A method and system for inverting partial discharge quantity of a generator stator winding
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUANENG JINGMEN THERMAL POWER CO LTD
- Filing Date
- 2026-03-11
- Publication Date
- 2026-05-29
Smart Images
Figure CN122109744A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of insulation condition diagnosis technology for large rotating electrical machines, and specifically relates to a method and system for inverting the partial discharge quantity of generator stator windings. Background Technology
[0002] Partial discharge is an important early indicator of insulation degradation in high-voltage electrical equipment. The pulse current method is a classic quantitative detection method that calculates the apparent charge by measuring the instantaneous pulse current or voltage generated across the coupling capacitance and detection impedance during discharge. However, the physical nature of this method dictates that its measurement values have inherent biases.
[0003] When discharge occurs inside the insulation (e.g., within air bubbles), the actual amount of charge exchanged (the true discharge) is divided by the distributed capacitance of the insulation structure. For structures like generator stator windings with complex multilayer mica-epoxy composite insulation, the capacitance parameters exhibit distributed characteristics, making them difficult to obtain. Current industry practice generally involves directly using the apparent discharge quantity measured by the pulse current method as a criterion for insulation condition, and evaluating it based on thresholds set according to general standards (such as IEC 60034-27) or field experience.
[0004] However, due to the conduction attenuation effect of the detection circuit, the assessment is based on an underestimation of the actual degree of internal insulation degradation. This makes the assessment results overly conservative and may mask defects. It fails to accurately deduce the true severity of defects and the true energy consumed by each discharge from the distorted data, instead focusing on key physical quantities for assessing the aging rate of insulation materials, making it difficult to establish criteria for insulation assessment, damage determination, and life extension. Different types of stator winding defects (such as internal bubbles in the main insulation, slot discharge between the anti-corona layer and the slot wall, and surface creepage in the end windings) correspond to drastically different equivalent circuit parameters. Traditional methods ignore this difference, leading to the same measurement value potentially corresponding to defects with completely different electrical characteristics, failing to provide effective electrical features for multi-source discharge pulse separation and identification. Therefore, in summary, current measurements of partial discharge in generator stator windings, due to the use of apparent discharge quantities, result in distorted physical quantities, inaccurate defect quantification, weak identification capabilities, and difficulty in specifically correcting the measurement results of the general pulse current method, thus failing to accurately and efficiently analyze the true physical state of internal discharge within the insulation. Summary of the Invention
[0005] This invention provides a method and system for inverting the partial discharge quantity of generator stator windings. The purpose is to solve the problems in the current measurement of partial discharge quantity of generator stator windings, which are caused by the use of apparent discharge quantity, resulting in distortion of physical quantities, inaccurate quantification of defects, weak identification ability, and difficulty in targeted correction of measurement results of the general pulse current method, thus failing to accurately and efficiently analyze the true physical state of discharge inside the insulation.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for inverting the partial discharge quantity of a generator stator winding, comprising the following steps: S1. Obtain or estimate the critical distributed capacitance parameters in the equivalent circuit model of the multi-capacitor insulation structure, and establish a database of mapping relationships between defect locations or types and critical distributed capacitance parameters. Among them, the equivalent circuit model of the multi-capacitor insulation structure is used for partial discharge analysis and is constructed for the stator winding of the large synchronous generator to be evaluated. S2. Partial discharge detection is performed on the generator stator winding under applied test voltage using the pulse current method, and the characteristic information of the discharge pulse is collected simultaneously. S3. Based on the key distributed capacitance parameters in the mapping relationship database and the pre-generated pulse waveform-defect capacitance calibration curve, perform nonlinear iterative inversion calculation on the characteristic information of the collected discharge pulse to obtain the real discharge physical quantities and the corrected statistical characteristic parameters. S4. Based on the actual discharge physical quantities and the corrected statistical characteristic parameters, conduct quantitative assessment, type identification and health diagnosis of insulation defects in the generator stator winding, and generate a diagnostic report.
[0007] In some implementations, the methods for obtaining or estimating the key distributed capacitance parameters in the equivalent circuit model of the multi-capacitor insulation structure in S1 include: using one or more of the following methods in combination: offline precision measurement, online coupling estimation, and design parameter calculation. The equivalent circuit model of the insulation structure includes defective capacitors, series insulation capacitors, and total capacitance to ground. Defective capacitors are used to simulate defects inside the insulation, series insulation capacitors are used to simulate the healthy insulation part connected in series between the defect point and the copper conductor of the stator bar and the stator core, and total capacitance to ground is used to simulate the capacitance of the remaining healthy part of the bar unit to the stator core.
[0008] In some implementations, in S2, the characteristic information of the discharge pulse includes: apparent discharge quantity, discharge phase, absolute pulse occurrence time, and original waveform data.
[0009] In some implementations, the method for establishing the pre-generated pulse waveform-defect capacitance calibration curve in S3 includes: preparing artificial defect samples of different sizes through a controllable defect simulation experiment; measuring the rise time of the discharge pulse using a detection system with the same bandwidth as the detection system; and establishing an empirical formula for the pulse rise time and defect capacitance using least-squares fitting as the pulse waveform-defect capacitance calibration curve; the empirical formula is as follows: (1); in, The rise time of the discharge pulse. and The coefficients are those of the empirical fitting formula. This is a defective capacitor.
[0010] In some implementations, the nonlinear iterative inversion calculation in S3 uses the Newton-Raphson method, which specifically includes: initializing the defect capacitance estimate, calculating the theoretical rise time based on the empirical formula of pulse rise time and defect capacitance, calculating the residual and determining whether it has converged; if it has not converged, calculating the Jacobian matrix elements and updating the defect capacitance estimate, and repeating the above iterative operation until the residual converges or the set upper limit of the number of iterations is reached.
[0011] Furthermore, in S3, the formula for calculating the elements of the Jacobian matrix is as follows: (2); The update formula for the defect capacitance estimate is: (3); in, For elements of the Jacobian matrix, Empirical fitting formula coefficients, For the first Defect capacitance estimate in the next iteration For the first The residual of the next iteration For the first Defect capacitance estimate for the next iteration.
[0012] In some implementations, in S3, the nonlinear iterative inversion calculation specifically includes: first, substituting the defect capacitance after iterative convergence into the charge inversion equation to obtain the true discharge charge, the charge inversion equation being as follows: (4); in, This represents the actual discharge charge. Apparent discharge quantity For series insulating capacitors, The defect capacitance is determined after iterative convergence. Then, the energy of a single discharge is calculated based on the instantaneous value of the power frequency test voltage corresponding to the actual discharge charge and discharge phase. The formula for calculating the energy of a single discharge is as follows: (5); in, Energy for a single discharge. Discharge phase The corresponding instantaneous value of the power frequency test voltage, This represents the actual discharge charge.
[0013] In some implementations, in S3, the corrected statistical characteristic parameters include: the corrected average discharge current obtained by statistically analyzing all effective discharge pulses within a set time window; the corrected discharge power obtained by statistically analyzing all effective discharge pulses within a set time window; and a three-dimensional spectrum generated with discharge phase as the horizontal axis, actual discharge quantity as the vertical axis, and discharge repetition rate as the color level.
[0014] In some implementations, in S4, the quantitative assessment, type identification, and health diagnosis of insulation defects specifically include: comparing the actual discharge charge and corrected discharge power with a library of actual discharge quantities or energy thresholds established based on electrical aging experiments of insulating materials to complete the quantitative assessment of insulation defects; analyzing the degree of agreement between the inversion result spectrum and the measured spectrum under the ratio of series insulation capacitance to defect capacitance corresponding to different assumed defect types to complete the type identification of insulation defects; generating a diagnostic report by combining the results of quantitative assessment and defect type identification; the diagnostic report clarifies the difference between the assessment conclusion based on apparent discharge quantity and the assessment conclusion based on actual discharge quantity, and provides suggested defect types and location probabilities.
[0015] This invention also provides an inversion system for the partial discharge quantity of a generator stator winding, used to implement the above-mentioned inversion method for the partial discharge quantity of a generator stator winding, including a mapping relationship establishment module, a feature information acquisition module, an inversion calculation module, and an evaluation and diagnosis module, wherein: The mapping relationship establishment module is used to: obtain or estimate the key distributed capacitance parameters in the equivalent circuit model of multiple capacitors in the insulation structure, and establish a mapping relationship database between the location or type of defects and the key distributed capacitance parameters; Among them, the equivalent circuit model of the multi-capacitor insulation structure is used for partial discharge analysis and is constructed for the stator winding of the large synchronous generator to be evaluated. The feature information acquisition module is used to: detect partial discharge of the generator stator winding under test voltage using the pulse current method, and simultaneously acquire the feature information of the discharge pulse; The inversion calculation module is used to: perform nonlinear iterative inversion calculations on the characteristic information of the collected discharge pulses based on the key distributed capacitance parameters in the mapping relationship database and the pre-generated pulse waveform-defect capacitance calibration curve, to obtain the real discharge physical quantities and the corrected statistical characteristic parameters; The assessment and diagnosis module is used to: quantitatively assess, identify, and diagnose insulation defects in generator stator windings based on actual discharge physical quantities and corrected statistical characteristic parameters, and generate a diagnostic report.
[0016] Compared with the prior art, the present invention provides a method and system for inverting the partial discharge quantity of a generator stator winding, which has the following advantages: This invention provides a method for inverting the partial discharge quantity of generator stator windings. Addressing the problem that the apparent discharge quantity is severely distorted due to the voltage division effect of the distributed capacitance of the insulation structure when using the pulse current method to detect partial discharge in the generator stator, failing to reflect the true degree of internal insulation degradation, this invention establishes a physical mapping relationship between the apparent discharge quantity and the actual discharge quantity by constructing an equivalent circuit model of the multi-capacitors of the generator stator bars. An offline calibration experiment is used to establish a correlation model between the pulse rise time and the defect capacitance. Then, the apparent discharge quantity, discharge phase, and pulse rise time are simultaneously acquired on the same discharge pulse. Using the pulse rise time as an independent observation constraint, the Newton-Raphson method is used to iteratively solve for the defect capacitance until the residual between the theoretical rise time and the measured value converges. Based on the converged defect capacitance, this invention inverts the actual discharge charge and single discharge energy, generating a spectrum. By introducing pulse waveform characteristics into the inversion of partial discharge physical quantities, this invention improves the accuracy, quantification level, and defect identification capability of generator stator insulation condition assessment, providing technical support for generator life extension and condition-based maintenance. Attached Figure Description
[0017] The accompanying drawings are provided to further illustrate the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0018] Figure 1 This is an overall flowchart of the method for inverting the true partial discharge quantity of a generator stator winding, provided as an embodiment of the present invention. Figure 2 This is a schematic diagram of the equivalent circuit model of the multi-capacitor of the generator stator bar insulation defect used in an embodiment of the method for inverting the partial discharge quantity of the generator stator winding of the present invention. Figure 3 This is a block diagram of the architecture of an intelligent analysis system for partial discharge of generator stator provided as an embodiment of the present invention, which provides a method for inverting the partial discharge quantity of generator stator windings. Figure 4A schematic diagram of the human-machine interface of a partial discharge detection device with integrated inversion function provided in an embodiment of the method for inverting the partial discharge quantity of a generator stator winding according to the present invention; Figure 5 This is a schematic diagram comparing the spectra obtained from analyzing the same discharge signal before and after applying the method of this invention; wherein, the left figure is the existing φ- -n spectrum, the right figure is the φ- after inversion according to the present invention. -n spectrum. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0020] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0021] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0022] It should be noted that the apparatus and methods disclosed in the embodiments herein can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings show the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments herein. In this regard, each block in a flowchart or block diagram may represent a module, program, or part of code containing one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system to perform the specified function or action, or can be implemented using a combination of dedicated hardware and computer instructions.
[0023] In addition, the functional modules in the various embodiments of this article can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.
[0024] How to provide an analytical method and system that can closely integrate with the physical model of the specific insulation structure of the generator stator winding, and specifically correct the measurement results of the general pulse current method, thereby approximating the actual physical state of discharge inside the insulation.
[0025] Based on this, the present invention provides a method for inverting the partial discharge quantity of a generator stator winding, comprising the following steps: S1. Obtain or estimate the critical distributed capacitance parameters in the equivalent circuit model of the multi-capacitor insulation structure, and establish a database of mapping relationships between defect locations or types and critical distributed capacitance parameters. Among them, the equivalent circuit model of the multi-capacitor insulation structure is used for partial discharge analysis and is constructed for the stator winding of the large synchronous generator to be evaluated. S2. Partial discharge detection is performed on the generator stator winding under applied test voltage using the pulse current method, and the characteristic information of the discharge pulse is collected simultaneously. S3. Based on the key distributed capacitance parameters in the mapping relationship database and the pre-generated pulse waveform-defect capacitance calibration curve, perform nonlinear iterative inversion calculation on the characteristic information of the collected discharge pulse to obtain the real discharge physical quantities and the corrected statistical characteristic parameters. S4. Based on the actual discharge physical quantities and the corrected statistical characteristic parameters, conduct quantitative assessment, type identification and health diagnosis of insulation defects in the generator stator winding, and generate a diagnostic report.
[0026] like Figure 1 As shown, this invention provides a method for inverting the partial discharge quantity of generator stator windings, offering a new standard for accurately quantifying the degree of insulation degradation. This provides a quantitative indicator directly based on actual discharge physical quantities for generator condition-based maintenance, life assessment, and life extension decisions. It significantly enhances defect identification and location capabilities. By analyzing the differences in results under different inversion parameter assumptions, it provides a powerful new feature dimension for distinguishing various types of discharges, such as internal, slot, and end discharges, supporting the identification of multi-source partial discharge pulses and demonstrating excellent practicality.
[0027] In some embodiments, the method for inverting the partial discharge quantity of a generator stator winding according to the present invention is applied to the scenario of pulse current method partial discharge detection of a large synchronous generator stator winding, and is specifically performed according to the following steps: Step S100: Construct an equivalent circuit model of the insulation structure of the target generator stator winding with multiple capacitors.
[0028] For the generator to be evaluated, a lumped-parameter equivalent circuit model for partial discharge analysis is established based on its stator winding design drawings, insulation material properties, and winding structure. A model is created for a typical bar cell or a localized area with suspected defects. The model specifically includes: Defective capacitors Capacitance that simulates specific types of defects inside insulation (such as internal bubbles, delamination, voids).
[0029] Series insulating capacitor This simulates the capacitance of the intact, undamaged insulator portion connected in series between the defect and the copper conductor of the stator bar (high-voltage pole) and / or with the stator core (ground potential). The value of this capacitance is closely related to the physical location of the defect.
[0030] Total capacitance to ground : Simulate the total capacitance of the remaining healthy parts of the bar unit to the stator core (ground).
[0031] in, , , Together, these three elements constitute a physical model describing the propagation and voltage division of partial discharge pulses in the winding.
[0032] Step S200: Obtain or estimate the key distributed capacitance parameters in the equivalent circuit model.
[0033] This step aims to provide specific numerical parameters for the model established in step S100. Depending on the generator's status (offline or online), one or more of the following methods are combined: Method M210 (Offline Precision Measurement): During generator shutdown and maintenance, the test bar or a spare test bar sample obtained from the same model generator is operated. Using a precision impedance analyzer or a wideband dielectric spectrometer, the end-to-ground capacitance of the test bar is measured at power frequency and high frequency (e.g., the detection band of 40kHz-1MHz) under different simulated defect settings (e.g., drilling holes at specific locations to simulate air bubbles). C a (Change amount) and loss factor. Through inversion calculations of measurement data or comparison with finite element simulation results, the loss factor at specific defect types and locations can be estimated. and Parameter range, and establish defect location / type with capacitance parameters ( , Mapping relationship database.
[0034] Method M220 (Online Coupled Estimation): This method incorporates multi-source information fusion technology. When the online monitoring system (such as vibration, acoustic signature, and temperature monitoring) detects an abnormal signal in a specific slot number or end area, it triggers partial discharge detection. At this time, based on the area information of the abnormal signal, the system can retrieve the typical type of defect most likely to occur in that area from the mapping database. and The parameter values are used for subsequent inversion calculations.
[0035] Method M230 (Design Parameter Calculation): Based on the original design data of the generator stator winding, including insulation thickness, dielectric constant, and bar dimensions, a two-dimensional or three-dimensional electrostatic model is established using finite element analysis software (such as COMSOL Multiphysics). The capacitance distribution under defect-free conditions is calculated, and the effects of introducing defects at different locations are simulated. and The theoretical change value is used as a supplement to the parameter estimation.
[0036] Step S300: Perform partial discharge detection and synchronous signal acquisition using the pulse current method.
[0037] A pulse current method detection device conforming to IEC 60270 standard is used to detect the stator winding of a generator under a test voltage (typically 0.8Un~1.0Un, where Un is the rated voltage). This device acquires the pulse voltage signal across the coupling impedance in real time, and after amplification, filtering, and analog-to-digital conversion, the built-in processor analyzes it to obtain at least the following characteristics for each effective discharge pulse: Apparent discharge quantity q a _ i (Unit: picoliters, pC) Discharge phase φ _ i(Phase angle relative to power frequency voltage, unit: degrees); absolute time of pulse occurrence t _ i ; (Optional) Raw waveform data of the pulse.
[0038] Step S400: Perform iterative inversion calculations of the actual discharge physical quantities based on the equivalent circuit model and parameters.
[0039] The present invention is for the first one collected in step S300 i For each discharge pulse, using the capacitance parameter library obtained in step S200 and the pre-generated pulse waveform-defect capacitance calibration curve, the following nonlinear iterative inversion calculation is performed: S410 initial defect capacitance estimate: From the sample defect type / location-capacitance parameter mapping database established in step S200, the initial defect capacitance value is read or estimated according to the current detection scenario (offline / online, suspected fault area). If prior information is lacking, then typical empirical values should be used. =3.0pF.
[0040] S420 establishes a correlation model between pulse rise time and defect capacitance: This invention pre-prepared controlled defect simulation experiments to fabricate specimens of different sizes (corresponding to different...) under laboratory conditions. Artificial defect samples were analyzed, and their discharge pulse rise times were measured using a detection system with the same bandwidth as this device. Through least squares fitting, the following empirical formula is established (stored in the system parameter library): (1); in, and These are the coefficients of the empirical fitting formula obtained in this invention. The physical basis of this formula is that the discharge circuit can be approximated as a second-order underdamped RLC system, and the rise time is related to the circuit inductance. L and defective capacitors The product is proportional to the square root, in the winding geometry ( L Under the premise of a fixed value, Only by leading.
[0041] S430: Nonlinear iterative solution (Newton-Raphson method).
[0042] Set the iteration counter m=0 and set the convergence threshold ε (less than or equal to the system sampling interval).
[0043] 1) Based on the current The theoretical rise time is calculated using formula (1). .
[0044] 2) Calculate the residuals ,in This refers to the pulse rise time measured in step S300.
[0045] Step 3: If If the iteration converges, jump to S440.
[0046] Step 4: If Then calculate the elements (derivatives) of the Jacobian matrix: (2); Step 5: Update the defect capacitance estimate: (3); in, For elements of the Jacobian matrix, Empirical fitting formula coefficients, For the first Defect capacitance estimate in the next iteration For the first The residual of the next iteration For the first Defect capacitance estimate for the next iteration.
[0047] Step 6: Enforce constraints: If Then take ;like Then take 10.0pF (set reasonableness constraint boundary).
[0048] Step 7: If m > 5, then force convergence and return to step 1.
[0049] S440: Retrieve the actual discharge charge After iterative convergence C c Substitute into the charge inversion equation: (4); in, This represents the actual discharge charge. Apparent discharge quantity For series insulating capacitors, The defect capacitance is the result of iterative convergence.
[0050] S450: Retrieval of Single Discharge Energy Calculate the actual energy consumed in this discharge. The energy consumed in a single discharge is related to the actual discharged charge and the instantaneous value of the applied voltage. Use the inversion result... Perform the calculation: (5); in, Energy for a single discharge. Discharge phase The corresponding instantaneous value of the power frequency test voltage, This represents the actual discharge charge.
[0051] S460: Calculate the corrected statistical characteristic parameters: Statistical analysis was performed on all valid pulses within the time window T (typically 1 minute): Corrected average discharge current: ; Corrected discharge power: ; Generate φ- -n Three-dimensional spectrum: with phase φ as the horizontal axis, the true discharge quantity is inverted. The vertical axis is denoted by n, and the discharge repetition rate n represents the color level.
[0052] Step S500: Based on the inversion results, perform quantitative assessment, type identification and health diagnosis of insulation defects.
[0053] The inversion physical quantities output in step S400 and φ- -n Spectrum shape features, input into the advanced diagnostic engine: Quantitative assessment: , By comparing the data with a database of actual discharge / energy thresholds established based on electrical aging experiments of insulating materials, the absolute severity of the defect can be directly assessed.
[0054] Defect type identification: Analysis of different assumed defect types (corresponding to different...) during the inversion process The degree of agreement between the inversion result spectrum and the measured spectrum at a ratio of (e.g., the ratio between surface discharge and internal discharge). Different ranges will lead to different φ- values after inversion. -n The shape of the spectrum produces distinguishable differences, thus aiding in classification.
[0055] Health Diagnosis and Report Generation: Based on the above analysis, a diagnostic report is generated. The report clearly indicates the basis for the apparent discharge level. The assessment conclusions are based on the inverted actual discharge quantity. The report analyzes the differences between the assessment conclusions and provides suggested defect types and location probabilities. The final report is output through a standard data interface.
[0056] The present invention will be further described in detail below through specific embodiments.
[0057] This embodiment uses a 350MW water-hydrogen-cooled steam turbine generator as an example to illustrate the implementation process of the method of the present invention. (Refer to...) Figure 1 ,include: Step 1, Model Construction (S100): For the stator bars of this generator model, the main insulation is an epoxy mica multilayer structure. Based on the design, a model is constructed as follows... Figure 2 The equivalent circuit is shown. Wherein, Approximately 2800pF (entire bar to ground), for internal bubble defects near the copper conductor, estimate its... Approximately 65pF (thin layer of insulation between the defect and the conductor). Initially set at 2.5 pF (small air bubbles).
[0058] Step 2, Parameter Acquisition (S200): A combination of methods M210 and M230 is used. In the laboratory, micro-hole defects at different depths (1mm, 3mm) from the conductor are simulated using identical wire bars. The capacitance change is measured, and the following is obtained through fitting: Defect Depth - Relationship curve. Store the curve in the database.
[0059] Step 3, On-site testing (S300): Using a partial discharge instrument that meets the technical specifications, an offline voltage test is performed with the generator off, with a sampling interval of 2ns. A stable discharge signal is detected at 0.8Un voltage, and the apparent discharge quantity of a single pulse is measured. phase φ =48°, pulse rise time =38.5ns, the instantaneous voltage value corresponding to this phase: .
[0060] Step 4, Inversion Calculation (S400): After empirical fitting, the calibration coefficients are taken as follows: ; a) Assuming the defect is an internal discharge with a depth of 1 mm, find the corresponding... .Pick Initial value = 2.5pF.
[0061] b) Iteration 1: Calculate the theoretical rise time: ; Residual: ; Jacobi: ; renew: ; c) Iteration 2: ; Residual: ; Convergence results: ; Inverting the actual discharge quantity: ; Inverting the energy of a single discharge: ; Current methods for calculating energy (using apparent discharge): ; Step 5, Diagnostic Assessment (S500): The system compares the retrieved actual discharge quantity of 547.6 pC with the discharge quantity threshold library, determining that the defect is quite significant; the retrieved discharge energy is 6.52 μJ, an improvement of 5.3% compared to the traditional estimate; after convergence... =3.45pF, corresponding to an equivalent defect diameter of approximately 0.8mm; φ- The -n spectrum shows that the pulses are mainly concentrated in the first and third quadrants, consistent with typical characteristics of internal bubble discharge; a report is generated, and this conclusion is verified. Figure 3 The communication interface of the system shown is uploaded to the platform.
[0062] In some embodiments, the present invention also provides a generator stator partial discharge detection device with integrated inversion function. (Refer to...) Figure 4 This device, based on traditional partial discharge instrument hardware, incorporates the analysis system software described in Example 1. Its touchscreen interface is divided into two columns: the left column displays the conventional... Spectrum Real-time value; the right column synchronously displays the inverted calculated φ- -n spectrum, highlighted Real-time values and a brief diagnostic conclusion. For example... Figure 5 As shown, for the same group of discharges, the right figure shows φ- The discharge quantity axis (q-axis) of the -n spectrum has a significantly larger range than the left graph, and its shape is sharper, better reflecting the physical nature of the discharge. The communication interface on the back of the device can simultaneously output... and Two sets of MODBUS register data are available for use by the upper-layer system.
[0063] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Anyone skilled in the art can readily implement the present invention according to the description and above. Any modifications, alterations, or equivalent variations made using the technical content disclosed above are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.
Claims
1. A method for inverting the partial discharge quantity of a generator stator winding, characterized in that, Includes the following steps: S1. Obtain or estimate the critical distributed capacitance parameters in the equivalent circuit model of the multi-capacitor insulation structure, and establish a database of mapping relationships between defect locations or types and critical distributed capacitance parameters. Among them, the equivalent circuit model of the multi-capacitor insulation structure is used for partial discharge analysis and is constructed for the stator winding of the large synchronous generator to be evaluated. S2. Partial discharge detection is performed on the generator stator winding under applied test voltage using the pulse current method, and the characteristic information of the discharge pulse is collected simultaneously. S3. Based on the key distributed capacitance parameters in the mapping relationship database and the pre-generated pulse waveform-defect capacitance calibration curve, perform nonlinear iterative inversion calculation on the characteristic information of the collected discharge pulse to obtain the real discharge physical quantities and the corrected statistical characteristic parameters. S4. Based on the actual discharge physical quantities and the corrected statistical characteristic parameters, conduct quantitative assessment, type identification and health diagnosis of insulation defects in the generator stator winding, and generate a diagnostic report.
2. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S1, the methods for obtaining or estimating the key distributed capacitance parameters in the equivalent circuit model of the multi-capacitor insulation structure include: one or more of the following methods combined: offline precision measurement, online coupling estimation, and design parameter calculation. The equivalent circuit model of the insulation structure includes defective capacitors, series insulation capacitors, and total capacitance to ground. Defective capacitors are used to simulate defects inside the insulation, series insulation capacitors are used to simulate the healthy insulation part connected in series between the defect point and the copper conductor of the stator bar and the stator core, and total capacitance to ground is used to simulate the capacitance of the remaining healthy part of the bar unit to the stator core.
3. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S2, the characteristic information of the discharge pulse includes: apparent discharge quantity, discharge phase, absolute time of pulse occurrence, and original waveform data.
4. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S3, the method for establishing the pre-generated pulse waveform-defect capacitance calibration curve includes: preparing artificial defect samples of different sizes through a controllable defect simulation experiment; measuring the rise time of the discharge pulse using a detection system with the same bandwidth as the detection system; and establishing an empirical formula for the pulse rise time and defect capacitance using least-squares fitting as the pulse waveform-defect capacitance calibration curve; the empirical formula is as follows: （1）； in, The rise time of the discharge pulse. and The coefficients are those of the empirical fitting formula. This is a defective capacitor.
5. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S3, the nonlinear iterative inversion calculation uses the Newton-Raphson method, which specifically includes: initializing the defect capacitance estimate, calculating the theoretical rise time based on the empirical formula of pulse rise time and defect capacitance, calculating the residual and determining whether it converges; if it does not converge, calculating the Jacobian matrix elements and updating the defect capacitance estimate, and repeating the above iterative operation until the residual converges or the set upper limit of the number of iterations is reached.
6. The method for inverting the partial discharge quantity of the generator stator winding according to claim 5, characterized in that, In S3, the formula for calculating the elements of the Jacobian matrix is as follows: （2）； The update formula for the defect capacitance estimate is: （3）； in, For elements of the Jacobian matrix, Empirical fitting formula coefficients, For the first Defect capacitance estimate in the next iteration For the first The residual of the next iteration For the first Defect capacitance estimate for the next iteration.
7. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S3, the nonlinear iterative inversion calculation specifically includes: first, substituting the defect capacitance after iterative convergence into the charge inversion equation to obtain the true discharge charge, the charge inversion equation is as follows: （4）； in, This represents the actual discharge charge. Apparent discharge quantity For series insulating capacitors, The defect capacitance is determined after iterative convergence. Then, the energy of a single discharge is calculated based on the instantaneous value of the power frequency test voltage corresponding to the actual discharge charge and discharge phase. The formula for calculating the energy of a single discharge is as follows: （5）； in, Energy for a single discharge. Discharge phase The corresponding instantaneous value of the power frequency test voltage, This represents the actual discharge charge.
8. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S3, the corrected statistical characteristic parameters include: the corrected average discharge current obtained from the statistics of all effective discharge pulses within the set time window; the corrected discharge power obtained from the statistics of all effective discharge pulses within the set time window; and a three-dimensional spectrum generated with the discharge phase as the horizontal axis, the actual discharge quantity as the vertical axis, and the discharge repetition rate as the color level.
9. The method for inverting the partial discharge quantity of the generator stator winding according to claim 1, characterized in that, In S4, the quantitative assessment, type identification, and health diagnosis of insulation defects specifically include: comparing the actual discharge charge and corrected discharge power with a library of actual discharge quantities or energy thresholds established based on electrical aging experiments of insulating materials to complete the quantitative assessment of insulation defects; analyzing the consistency between the inversion result spectrum and the measured spectrum under the ratio of series insulation capacitance to defect capacitance corresponding to different assumed defect types to complete the type identification of insulation defects; generating a diagnostic report by combining the results of quantitative assessment and defect type identification; and clarifying the difference between the assessment conclusion based on apparent discharge quantity and the assessment conclusion based on actual discharge quantity, and providing suggested defect types and location probabilities.
10. A system for inverting the partial discharge quantity of a generator stator winding, used to implement the method for inverting the partial discharge quantity of a generator stator winding as described in any one of claims 1-9, characterized in that, It includes a mapping relationship establishment module, a feature information acquisition module, an inversion calculation module, and an evaluation and diagnosis module, among which: The mapping relationship establishment module is used to: obtain or estimate the key distributed capacitance parameters in the equivalent circuit model of multiple capacitors in the insulation structure, and establish a mapping relationship database between the location or type of defects and the key distributed capacitance parameters; Among them, the equivalent circuit model of the multi-capacitor insulation structure is used for partial discharge analysis and is constructed for the stator winding of the large synchronous generator to be evaluated. The feature information acquisition module is used to: detect partial discharge of the generator stator winding under test voltage using the pulse current method, and simultaneously acquire the feature information of the discharge pulse; The inversion calculation module is used to: perform nonlinear iterative inversion calculations on the characteristic information of the collected discharge pulses based on the key distributed capacitance parameters in the mapping relationship database and the pre-generated pulse waveform-defect capacitance calibration curve, to obtain the real discharge physical quantities and the corrected statistical characteristic parameters; The assessment and diagnosis module is used to: quantitatively assess, identify, and diagnose insulation defects in generator stator windings based on actual discharge physical quantities and corrected statistical characteristic parameters, and generate a diagnostic report.