Defect monitoring system and method for a damping bar of a tubular hydrogenerator

Abstract

The application discloses a kind of damping strip defect monitoring system and method of tubular turbine generator, it is related to damping strip early defect monitoring field, solve the problem that existing damping strip monitoring is strong, early defect identification is difficult, positioning accuracy is low, anti-interference ability is poor.System includes magnetic gradient sensor array, optical angle synchronization device, signal acquisition conditioning module and industrial computer diagnosis module;Magnetic gradient sensor array adopts differential coil pair and limited ring redundant structure, is installed in stator ventilation ditch in non-invasive manner, and collects local magnetic field gradient signal;Optical angle synchronization device generates rotor absolute angle mark and synchronous sampling clock;Industrial computer realizes defect monitoring, positioning and trend prediction by multidimensional verification.The application does not need to change rotor structure, can identify early small defect, realize accurate positioning and predictive maintenance in all operating conditions, and guarantee the safe operation of unit.

Description

Technical Field

[0001] This invention relates to the field of early defect monitoring of damping bars, specifically, a system and method for monitoring defects in damping bars of a cross-flow turbine generator. Background Technology

[0002] Currently, axial-flow turbine generators are widely used in hydropower. As a core component of the axial-flow turbine generator rotor, the damping bar plays a crucial role in suppressing unit oscillations, stabilizing operating conditions, and bearing asynchronous torque. During actual operation, the axial-flow turbine generator rotor has a relatively small diameter, and the central area of ​​the damping bar is prone to concentrated heat generation due to harmonic currents and alternating magnetic fields. Simultaneously, the unit's heat dissipation conditions are relatively poor. Combined with the vibration collision and discharge wear effects between the damping bar and the mounting hole wall, early defects such as localized high temperatures, microcracks, and incomplete welds are easily caused in the damping bar. The enormous centrifugal force generated by the high-speed rotation of the unit further accelerates the expansion of these defects, ultimately leading to damping bar breakage. Damping bar breakage directly results in increased unit vibration, magnetic pole damage, stator insulation breakdown, and even unplanned shutdowns and equipment damage, causing severe economic losses and personnel safety risks. Therefore, real-time online monitoring, early defect identification, and precise location of the damping bar's operating status are core requirements for ensuring the safe and stable operation of the axial-flow turbine generator.

[0003] Currently, the mainstream monitoring technology for generator damping bar faults mainly relies on temperature monitoring, supplemented by airflow monitoring, traditional magnetic flux monitoring, and other techniques. However, all of these solutions have significant technical shortcomings in practical engineering applications.

[0004] Firstly, while the embedded temperature measurement solution is simple in principle, it requires slotting on the rotor for installation, which damages the original rotor structure and poses safety hazards to the unit's operation. Secondly, retrofitting existing old units requires disassembling the rotor, resulting in long downtime and difficult construction. Furthermore, the electrical signal of the temperature measuring resistor is susceptible to electromagnetic coupling interference from the unit's strong magnetic field environment, and the connector of the fiber optic temperature measurement is easily affected by oil contamination and unit vibration, which can lead to inaccurate measurement data and component damage, resulting in insufficient long-term operational reliability.

[0005] Secondly, the stator-side infrared temperature measurement scheme is adopted. This scheme is easy to install and does not require modification of the rotor structure. However, the infrared sensor is easily affected by the high temperature, radiation and component obstruction inside the unit, resulting in a large deviation in the measurement results. In particular, when the damping bar has early defects such as microcracks or poor welding, the local temperature rise caused by the change in current distribution is usually less than 1°C. Under the air cooling effect brought about by the high speed rotation of the unit, this temperature change is difficult to be captured in time, and it is impossible to achieve effective early warning of early defects in the damping bar.

[0006] Third, the airflow velocity monitoring scheme has the advantages of being resistant to electromagnetic interference and having a fast response speed. However, after long-term operation of the unit, the air duct is prone to dust accumulation and blockage, which can easily lead to misjudgment of monitoring results. At the same time, the scheme cannot identify the tiny cracks and early fracture defects of the damping strip, which can easily cause the best maintenance window to be missed.

[0007] Fourth, existing magnetic flux monitoring-based solutions mostly use single-turn or multi-turn ordinary coils to collect induced electromotive force. They measure the rate of change of total magnetic flux in the area surrounded by the coil. This results in a strong response to the background magnetic field, which is widely and uniformly distributed, such as the main magnetic field of the unit, power supply harmonics, and environmental magnetic noise. This forms extremely strong common-mode noise. Even with post-processing filtering, it is difficult to separate the localized small magnetic field distortion caused by damping bar defects from the strong background noise, resulting in extremely low monitoring sensitivity. At the same time, this type of solution is affected by the skew of the air gap magnetic field during load operation, resulting in poor fault location accuracy. Calibration is required during the unit's no-load phase, making it impossible to achieve accurate location under all operating conditions. It is also impossible to identify the location of axial defects in the damping bar, distinguish between inherent magnetic pole asymmetry and independent defects in the damping bar, and make it impossible to quantify the trend of defect deterioration and perform predictive maintenance. Summary of the Invention

[0008] The purpose of this invention is to provide a damping bar defect monitoring system and method for a cross-flow turbine generator, which solves the problem that existing damping bar defect monitoring methods cannot achieve integrated and accurate monitoring and location of damping bar defects.

[0009] To achieve the above objectives, the present invention provides a damping bar defect monitoring system for a axial-flow turbine generator, the system comprising:

[0010] A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap. It is used to collect the local magnetic field gradient signal corresponding to the damping bar of the generator rotor and output a differential voltage signal.

[0011] An optical angle synchronization device is used to acquire the real-time rotation angle signal of the rotor and generate the rotor absolute angle mark and angle synchronization sampling clock.

[0012] The signal acquisition and conditioning module is used to synchronously condition the acquired differential voltage signal based on the angle synchronous sampling clock and output a digital differential signal.

[0013] The industrial control computer diagnostic module is used to determine the defects of the damping bar based on the rotor absolute angle mark and the digital differential signal; it is also used to identify defects based on multi-dimensional verification and collaborative identification, eliminate interference, and complete the monitoring and location of rotor damping bar defects.

[0014] This invention utilizes a magnetic gradient sensor array installed within the stator ventilation trench to acquire local magnetic field gradient signals of the damping strip. This allows for the acquisition of the magnetic field characteristics corresponding to the damping strip's state without altering the rotor structure, fundamentally avoiding the operational safety hazards associated with intrusive installations. An optical angle synchronization device generates an absolute rotor angle mark and an angle synchronization sampling clock, providing a synchronization reference that matches the rotor rotation in real time for signal acquisition. This solves the problem of signal decoupling from rotor position caused by speed fluctuations in fixed-frequency sampling. A signal acquisition and conditioning module synchronously conditions the differential voltage signal, providing a reliable data source for subsequent defect analysis. An industrial control computer diagnostic module monitors and locates rotor damping strip defects. This invention achieves end-to-end collaboration from signal acquisition to defect identification and location, improving the reliability and accuracy of damping strip defect monitoring and location.

[0015] Furthermore, the magnetic gradient sensor array includes several uniformly arranged pairs of rectangular differential coils;

[0016] The rectangular differential coil pair is composed of a first rectangular multi-turn copper coil and a second rectangular multi-turn copper coil connected in series. The first rectangular multi-turn copper coil and the second rectangular multi-turn copper coil have the same parameters, but the coils are wound in opposite directions.

[0017] The generator contains a strong background magnetic field and a large amount of common-mode noise, including power supply harmonics. A single coil only samples the change in total magnetic flux, making it difficult to separate the weak local magnetic field changes caused by damping strip defects from the strong common-mode background, resulting in extremely low defect detection sensitivity. In this invention, the magnetic gradient sensor array includes several uniformly arranged pairs of rectangular differential coils. Each pair consists of a first rectangular multi-turn copper coil and a second rectangular multi-turn copper coil with identical parameters connected in series, with the two coils wound in opposite directions. Based on Faraday's principle of electromagnetic induction, the uniformly distributed common-mode background magnetic field will generate induced electromotive forces (EMFs) of similar amplitude in the two coils with identical parameters. The series connection with opposite winding directions allows these two sets of common-mode induced EMFs to cancel each other out, achieving common-mode noise suppression at the physical level. Furthermore, the local magnetic field gradient change caused by damping strip defects will generate significantly different induced EMFs in the two adjacent coils. The series connection with opposite winding directions allows these difference signals to be superimposed and amplified, greatly improving the detection sensitivity of weak local magnetic field changes caused by defects and effectively reducing the probability of missing early-stage minor defects in the damping strip.

[0018] Furthermore, the magnetic gradient sensor array is characterized by comprising an axial main array P0 and two circumferential redundant reference arrays P1 and P2. -2 and P +2 ;

[0019] The main array P0 is set in a single ventilation groove on the circumference of the stator and arranged along the rotor axis to collect magnetic field gradient signals at different positions along the rotor axis.

[0020] Redundant reference array P -2 and P +2 They are respectively set in the ventilation trenches on both sides of the ventilation trench corresponding to the main array P0, and are separated from the main array P0 by at least one ventilation trench, for collecting local background magnetic field signals.

[0021] Among them, the main array P0 can collect magnetic field gradient signals at different positions along the rotor axis, so that each group of coils corresponds to a fixed position along the length of the damping bar. Subsequently, the specific distribution of defects along the length of the damping bar can be locked by the signal differences of different coils, thus solving the problem of axial defect location of the damping bar. The two circumferential redundant reference arrays can collect local background magnetic field signals in the region adjacent to the position of the main array, providing a reference benchmark for distinguishing between local magnetic field distortion caused by defects and regional background magnetic field interference, and providing data support for the accurate identification of subsequent defect signals.

[0022] Furthermore, the optical angle synchronization device includes: a fiber-coupled semiconductor laser, a photodetector, a DSP processing unit, and a microprism array;

[0023] The fiber-coupled semiconductor laser and photodetector are integrated with the rectangular differential coil pair of the main array P0 inside the insulating housing. An optical window is provided on the side of the insulating housing facing the air gap, and the optical window is used to transmit the laser emitted by the fiber-coupled semiconductor laser.

[0024] The microprism array is mounted on at least one rotor damping bar and is used to reflect the laser emitted by the fiber-coupled semiconductor laser to the photodetector.

[0025] The photoelectric receiver is used to receive reflected laser light and output reflected pulse signals;

[0026] The DSP processing unit is used to calculate the instantaneous angular velocity of the rotor in real time based on the reflected pulse signal, generate a synchronous sampling clock that matches the rotor rotation angle, and output the rotor absolute 0° angle mark.

[0027] The optical acquisition element and the sensing element form an integrated structure, which simplifies the on-site installation process of the device, reduces signal interference caused by scattered wiring, and improves the stability of the device operation. The microprism array is installed on at least one rotor damping bar, which can reflect the laser emitted by the fiber-coupled semiconductor laser to the photodetector. After receiving the reflected laser, the photodetector outputs a reflected pulse signal. This reflected pulse signal is uniquely bound to the physical position of the damping bar on which the microprism array is installed, forming an absolute position reference during the rotor rotation process. The DSP processing unit calculates the instantaneous angular velocity of the rotor in real time based on the reflected pulse signal, generates a synchronous sampling clock that matches the rotor rotation angle, and outputs an absolute 0° angle mark of the rotor. This provides a clock reference that is synchronized with the rotor rotation in real time for subsequent signal acquisition, and also provides an absolute angle origin for the precise positioning of the damping bar.

[0028] Furthermore, based on the reflected pulse signal, the instantaneous angular velocity of the rotor is calculated in real time, and a synchronous sampling clock matching the rotor rotation angle is generated, including:

[0029] The rotor's single-turn rotation time is obtained based on the interval between the two reflected pulse signals.

[0030] The instantaneous angular velocity of the rotor is calculated based on the rotor's single-turn rotation time.

[0031] Based on the number of damping bars, the mechanical angle of one revolution of the rotor is divided into N fixed angle steps Δθ.

[0032] Based on the instantaneous angular velocity of the rotor, the sampling time interval corresponding to the rotor rotating through a fixed angular step Δθ is calculated;

[0033] A synchronous sampling clock is generated based on the sampling time interval.

[0034] This invention first obtains the rotor's single-rotation time based on the interval between two reflected pulse signals, and then calculates the rotor's instantaneous angular velocity based on the rotor's single-rotation time, achieving real-time tracking of rotor speed changes. Subsequently, based on the number of damping bars, the mechanical angle of one rotor rotation is divided into N fixed angular steps Δθ, ensuring that each angular step accurately matches the circumferential distribution of the damping bars, guaranteeing the correspondence between the sampling scale and the monitoring target. Then, based on the rotor's instantaneous angular velocity, the sampling time interval corresponding to the rotor rotating through the fixed angular step Δθ is calculated. Finally, a synchronous sampling clock is generated based on the sampling time interval, realizing dynamic adjustment of the sampling frequency with the rotor speed. This ensures that regardless of rotor speed fluctuations, each sampling point corresponds to a fixed mechanical angular position on the rotor, solving the problem of signal and position misalignment caused by speed fluctuations in fixed-frequency sampling.

[0035] Furthermore, based on the rotor absolute angle mark and the digital differential signal, the defect status of the damping bar is determined, including:

[0036] Based on the absolute 0° angle mark, and according to the number of damping strips, establish the correspondence between each sampling point and the damping strip;

[0037] Acquire the digital differential signal for M consecutive rotation cycles under normal generator operation, calculate the signal average value at any sampling point, and establish a stable sequence baseline based on the signal average value of all sampling points;

[0038] Calculate the abnormal residual between the digital differential signal and the stable sequence baseline during the current rotation cycle. If the abnormal residual exceeds a preset residual threshold, it is preliminarily determined that the damping strip has a defect.

[0039] Specifically, using the absolute 0° angle mark as a benchmark, a correspondence between each sampling point and a damping strip is established based on the number of damping strips, ensuring that each sampling data point can be accurately matched to a specific damping strip, thus achieving the binding of sampling data with the monitoring target. The stable sequence baseline, through the averaging of multiple cycles of normal operating data, eliminates the influence of random noise and small fluctuations in operating conditions, accurately characterizing the magnetic field characteristics of the damping strip under normal operating conditions, and providing a unified quantitative reference standard for defect judgment. Finally, by calculating the residual between the current signal and the normal baseline, the magnetic field change characteristics caused by damping strip defects can be accurately extracted. Even the weak signal changes caused by early minor defects can be effectively identified, solving the problems of traditional methods where defect judgment is greatly affected by operating condition fluctuations and early defects are easily missed.

[0040] The multi-dimensional verification includes: spatial dimension verification and circumferential dimension verification;

[0041] The spatial dimension verification includes:

[0042] By comparing the abnormal residuals of the main array P0 and the redundant reference array P0 at the same sampling point, the spatial confidence of the defect signal is calculated.

[0043] If the spatial confidence level exceeds a preset confidence threshold, the defect signal is determined to be a real defect.

[0044] If the spatial confidence level does not exceed the preset confidence threshold, the defect signal is determined to be an interference signal.

[0045] When the defect signal is determined to be a real defect, the abnormal residuals corresponding to each rectangular differential coil pair in the main array P0 are compared to determine the axial sampling position corresponding to the peak value of the abnormal residual, and the specific axial position of the defect is obtained.

[0046] Among them, the magnetic field distortion caused by the damping strip defect is highly localized, producing obvious abnormal residuals only at the main array position, while the abnormal residuals corresponding to the two redundant reference arrays are significantly smaller. Regional magnetic field interference such as stator static eccentricity will produce abnormal residuals with similar amplitudes at the same sampling point of the three arrays. The spatial confidence score calculated based on this signal characteristic can accurately distinguish the source of signal change. If the spatial confidence score exceeds the preset confidence score threshold, the defect signal is determined to be a real defect; if it does not exceed it, it is determined to be an interference signal, effectively eliminating interference from the regional magnetic field on the stator side. When the defect signal is determined to be a real defect, the abnormal residuals corresponding to each rectangular differential coil pair in the main array P0 are compared to determine the axial sampling position corresponding to the peak value of the abnormal residual, obtaining the specific axial position of the defect. This allows maintenance personnel to accurately grasp the distribution of the defect along the length of the damping strip, providing clear location guidance for on-site maintenance.

[0047] The circumferential dimension verification includes:

[0048] Based on the correspondence between sampling points and damping bars, the digital differential signal intervals corresponding to the damping bar K under test and the adjacent damping bar K-1 are obtained respectively. The signal difference value between damping bar K and damping bar K-1 is calculated to obtain the circumferential anomaly degree.

[0049] If the circumferential anomaly exceeds the preset anomaly threshold, the defect signal is determined to be an independent defect signal of the damping strip K to be tested.

[0050] If the circumferential anomaly does not exceed the preset anomaly threshold, the defect signal is determined to be an interference signal.

[0051] Existing monitoring methods cannot distinguish between signal changes caused by independent defects in damping bars and signal characteristics resulting from inherent structural asymmetries in the generator's magnetic poles and stator. This can easily lead to misjudging inherent structural features of the generator as damping bar defects. This invention addresses this issue by establishing a correspondence between sampling points and damping bars. It obtains the digital differential signal intervals corresponding to the damping bar under test (K) and its adjacent damping bar (K-1), calculates the signal difference between K and K-1 to obtain the circumferential anomaly. If the signal change originates from inherent structural asymmetries in the generator's magnetic poles or stator, the signals corresponding to the two adjacent damping bars will exhibit similar characteristics, with a low signal difference. However, if the signal change originates from an independent defect in the damping bar under test (K), the signal corresponding to that damping bar will show a significant difference from the signals of adjacent damping bars, with a significantly higher signal difference. Therefore, by comparing the circumferential anomaly with a preset anomaly threshold, interference from inherent structural asymmetries in the generator can be effectively eliminated, further improving the accuracy of damping bar defect detection.

[0052] Furthermore, the system also includes:

[0053] The defect trend prediction module is used to predict the deterioration trend of damping strip defects based on historical data.

[0054] Based on historical data tracking, the deterioration trend of damping strip defects is predicted, including:

[0055] Based on the abnormal residual of the defect signal in the current rotation cycle, the fault severity of the current cycle is calculated using the L2 norm.

[0056] The fault severity was continuously collected over multiple rotation cycles to establish a time-varying sequence of fault severity.

[0057] The deterioration rate of the defect is obtained by fitting the time-varying sequence of the fault severity.

[0058] Based on the rate of deterioration, the subsequent development trend of defects and the remaining usable lifespan are predicted, and predictive maintenance early warning signals are output.

[0059] Existing monitoring methods can only identify damping strip defects after the fact, and cannot analyze and predict the deterioration trend of defects, which can easily cause the unit to miss the optimal maintenance window. This system also includes a defect trend prediction module. First, based on the abnormal residual of the defect signal in the current rotation cycle, the fault severity of the current cycle is calculated using the L2 norm. The L2 norm can quantitatively characterize the overall distribution of the abnormal residual, accurately reflecting the overall degree of magnetic field distortion caused by the defect. Then, the fault severity of multiple rotation cycles is continuously collected to establish a time-varying sequence of fault severity, which fully records the development and change of the defect over time. Next, the time-varying sequence of fault severity is fitted to obtain the deterioration rate of the defect. Through data fitting, the law of defect development over time can be accurately grasped, and the deterioration speed of the defect can be quantified. Finally, based on the deterioration rate, the subsequent development trend of the defect and the remaining available cycles are predicted, and predictive maintenance early warning signals are output. This allows maintenance personnel to grasp the development of the defect in advance, formulate reasonable maintenance plans, avoid sudden downtime accidents, and realize predictive maintenance of damping strip defects.

[0060] This invention also provides a method for monitoring defects in damping bars of a axial-flow turbine generator, the method comprising:

[0061] A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap to collect the local magnetic field gradient signal corresponding to the rotor damping bar of the generator and output a differential voltage signal.

[0062] The real-time rotation angle signal of the rotor is acquired by an optical angle synchronization device, and the rotor absolute angle mark and angle synchronization sampling clock are generated.

[0063] Based on the angle synchronization sampling clock, the acquired differential voltage signal is synchronously conditioned and a digital differential signal is output.

[0064] The defects of the damping bar are determined based on the absolute angle mark of the rotor and the digital differential signal; the defects are identified through multi-dimensional verification and collaborative identification, interference is eliminated, and the monitoring and location of rotor damping bar defects are completed.

[0065] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0066] 1. All sensing modules of this invention are installed in the stator ventilation groove, without the need to modify the rotor structure, without slotting, and without disassembling the core components of the unit. This results in low retrofitting costs and short downtime for in-service units, and completely avoids the operational safety risks caused by installing equipment on the rotor side.

[0067] 2. By using differential coils to achieve physical layer cancellation of common-mode noise, the local magnetic field distortion caused by early minor defects in the damping strip can be amplified in a targeted manner. This can effectively identify early defects such as microcracks and poor welding with a temperature rise of less than 1°C, providing sufficient buffer time for unit maintenance and avoiding sudden unplanned shutdown accidents.

[0068] 3. The sampling signal and the physical position of the rotor are rigidly bound by the optical angle synchronization device, which is not affected by the unit speed fluctuation and load condition change, and achieves dual accurate positioning of the defect damping strip number and axial position under all working conditions; through multi-dimensional verification and collaborative identification, various interferences such as stator static eccentricity, inherent magnetic pole asymmetry, and regional magnetic field inhomogeneity can be effectively eliminated, and the confidence of defect judgment is high.

[0069] 4. By tracking and quantifying the severity and rate of deterioration of defects through historical dimensions, the development trend of defects and the remaining service life can be predicted, and predictive maintenance warnings can be output. This provides accurate quantitative basis for the formulation of unit maintenance plans and greatly improves the level of intelligence in unit operation and maintenance. Attached Figure Description

[0070] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0071] Figure 1 This is a schematic diagram of the composition of a damping bar defect monitoring system for a axial-flow turbine generator according to the present invention;

[0072] Figure 2 This is a schematic diagram of the rectangular differential coil in this invention;

[0073] Figure 3 This is one of the schematic diagrams of the installation structure of a damping bar defect monitoring system for a axial-flow turbine generator in this invention;

[0074] Figure 4 This is the second schematic diagram of the installation structure of a damping bar defect monitoring system for a axial-flow turbine generator in this invention;

[0075] In the diagram, 1-stator, 2-rotor, 3-rotor core, 4-end ring, 5-magnetic pole, 6-rotor damping bar, 7-air gap, 8-main array P0, 9-redundant reference array P -2 10-Redundant Reference Array P +2 11-Fiber-coupled semiconductor laser, 12-Photodetector, 13-Microprism array, 14-Optical window. Detailed Implementation

[0076] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0077] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0078] Example 1

[0079] Please refer to Figure 1 Embodiment 1 of the present invention provides a damping bar defect monitoring system for a axial-flow hydro generator, the system comprising:

[0080] A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap. It is used to collect the local magnetic field gradient signal corresponding to the damping bar of the generator rotor and output a differential voltage signal.

[0081] An optical angle synchronization device is used to acquire the real-time rotation angle signal of the rotor and generate the rotor absolute angle mark and angle synchronization sampling clock.

[0082] The signal acquisition and conditioning module is used to synchronously condition the acquired differential voltage signal based on the angle synchronous sampling clock and output a digital differential signal.

[0083] The industrial control computer diagnostic module is used to determine the defects of the damping bar based on the rotor absolute angle mark and the digital differential signal; it is also used to identify defects based on multi-dimensional verification and collaborative identification, eliminate interference, and complete the monitoring and location of rotor damping bar defects.

[0084] In this system, the magnetic gradient sensor array and optical angle synchronization device are both fixedly installed on the side of the generator stator ventilation groove near the air gap, requiring no grooving, drilling, or structural modifications to the rotor or damping bars, achieving a completely non-intrusive deployment. The signal acquisition and conditioning module is installed in a local control cabinet next to the generator stator and is electrically connected to the magnetic gradient sensor array and optical angle synchronization device via shielded cables. The industrial control computer diagnostic module is deployed in the generator central control room and is connected to the signal acquisition and conditioning module via an RS485 industrial communication cable. This embodiment is designed for retrofitting in-service units, requiring only shutdown and opening of the stator end cover to complete module installation, without disassembling the rotor or stator windings. The downtime for retrofitting a single unit is short, significantly reducing retrofit costs and construction difficulty. The entire system draws power from the auxiliary power circuit of the generator control cabinet and obtains a stable power supply through an industrial-grade power isolation module, ensuring long-term uninterrupted operation.

[0085] The magnetic gradient sensor array includes several uniformly arranged pairs of rectangular differential coils.

[0086] The rectangular differential coil pair is composed of a first rectangular multi-turn copper coil and a second rectangular multi-turn copper coil connected in series. The parameters (such as number of turns, wire diameter, rectangular frame size, area, resistance, etc.) of the first rectangular multi-turn copper coil and the second rectangular multi-turn copper coil are the same, but the coils are wound in opposite directions.

[0087] Please refer to the detailed structure. Figure 2 The first rectangular multi-turn copper coil and the second rectangular multi-turn copper coil are placed adjacent to each other in space. Figure 2 The middle arrow indicates the direction of current. During operation, the output of the rectangular differential coil pair is the difference in the induced electromotive force between the two coils, i.e., the differential voltage. .in, , in the formula, , These are the induced electromotive forces of the first rectangular multi-turn copper coil and the second rectangular multi-turn copper coil, respectively. , These represent the magnetic flux of the first and second rectangular multi-turn copper coils, respectively, where n is the number of turns and t is time. This design realizes differential magnetic gradient measurement, which physically measures the difference in the rate of change of magnetic flux between two adjacent positions, rather than the total magnetic flux.

[0088] The differential coils are all protected by being encapsulated in a PTFE (polytetrafluoroethylene) insulating shell and tubular structure. A loosely spaced, thin copper mesh is provided on the outside of the coils. This mesh provides very weak magnetic field shielding to ensure effective magnetic signal penetration, but provides sufficient Faraday cage effect to isolate high-voltage electric field interference near the stator windings. To further protect subsequent circuitry, a protective resistor is connected in parallel at the signal leads of the coils to prevent damage caused by transient voltage fluctuations.

[0089] Please refer to Figure 3 , Figure 3 This is one of the schematic diagrams of the installation structure of the monitoring system described in this invention. In this diagram, the generator stator 1 is fixed, the rotor 2 rotates around the rotor core 3, an end ring 4 is installed on the rotor, magnetic poles 5 are provided on both sides of the rotor, the rotor damping strip 6 is provided on the surface of the rotor rotating end, there is an air gap 7 between the rotor 2 and the stator 1, and multiple parallel ventilation grooves are opened inside the stator.

[0090] The magnetic gradient sensor array includes an axial main array P08 and two circumferential redundant reference arrays P -2 9 and P + 210;

[0091] The main array P08 is set in a single ventilation groove on the circumference of the stator and arranged along the rotor axis to collect magnetic field gradient signals at different positions along the rotor axis.

[0092] Redundant reference array P -2 9 and P +2 10 are respectively set in the ventilation trenches on both sides of the ventilation trench corresponding to the main array P08, and are separated from the main array P08 by at least one ventilation trench, for collecting local background magnetic field signals.

[0093] Please refer to Figure 4 , Figure 4 This is the second schematic diagram of the installation structure of the monitoring system described in this invention. The main array P08 includes P 01 ,P 02 ,P 03 ,...,P y Multiple differential coil pairs are used, and the value of y is determined based on the turbine dimensions and the required axial positioning accuracy. Its core function is to achieve precise axial (longitudinal) positioning of the damping bar crack. Redundant reference array P -2 9 and P +2 Unit 10 contains at least one differential coil pair, forming a redundant reference that serves as a real-time reference point for the local background magnetic field. Further comparisons with P08 and P... -2 9. P +2 The signal of 10 can distinguish whether the signal peak measured at P0 is caused by a real local distorted magnetic field due to a tiny crack, or by regional magnetic field inhomogeneity caused by the static eccentricity of the stator, thus achieving spatial discrimination.

[0094] Continue to refer to Figure 3 and Figure 4 The optical angle synchronization device (OSM) includes: a fiber-coupled semiconductor laser (LD) 11, a photodetector (PD) 12, a DSP processing unit (not shown in the figure) and a microprism array 13;

[0095] The fiber-coupled semiconductor laser 11 and the photodetector 12 are integrated with the rectangular differential coil pair of the main array P08 inside the insulating shell (PTEE). An optical window 14 is provided on the side of the insulating shell facing the air gap. The optical window 14 is used to transmit the laser emitted by the fiber-coupled semiconductor laser 11.

[0096] The microprism array 13 is mounted on at least one rotor damping bar 6 and is used to reflect the laser emitted by the fiber-coupled semiconductor laser 11 to the photodetector 12.

[0097] The photoelectric receiver 12 is used to receive reflected laser light and output reflected pulse signals;

[0098] The DSP processing unit is used to calculate the instantaneous angular velocity of the rotor in real time based on the reflected pulse signal, generate a synchronous sampling clock that matches the rotor rotation angle, and output the rotor absolute 0° angle mark.

[0099] The optical window 14 can be made of materials such as sapphire to ensure high-quality projection of the laser beam and efficient reception of reflected light, while avoiding scattering of light by the PTFE material. In some preferred embodiments, the microprism array 13 is mounted on the end ring 4 of the rotor 2. This array consists of a large number of tiny cubic prisms and has the optical characteristic of accurately returning the incident light along its original path.

[0100] During operation, the laser continuously irradiates the rotor 2. For each rotation of the rotor 2, the microprism array 13 reflects the light once, and the photodetector 12 outputs a synchronization pulse, which is received by the DSP processing unit.

[0101] The rotor's absolute 0° angle mark corresponds to the damping strip on which the microprism array 13 is installed (e.g., defined as damping strip number 1). In some embodiments, the number of damping strips on which the microprism array 13 is installed can be appropriately increased if more accurate positioning is required under rotor 2 speed change conditions.

[0102] The process of calculating the instantaneous angular velocity of the rotor in real time based on the reflected pulse signal and generating a synchronous sampling clock that matches the rotor rotation angle includes:

[0103] The rotor's single-turn rotation time is obtained based on the interval between the two reflected pulse signals.

[0104] The instantaneous angular velocity of the rotor is calculated based on the rotor's single-turn rotation time.

[0105] Based on the number of damping bars, the mechanical angle of one revolution of the rotor is divided into N fixed angle steps Δθ.

[0106] Based on the instantaneous angular velocity of the rotor, the sampling time interval corresponding to the rotor rotating through a fixed angular step Δθ is calculated;

[0107] A synchronous sampling clock is generated based on the sampling time interval.

[0108] For example, the current pulse P j With the previous pulse P j-1 The time interval between them is Δt j That is, the current rotation period of the rotor is T. round Therefore, the instantaneous angular velocity of the rotor is: ω j =2π / T round =2π / Δt j .

[0109] When dividing the angular step size, the density needs to ensure the discrimination accuracy. In this embodiment, N=4×N is set. bar (N) bar (where N is the total number of damping bars), then Δθ = 2π / N = π / (2 × N) bar The angular period corresponding to each damping bar is Δθ. bar =4×Δθ. Therefore, the sampling time interval Δt θ =Δθ / ω j =Δt j / 4N bar .

[0110] During system operation, the magnetic gradient sensor array outputs a differential voltage signal, which is transmitted through shielded twisted-pair cable to suppress interference along the way. The signal first enters an amplification and filtering circuit for purification, and then is sent to the ADAM-4017+ multi-channel data acquisition module. The sampling action of this module is strictly controlled by the synchronous sampling clock generated in real time by the DSP processing unit, ensuring that the rotor rotates exactly through a preset fixed angle step Δθ when each pulse triggers sampling. Driven by the clock pulse, the ADAM-4017+ module synchronously samples the axial main array P0 and the circumferential redundant reference array P... -2 and P +2 All channel signals are instantaneously sampled and converted from analog to digital, converting the analog voltage values ​​of each channel into digital values. This process ensures strict synchronization of multi-channel data in time. Finally, the generated digital differential signal is uploaded to the industrial control computer diagnostic module in real time via the RS-485 communication bus.

[0111] The determination of the damping bar defect based on the rotor absolute angle mark and the digital differential signal includes:

[0112] Based on the absolute 0° angle mark, and according to the number of damping strips, establish the correspondence between each sampling point and the damping strip;

[0113] Acquire the digital differential signal for M consecutive rotation cycles under normal generator operation, calculate the signal average value at any sampling point, and establish a stable sequence baseline based on the signal average value of all sampling points;

[0114] Calculate the abnormal residual between the digital differential signal and the stable sequence baseline during the current rotation cycle. If the abnormal residual exceeds a preset residual threshold, it is preliminarily determined that the damping strip has a defect.

[0115] For example, an absolute 0° angle mark corresponds to damping bar number 1. The industrial control computer diagnostic module uses a preset damping bar angle mapping table to map the angle domain signal to the specific damping bar number. For example, if there are a total of 60 damping bars, the theoretical angle interval of each damping bar is π / 30 radians.

[0116] When establishing a stable sequence baseline, the system provides each independent sensor channel with an axial master array P0 and a circumferential redundant reference array P. -2 and P +2 Each differential coil pair in the circuit establishes its own stable sequence baseline. This means that each channel has a reference curve characterizing its signal features under normal conditions.

[0117] Among them, stable sequence baseline The expression is: Where j refers to the j-th period, For a sampling point at a certain angle, the corresponding signal is .

[0118] Further calculations of the abnormal residuals are performed. For each differential coil pair of the main array P0, the current period signal S is calculated. current (θ) and baseline The residual ΔS current (θ), where ΔS current (θ)=S current (θ)- If the abnormal residual of any differential coil pair exceeds a preset residual threshold, a preliminary judgment is made. The angle corresponds to a defect in the damping strip.

[0119] The multi-dimensional verification includes: spatial dimension verification and circumferential dimension verification;

[0120] The spatial dimension verification includes:

[0121] Compare the primary array P0 with the redundant reference array P -2 and P +2 Calculate the spatial confidence of the defect signal from the abnormal residuals at the same sampling point;

[0122] If the spatial confidence level exceeds a preset confidence threshold, the defect signal is determined to be a real defect.

[0123] If the spatial confidence level does not exceed the preset confidence threshold, the defect signal is determined to be an interference signal.

[0124] When the defect signal is determined to be a real defect, the abnormal residuals corresponding to each rectangular differential coil pair in the main array P0 are compared to determine the axial sampling position corresponding to the peak value of the abnormal residual, and the specific axial position of the defect is obtained.

[0125] For example, assuming a preliminary judgment The damping bar with the corresponding angle number K has a defect, and the system synchronously acquires the circumferential redundant reference channel P. -2 and P +2 exist Abnormal residuals at the location and (If redundant reference channel P) -2 and P +2 If multiple differential coil pairs are set up, the outlier residual with the largest value is selected, and the spatial confidence level is calculated. : ,in, Represents the angle At this location, the current maximum abnormal residual value within channel P0 of the main array. To find the average value function.

[0126] The preset reliability threshold is set by those skilled in the art based on the actual situation.

[0127] Based on the determination that it is a real defect, by comparing the signals of each axial coil pair inside the main array P0, the axial sampling position where the abnormal residual peak is located can be determined, and the specific position of the defect in the damping strip axis can be obtained.

[0128] The circumferential dimension verification includes:

[0129] Based on the correspondence between sampling points and damping bars, the digital differential signal intervals corresponding to the damping bar K under test and the adjacent damping bar K-1 are obtained respectively. The signal difference value between damping bar K and damping bar K-1 is calculated to obtain the circumferential anomaly degree.

[0130] If the circumferential anomaly exceeds the preset anomaly threshold, the defect signal is determined to be an independent defect signal of the damping strip K to be tested.

[0131] If the circumferential anomaly does not exceed the preset anomaly threshold, the defect signal is determined to be an interference signal.

[0132] During verification, the system first extracts the entire differential signal interval corresponding to the damping bar K from the angle domain signal sequence. This interval refers to the set of all signal values ​​independently acquired by each differential coil pair in the axial main array P0 channel, covering the entire angle range from the entry to the exit of the sensor monitoring range of the damping bar; at the same time, it extracts the corresponding differential signal interval of the adjacent damping bar K-1 in the same rotation cycle.

[0133] Calculate the signal difference between the two at the same physical relative location, i.e., the longitudinal anomaly: ,in This represents the abnormal residual of the damping strip K at angle θ. Represents the damping bar K-1 at the angle Abnormal residuals at the location This refers to the fixed angular interval between adjacent damping strips.

[0134] When the longitudinal anomaly of multiple consecutive sampling points in the signal interval corresponding to damping strip K exceeds the preset anomaly threshold, or the proportion of sampling points exceeding the threshold reaches a certain threshold, it indicates that there is a significant difference in the signals of two adjacent damping strips at comparable positions, thus confirming that the anomaly is an independent defect of damping strip K.

[0135] The system also includes:

[0136] The defect trend prediction module is used to predict the deterioration trend of damping strip defects based on historical data.

[0137] Based on historical data tracking, the deterioration trend of damping strip defects is predicted, including:

[0138] Based on the abnormal residual of the defect signal in the current rotation cycle, the fault severity of the current cycle is calculated using the L2 norm.

[0139] The fault severity was continuously collected over multiple rotation cycles to establish a time-varying sequence of fault severity.

[0140] The deterioration rate of the defect is obtained by fitting the time-varying sequence of the fault severity.

[0141] Based on the rate of deterioration, the subsequent development trend of defects and the remaining usable lifespan are predicted, and predictive maintenance early warning signals are output.

[0142] For confirmed defects, the abnormal residual sequence of the angular region where the defect is located is extracted. (i=1,2,...,Z). Z is the total number of abnormal residual sampling points within the angular region where the defect is located. Calculate the fault severity Dc in the Mth cycle using the L2 norm: , where p is the total number of abnormal residual sampling points taken within the fault angle region.

[0143] Fault severity values ​​are continuously collected for multiple operating cycles (M=1,2,3...) to form a time-varying fault severity sequence. Trend fitting is then performed on this sequence, for example, using linear fitting. .in, This is the initial value for the fault baseline. Let j be the rate of deterioration, and j be the j-th cycle.

[0144] The system presets a positive deterioration rate threshold. When the fitting results show > At that time, it was determined that the defect showed a clear trend of worsening. Furthermore, the system presets a danger threshold Dc for safe operation. critical This threshold can be determined based on the motor design safety margin, historical fault data, or industry standards; this invention does not limit it. The severity Dc is based on the current cycle. current and rate of deterioration The remaining number of operating cycles required for a defect to develop into a dangerous state can be estimated: N remaining =(Dc critical -Dc current ) / .

[0145] Example 2

[0146] This invention also provides a method for monitoring defects in damping bars of a axial-flow turbine generator, the method comprising:

[0147] A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap to collect the local magnetic field gradient signal corresponding to the rotor damping bar of the generator and output a differential voltage signal.

[0148] The real-time rotation angle signal of the rotor is acquired by an optical angle synchronization device, and the rotor absolute angle mark and angle synchronization sampling clock are generated.

[0149] Based on the angle synchronization sampling clock, the acquired differential voltage signal is synchronously conditioned and a digital differential signal is output.

[0150] The defects of the damping bar are determined based on the absolute angle mark of the rotor and the digital differential signal; the defects are identified through multi-dimensional verification and collaborative identification, interference is eliminated, and the monitoring and location of rotor damping bar defects are completed.

[0151] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0152] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A damping bar defect monitoring system for a axial-flow turbine generator, characterized in that, The system includes: A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap. It is used to collect the local magnetic field gradient signal corresponding to the damping bar of the generator rotor and output a differential voltage signal. An optical angle synchronization device is used to acquire the real-time rotation angle signal of the rotor and generate the rotor absolute angle mark and angle synchronization sampling clock. The signal acquisition and conditioning module is used to synchronously condition the acquired differential voltage signal based on the angle synchronous sampling clock and output a digital differential signal. The industrial control computer diagnostic module is used to determine the defects of the damping bar based on the rotor absolute angle mark and the digital differential signal; it is also used to identify defects based on multi-dimensional verification and collaborative identification, eliminate interference, and complete the monitoring and location of rotor damping bar defects.

2. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 1, characterized in that, The magnetic gradient sensor array includes several pairs of rectangular differential coils arranged in a uniform manner; The rectangular differential coil pair is composed of a first rectangular multi-turn copper coil and a second rectangular multi-turn copper coil connected in series. The first rectangular multi-turn copper coil and the second rectangular multi-turn copper coil have the same parameters, but the coils are wound in opposite directions.

3. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 2, characterized in that, The magnetic gradient sensor array includes an axial main array P0 and two circumferential redundant reference arrays P1 and P2. -2 and P +2 ; The main array P0 is set in a single ventilation groove on the circumference of the stator and arranged along the rotor axis to collect magnetic field gradient signals at different positions along the rotor axis. Redundant reference array P -2 and P +2 They are respectively set in the ventilation trenches on both sides of the ventilation trench corresponding to the main array P0, and are separated from the main array P0 by at least one ventilation trench, for collecting local background magnetic field signals.

4. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 3, characterized in that, The optical angle synchronization device includes: a fiber-coupled semiconductor laser, a photodetector, a DSP processing unit, and a microprism array; The fiber-coupled semiconductor laser and photodetector are integrated with the rectangular differential coil pair of the main array P0 inside the insulating housing. An optical window is provided on the side of the insulating housing facing the air gap, and the optical window is used to transmit the laser emitted by the fiber-coupled semiconductor laser. The microprism array is mounted on at least one rotor damping bar and is used to reflect the laser emitted by the fiber-coupled semiconductor laser to the photodetector. The photoelectric receiver is used to receive reflected laser light and output reflected pulse signals; The DSP processing unit is used to calculate the instantaneous angular velocity of the rotor in real time based on the reflected pulse signal, generate a synchronous sampling clock that matches the rotor rotation angle, and output the rotor absolute 0° angle mark.

5. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 4, characterized in that, Based on the reflected pulse signal, the instantaneous angular velocity of the rotor is calculated in real time, and a synchronous sampling clock matching the rotor rotation angle is generated, including: The rotor's single-turn rotation time is obtained based on the interval between the two reflected pulse signals. The instantaneous angular velocity of the rotor is calculated based on the rotor's single-turn rotation time. Based on the number of damping bars, the mechanical angle of one revolution of the rotor is divided into N fixed angle steps Δθ. Based on the instantaneous angular velocity of the rotor, the sampling time interval corresponding to the rotor rotating through a fixed angular step Δθ is calculated; A synchronous sampling clock is generated based on the sampling time interval.

6. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 4, characterized in that, Based on the rotor absolute angle mark and the digital differential signal, the defect status of the damping bar is determined, including: Based on the absolute 0° angle mark, and according to the number of damping strips, establish the correspondence between each sampling point and the damping strip; The digital differential signal is acquired for M consecutive rotation cycles under normal generator operation, the average signal value at any sampling point is calculated, and a stable sequence baseline is established based on the average signal value of all sampling points. Calculate the abnormal residual between the digital differential signal and the stable sequence baseline during the current rotation cycle. If the abnormal residual exceeds a preset residual threshold, it is preliminarily determined that the damping strip has a defect.

7. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 6, characterized in that, The multi-dimensional verification includes: spatial dimension verification and circumferential dimension verification; The spatial dimension verification includes: Compare the primary array P0 with the redundant reference array P -2 and P +2 Calculate the spatial confidence of the defect signal from the abnormal residuals at the same sampling point; If the spatial confidence level exceeds a preset confidence threshold, the defect signal is determined to be a real defect. If the spatial confidence level does not exceed the preset confidence threshold, the defect signal is determined to be an interference signal. When the defect signal is determined to be a real defect, the abnormal residuals corresponding to each rectangular differential coil pair in the main array P0 are compared to determine the axial sampling position corresponding to the peak value of the abnormal residual, and the specific axial position of the defect is obtained.

8. The damping bar defect monitoring system for a axial-flow turbine generator according to claim 7, characterized in that, The circumferential dimension verification includes: Based on the correspondence between sampling points and damping bars, the digital differential signal intervals corresponding to the damping bar K under test and the adjacent damping bar K-1 are obtained respectively. The signal difference value between damping bar K and damping bar K-1 is calculated to obtain the circumferential anomaly degree. If the circumferential anomaly exceeds the preset anomaly threshold, the defect signal is determined to be an independent defect signal of the damping strip K to be tested. If the circumferential anomaly does not exceed the preset anomaly threshold, the defect signal is determined to be an interference signal.

9. A damping bar defect monitoring system for a axial-flow turbine generator according to claim 6, characterized in that, The system also includes: The defect trend prediction module is used to predict the deterioration trend of damping strip defects based on historical data. Based on historical data tracking, the deterioration trend of damping strip defects is predicted, including: Based on the abnormal residual of the defect signal in the current rotation cycle, the fault severity of the current cycle is calculated using the L2 norm. The fault severity was continuously collected over multiple rotation cycles to establish a time-varying sequence of fault severity. The deterioration rate of the defect is obtained by fitting the time-varying sequence of the fault severity. Based on the rate of deterioration, the subsequent development trend of defects and the remaining usable lifespan are predicted, and predictive maintenance early warning signals are output.

10. A method for monitoring defects in damping bars of a axial-flow turbine generator, characterized in that, The method includes: A magnetic gradient sensor array is fixedly installed on the side of the stator ventilation groove of the axial-flow turbine generator near the air gap to collect the local magnetic field gradient signal corresponding to the rotor damping bar of the generator and output a differential voltage signal. The real-time rotation angle signal of the rotor is acquired by an optical angle synchronization device, and the rotor absolute angle mark and angle synchronization sampling clock are generated. Based on the angle synchronization sampling clock, the acquired differential voltage signal is synchronously conditioned and a digital differential signal is output. The defects of the damping bar are determined based on the absolute angle mark of the rotor and the digital differential signal; the defects are identified through multi-dimensional verification and collaborative identification, interference is eliminated, and the monitoring and location of rotor damping bar defects are completed.

Images