Condition monitoring system

Abstract

The invention relates to a condition monitoring system. The present invention describes a condition monitoring system for a journal bearing arranged to support a rotating component mounted in a rotating machine, the condition monitoring system comprising: a pair of electrical terminals respectively arranged on both sides of an oil-filled gap between the journal and the rotating component; a capacitance meter connected between the terminals and adapted to output a measurement reading indicative of a capacitance between the terminals during operation of the rotating machine; and an evaluation unit adapted to receive readings from the capacitance meter and determine a health of the journal bearing based on the measured readings. A method of determining the health of a journal bearing based on capacitance measurement readings across an oil charge gap between a bearing journal and a supported rotating component is also described.

Description

BACKGROUND

[0001] Journal bearings are a class of plain bearings suitable for use in various types of machines, for example to support the shafts ("journals") of rotating components such as planetary gears of a gearbox. An oil film in the gap between the journal and the bearing surface ensures smooth operation of the rotating components.

[0002] In order to avoid downtime and costs due to component failure, some kind of condition monitoring is typically implemented in such machines in order to monitor the health of various critical components. Ideally, a condition monitoring system (CMS) would identify potential problems before they develop into a failure.

[0003] For journal bearings used to support planetary gears, condition monitoring can be difficult to implement. It is known to deploy ultrasonic sensors to collect data during operation of the journal bearing, but the journal bearing has to be designed around the sensor arrangement. However, it can be difficult and thus expensive to install ultrasonic sensors in a gearbox of a wind turbine.

[0004] In another approach, vibration analysis can be implemented using accelerometers placed to detect vibrations of the rotating components and a dedicated algorithm for analyzing the collected data. This approach is effective for roller bearings, which have a specific frequency that can be tracked during condition monitoring. However, in the case of journal bearings, this approach is of limited effectiveness, as journal bearings do not have any contact surface to provide a trackable reference frequency. It is also known to deploy temperature sensors, oil particle counters, resistance sensors, etc. in prior art condition monitoring systems. However, these known condition monitoring systems can only provide limited information related to the actual state of the journal bearing. These systems typically cannot give a clear indication about the actual condition of the journal bearing and can only identify a failure a short time before the bearing fails.

[0005] The limitations of known condition monitoring systems make them unsuitable for use in wind turbine applications such as planetary gearboxes, as the various possible operating modes of a wind turbine with fluctuating torque levels put high demands on all rotating components of the journal bearings. Undetected problems in the journal bearings can lead to severe damage of the gearbox, followed by downtime, loss of revenue, and expensive repair costs.

[0006] It is therefore an object of the present invention to provide an improved method of monitoring the health of a journal bearing.

[0007] This object is achieved by the claimed journal bearing condition monitoring system and by the claimed method of implementing condition monitoring of a journal bearing. SUMMARY

[0008] In the context of the present invention, a journal bearing should be understood as a bearing supporting a rotating component of a machine, such as a planet gear of a planetary gearbox supporting a power train of a wind turbine. In the following, without limiting the invention in any way, the rotating component supported by the journal bearing is assumed to be a planet gear of a planetary gearbox. The journal bearing can be designed to suit its intended particular application. The journal bearing comprises a stationary bearing part, i.e. a journal, a sliding surface or sleeve arranged between the journal and the rotating component, and a lubricating oil film between the stationary and rotating parts. The material of the journal, such as steel, is typically harder than the material of the sliding surface of the bearing, such as an aluminium alloy. The journal bearing can be designed according to various possible configurations known to the skilled person. For example, the sleeve can be mounted to the stationary journal and the lubricating oil film is between the sleeve and the rotating component; the sleeve can be free to move between the journal and the rotating component ("rotating sleeve" journal bearing); the sleeve can be provided as an inner lining inside the gear, etc. The terms "planet gear shaft" and "journal" can be used interchangeably; similarly, the terms "sleeve" and "bearing sleeve" can be used interchangeably.

[0009] The present invention describes a way of determining the health condition of a journal bearing, i.e. a way of monitoring the condition of a journal bearing. In the context of the present invention, the terms "health condition" and "condition" can be considered synonyms.

[0010] According to the present invention, a journal bearing condition monitoring system comprises a pair of terminals arranged on both sides of the oil-filled gap, e.g. a first terminal can be arranged in electrical contact with the gear and a second terminal can be arranged in electrical contact with the journal. The condition monitoring system further comprises a capacitance meter connected to the pair of terminals and adapted to measure the capacitance between the terminals during operation of the rotating machine and output the measured capacitance in the form of an electrical signal or a measurement reading. The condition monitoring system further comprises an evaluation unit adapted to receive such readings from the capacitance meter and determine the health condition of the journal bearing based on the readings. In other words, in the method of the present invention, the condition monitoring of the journal bearing is performed by observing the capacitance across the gap and inferring the health condition of the bearing from changes in the observed capacitance over time.

[0011] According to the present invention, a method of determining the health condition of a journal bearing, i.e. for performing condition monitoring of a journal bearing, comprises the steps of arranging a pair of electrical terminals on both sides of the oil-filled gap; connecting a capacitance meter between the terminals; and operating the capacitance meter to output readings indicative of the capacitance between the terminals during operation of the rotating machine; and determining the health condition of the journal bearing based on the readings. Since the service life of a rotating machine can be up to several years, it should be understood that the readings can be generated over a similar time span.

[0012] The present invention is based on the insight that a journal bearing essentially acts as a capacitor, as it comprises opposing metal surfaces separated by a gap filled with a dielectric (the lubricating oil film). During the lifetime of a journal bearing, surface defects can occur during its normal operation. For example, an impacted particle trapped between the bearing surfaces can cause physical defects such as grooves, pits, ridges, etc. on the bearing surfaces. Likewise, smaller impacted particles can cause gradual wear of one or both surfaces, thereby changing the gap, which in turn can change the load distribution on the bearing. Even a small change in the size of the gap will change the electrical properties of the journal bearing. The inventors have realized that such changes can be exploited to infer the condition of the bearing.

[0013] An advantage of the method of the present invention is that it can determine the condition of a journal bearing at any time during its lifetime. Even very early stages of deterioration can be detected. In this way, the present invention can be used to identify potential failures well before they develop into actual failures, i.e. it is not necessary to wait until the potential failure has deteriorated to the extent of excessive vibrations or excessive temperatures, which only manifest themselves when the failure has progressed to a severe stage, thereby not only affecting the journal bearing itself, but also causing damage to neighboring components.

[0014] A further advantage of the present invention is that it can be implemented at a favorably low cost, as it does not require expensive sensors and does not require any changes to the design of the journal bearing.

[0015] Particular advantageous embodiments and features of the present invention are given by the dependent claims, as disclosed in the following description. Features of different claim categories can be combined as appropriate to give further embodiments not described herein.

[0016] The present invention can be applied to implement condition monitoring of journal bearings deployed in various types of machines. In the following, without limiting the invention in any way, it can be assumed that the rotating machine is a planetary gearbox of a wind turbine power train, and that the journal bearing supports a planet gear. In this configuration, the planet gear is placed around a bearing sleeve, and a journal or "planet shaft" is attached to the planet carrier. The planet carrier (and the arrangement of its planet shafts) is turned by a preceding stage of the power train. For example, the planet carrier of the first stage of the gearbox can be turned by the low speed shaft of the wind turbine.

[0017] In a preferred embodiment of the present invention, a wind turbine comprises a power train with a planetary gearbox comprising at least one rotating component supported by a journal bearing, and an instance of the condition monitoring system (CMS) of the present invention arranged to implement condition monitoring of the journal bearing.

[0018] A planetary gearbox can be arranged between a low speed shaft of a wind turbine and a generator. The low speed shaft of the power train is arranged to rotate a planet carrier of a first stage of the gearbox. The planetary gearbox can comprise several stages. At least the first stage comprises a plurality of planetary gears, each planetary gear being supported by a journal bearing. Depending on the size of the gearbox, the first stage planetary gears and their bearings can be relatively large. For example, the diameter of the planetary shaft, i.e. the journal, can be about 350 mm and the nominal clearance or gap of the bearing can be about 0.3 mm, with an operational clearance of about 1 pm (load side).

[0019] As explained above, the planetary gears are placed around a bearing sleeve, which in turn is arranged around a journal or "planetary shaft", which in turn is attached to the planet carrier. As explained above, the bearing sleeve can be mounted to the journal and thus be stationary; the sleeve can be free to rotate between the journal and the gear; the sleeve can be mounted to the gear. Regardless of the chosen configuration, the terminals of the inventive journal bearing CMS are arranged at both ends of the gap between the journal and the gear. This can be achieved in any suitable way. In a particularly preferred embodiment of the invention, the terminals arranged in electrical contact with the gear comprise spring-loaded carbon brushes. In a particularly preferred embodiment of the invention, the spring-loaded carbon brushes are arranged in contact with the face (windward surface) of the planetary gear. For this purpose, a cavity or recess can be formed in the planet carrier to accommodate such a carbon brush for each monitored planetary gear bearing. The carbon brush can be pressed against the substantially flat windward face of the planetary gear. Alternatively, to always ensure a favorable electrical contact, the planetary gear can be manufactured to comprise a raised torus or ring on its face, and the carbon brush can be positioned to press against this raised ring.

[0020] Since the planetary gears are carried by a planet carrier rotating around the sun gear, i.e. around the rotational axis of the gearbox, this aspect must be taken into account when arranging the terminals and any electrical wires between the terminals and the capacitance meter. Therefore, in a particularly preferred embodiment of the invention, the electrical connection between the capacitance meter and the terminals is fixed to the rotating part of the gearbox, preferably the planet carrier of the stage or supported by it.

[0021] The measured readings can be transmitted to an evaluation unit located in the hub. The evaluation unit can be implemented as part of an already available I / O module of the wind turbine controller, e.g. as part of an already available module of the pitch controller terminal board, which module rotates with the hub and can be connected by a slip ring interface to the stationary level of the wind turbine controller, as known to the skilled person. In a particularly preferred embodiment of the invention, the journal bearing CMS can be battery operated and integrated in the planet carrier, with a transmitter for sending data to a higher level CMS of the wind turbine or to the wind turbine controller over a wireless interface.

[0022] The journal bearing CMS of the present application can be configured to monitor the condition of any number of planetary gear bearings. In a particularly preferred embodiment of the present application, the CMS of the present application can be configured to monitor the condition of at least the set of planetary gear bearings in the first stage of the gearbox. At times, hereinafter, the present application will be explained with respect to a single journal bearing, however, it should be understood that the present condition monitoring system can be configured to monitor the health of several journal bearings simultaneously.

[0023] The capacitance meter can be implemented using any suitable electrical circuit. Preferably, the capacitance meter is implemented as a suitable bridge circuit, such as a Wheatstone bridge, a Wien bridge, etc. The capacitance meter can be implemented to measure the capacitance between the terminals (i.e. across the journal bearing) substantially continuously or at predetermined intervals (e.g. every 10 minutes). The measurement readings generated as output from the capacitance meter can be in the form of an analogue signal, e.g. a voltage or current indicative of the measured capacitance. Likewise, the measurement readings can be in the form of a digital signal. Over time, the evaluation unit receives a series of readings from the capacitance meter. These readings can be processed in any suitable manner. In a preferred embodiment, the present system for monitoring the health of the journal bearing(s) is compatible with a more advanced condition monitoring system. For example, a wind turbine can deploy a condition monitoring system that collects data from various subsystems and transmits relevant data to a wind farm control centre via SCADA. The evaluation unit of the present journal bearing CMS can be a stand-alone unit. In a particularly preferred embodiment of the present application, the evaluation unit can be implemented in the form of a software module running on a processor of the wind turbine controller.

[0024] It is expected that the capacitance of a "healthy" journal bearing fluctuates within a certain acceptable range. This range can be established, for example, using the same type of capacitance meter prior to installing the journal bearing in a rotating machine, and / or by implementing condition monitoring of new (i.e. fault-free or "as- new") journal bearings installed in an operational wind turbine. Fluctuations in the capacitance within this acceptable range can be considered a "capacitance signature" that reflects the behaviour of the journal bearing under normal operating conditions.

[0025] In a rotating machine such as a planetary gearbox, various component parts can comprise electrically conductive material and can be in direct or indirect contact with each other. Any such component in contact with the journal bearing monitored by the inventive CMS can distort the capacitance measurement across the journal bearing. Therefore, in a preferred embodiment of the invention, insulation is provided at one or more suitable locations in order to electrically isolate the rotating components from other components of the rotating machine. The electrical insulation is placed so as to prevent the transmission of current to any other electrically conductive parts due to the voltage applied between the terminals by the capacitance meter. In this way, the capacitance meter can reliably measure the capacitance of the journal bearing. For example, one or more surfaces of the planet carrier can be coated with an insulating coating in order to electrically isolate the journal bearing from any other journal bearing in the first gearbox stage. Preferably, the placement of the electrical insulation is determined prior to assembly of the rotating machine, for example during the design phase of the planetary gearbox.

[0026] During the lifetime of the gearbox, the evaluation unit compares each new reading to the expected value, for example to see if the new reading is within an acceptable range. As long as the readings tend to be within this acceptable range of values, the inventive method concludes that the journal bearing is healthy.

[0027] In a preferred embodiment of the invention, the evaluation unit can issue a report when the readings tend to be outside the acceptable range. This report can be in the form of an alarm if a large number of recent readings fall outside the acceptable range. Likewise, the evaluation unit can issue an alarm if the readings are outside the acceptable range for a predefined duration of time, for example if a significant deviation is observed over a number of minutes, or a slight deviation is observed over a number of days.

[0028] Maintenance of components of a machine such as a wind turbine power train can be managed based on the condition number. For example, a component with a low condition number, for example 1 or 2, can be considered healthy and does not require any maintenance; a high condition number, for example 4 or 5, can mean that the component is faulty and should be replaced; an intermediate number, for example 3, can indicate that the component requires routine maintenance. Therefore, in a preferred embodiment of the invention, the evaluation unit is implemented to output a condition number for each monitored journal bearing. A wind turbine controller or wind park controller, upon receiving an intermediate condition number for a journal bearing of a gearbox, can schedule a gearbox replacement in time, thereby avoiding the cost of a severe failure in the gearbox.

[0029] In a further preferred embodiment of the invention, the evaluation unit is implemented to identify a trend in the collected readings, for example to identify a rising trend or a falling trend in the readings of each monitored bearing. For example, a falling trend, i.e. a gradually decreasing capacitance, can indicate wear on the bearing surface of a particular planet gear.

[0030] This condition trend cannot be established using existing condition monitoring systems because these systems cannot distinguish between fault-free bearings and bearings in the early stages of deterioration. This is because information collected by existing vibration-based or temperature-based condition monitoring systems can only identify established faults (e.g., faults manifested as measurable vibration and / or measurable temperature increases), but cannot identify any early signs that might indicate potential faults. Such condition monitoring systems cannot identify early stages of deterioration that could lead to severe damage requiring drastic responses such as shutting down wind turbines to perform (often costly) repairs on the gearbox. Attached Figure Description

[0031] Other objects and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are designed for illustrative purposes only and are not intended to limit the scope of the invention.

[0032] Figure 1 and Figure 2 The type of gearbox used in the power transmission system of a wind turbine is shown;

[0033] Figure 3 It shows in Figure 1 Details of the journal bearings used in the gearbox;

[0034] Figure 4 and Figure 5 An exemplary embodiment of the condition monitoring system of the present invention is illustrated;

[0035] Figure 6 and Figure 7 The diagram illustrates various problems that may occur in journal bearings during operation;

[0036] Figure 8 Exemplary data collected by the condition monitoring system of the present invention is shown;

[0037] Figure 9 The illustration shows data collected using existing technological methods.

[0038] In the accompanying drawings, similar reference numerals always refer to similar objects. Objects in the accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0039] Figure 1 – Figure 5 An exemplary embodiment of the journal bearing CMS1 of the present invention, deployed in a gearbox 3 of a common type of wind turbine, is illustrated. Figure 1The main components of the gearbox 3 are, as illustrated in Fig. 1, a first stage planet carrier 30C (rotated by the low speed shaft), a ring gear 32, a set of planet gears 30 and a sun gear 31 (for clarity, the meshing gear teeth are not shown, and subsequent gearbox stages are not shown). Each first stage planet gear 30 is supported by a journal bearing 30B. During operation of the wind turbine, the low speed shaft 2 and the planet carrier 30C rotate as one. As Figure 2 The stationary ring gear 32 and the rotating planet carrier 30C cause rotation of the planet gears 30, which in turn causes the sun gear 31 to rotate about its axis 3A, as illustrated in Fig. 2. Each planet shaft 302 or journal 302 orbits around the sun gear 31 as indicated by the dashed lines, and each planet gear 30 rotates about its own axis (i.e. about its journal 302).

[0040] Figure 3 A cross-section through a planet gear 30 in a commonly used wind turbine power train configuration is shown. Here, the gear 30 is supported by a journal bearing 30B, which comprises a sleeve 301 mounted around the journal 302, and a lubricating oil film 303 in the gap G between the stationary elements 301, 302 and the rotating gear 30. The present invention is based on the insight that the assembly 30, 303, 30B essentially acts as a capacitor when a voltage is applied across the gap G. The capacitance can be measured between any two suitable points, for example between the journal 302 and the planet gear 30 itself. The resulting "capacitor" is denoted with the electrical symbol. The capacitance C 30B is determined by the size of the gap G and the dielectric constant of the dielectric or oil 303. Since it can be expected that the load on the gearbox 3 fluctuates, the gap G between the bearing surfaces S1, S2 can change during normal operation of the wind turbine. Likewise, the composition of the lubricating oil film 303 can change, such that its dielectric constant can increase or decrease. Therefore, it can be expected that the capacitance C 30B of the journal bearing 30B (i.e. the capacitance of the assembly 30, 303, 30B) fluctuates within a certain acceptable range.

[0041] The present journal bearing CMS1 takes advantage of the capacitive behaviour of the journal bearing by placing the electrical contacts 1 1, 12 at appropriate locations, as shown in Figs. 3 and 4. The figures show how the contacts or terminals 1 1, 12 can be placed to measure the capacitance of the journal bearing 30B, and how the electrical wires or cables 13, 14 from these terminals 1 1, 12 can be routed. For example, by routing the electrical wires 13, 14 from the terminals 1 1, 12 in the hollow interior of the low speed shaft 2 as shown, the electrical wires 13, 14 can be routed through the planet carrier 30C to the hub of the wind turbine. Figure 4 and Figure 5 The electrical contacts 1 1, 12 are placed at appropriate locations to take advantage of the capacitive behaviour of the journal bearing, as shown in Figs. 3 and 4. The figures show how the contacts or terminals 1 1, 12 can be placed to measure the capacitance of the journal bearing 30B, and how the electrical wires or cables 13, 14 from these terminals 1 1, 12 can be routed. For example, by routing the electrical wires 13, 14 from the terminals 1 1, 12 in the hollow interior of the low speed shaft 2 as shown, the electrical wires 13, 14 can be routed through the planet carrier 30C to the hub of the wind turbine.

[0042] The drawings show a first electrical contact 11 in the form of a carbon brush 11 which is in contact with the windward face of the planet gear 30 when the planet gear 30 is turned around its journal 302. An electrical wire or cable 13 leads from the brush 11 to the outside of the gearbox 3. A second terminal 12 is arranged in contact with the journal 302 of the planet gear 30. An electrical wire or cable 14 leads to the outside of the gearbox 3. Since the planet shaft (journal) 302 is fixed to the planet carrier 30C, the second electrical contact 12 can be fixed directly to the journal 302, e.g. by welding, by means of a clamp or fastener, etc. The electrical contacts 11, 12 and their electrical wires 13, 14 are stationary with respect to the planet carrier 30C and thus also "orbit" around the axis of rotation of this gearbox stage. The carbon brush will eventually wear out and will need to be replaced. For this purpose, the carbon brush 11 is preferably arranged such that, during maintenance of the inventive CMS 1, it can be reached with relatively little effort, e.g. by providing a service / inspection aperture in the housing of the first stage of the gearbox.

[0043] Each of the planet gears 30 can be included in the condition monitoring system in this way, e.g. a gearbox with four planet gears in its first stage can have four such sets of contacts 11, 12 and electrical wires 13, 14, as illustrated in the simplified front view of Figure 5 Of course, the first stage of the gearbox 3 can have any number of planet gears, as is known to the person skilled in the art.

[0044] Each pair of terminals 11, 12 can be connected to a capacitance meter 15 as indicated in Figure 4 A multiplexer or other switching circuit can connect the individual capacitance meters to each of the four gear / bearing assemblies in turn. The capacitance of the bearing 30B can be measured at appropriate intervals, e.g. every 15 minutes, or at shorter intervals if the readings indicate a potential fault. An analog-to-digital converter (ADC) can convert the electrical signal to a digital reading 150 which is forwarded to an evaluation module 16. The evaluation module 16 can process the received values or readings 150 for the bearing 30B in many ways and report its findings, e.g. as a fault status 160 of this bearing 30B, to the wind turbine controller 60.

[0045] The measured readings 150 can be transmitted to an evaluation unit 16 located in the hub. The evaluation unit 16 can be implemented as part of an already available I / O module such as a pitch controller terminal board, which module turns with the hub and can be connected by a slip ring interface to the stationary stage of the wind turbine controller, as is known to the person skilled in the art.

[0046] As explained above, as long as the bearing 30B is "healthy", the capacitance C30B within a certain acceptable range R OK fluctuates. The invention is based on the insight that if the bearing surfaces S1, S2 become damaged, the capacitance C 30B will change beyond this range R OK . For example, a worn or eroded surface will widen the gap on the unloaded side and cause an uneven gap on the loaded side, thereby changing the "capacitive signature" of the bearing. Such damage can be limited to a relatively small portion of the bearing, or can extend to a large portion of the bearing surface. Deterioration of the surfaces S1, S2 relative to their initial state can result in a significant decrease in the capacitance of the bearing 30B. Figure 6 A partial cross-section through the journal bearing 30B is shown to (in a very simplified manner) illustrate an eroded bearing surface S1, S2 relative to the initial surface profile (indicated by the dashed line) and the corresponding decrease in capacitance. Even if such damage is typically limited to a relatively small area in the bearing, it can measurably change the capacitive signature of the bearing due to the decreased gap over the loaded area of the bearing and the increased gap over the unloaded area.

[0047] This example shows how the capacitance reading 150 can move out of the acceptable range R OK towards a lower, "problematic" level, as indicated by the downward trend 150T. Depending on the severity of the deterioration, any such deviation from the acceptable range R OK may be observed over several days, several weeks or even several months.

[0048] As Figure 7 illustrated in Fig. 2, an increase in the capacitance C 30B may be observed due to physical changes in the bearing surfaces, for example when material of one or both surfaces S1, S2 protrudes into the gap G. A narrower gap G between the opposing surfaces S1, S2 can cause the capacitance to increase away from the acceptable range R OK towards an undesirably higher level.

[0049] Likewise, a deterioration of the oil quality, for example the presence of too many particulate contaminants in the oil, can also cause the capacitance reading 150 to increase, thereby leaving the acceptable range R OK towards an undesirably higher level, as indicated by the upward trend 150T.

[0050] Figure 8 is a schematic representation of data collected by the method of the invention. This figure illustrates information obtained from the condition monitoring system of the invention for monitoring the health of a journal bearing as described above. Initially, the bearing is in an original state and functioning properly, such that the reading 150 is within the acceptable range R OKTherefore, the condition value of this bearing may be "1", indicating that everything is normal. At some point during the service life of gearbox 3, t... X Significant surface degradation may occur in journal bearing 30B, thereby altering the component's capacitance C. 30B Although surface degradation does not initially affect the bearing's behavior (the planetary gears still function normally), the present invention, CMS1, can detect this change very quickly because the capacitance reading 150 will (potentially very gradually) shift to an acceptable range R. OK In addition, it will follow a trend of deviation 150T from the average value within the acceptable range. Therefore, even if there is no actual fault at that time, the output 160 of the evaluation unit 16 reports the problem, in which case it is reported as the next condition value "2", thus indicating that there may be a problem with this bearing. The wind turbine controller 60 can increase the rate at which readings are collected for this bearing. In this way, the method of the present invention helps to avoid a situation in which such deterioration of the journal bearing is not detected until it develops into an actual fault.

[0051] Regardless of the reason, from the acceptable range R OK Any deviation can be interpreted as an indication that the condition of bearing 30B has deteriorated and may require closer monitoring. In this case, more relevant data can be collected, such as the particle count of an oil sample collected from the bearing. A high particle count can be interpreted as evidence of a problem in the journal bearing. If the evaluation unit 16 reports the observed deviation as “significant,” indicating an evolving fault, the wind turbine controller 60 can avoid high-load operating modes until an inspection can be carried out (using indirect indicators). If the evaluation unit 16 reports the observed deviation as “critical,” the wind turbine controller 60 can initiate a shutdown and schedule an immediate inspection.

[0052] As shown in the example above, the evaluation unit 16 can be implemented as a module of a higher-level condition monitoring system 60 that reports conditions to the wind turbine. Similarly, the evaluation unit 16 can be implemented as a standalone unit that can report conditions to the wind turbine controller.

[0053] Figure 9 This is a schematic representation of data collected using existing technological methods (e.g., methods that rely on monitoring a suitable parameter P, such as the vibration of a journal bearing). This figure uses the example given above, where surface degradation begins at time t. X Initially, the bearing was fault-free and operating normally, exhibiting an acceptable vibration profile (e.g., within acceptable interpeak amplitudes), causing the existing condition monitoring system to report a "fault-free" status.9 OKMinor surface degradation does not affect bearing behavior in any way that can be measured by the existing condition monitoring system, and the system continues to report a "fault-free" state for a period of time. OK Surface degradation becomes more severe, eventually manifesting as significant vibration in the journal bearing, causing condition monitoring system 1 to eventually detect it at time t. y Report fault status 9 故障 However, at this much later stage (e.g., weeks after the bearing begins to deteriorate), the bearing damage can be so severe that the wind turbine must be shut down immediately so that the gearbox can be repaired. Existing condition monitoring systems that deploy temperature sensors may suffer from the same drawback, as slight surface degradation will not result in an increased temperature, and such condition monitoring systems have a limited lifespan of 100 days. X The "no fault" status will continue to be reported. OK Until surface degradation leads to excessive friction and a corresponding increase in temperature.

[0054] While the invention has been disclosed in the form of preferred embodiments and variations thereof, it will be understood that many additional modifications and variations can be made thereto without departing from the scope of the invention. For example, the connection between the terminals and the evaluation unit can be implemented in any suitable manner and is not limited to the embodiments shown in the drawings. For example, the journal bearing CMS of the present invention is electrically isolated from other rotating components. Furthermore, the condition monitoring system of the present invention can be used in any stage of the gearbox.

[0055] For clarity, it should be understood that the use of “a” or “one” throughout this application does not exclude multiple, and “including” does not exclude other steps or elements.

Claims

1. A condition monitoring system (1) for a journal bearing (30B), said journal bearing (30B) being arranged to support a rotating component (30) mounted in a rotating machine (3), said condition monitoring system (1) comprising - A pair of electrical terminals (11, 12), the terminals (11, 12) being arranged on both sides of the oil-filled gap (G, 303) between the journal (302) and the rotating component (30); - A capacitance meter (15), said capacitance meter (15) being connected between said terminals (11, 12) and adapted to output an indication of the capacitance (C) between said terminals (11, 12) during operation of said rotating machine (3). 30B The measurement reading (150); and - Evaluation unit (16), which is adapted to receive readings (150) from the capacitance meter (15) and determine the health condition of the journal bearing (30B) based on the measurement readings (150).

2. The condition monitoring system according to the preceding claim, wherein, The first terminal (11) is arranged to make electrical contact with the rotating component (30).

3. The condition monitoring system according to the preceding claim, wherein, The first terminal (11) includes any of the following: an electrical contact brush, a spring-loaded carbon brush.

4. The condition monitoring system according to any one of the preceding claims, wherein, The evaluation unit (16) is adapted to compare the received measurement readings (150) with the acceptable capacitance range (R) of the journal bearing (30B). OK (Compare) 5. The condition monitoring system according to the preceding claim, wherein, The evaluation unit (16) is adapted to measure the received measurement readings (150) within the acceptable range (R). OK An alarm will be issued when the number of cases is outside of the specified range (160).

6. The condition monitoring system according to any one of the preceding claims, wherein, The evaluation unit (16) is adapted to output the condition value (160) of the journal bearing (30B).

7. A wind turbine (6), comprising: - A power transmission system (2, 3, 4) with a planetary gearbox (3), the planetary gearbox (3) including at least one rotating component (30) supported by a journal bearing (30B); and - The condition monitoring system (1) according to any one of claims 1 to 6, the condition monitoring system (1) being arranged to perform condition monitoring on at least one journal bearing (30B).

8. The wind turbine according to the preceding claim, wherein, The rotating component (30) is a planetary gear.

9. The wind turbine according to claim 7 or claim 8, wherein, The electrical connection (13, 14) between the capacitance meter (15) and the terminals (11, 12) extends through the planetary carrier (30C).

10. The wind turbine according to any one of claims 7 to 9, wherein, The evaluation unit (16) is implemented as a module of the controller (60) of the wind turbine (6).

11. The wind turbine according to any one of claims 7 to 10, wherein, The gearbox (3) includes multiple stages, and the condition monitoring system (1) is configured to perform condition monitoring on the journal bearings (30B) of the planetary gears (30) of the first gearbox stage.

12. A method for determining the health condition of a journal bearing (30B) arranged to support a rotating component (30) mounted in a rotating machine (3), the method comprising the steps of - A pair of electrical terminals (11, 12) are respectively arranged on both sides of the oil-filled gap (G, 303) between the bearing journal (302) and the rotating component (30); - A capacitance meter (15) is connected between the terminals (11, 12), and the capacitance meter (15) is operated to generate a measurement reading (150) indicating the capacitance between the terminals (11, 12) during operation of the rotating machine (3); and - The health condition of the journal bearing (30B) is determined based on the measurement readings (150).

13. The method according to the preceding claim, further comprising analyzing the measurement readings (150) to identify an acceptable range (R) relative to the value. OK The steps of the trend (150T).

14. The method according to any of the preceding method claims, comprising the step of providing electrical insulation to electrically isolate the journal bearing (30B) from other components of the rotating machine (3).

15. A computer program product comprising a computer program capable of being directly loaded into the memory of a controller (60) of a wind turbine (6) according to any one of claims 7 to 11, and the computer program product comprising program elements for implementing the steps of the method according to any one of claims 12 to 14 when the computer program is executed by the controller (60).

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