A method and system for dynamic risk assessment of wind turbine generator bearing oil film breakdown

Abstract

This invention provides a method and system for dynamic risk assessment of oil film breakdown in wind turbine generator bearings, belonging to the field of online monitoring and fault diagnosis technology for wind turbine generator bearings. It can significantly alleviate or solve the problems of poor adaptability, inability to dynamically adjust to changes in speed, temperature, load, and lubricating oil aging, and susceptibility to false alarms and missed alarms in existing fixed empirical threshold methods. This invention acquires bearing structural parameters, material parameters, operating condition parameters, and lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient. It calculates the oil film thickness and dynamic breakdown threshold under the current operating conditions and compares them with shaft voltage characteristics to output the risk level and maintenance prompts. This solution enables individualized, online dynamic assessment, improving the accuracy and universality of the assessment.

Description

Technical Field

[0001] This invention belongs to the field of online monitoring and fault diagnosis technology for wind turbine generator bearings, specifically relating to a dynamic risk assessment method and system for oil film breakdown in wind turbine generator bearings. Background Technology

[0002] With the continuous development of new energy power generation technologies, wind turbine generators, as important equipment in new energy power generation systems, have been widely used in onshore wind farms, offshore wind farms, and distributed energy systems. Wind turbine generators typically operate continuously, under frequent changing operating conditions, and in complex alternating environments. Their operational reliability directly affects the generator's power generation efficiency, operational safety, maintenance costs, and overall lifecycle economics. Especially in modern wind turbine generators, the application of converters, power electronics, and variable frequency drive technology is increasingly common. While this improves the generator's speed regulation capability and grid connection performance, it also makes the electromagnetic environment of the generator shaft system more complex. This leads to shaft voltage, shaft current, and the resulting bearing erosion problems gradually becoming one of the important factors affecting the safe and stable operation of the generator. For in-service wind turbine generators, failure to promptly identify the risk of bearing oil film breakdown can result in anything from deteriorated lubrication, shortened bearing life, and increased maintenance frequency, to serious issues such as bearing failure, abnormal rotor vibration, and even unplanned generator shutdowns. Therefore, how to accurately assess the risk of bearing oil film breakdown in in-service wind turbine generators has become an urgent technical problem to be solved in the field of wind power operation and maintenance and condition monitoring.

[0003] In existing technologies, the threshold method is commonly used to assess the risk of electrolytic corrosion in motor bearings, especially those of variable frequency drive generators. This method typically measures the shaft voltage amplitude and compares it to a pre-set empirical threshold. When the shaft voltage amplitude reaches or exceeds the threshold, the bearing is considered to be at risk of electrolytic breakdown corrosion. This method is relatively simple to implement and easy to deploy on-site, thus having a certain application basis in the condition monitoring of existing wind turbines, motors, and related rotating electrical equipment. However, the oil film breakdown process of wind turbine generator bearings is not solely determined by the shaft voltage amplitude, but is related to multiple factors, including bearing structural dimensions, contact pair material characteristics, rotational speed, temperature, load, lubricating oil dynamic viscosity, lubricating oil viscosity-pressure coefficient, and lubricating oil breakdown field strength. Especially during the long-term service of wind turbines, the lubricating oil will age with the extension of operating time and temperature, and its insulation and rheological properties will change. At the same time, the contact state of the inner ring contact area and the outer ring contact area of ​​the bearing is not exactly the same, and the oil film thickness will also be different. Therefore, relying solely on a single fixed voltage threshold for risk assessment is difficult to truly reflect the actual pressure resistance of the bearing oil film under the current operating conditions.

[0004] However, existing technologies have at least the following shortcomings: First, the problem of fixed thresholds is prominent. Traditional empirical thresholds are mostly derived from statistical averages or empirical databases, lacking differentiated corrections for specific bearing models, specific geometric dimensions, and specific contact conditions. Therefore, for small-sized bearings, there may be cases where discharge has actually occurred but the voltage has not yet reached the threshold, while for large-sized bearings, there may be cases where the empirical threshold has been exceeded but breakdown has not yet occurred due to the thick oil film. Second, they cannot reflect dynamic changes in operating conditions. In actual operation, the speed, temperature, and load of wind turbine generators may continuously change, and the oil film thickness will change with these operating conditions. Fixed thresholds cannot reflect the real-time changes in the oil film's pressure resistance. Third, they do not fully consider the impact of lubricating oil aging. After long-term operation, the breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient of lubricating oil may decrease or drift. Existing single-threshold judgment methods usually do not incorporate the aging state of lubricating oil into the risk model, leading to deviations between the assessment results and actual operating conditions. Fourth, they lack individualization and online capabilities. Existing technologies struggle to generate personalized breakdown thresholds for different turbine models, bearing structures, and service stages, and also fail to provide continuous online risk assessment results for in-service wind turbines. Fifth, there is a lack of effective coordination between risk assessment and maintenance decisions. Existing technologies often rely on a rough assessment of "whether the threshold has been exceeded," making it difficult to provide more targeted guidance for lubricant replacement, bearing overhaul, or operational parameter adjustments.

[0005] To address this, a dynamic risk assessment method and system for oil film breakdown in wind turbine generator bearings is proposed. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art, and provides a method and system for dynamic risk assessment of oil film breakdown in wind turbine generator bearings.

[0007] This invention provides a method for dynamic risk assessment of oil film breakdown in wind turbine generator bearings, comprising the following steps: S1: Obtain the structural and material parameters of the target wind turbine generator bearing; and obtain the operating condition parameters and lubricating oil status parameters of the target wind turbine generator during operation. S2: Based on the structural parameters, material parameters, operating condition parameters and lubricating oil state parameters, determine the oil film thickness of the target wind turbine generator bearing under the current operating condition, and determine the corresponding dynamic breakdown threshold based on the oil film thickness and the lubricating oil breakdown field strength determined by the preset parameter relationship model according to the current temperature. S3: The shaft voltage characteristic value obtained during the operation of the target wind turbine generator is compared with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result; S4: Based on the risk assessment results, output the risk level information or maintenance prompt information corresponding to the risk assessment results.

[0008] Further, in step S1, the structural parameters include the rolling element radius, the inner raceway radius of curvature, the outer raceway radius of curvature, and the average bearing diameter; the material parameters include the elastic modulus and Poisson's ratio of the contact materials; the operating condition parameters include the bearing speed, bearing temperature, and load parameters; and the lubricating oil condition parameters include the lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient. The lubricating oil condition parameters are obtained by conducting insulation performance tests and rheological performance tests on the target lubricating oil under different temperatures and aging times, obtaining test data, and constructing a parameter relationship model based on the test data to show the changes in lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient with temperature and aging time. During operation, the parameter relationship model is invoked according to the current temperature and lubricating oil aging state to determine the lubricating oil condition parameters.

[0009] Specifically, step S1 further includes determining lubricating oil aging state parameters, which are determined based on one or more of the following: cumulative operating time, historical temperature data, number of start-stop cycles, and historical discharge pulse events. The lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient are dynamically corrected based on the lubricating oil aging state parameters.

[0010] Specifically, step S2 includes: The equivalent radius of curvature of the inner ring contact area is determined based on the radius of curvature of the rolling elements of the bearing and the radius of curvature of the inner ring raceway; the equivalent radius of curvature of the outer ring contact area is determined based on the radius of curvature of the rolling elements of the bearing and the radius of curvature of the outer ring raceway. Based on the equivalent radius of curvature of the inner ring contact area, the equivalent radius of curvature of the outer ring contact area, the bearing speed, load parameters, dynamic viscosity, viscosity-pressure coefficient, and material parameters, the oil film thickness of the inner ring contact area and the oil film thickness of the outer ring contact area are determined respectively. Based on the oil film thickness in the inner ring contact area, the oil film thickness in the outer ring contact area, and the lubricating oil breakdown field strength, the inner ring breakdown threshold and the outer ring breakdown threshold are determined respectively; and The smaller of the inner ring breakdown threshold and the outer ring breakdown threshold is determined as the dynamic breakdown threshold.

[0011] Preferably, in step S2, the dynamic breakdown threshold is determined by the oil film thickness, the lubricating oil breakdown field strength, and the safety margin coefficient, which is pre-calibrated based on one or more of the bearing type, lubricating oil type, temperature range, and historical operating data.

[0012] Specifically, in step S3, the shaft voltage characteristic quantity includes one or more of the following: instantaneous peak voltage, peak-to-peak voltage, number of over-threshold pulses within a preset time window, pulse repetition frequency, and accumulated voltage energy within the time window.

[0013] Furthermore, in step S3, when the shaft voltage characteristic is an instantaneous peak voltage or a peak-to-peak voltage, a risk index is constructed by the ratio of the shaft voltage characteristic to the dynamic breakdown threshold, and the bearing oil film breakdown risk is classified into normal, attention, warning and danger according to the risk index.

[0014] Furthermore, step S4 includes: When the risk index, constructed by the ratio of the shaft voltage characteristic to the dynamic breakdown threshold, is greater than the first preset threshold for multiple consecutive sampling periods within a preset time window, a warning message is output. When the risk index exceeds a second preset threshold for multiple consecutive sampling periods within a preset time window, or when the cumulative number of exceedances per unit time reaches a preset number, a danger message is output; and Based on the output risk level information, one or more maintenance prompts are generated, including lubricant replacement prompt, bearing maintenance prompt, operating load limit prompt, and speed adjustment prompt; wherein, the second preset threshold is greater than the first preset threshold.

[0015] Another aspect of the present invention provides a dynamic risk assessment system for oil film breakdown in wind turbine generator bearings. The system is adapted to implement the aforementioned dynamic risk assessment method for oil film breakdown in wind turbine generator bearings, comprising: The parameter acquisition module is used to acquire the structural parameters, material parameters, and operating condition parameters of the target wind turbine generator bearing. The oil condition determination module is used to obtain or determine the breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient of the lubricating oil. The dynamic threshold generation module is used to determine the dynamic breakdown threshold under the current operating condition based on the structural parameters, material parameters, operating condition parameters and lubricating oil state parameters. The shaft voltage acquisition module is used to acquire the shaft voltage characteristics during the operation of the target wind turbine generator; The risk assessment module is used to compare the shaft voltage characteristic with the dynamic breakdown threshold to obtain a bearing oil film breakdown risk assessment result; and The result output module is used to output risk level information or maintenance prompt information corresponding to the risk assessment result.

[0016] Specifically, the parameter acquisition module is communicatively connected to the wind turbine SCADA system, speed sensor, bearing temperature sensor and load information source, respectively; The shaft voltage acquisition module is located between the generator shaft and the housing, and is used to acquire shaft voltage signals and extract shaft voltage characteristic quantities. The dynamic threshold generation module includes a bearing parameter library and an oil parameter model library, which are used to generate the dynamic breakdown threshold. The risk assessment module contains a risk determination rule library, which is used to determine the risk level based on the comparison result between the shaft voltage characteristic quantity and the dynamic breakdown threshold.

[0017] The beneficial effects of this invention are as follows: By incorporating bearing geometric parameters, material parameters, operating condition parameters, and state parameters such as lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient into the bearing oil film breakdown risk assessment process, this invention can generate corresponding dynamic breakdown thresholds for wind turbine generator bearings of different models, sizes, and operating conditions. This solves the problems of poor adaptability and single standard in the traditional fixed threshold method. Simultaneously, this invention dynamically corrects the breakdown threshold by combining oil film thickness and lubricating oil insulation performance, which can more realistically reflect the actual pressure resistance of the bearing oil film under current operating conditions, significantly improving the accuracy of risk assessment and reducing false alarm and false negative rates. Furthermore, this invention can continuously update the threshold based on real-time operating conditions and compare it with shaft voltage characteristics to achieve online dynamic assessment of bearing oil film breakdown risk. It can also output maintenance prompts such as lubricating oil replacement, bearing overhaul, and operating parameter adjustment based on the risk level, thereby facilitating personalized maintenance of wind turbine generators and improving operational reliability. Attached Figure Description

[0018] Figure 1 A flowchart illustrating the steps of a dynamic risk assessment method for oil film breakdown in wind turbine generator bearings according to a specific embodiment of the present invention; Figure 2 This is a connection block diagram of a dynamic risk assessment system for oil film breakdown of wind turbine generator bearings, according to a specific embodiment of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] like Figure 1 As shown in the figure, a dynamic risk assessment method for oil film breakdown in wind turbine generator bearings provided by a specific embodiment of the present invention includes the following steps: S1: Obtain the structural and material parameters of the target wind turbine generator bearing; and obtain the operating condition parameters and lubricating oil status parameters of the target wind turbine generator during operation. S2: Based on the structural parameters, material parameters, operating condition parameters and lubricating oil state parameters, determine the oil film thickness of the target wind turbine generator bearing under the current operating condition, and determine the corresponding dynamic breakdown threshold based on the oil film thickness and the lubricating oil breakdown field strength determined by the preset parameter relationship model according to the current temperature. S3: The shaft voltage characteristic value obtained during the operation of the target wind turbine generator is compared with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result; S4: Based on the risk assessment results, output the risk level information or maintenance prompt information corresponding to the risk assessment results.

[0021] In one implementation, steps S1 to S4 are executed by a processor deployed in a wind turbine generator field monitoring terminal, edge computing unit, or background monitoring platform. The processor receives the wind turbine generator's operating data cyclically according to a preset sampling period and updates the dynamic breakdown threshold in real time based on the latest collected operating parameters and lubricating oil status parameters. By comparing the real-time updated dynamic breakdown threshold with the shaft voltage characteristic at the current moment, an individualized risk assessment result is formed for the current unit, the current bearing, and the current operating state, thereby avoiding the problem that fixed experience thresholds are insufficiently adaptable to different turbine models, different bearing sizes, and different service stages.

[0022] Preferably, steps S1 and S3 are executed with the same sampling period, while steps S2 and S4 are executed after each parameter update and signal acquisition, ensuring that the oil film thickness, dynamic breakdown threshold, and risk assessment results maintain a temporal correspondence. This processing method reflects both the current oil film pressure resistance of the bearing and the instantaneous changes in shaft voltage, thereby improving the timeliness and accuracy of the risk assessment results.

[0023] Furthermore, the risk level information output in step S4 is used to characterize the change in bearing oil film breakdown risk from low to high, and the maintenance prompt information is used to provide maintenance personnel with targeted intervention guidelines. The maintenance prompt information includes at least one of the following: lubricating oil condition check, lubricating oil replacement, bearing overhaul, operating load limitation, and speed adjustment. By correlating the risk assessment results with maintenance actions, this invention not only reaches the level of determining "whether a risk exists," but also further serves unit operation and maintenance decisions.

[0024] Based on the above basic implementation method, in step S1, the structural parameters include the rolling element radius, the inner raceway curvature radius, the outer raceway curvature radius, and the average bearing diameter; the material parameters include the elastic modulus and Poisson's ratio of the contact materials; the operating parameters include the bearing speed, bearing temperature, and load parameters; and the lubricating oil condition parameters include the lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient. The lubricating oil condition parameters are obtained by conducting insulation performance tests and rheological performance tests on the target lubricating oil under different temperatures and aging times, obtaining test data, and constructing a parameter relationship model based on the test data to show the changes in lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient with temperature and aging time. During operation, the parameter relationship model is invoked according to the current temperature and lubricating oil aging state to determine the lubricating oil condition parameters. The parameter relationship model refers to a function model, lookup table model, or interpolation model that takes temperature and aging state as input and lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient as output. The oil parameter model library is used to store parameter relationship models and corresponding model parameters of different lubricating oils under different temperatures and aging conditions, so as to quickly determine the lubricating oil status parameters according to the current operating conditions during operation.

[0025] Furthermore, structural and material parameters are entered into the monitoring system before the unit is put into operation. The data sources include at least one of the following: bearing selection parameters, design drawing parameters, parameters from the manufacturer's product manual, and measured parameters before installation. The operating condition parameters are provided in real-time by the wind turbine's SCADA system, bearing temperature sensors, speed sensors, and load information sources. By pre-entering structural and material parameters that do not change frequently during operation and by collecting dynamic parameters related to operating conditions in real time, redundant measurements can be avoided, improving the efficiency of online evaluation.

[0026] Specifically, in the process of acquiring lubricating oil condition parameters, multiple oil sample test groups are set up for different temperatures and aging time conditions. The breakdown field strength E, dynamic viscosity η0, and viscosity-pressure coefficient α are measured for each group of oil samples to obtain three-dimensional correlation data of temperature-time-performance. Then, based on the correlation data, a parameter relationship model of lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient is established, so that the system can directly call the corresponding performance parameters according to the current oil temperature and aging state during operation, without having to repeat the oil sample test in each monitoring cycle.

[0027] In one specific embodiment, step S1 further includes determining lubricating oil aging state parameters. These parameters are determined based on one or more of the following: cumulative operating time, historical temperature data, number of start-stop cycles, and historical discharge pulse events. The lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient are dynamically corrected based on these parameters. A historical discharge pulse event refers to a pulse-type abnormal voltage event identified and recorded by the shaft voltage acquisition unit within a preset monitoring period. The historical discharge pulse event includes at least one or more of the following: pulse occurrence time, pulse peak value, pulse duration, and number of pulses per unit time. In one embodiment, an event where the number of pulses per unit time exceeds a preset threshold is recorded as a historical discharge pulse event, and the cumulative number or intensity of historical discharge pulse events is incorporated into the lubricating oil aging state parameters as an electrical aging correction.

[0028] In this embodiment, the lubricating oil aging state parameter is used to characterize the degree of performance degradation of the current lubricating oil relative to its new state. Preferably, under the condition that the unit does not experience significant and continuous discharge, the aging state parameter mainly represents the degree of thermal aging by cumulative operating time, historical temperature data, and number of start-stop cycles; when the monitoring system records historical discharge pulse events, these are introduced into the aging state parameter as electrical aging corrections to characterize the additional effects of impurities, polarity changes, or local insulation degradation caused by the discharge on the insulating performance of the lubricating oil.

[0029] Furthermore, the lubricating oil aging state parameters are obtained by weighted combination of normalized cumulative operating time, historical temperature integral values, number of start-stop cycles, and number of historical discharge pulses, or by table lookup, interpolation, or model fitting. The purpose of this method is to uniformly map aging influencing factors from different sources and with different dimensions into a single state quantity characterizing the degree of oil aging, facilitating unified correction of breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient in subsequent steps. The lubricating oil aging state parameter Aging is determined according to the following formula: Aging = w1 × T nor +w2×H nor +w3×S nor +w4×D nor ; Among them, T nor H is the time factor after normalization of the cumulative running time. nor S is the temperature factor obtained by normalizing the historical temperature integral values. nor D is the start / stop factor after normalizing the number of start / stop cycles. nor The discharge influence factor is the normalized number of historical discharge pulses, where w1, w2, w3, and w4 are the corresponding weighting coefficients, and w1 + w2 + w3 + w4 = 1.

[0030] Under conditions where no obvious discharge pulse event is detected, w4 can be set to 0, and the lubricating oil aging state parameters can be determined based on the cumulative running time, historical temperature integral value, and number of start-stop cycles.

[0031] In another specific embodiment, step S2 includes: The equivalent radius of curvature of the inner ring contact area is determined based on the rolling element radius and the radius of curvature of the inner ring raceway. The equivalent radius of curvature of the outer ring contact area is determined based on the rolling element radius and the radius of curvature of the outer ring raceway. The oil film thickness of the inner ring contact area and the oil film thickness of the outer ring contact area are determined based on the equivalent radius of curvature of the inner ring contact area, the equivalent radius of curvature of the outer ring contact area, the bearing speed, load parameters, dynamic viscosity, viscosity-pressure coefficient, and material parameters. The breakdown threshold of the inner ring and the breakdown threshold of the outer ring are determined based on the oil film thickness of the inner ring contact area, the oil film thickness of the outer ring contact area, and the breakdown field strength of the lubricating oil. The smaller of the inner ring breakdown threshold and the outer ring breakdown threshold is determined as the dynamic breakdown threshold.

[0032] In this embodiment, the inner ring contact area and the outer ring contact area correspond to the contact areas between the rolling element and the inner ring raceway, and between the rolling element and the outer ring raceway, respectively. Since the curvature conditions of the inner and outer rings are different, the resulting oil film thicknesses may also differ. Therefore, the oil film thicknesses of the inner ring contact area and the outer ring contact area are calculated separately, and the smaller of the corresponding breakdown thresholds is used as the dynamic breakdown threshold. This reflects the actual pressure resistance of the bearing on the weaker side of the two contact areas, thereby improving the conservatism and reliability of the risk assessment.

[0033] Specifically, the equivalent radius of curvature of the inner contact area Equivalent radius of curvature of the contact area with the outer ring Determine them according to the following formulas respectively:

[0034]

[0035] in, Let be the equivalent radius of curvature of the inner circle. The equivalent radius of curvature of the outer ring. The radius of the rolling element (convex surface, positive sign). The radius of curvature of the inner raceway (concave, negative sign). The radius of curvature of the outer raceway (concave surface, negative sign); Sucking speed Determined according to the following formula:

[0036] in, For bearing speed, This represents the average diameter of the bearing. Equivalent elastic modulus satisfy:

[0037] in, , These are the elastic moduli of the contact pair materials (material properties of the contact surface, parameters of the bearing track and roller). , These are the Poisson's ratios of the contact pair materials, respectively.

[0038] Furthermore, in one embodiment, the velocity parameter V, load parameter W, and material parameter G are determined based on the elastohydrodynamic lubrication theory, wherein:

[0039]

[0040]

[0041] in, For dynamic viscosity, The suction speed is the speed at which the suction is drawn in. Equivalent elastic modulus This is the equivalent radius of curvature of the corresponding contact area. For radial load, The effective length of the roller. The viscosity-pressure coefficient was used, and then the minimum oil film thickness was estimated using the Dowson-Higginson formula. :

[0042] After calculating the minimum oil film thickness in the inner and outer contact areas respectively, the breakdown threshold corresponding to the thinner oil film is taken as the dynamic breakdown threshold. Determination of dynamic viscosity

[0043] Dynamic viscosity was measured using a capillary viscometer at specific temperatures and aging conditions. The dynamic viscosity value is calculated by precisely measuring the time it takes for a quantitative liquid to flow through a standard-sized capillary tube under gravity, combined with the Hagen-Poiseuille equation.

[0044]

[0045] Where Q is the volumetric flow rate through the cross-section per unit time; r is the pipe radius; and L is the pipe length. To extend the pressure difference in the pipeline. Viscosity coefficient. Measurement: Using a high-pressure rheometer, the viscosity-pressure coefficient of the lubricating oil at a specific temperature and aging degree is measured , and the corresponding curve is plotted.

[0046] Through this step, the insulation performance (electric field strength at breakdown) at different temperatures and aging times is obtained , dynamic viscosity , and viscosity-pressure coefficient . Through fitting calculation, the functions of the relevant parameters with temperature and time are obtained.

[0047] Parameter fitting:

[0048] is the aging reaction rate constant, determined by fitting; : the initial (without aging) dynamic viscosity at different temperatures .

[0049] Similarly, the insulation performance (electric field strength at breakdown) :

[0050] is the breakdown field strength of fresh oil at different temperatures.

[0051] m is the shape factor (0<m ≤ 1, generally m = 0.5~1.0) Viscosity-pressure coefficient fitting:

[0052] is the viscosity-pressure coefficient of fresh oil; t is the aging time; A and B are parameters to be fitted. A reflects the initial change rate of oil aging. reflects the nonlinear degree of the aging process.

[0053] In another specific embodiment, in step S2, the dynamic breakdown threshold is jointly determined by the oil film thickness, the breakdown field strength of the lubricating oil and the safety margin coefficient, and the safety margin coefficient is pre-calibrated according to one or more of the bearing type, the lubricating oil type, the temperature interval and historical operation data.

[0054] Further, in one embodiment, the dynamic breakdown threshold U is determined according to the following formula:

[0055] wherein, is the breakdown threshold voltage of the shaft, To provide a safety margin, a safety margin coefficient is introduced to correct the theoretical breakdown threshold calculated based on the ideal model, making the generated dynamic breakdown threshold closer to the conservative judgment requirements in engineering applications. 0.8 is acceptable.

[0056] Specifically, in one implementation, the safety margin factor is determined through at least one of the following methods: regression analysis of historical operating data, bench test calibration, or field test calibration. In one example, for a known bearing type and lubricant combination, the safety margin factor... The value is set to 0.8; for other models, the safety margin coefficient is adjusted based on historical discharge event records under different speeds, temperatures, and loads. This method establishes a stable mapping relationship between the theoretical model and engineering practice.

[0057] In another specific embodiment, in step S3, the shaft voltage characteristic quantities include one or more of the following: instantaneous peak voltage, peak-to-peak voltage, number of over-threshold pulses within a preset time window, pulse repetition frequency, and accumulated voltage energy within the time window; instantaneous peak voltage refers to the maximum amplitude of the shaft voltage signal within a single sampling window, peak-to-peak voltage refers to the difference between the maximum and minimum values ​​of the shaft voltage signal within the same sampling window, number of over-threshold pulses refers to the number of pulses exceeding a preset voltage threshold within the preset time window, pulse repetition frequency refers to the number of effective pulses occurring per unit time, and accumulated voltage energy within the time window refers to the cumulative response of the shaft voltage signal in the time dimension within the preset time window.

[0058] Furthermore, in one embodiment, the shaft voltage signal is acquired by a shaft voltage acquisition unit located between the generator shaft and the casing. After the acquired raw signal undergoes isolation, filtering, noise reduction, and sampling window segmentation, the instantaneous peak voltage, peak-to-peak voltage, number of over-threshold pulses, pulse repetition frequency, and accumulated voltage energy within a time window are extracted. By simultaneously extracting multiple shaft voltage characteristics, both the amplitude level of the shaft voltage and its impulsive and cumulative changes within a certain time window can be reflected.

[0059] Specifically, in one embodiment, when the monitoring target is to evaluate the direct proximity between the voltage amplitude and the dynamic breakdown threshold, the instantaneous peak voltage or peak-to-peak voltage is preferentially extracted as the axis voltage characteristic quantity; when the monitoring target is to evaluate the frequency of pulse discharge activity, the number of over-threshold pulses or the pulse repetition frequency within a preset time window is preferentially extracted as the axis voltage characteristic quantity; when the monitoring target is to evaluate the cumulative degree of partial discharge impact, the accumulated voltage energy within the time window is preferentially extracted as the axis voltage characteristic quantity.

[0060] In another specific embodiment, in step S3, when the shaft voltage characteristic is an instantaneous peak voltage or a peak-to-peak voltage, a risk index is constructed by the ratio of the shaft voltage characteristic to the dynamic breakdown threshold, and the bearing oil film breakdown risk is classified into normal, attention, warning and danger according to the risk index.

[0061] Furthermore, in one implementation, the risk index Determined according to the following formula:

[0062] This refers to the instantaneous peak voltage or peak-to-peak voltage extracted during the current sampling period. This is the dynamic breakdown threshold under the current operating conditions. When the voltage increases, it indicates that the actual shaft voltage is gradually approaching or exceeding the upper limit of the breakdown withstand voltage corresponding to the oil film, and the risk of bearing oil film breakdown increases accordingly.

[0063] Furthermore, in one example, according to the risk index Risks are classified into the following levels: when A value less than 0.7 is considered normal; when... When the value is greater than or equal to 0.7 and less than 0.9, it is considered a warning; when... A value greater than or equal to 0.9 and less than 1.0 is considered a warning; when... A value greater than or equal to 1.0 is considered dangerous. It should be understood that the above classification thresholds are merely examples and can be adjusted in practice based on different machine models, bearing types, and lubricant types.

[0064] In another specific embodiment, step S4 includes: When the risk index, constructed by the ratio of shaft voltage characteristic quantity to dynamic breakdown threshold, exceeds the first preset threshold for multiple consecutive sampling periods within a preset time window, a warning message is output; when the risk index exceeds the second preset threshold for multiple consecutive sampling periods within a preset time window, or when the cumulative number of exceedances per unit time reaches a preset number, a danger message is output; and based on the output risk level information, one or more maintenance reminders are generated, including lubricant replacement reminder, bearing maintenance reminder, operating load limit reminder, and speed adjustment reminder; wherein, the second preset threshold is greater than the first preset threshold; the sampling period refers to the time interval between the monitoring system updating operating parameters, extracting shaft voltage characteristic quantity, and performing a risk assessment; the sampling window refers to the signal time period used to extract shaft voltage characteristic quantity; the preset time window is a judgment time interval composed of one or more consecutive sampling periods, used for continuous exceedance judgment or cumulative exceedance judgment. In one embodiment, the sampling window is the same as the sampling period; in another embodiment, the sampling window is smaller than the sampling period, and multiple local characteristic quantities are extracted within one sampling period before comprehensive judgment is performed.

[0065] Furthermore, in one embodiment, a first preset threshold is used to identify operating conditions where the oil film's pressure resistance has significantly decreased but has not yet reached a sustained dangerous state, and a second preset threshold is used to identify operating conditions where the oil film is approaching or exceeding the breakdown boundary. In one example, the first preset threshold corresponds to the warning level boundary, and the second preset threshold corresponds to the danger level boundary. By requiring the risk index to remain above the limit for multiple consecutive sampling cycles within a preset time window, rather than judging based solely on a single sampling point, the interference of occasional noise spikes on the risk assessment results can be reduced.

[0066] Furthermore, in one implementation, when an early warning message is output, the system generates a lubricating oil status verification prompt or a short-cycle retest prompt; when a danger message is output, the system generates at least one maintenance prompt message among lubricating oil replacement prompt, bearing maintenance prompt, operating load limit prompt, and speed adjustment prompt, so as to guide maintenance personnel to take timely intervention measures and reduce the probability of further development of discharge corrosion.

[0067] In one specific implementation, such as Figure 2As shown, this invention provides a dynamic risk assessment system for oil film breakdown of wind turbine generator bearings. The system is suitable for implementing the aforementioned dynamic risk assessment method for oil film breakdown of wind turbine generator bearings, and includes: a parameter acquisition module for acquiring structural parameters, material parameters, and operating condition parameters of the target wind turbine generator bearing; an oil condition determination module for acquiring or determining the lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient; a dynamic threshold generation module for determining the dynamic breakdown threshold under the current operating condition based on the structural parameters, material parameters, operating condition parameters, and lubricating oil condition parameters; a shaft voltage acquisition module for acquiring shaft voltage characteristic quantities during the operation of the target wind turbine generator; a risk assessment module for comparing the shaft voltage characteristic quantities with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result; and a result output module for outputting risk level information or maintenance prompt information corresponding to the risk assessment result. Load parameters are directly measured by load sensors or determined through a load conversion model based on the power, torque, shaft system structural parameters, and operating condition data of the wind turbine generator. Load information sources include at least one of load sensors, SCADA operating data interfaces, or preset load calculation models.

[0068] Specifically, the parameter acquisition module receives basic bearing parameters and real-time operating condition data; the oil condition determination module determines the lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient based on the oil sample test model, current temperature, and aging state; the dynamic threshold generation module calculates the oil film thickness and dynamic breakdown threshold; the shaft voltage acquisition module acquires shaft voltage signals and extracts features; the risk assessment module calculates the risk index, determines the risk level, and identifies exceedance rules; and the result output module outputs risk level information and maintenance prompts to the upper-level monitoring platform, human-machine interface, or alarm terminal. Through this modular configuration, the method steps of this invention can be implemented in a hardware or software system.

[0069] Furthermore, in one embodiment, the dynamic threshold generation module and the risk assessment module work together according to the same sampling period. The dynamic threshold generation module first generates a dynamic breakdown threshold based on the latest operating conditions, and the risk assessment module then compares the dynamic breakdown threshold with the current shaft voltage characteristic quantity to ensure that the risk assessment process and the threshold update process correspond to the data at the same time or within the same sampling window.

[0070] In one specific implementation, the parameter acquisition module is communicatively connected to the wind turbine SCADA system, speed sensor, bearing temperature sensor, and load information source, respectively; the shaft voltage acquisition module is located between the generator shaft and the casing to acquire shaft voltage signals and extract shaft voltage characteristic quantities; the dynamic threshold generation module contains a bearing parameter library and an oil parameter model library to generate dynamic breakdown thresholds; the risk assessment module contains a risk judgment rule library to determine the risk level based on the comparison results of shaft voltage characteristic quantities and dynamic breakdown thresholds; the wind turbine SCADA system refers to the monitoring and data acquisition system of the wind turbine generator set.

[0071] In this embodiment, the bearing parameter library stores parameters such as rolling element radius, raceway curvature radius, average bearing diameter, elastic modulus, and Poisson's ratio corresponding to different bearing models; the oil parameter model library stores models of breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient for different lubricants under different temperatures and aging times; and the risk assessment rule library stores risk index grading rules, continuous over-limit assessment rules, and maintenance prompt output rules. Through the cooperation of the above parameter and rule libraries, the system can quickly generate corresponding dynamic breakdown thresholds and complete risk assessment for different aircraft models, different oils, and different service conditions.

[0072] Specifically, in one implementation, the result output module outputs the risk level information in at least one of the following ways: text, graphics, color coding, alarm signals, or historical trend curves. It also sends maintenance prompts to the wind turbine monitoring interface or operation and maintenance terminal so that operation and maintenance personnel can promptly perform inspections, oil changes, repairs, or adjustments to operating parameters based on the risk level.

[0073] In one specific implementation, taking the drive-end bearing of an in-service doubly-fed wind turbine generator as an example, the dynamic risk of bearing oil film breakdown is assessed. The bearing is a rolling bearing with a rolling element radius of 6.0 mm, an inner raceway curvature radius of -28.0 mm, an outer raceway curvature radius of -32.0 mm, an average bearing diameter of 120 mm, and an effective roller length of 12 mm. Both the rolling elements and raceways are made of bearing steel with an elastic modulus of 206 GPa and a Poisson's ratio of 0.30. The implementation follows the sequence of "parameter acquisition—oil film thickness calculation—dynamic breakdown threshold generation—shaft voltage comparison and judgment."

[0074] In this embodiment, step S1 involves obtaining the structural and material parameters of the target wind turbine generator bearing, and obtaining the operating condition parameters and lubricating oil status parameters of the target wind turbine generator during operation.

[0075] In this embodiment, the target wind turbine generator is currently operating at a speed of 1800 r / min, a bearing temperature of 82°C, a radial load of 8.5 kN, a cumulative operating time of 1680 h, and 215 start-stop cycles. For the lubricating oil used, thermal aging tests were conducted beforehand at 70°C, 80°C, 90°C, and 100°C, and the breakdown field strength was measured every 100 h within the range of 0 h to 2500 h. Dynamic viscosity and viscosity coefficient The corresponding experimental data were obtained; then, based on the experimental data, a parametric relationship model was constructed to show the changes in lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient with temperature and aging time. Using the current temperature of 82℃ and the cumulative operating time of 1680 h, the parametric relationship model was called to determine that the lubricating oil breakdown field strength under the current operating conditions is 18 kV / mm, the dynamic viscosity is 0.018 Pa·s, and the viscosity-pressure coefficient is 1.8 × 10⁻⁸ Pa⁻¹.

[0076] Step S2: Based on structural parameters, material parameters, operating condition parameters, and lubricating oil state parameters, determine the oil film thickness of the target wind turbine generator bearing under the current operating condition, and determine the corresponding dynamic breakdown threshold based on the oil film thickness and the lubricating oil breakdown field strength.

[0077] In this embodiment, the equivalent radius of curvature of the inner ring contact area is first determined based on the radius of the rolling element and the radius of curvature of the inner ring raceway. Then, the equivalent radius of curvature of the outer ring contact area is determined based on the radius of the rolling element and the radius of curvature of the outer ring raceway. Finally, the equivalent radius of curvature of the inner ring contact area is calculated. Approximately 4.94 mm, equivalent radius of curvature of the outer contact area. The thickness is approximately 5.05 mm. Subsequently, the entrainment speed is determined based on the bearing speed and average bearing diameter. Combining dynamic viscosity, viscosity-pressure coefficient, load parameters, and material parameters, the oil film thickness in the inner ring contact area and the outer ring contact area are calculated using the elastohydrodynamic lubricating oil film thickness calculation model adopted in this invention. In this embodiment, the oil film thickness calculation further incorporates surface roughness correction coefficients and thermal shear correction coefficients to reflect the actual oil film formation state under the field operating conditions of the wind turbine generator bearing. The calculated oil film thickness in the inner ring contact area is 0.42 μm, and the oil film thickness in the outer ring contact area is 0.47 μm. Since the oil film in the inner ring contact area is relatively thin, the breakdown threshold corresponding to the inner ring contact area is the focus of the evaluation.

[0078] In this embodiment, the dynamic breakdown threshold is determined by the oil film thickness, the lubricating oil breakdown field strength, and the safety margin factor. The safety margin factor is set to 0.8 based on historical operating data and field calibration results of the same bearing model. Substituting the inner ring contact area oil film thickness of 0.42 μm, the lubricating oil breakdown field strength of 18 kV / mm, and the safety margin factor of 0.8 into the threshold calculation formula, the inner ring breakdown threshold is approximately 6.05 V; similarly, the outer ring breakdown threshold is approximately 6.77 V. The smaller value, 6.05 V, is taken as the dynamic breakdown threshold under the current operating condition.

[0079] Step S3: Collect the shaft voltage characteristic quantity during the operation of the target wind turbine generator, and compare the shaft voltage characteristic quantity with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result.

[0080] In this embodiment, the shaft voltage characteristic is extracted using a 1-second sampling window. Within the current sampling window, the instantaneous peak voltage is extracted to be 5.72V, the peak-to-peak voltage is 8.10V, and the number of over-threshold pulses within the preset time window is 12. Since this embodiment uses the ratio of instantaneous peak voltage to dynamic breakdown threshold to construct a risk index, the instantaneous peak voltage is used as the basis for calculating the risk index. Based on the risk index... To obtain the current risk index =5.72 / 6.05≈0.946; In this embodiment, peak-to-peak voltage and the number of over-threshold pulses are recorded as auxiliary monitoring features, and the risk level is mainly determined by the ratio of instantaneous peak voltage to dynamic breakdown threshold; when peak-to-peak voltage is used as the basis for calculating the risk index, it is judged independently according to the corresponding peak-to-peak voltage judgment rule; the danger judgment threshold for the cumulative number of over-limits is set to 20 times / preset time window. The current number of over-threshold pulses is 12 times, which has not reached the cumulative over-threshold danger judgment threshold, so no danger information is triggered separately.

[0081] Step S4: Output the risk level information or maintenance prompt information corresponding to the risk assessment results.

[0082] In this embodiment, a first preset threshold is set to 0.90, and a second preset threshold is set to 1.00, with the second preset threshold being greater than the first preset threshold. When the risk index is greater than 0.90 and less than 1.00 for multiple consecutive sampling periods, a warning state is determined; when the risk index is greater than 1.00 for multiple consecutive sampling periods, a dangerous state is determined. Since the risk indices for the five consecutive sampling windows in this embodiment are 0.93, 0.95, 0.94, 0.96, and 0.95, respectively, all greater than the first preset threshold and less than the second preset threshold, the current bearing oil film breakdown risk level is determined to be a warning. Based on this risk level, a lubricating oil status review prompt and a short-cycle retest prompt are output, prompting maintenance personnel to check the lubricating oil status and shorten the subsequent monitoring interval.

[0083] Specifically, in the same embodiment, after the unit continues to operate and the bearing temperature rises to 90°C and the cumulative operating time increases to 1900 h, the lubricating oil state parameters are updated again according to the parameter relationship model. This results in the lubricating oil breakdown field strength decreasing to 16 kV / mm, the dynamic viscosity decreasing to 0.015 Pa·s, and the viscosity-pressure coefficient being adjusted to 1.6 × 10⁻⁸ Pa⁻¹. Based on the updated parameters, the oil film thickness in the inner ring contact area is recalculated to decrease to 0.36 μm, corresponding to a dynamic breakdown threshold of approximately 4.61 V. At this time, the instantaneous peak voltage measured within the new sampling window is 5.10 V, yielding the risk index. =5.10 / 4.61≈1.11. Since the risk index exceeds the second preset threshold for multiple consecutive sampling periods, the risk level is upgraded from warning to danger, and a lubricant replacement reminder, bearing maintenance reminder, and operating load limit reminder are output. The calculation results for the same bearing under different temperatures and aging conditions show that this invention does not use a fixed voltage threshold, but rather generates a dynamic breakdown threshold in real time based on the current operating conditions, thereby achieving online dynamic assessment of the risk of oil film breakdown in wind turbine generator bearings.

[0084] In summary, this embodiment has at least the following technical effects: This invention no longer uses a single fixed empirical threshold for judgment, but instead incorporates bearing geometric parameters, material parameters, operating condition parameters, and lubricating oil condition parameters into the risk assessment process. This can be adapted to wind turbine generator bearings of different models, sizes, and operating conditions, avoiding the problems of single standard and poor adaptability of the traditional fixed threshold method. By combining oil film thickness and lubricating oil breakdown field strength to generate a dynamic breakdown threshold, the threshold can be adjusted in real time with changes in rotational speed, temperature, load and lubricating oil aging state, thereby more realistically reflecting the actual pressure resistance of the bearing oil film under the current working conditions, and effectively reducing false alarm rate and false alarm rate. It can continuously update the dynamic breakdown threshold and make comparisons based on the operating condition data and shaft voltage characteristics collected in real time during the operation of the wind turbine generator, so as to realize the online dynamic assessment of the risk of bearing oil film breakdown. Compared with the traditional offline or fixed threshold judgment method, it is more timely. By testing and modeling the breakdown field strength, dynamic viscosity and viscosity-pressure coefficient of lubricating oil under different temperatures and aging times, the evaluation process not only considers the bearing structure and operating conditions, but also the impact of lubricating oil performance degradation on the oil film pressure resistance. Therefore, the evaluation results are more consistent with the actual service conditions. This invention considers the oil film thickness and corresponding breakdown threshold of the inner ring contact area and the outer ring contact area respectively, and takes the smaller one as the dynamic breakdown threshold. It can evaluate the weaker contact area of ​​a specific bearing, thereby forming a more targeted and individualized risk assessment result. In addition to outputting risk level information, this invention can further trigger maintenance prompts such as lubricant replacement, bearing overhaul, or operating parameter adjustment, so that the risk assessment results can directly serve wind turbine operation and maintenance decisions, improve equipment operation reliability, and reduce the risk of unplanned downtime.

[0085] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for dynamic risk assessment of oil film breakdown in wind turbine generator bearings, characterized in that, Includes the following steps: S1: Obtain the structural and material parameters of the target wind turbine generator bearing; and obtain the operating condition parameters and lubricating oil status parameters of the target wind turbine generator during operation. S2: Based on the structural parameters, material parameters, operating condition parameters and lubricating oil state parameters, determine the oil film thickness of the target wind turbine generator bearing under the current operating condition, and determine the corresponding dynamic breakdown threshold based on the oil film thickness and the lubricating oil breakdown field strength determined by the preset parameter relationship model according to the current temperature. S3: The shaft voltage characteristic value obtained during the operation of the target wind turbine generator is compared with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result; S4: Based on the risk assessment results, output the risk level information or maintenance prompt information corresponding to the risk assessment results.

2. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, In step S1, the structural parameters include the rolling element radius, the inner raceway radius of curvature, the outer raceway radius of curvature, and the average bearing diameter; the material parameters include the elastic modulus and Poisson's ratio of the contact materials; the operating parameters include the bearing speed, bearing temperature, and load parameters; and the lubricating oil condition parameters include the lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient. The lubricating oil condition parameters are obtained by conducting insulation performance tests and rheological performance tests on the target lubricating oil under different temperatures and aging times, and based on the test data, a parametric relationship model is constructed showing the changes in lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient with temperature and aging time. During operation, the parameter relationship model is invoked based on the current temperature and the aging state of the lubricating oil to determine the lubricating oil state parameters.

3. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, Step S1 further includes determining lubricating oil aging state parameters, which are determined based on one or more of the following: cumulative operating time, historical temperature data, number of start-stop cycles, and historical discharge pulse events. The lubricating oil breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient are dynamically corrected based on the lubricating oil aging state parameters.

4. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, Step S2 includes: The equivalent radius of curvature of the inner ring contact area is determined based on the radius of curvature of the rolling elements of the bearing and the radius of curvature of the inner ring raceway; the equivalent radius of curvature of the outer ring contact area is determined based on the radius of curvature of the rolling elements of the bearing and the radius of curvature of the outer ring raceway. Based on the equivalent radius of curvature of the inner ring contact area, the equivalent radius of curvature of the outer ring contact area, the bearing speed, load parameters, dynamic viscosity, viscosity-pressure coefficient, and material parameters, the oil film thickness of the inner ring contact area and the oil film thickness of the outer ring contact area are determined respectively. Based on the oil film thickness in the inner ring contact area, the oil film thickness in the outer ring contact area, and the lubricating oil breakdown field strength, the inner ring breakdown threshold and the outer ring breakdown threshold are determined respectively; and The smaller of the inner ring breakdown threshold and the outer ring breakdown threshold is determined as the dynamic breakdown threshold.

5. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, In step S2, the dynamic breakdown threshold is determined by the oil film thickness, the lubricating oil breakdown field strength, and the safety margin coefficient. The safety margin coefficient is pre-calibrated based on one or more of the bearing type, lubricating oil type, temperature range, and historical operating data.

6. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, In step S3, the shaft voltage characteristic quantity includes one or more of the following: instantaneous peak voltage, peak-to-peak voltage, number of over-threshold pulses within a preset time window, pulse repetition frequency, and accumulated voltage energy within the time window.

7. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to claim 1, characterized in that, In step S3, when the shaft voltage characteristic is an instantaneous peak voltage or a peak-to-peak voltage, a risk index is constructed by the ratio of the shaft voltage characteristic to the dynamic breakdown threshold, and the bearing oil film breakdown risk is classified into normal, attention, warning and danger based on the risk index.

8. The dynamic risk assessment method for oil film breakdown of wind turbine generator bearings according to any one of claims 1 to 7, characterized in that, Step S4 includes: When the risk index, constructed by the ratio of the shaft voltage characteristic to the dynamic breakdown threshold, is greater than the first preset threshold for multiple consecutive sampling periods within a preset time window, a warning message is output. When the risk index exceeds a second preset threshold for multiple consecutive sampling periods within a preset time window, or when the cumulative number of exceedances per unit time reaches a preset number, a danger message is output; and Based on the output risk level information, one or more maintenance prompts are generated, including lubricant replacement prompt, bearing maintenance prompt, operating load limit prompt, and speed adjustment prompt; wherein, the second preset threshold is greater than the first preset threshold.

9. A dynamic risk assessment system for oil film breakdown in wind turbine generator bearings, the system being suitable for implementing the dynamic risk assessment method for oil film breakdown in wind turbine generator bearings according to any one of claims 1 to 8, characterized in that, include: The parameter acquisition module is used to acquire the structural parameters, material parameters, and operating condition parameters of the target wind turbine generator bearing. The oil condition determination module is used to obtain or determine the breakdown field strength, dynamic viscosity, and viscosity-pressure coefficient of the lubricating oil. The dynamic threshold generation module is used to determine the dynamic breakdown threshold under the current operating condition based on the structural parameters, material parameters, operating condition parameters and lubricating oil state parameters. The shaft voltage acquisition module is used to acquire the shaft voltage characteristics during the operation of the target wind turbine generator; The risk assessment module is used to compare the shaft voltage characteristic with the dynamic breakdown threshold to obtain the bearing oil film breakdown risk assessment result; as well as The result output module is used to output risk level information or maintenance prompt information corresponding to the risk assessment result.

10. The dynamic risk assessment system for oil film breakdown of wind turbine generator bearings according to claim 9, characterized in that, The parameter acquisition module is communicatively connected to the wind turbine SCADA system, speed sensor, bearing temperature sensor and load information source respectively; The shaft voltage acquisition module is located between the generator shaft and the housing, and is used to acquire shaft voltage signals and extract shaft voltage characteristic quantities. The dynamic threshold generation module includes a bearing parameter library and an oil parameter model library, which are used to generate the dynamic breakdown threshold. The risk assessment module contains a risk determination rule library, which is used to determine the risk level based on the comparison result between the shaft voltage characteristic quantity and the dynamic breakdown threshold.

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