen capacitance.

[0046] The two-port network model after the inductor is connected in series is as follows Figure 3 shown.

[0047] 3. Design principles of inductor components analyze Figure 3 C t and L n The series branch will find that if for the series LC circuit, its resonance satisfies formula 1

[0048] Where, f is the resonant frequency of the LC series circuit; L is the inductance value; C is the capacitance value.

[0049] For the determined end screen, its capacitance C is a constant value, and a function of f and L is formed, as shown in Formula 2:

[0050] Since the frequency response method of winding deformation requires that the frequency f changes continuously from 1kHz to 1MHz, the above formula can determine that there is a function L(f) whose value range has a solution in the positive real number domain, and this function is continuous in the positive real number domain; this function shows that for different frequencies f, the reactance value L changes with the frequency f. It shows that in the test, as the frequency changes, adjusting a continuously changing reactance value can meet the design requirements.

[0051] A controller is designed to adjust the variable reactance according to the frequency of the input signal so that the LC maintains resonance at different frequencies. The controller and the variable reactance it controls form a filter.

[0052] 4. Hardware filter principle and design In the specific implementation path, consider designing a hardware filter to meet the needs.

[0053] 4.1、Hardware filtering principle refer to Figure 2 The two-port network structure with the end-screen element is designed to connect a filter device that can filter, compensate and adjust the input signal according to the characteristics of LC series resonance.

[0054] The design principle diagram of the hardware filter is as follows: Figure 4 As shown, combined Figure 5 The test wiring schematic diagram is shown.

[0055] 4.2 Filter Structure Figure 4 The structure of the hardware filter is introduced, which consists of a control unit and a controlled variable reactor; the control unit consists of four parts: a terminal screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit, and a variable reactor control unit.

[0056] 4.3. Filter wiring method and operating principle: The wiring schematic diagram of the filter during the test is as follows: Figure 5 As shown; before the test starts, the capacitance value of the end screen measured is input from the end screen parameter input unit; after the test starts, the test signal frequency measurement unit measures the test signal frequency, and then the end screen capacitance and the test signal frequency are input into the LC circuit calculation unit to calculate the reactance value L at different frequencies, and the appropriate reactance value is adjusted through the reactor control unit to meet the filter parameter requirements.

[0057] Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the preceding claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended to be a disclaimer of such subject matter, nor should it be considered that the applicants did not consider such subject matter to be part of the disclosed inventive subject matter.

[0058] The above content is a further detailed description of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, they can also make several simple deductions or substitutions, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A transformer frequency response analysis method based on a digital signal filter, characterized in that: The steps include: Constructing a two-port network model of a transformer winding with an end screen, wherein the distributed parameters of the two-port network model of the transformer winding with an end screen include linear resistance, inductance, capacitance and end screen capacitance; An active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding; The winding deformation tester is connected between the two-port network model of the transformer winding with the end screen and the filter to perform transformer frequency response analysis.

2. The transformer frequency response analysis method based on a digital signal filter according to claim 1 is characterized in that: An active compensation bandpass filter is connected to the last screen branch of the passive linear two-port network of the transformer winding, specifically: A variable inductor is connected to the end screen branch of the passive linear two-port network of the transformer winding to form an LC series circuit, and a control unit is connected in parallel at both ends of the variable inductor to form an active compensation bandpass filter.

3. The transformer frequency response analysis method based on a digital signal filter according to claim 2 is characterized in that: The control unit is composed of a terminal screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit and a variable reactor control unit.

4. The transformer frequency response analysis method based on a digital signal filter according to claim 3 is characterized in that: The steps for obtaining the parameters of the active compensation bandpass filter are as follows: After the end-screen capacitance value is input into the end-screen parameter input unit, the test signal frequency is measured by the test signal frequency measurement unit, the end-screen capacitance value and the test signal frequency are input into the LC circuit calculation unit to calculate the reactance value under different test signal frequencies, and the filter parameters are obtained by adjusting the reactance value through the reactor control unit.

5. The transformer frequency response analysis method based on digital signal filter according to claim 4 is characterized in that: The LC circuit calculation unit establishes a reactance frequency function of the winding deformation according to the resonant frequency formula of the LC series circuit to obtain a continuously changing reactance value.

6. The transformer frequency response analysis method based on digital signal filter according to claim 5, characterized in that: The resonant frequency formula of the LC series circuit is as follows: in, is the resonant frequency of the LC series circuit, L is the inductance value, and C is the capacitance value.

7. The transformer frequency response analysis method based on digital signal filter according to claim 6 is characterized in that: The reactance frequency function of the winding deformation is shown as follows: Where L(f) is the reactance frequency function of the winding deformation, is the resonant frequency of the LC series circuit, and C is the capacitance value.

8. An active compensation bandpass filter, characterized in that: It comprises a variable inductor, two ends of which are connected in parallel to a control unit, and the control unit comprises an end-screen parameter input unit, a test signal frequency measurement unit, an LC circuit calculation unit, and a variable reactor control unit.

9. An active compensation bandpass filter according to claim 8, characterized in that: Bandpass filter set up two ports.

10. A transformer frequency response analysis device based on a digital signal filter, characterized in that: It comprises a winding deformation test device, one end of which is connected to the end screen of the bushing of the transformer, the other end of which is connected to one end of an active compensation bandpass filter, and the other end of which is connected to the end screen of the bushing of the transformer.

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