METHOD AND DEVICE FOR INSPECTING A HYDRO TURBINE

Abstract

The invention relates to a device for inspecting a damage or a crack of part of a hydro turbine, comprising at least one underwater remote operated vehicle (20) or autonomous underwater vehicle, at least one floatable or buoyant probe (26) or at least one probe (26) and means to make said at least one probe floatable, said probe comprising at least one imaging device (32) and/or laser scaler, and means for transmitting data from said probe to said vehicle or to a ground station when it is distant from said vehicle.

Claims

1-15: (canceled)

16. A device for inspecting a component of a hydro turbine for detecting damage or cracks in the part, comprising: an underwater remote operated or autonomous vehicle; a floatable or buoyant probe configured to operate remote from the vehicle; the probe comprising one or both of an imaging device and a laser scaler; and means for transmitting data from the probe when the probe is remote from the vehicle.

17. The device according to claim 16, further comprising a cable or a tether that connects the probe to the vehicle or to a ground station that is in communication with the vehicle.

18. The device according to claim 16, wherein the probe comprises one or both of a buoy and a thruster.

19. The device according to claim 16, wherein the imaging device comprises a scanner or a camera.

20. The device according to claim 16, wherein the vehicle also comprises an on-board imaging device.

21. The device according to claim 20, further comprising a computer configured to process data received from the imaging device and the on-board imaging device and to generate a display or representation of the data to an operator.

22. The device according to claim 16, further comprising a light source configured with the probe.

23. The device according to claim 16, wherein the data transmitting means comprises an optical fiber connecting the probe to the vehicle or to a ground station that is in communication with the vehicle.

24. The device according to claim 16, wherein the data transmitting means comprise a wireless transmission connection between the probe and the vehicle or a ground station that is in communication with the vehicle.

25. The device according to claim 16, further comprising means for processing data from the probe and generating an image of the component of the hydro turbine having the damage or crack.

26. A method for inspecting a component of a hydro turbine for damage or cracking, the method comprising: using the device according to claim 16 to inspect the component; and processing data from the probe and generating an image of the component in order to detect damage or cracking in the component.

27. The method according to claim 26, comprising inspecting one or more of a runner blade, stay vane, wicket gate, or draft tube of the hydro turbine.

28. The method according to claim 26, further comprising positioning a lighting device with the vehicle or the probe to light the component inspected by the probe.

29. The method according to claim 26, further comprising displaying the image on a display device for viewing by an operator.

30. The method according to claim 26, wherein the hydro-turbine comprises one of a bulb, Kaplan, Francis, pump type, or reversible pump type machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] FIG. 1 shows a runner of a hydro turbine to which the invention can be applied;

[0054] FIGS. 2A and 2B show examples of cavitation damage in a runner of a hydro turbine;

[0055] FIG. 3A is a schematic representation of a system comprising a remote operating vehicle (ROV) according to the invention and performing an inspection of a blade of a hydro turbine;

[0056] FIG. 3B-3E are schematic representations of different configurations of a system comprising a remote operating vehicle (ROV) according to the invention and performing an inspection of a blade of a hydro turbine;

[0057] FIGS. 4A and 4B show a display of two images, one from a camera located on-board of the ROV and one from a 360 camera of the probe for a close inspection of a runner.

[0058] FIGS. 5A and 5B show examples of cracks in a runner of a hydro turbine;

[0059] FIGS. 6A and 6B are examples of a lighting device combined with a camera.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

[0060] The invention applies to bulb, Kaplan, Francis, pump turbine runners or pump impellers.

[0061] FIG. 1 represents a hydraulic machine 1, more precisely a pump turbine 2, for converting hydraulic energy into electrical energy. A shaft 3 is coupled to a runner 7 and to the rotor of a generator (not shown on the figure) which also has an alternator that converts mechanical energy into electrical energy. The machine also includes a volute 4 that is supported by concrete blocks 5 and 6.

[0062] A penstock (not shown on the figure) extends between a non-represented upstream reservoir and the volute 4. This penstock forces a water flow to power the turbine. Water flows between blades 8 of the runner 7 and rotates them around an axis x-x of the shaft 3.

[0063] The machine further comprises: [0064] a distributor, comprising a plurality of movable guide vanes or wicket gates 9 that are evenly distributed around the runner; each of them has an adjustable pitch around an axis parallel to x-x and can be swivelled to regulate the water flow rate, all guide vanes being oriented with a same angle relative to a closed position; [0065] a pre-distributor, which comprises a plurality of fixed vanes (or stay vanes) 10, evenly distributed around the axis of rotation x-x, and disposed upstream of and around the distributor.

[0066] Below the runner, water is evacuated through a draft tube and tail water tunnel 11.

[0067] Such a hydraulic machine must be inspected to detect defects, in particular local surface deformation, and/or cracks, and/or wear, and/or damages, and/or impacts, and/or material loss, for example due to cavitation, or damages or cracks due to fatigue or corrosion, which all appear during the use of the machine. Coating damages must also be detected.

[0068] The other kinds of turbines or pump impellers should also be inspected for at least one of the above-mentioned defects or damages, for example cavitation damages or cracks or damages or cracks due to fatigue or corrosion. In particular, the runners of such turbines also comprise blades that should be inspected for defects, for example cavitation damages or cracks.

[0069] Cavitation is the vaporization of a volume of a liquid. When this happens adjacent to a solid, the fluid momentum associated with the collapse of the vapour volume can damage the solid material. This problem can be persistent when high velocities and forces are used to move the fluid, as in a turbine or pump. Often, once cavitation damage has occurred in a given location, the likelihood of additional damage in the same place increases.

[0070] More precisely, cavitation damage usually consists of a surface damage from which material of the hydro-turbine or of the runner of said hydro-turbine is removed; a cavitation damage can have many different sizes; it can for example have a size of about 20 cm20 cm, but there are also very small cavitation damages (for example at the beginning of the damage) and then the damage can become larger. A first example of cavitation damage 12 (a crown cavitation damage, at a blade to crown junction) is shown on FIG. 2A. A second example is shown on FIG. 2B which represents a clearance cavitation damage 14 (blade tip diameter for a Kaplan turbine).

[0071] It has to be noted that a cavitation damage can occur anywhere on both sides of a blade 8 (FIG. 1), on the crown and on the band surface (not shown on FIG. 1). It is therefore preferable to be able to perform inspection in-between the blades. For Francis or pump turbines or pump impellers, the inter-blade distance is limited and can be for example of about 150 mm or more generally comprised between 500 mm or 300 mm and 50 mm or 100 mm or 200 mm. Even for the largest inter-blade distances (larger than 400 mm), it is very difficult to inspect the surfaces of the blades.

[0072] A cavitation damage can be first identified by its shininess, for example due to a loss of polish of the material.

[0073] An example of an inspection device according to the invention is schematically illustrated on FIG. 3A. A floatable or buoyant probe 26 (or a probe associated with means for making it floatable or buoyant) is connected to an underwater ROV (remote operated vehicle) by at least one cable or one tether 28, a tether being able to perform a mechanical and an electrical connection. Said probe 26 comprises for example at least one imaging device, for example at least one laser scanner and/or laser scaler and/or at least one camera, for example a 360 camera, and can be used to characterize a damage 12, for example a cavitation damage and/or measure the quantity of removed material. A laser scaler is used in combination with an imaging device, for example a camera. It provides a scale reference by generating 2 parallel laser beams at a given (known) distance which generate 2 points or marks which are visible on the mage provided by said imaging device. The probe has a smaller size than the ROV to access areas where the ROV could not fit, for instance inter-blade channels.

[0074] The tether 28 can be fully flexible or flexible only in one direction (which allows for instance a control of the orientation the probe, for example of the imaging device, for example a camera, and/or the ability to push the probe in the inspected machine, for example in a runner).

[0075] Specifically, the probe tether 28 can be flexible in bending and stiff in torsion (similar to how borescope probes are made). This property gives the inspector the ability to adjust the probe orientation by turning the ROV about the tether axis, the ROV thus turning the tether, which turns the probe. The advantage of this approach is greater when one or more laser scaler(s) is in use, giving the ability to precisely position the laser scaler(s) with respect to a defect, the dimensions of which are being estimated.

[0076] During an inspection, the probe 26 can be located close to surface(s) of the blades (or of any other inspected part) of a runner or of any other inspected part of a hydraulic machine and can perform data measurements and/or imaging to acquire images from said surfaces. The probe 26 sends data to the ROV 20, for example via the tether and/or an optical fibre and/or wireless. Said data can be recorded for example in a memory in the ROV and/or of the computer 24. Wireless communication can be optical (see for example: https://www.hydromea.com/underwater-wireless-communication/) or acoustic (see for example: https://popotomodem.com/?gclid=Cj0KCQiw59n8BRD2ARIsAAmgPmJWs6po5sL5HYh33u2D W-VjMOya7Tyi6QEZmsASTwx-tkQSrm6KHSMaAnCqEALw wcB).

[0077] For acoustic transmission, acoustic modems can be implemented on both the probe's side and on the ROV's side, see for example: https://dosits.org/people-and-sound/communication/how-is-sounds-used-to-transmit-data-underwater/.

[0078] The probe can comprise an optical or acoustic emitter and the ROV an optical or acoustic receptor.

[0079] Optical communication is favoured by the clear water and/or by the fact that the turbine is usually completely closed and therefore there is no external light to perturb the data transfer.

[0080] The cable or the tether 28 has a length, for example between 2 m and 10 m (but longer tether may be needed, for example for inspection of horizontal turbines) allowing positioning the probe within the runner, for example between two neighbouring blades, while the ROV remains below the runner, for example in the suction pipe 11. Thus, the probe can float up into the runner and its position can be controlled by moving the ROV and/or by varying the length of the cable or the tether. The ROV can be provided with a reel or a coil or a device to wind or unwind one or more cable and/or tether.

[0081] The floatability or buoyancy of the probe enables it to be inserted into the runner from below. The floatability or buoyancy of the probe can be natural, the probe being itself floatable or buoyant. Alternatively, the floatability or buoyancy of the probe can be achieved by coupling the probe 26 to at least one buoy and/or at least one thruster. An underwater thruster may comprise a motor and a propeller. An underwater thruster is disclosed on https://bluerobotics.com/store/thrusters/t100-1200-thrusters/t200-thruster/. Another underwater thruster is disclosed in WO2016075631.

[0082] For example, a negatively buoyant probe (a probe that would naturally sink in the water as its mass is superior to the mass of the equivalent volume of water) can be equipped with one or more buoy and/or one or more thrustor(s) that push(es) it upwards and compensate the negative buoyancy.

[0083] Using buoyant probes and probes with thrusters offer several advantages: [0084] a buoyant probe is the most economical way to have a probe that can enter in a turbine runner in a vertical shaft configuration; [0085] the use of one or more thrustor(s) may allow a more accurate positioning of the probe; it also allows entering in a turbine with a horizontal shaft arrangement.

[0086] Buoyancy of the probe can be adapted or varied by adding ballast and/or a floating device.

[0087] If the probe comprises at least one imaging device, for example at least one camera, it can be a camera with a 360 field of view or a different field of view, or a plurality of cameras with different fields of views, for example 2 cameras, each having a 180 field of view, or a plurality of cameras disposed so as to allow or create a 360 field of view. In an embodiment the probe comprises several imaging devices, for example several cameras (at least one of them or all of them having for example an improved resolution or being a lower cost option); several imaging devices, for example several cameras, can be used instead of a 360 camera.

[0088] A least one camera can be a camera at least partly in the visible range and/or in the ultra-violet (u.v.) range.

[0089] Preferably, a camera implemented as imaging device offers the ability to pan and/or zoom and/or focus on a specific area of interest, thus offering the possibility to inspect a defect without losing context of its surrounding. The panning may be virtual, for example in the case of a 360 camera and either virtual or mechanical in the case of another camera. The camera is for example a pan-tilt camera that can be orientated in two directions. The user interface, illustrated on FIG. 3, generally shows only a part of an image from a camera, the recorded image corresponding to what a standard camera would show. The user can orientate the view angle with the computer control that can be considered as a virtual panning system.

[0090] A 360 camera, or a live 360 video camera, offers the advantage of providing a panoramic view, which allows an inspection of the runner to maintain context awareness of the inspection areas, maintaining context allowing a systematic and thorough inspection.

[0091] The probe can contain or is provided with at least one battery and be supplied with power from said at least one battery; and/or the probe can be supplied with power from the ROV (through the tether 28). In specific embodiments: [0092] data are transmitted from the probe to the ROV wireless (as already explained above) and the probe is supplied with power from the ROV through tether 28; [0093] or data are transmitted from the probe to the ROV wireless (as already explained above) and the probe contains or is provided with at least one battery for power supply.

[0094] Alternatively, as explained below, the probe can be powered from a ground station 25, via a separate tether 29 between the probe and a ground station 25. Data or images from the probe can be sent from the probe to the ground station (in which case the tether 28 may not be implemented).

[0095] The underwater ROV itself can be provided with an on-board imaging device 21, for example a camera and/or a scanning device 21, that can be oriented. Said imaging device 21 can be used to orient the ROV; it can also be used to visualize the probe 26 in order to facilitate guiding and positioning steps of the probe with respect to the runner. Such an imaging device 21 can be a low-resolution device (which requires lower bandwidth to transfer real time data). Both images or data from said imaging device 21 and probe 26 can be displayed on one or more display devices or screens 27a, 27b of a ground station 25 so that an operator can adjust the position of the ROV and/or the probe and/or the intensity of the light of a lighting device based on both kinds of information. In particular, if the probe 26 comprises a camera, preferably a 360 camera, real-time live video on one or more display devices 27a, 27b during navigation and inspection process considerably improves navigation, precision and performance. Displaying images or videos from both imaging device 21 and probe 26, for example live streams of both ROV navigation imaging device 21 and probe 26, can be parallelized (for example via publish-subscribe architecture), thus enabling both imaging devices 21, 26 to simultaneously stream live videos, record videos and take still snapshots for offline inspection later.

[0096] During an inspection, images or videos or data from imaging device 21 and probe 26 can be recorded, for example at the same time, for example in a memory in the ROV and/or of the computer 24 to which they can be transmitted.

[0097] In a variant, a device according to the invention comprises one or several, for example 2, light sources or lighting devices, which can be transported by the ROV and remain(s) fixed with respect to the ROV; and/or at least one light source or lighting device can be positioned at one or more location(s) in the runner (by the same or another ROV). A light source or lighting device, for example in the visible range can be a LED or a lamp or a laser. The probe 26 can thus explore an area which is illuminated by said at least one light source or lighting device and take images which can then be processed, for example by photogrammetry.

[0098] A challenge of underwater navigation is the ability to see and resolve features underwater that provide navigation context. The environment underwater may contain particles or particulate, in case of turbidity, that makes this difficult. If the imaging device 21 used for navigation and context acquisition is located physically near the light source, light reflected off the floating particulate or underwater objects directly into the camera. This makes it difficult to resolve features beyond the particles reflecting light (sometimes a few cm).

[0099] Locating the light source away from the ROV 20 (close to or on the inspection probe 26 for example) reduces this effect and enables navigation and context tracking. FIG. 6A is an example of a lighting device 30 combined with an imaging device 32, for example a camera, preferably a 360 camera, and a tether 28 connecting this device with a ROV (not shown); thus, the lighting device 30 is close to the imaging device. In a preferred embodiment, it provides several lighting beams so as to illuminate a wide field, preferably of 360, around the device; for example, the top view of FIG. 6B shows 3 such fields 30.sub.1, 30.sub.2, 30.sub.3.

[0100] Both the probe and the ROV can be provided with one or more light source(s) or lighting device(s). This can allow an independent control of lighting from the ROV and/or from the probe and/or enables navigation from either the probe point of view or the ROV point of view. This greatly improves the ability to track the location within the confined space of a runner, enabling a much greater understanding of context.

[0101] In order to overcome specular highlights or effects, a polar light source and a polarizing filter can be implemented: the polar light source illuminates the inspected surface and the filter is disposed in front of the probe 26 (or of its imaging device, for example a camera), thus reducing specular highlights or effects.

[0102] In a variant, a device according to the invention is used in combination with another ROV or AUV, for example also according to the invention, which carries or comprises a lighting device, for example in the visible range, for example a lamp or a laser, said ROV or AUV being located closer to the probe than the ROV or AUV to which the probe is linked by the tether.

[0103] In a variant, a device according to the invention is able to transport one or several, for example 2, light sources to one or more location(s) in the runner and to deposit said light source(s) at said location(s). Then the probe 26 can explore the area which is illuminated and take data or images which are then processed, for example by photogrammetry.

[0104] A rail free ROV (Remote Operated Vehicle or underwater remote operated vehicle) can be used to implement the invention underwater; alternatively, it can be an AUV (autonomous underwater vehicle).

[0105] One example of a ROV which can be implemented in this invention is proposed by Blue Robotics (see https://bluerobotics.com/).

[0106] A ROV or an AUV of a device according to the invention: [0107] can be mounted on wheels or on tracks and moves along a surface, for example of the suction pipe 11; alternatively, an underwater ROV or AUV can be a propeller-driven vehicle; [0108] can be driven by driving means, for example by electric power, for example with help of a battery and/or by a motor 23 (FIG. 3A); a power source can be connected via a tether 22 or can be onboard; the ROV can be controlled wireless or via a tether 22 (FIG. 3).

[0109] The location of the probe can be controlled by the ROV. Alternatively, the location of the probe can be controlled independently of the ROV, for example by a ground station 25, which enables more thorough inspection of more complex internal spaces.

[0110] FIGS. 4A and 4B are examples of images recorded by a device according to the invention (the probe having a 360 camera) and displayed on two displaying devices 27a, 27b, for example screens like computer screens, respectively showing the 360 image from the probe 26 (on display device 27b) and the image from the on-board imaging device of the ROV (on display device 27a).

[0111] On both FIGS. 4A and 4B, display device 27a shows the turbine runner itself and the external probe 26 entered in the runner (on FIG. 4A one can only see the tether of the external probe 26; on FIG. 4B one can see the full probe 26 inserted in the runner tip). While viewing the external probe 26 from the ROV and thanks to the image synchronization (either the images are perfectly synchronized or there might be a small delay between the images of the ROV & the external probe) one can easily locate the probe 26 in the runner and therefore locate any defect that would be detected by the probe.

[0112] Real time or offline analysis of the data from the ROV and/or the probe can be used to identify defect and prompt an operator to accept, reject, or provide additional information for the candidate defect.

[0113] Once a defect has been identified, it can be automatically characterized by labelling the data with information about the defect, for example one or more data among the size, depth, defect type, location, severity classification, . . . .

[0114] A crack is another example of a defect of a hydro-turbine (or of the runner of said hydro-turbine) to be detected. Cracks are usually surface cracks and then evolve into through-cracks after some time of propagation; they have for example a size of around 5 mm (or more) length, 1 mm (or more) depth, 0.1 mm (or more) wide. A first example of a crack 16 is shown on FIG. 5A: it is a small crack (about 20 mm at band outlet) and should be repaired in a short or medium term in order to avoid a further propagation. A second example is shown on FIG. 5B which represents an advanced crack 18 (600 mm long at blade inlet); in such case, the hydraulic machine must be stopped in a short or medium term in order to avoid extreme failure. The repair can be done on site (by excavation, welding, grinding).

[0115] Cracks are essentially located at the inlet or the outlet of the runner, at the junction between the blades and the crown or the band which are the weakest locations of the runner where the highest stress concentrations occur. For Francis turbines, the majority of cracks is occurring at the runner outlet.

[0116] A plurality of devices according to the invention can be used at the same time to inspect different locations of a runner. For example, one of the probes of one such device provides vision with an imaging device, for example a camera, for example in the visible range, another one providing light or other wavelength (for example: IR) analysis with another camera.

[0117] On FIG. 3A the ROV 20 comprises an on-board imaging device 21, for example a camera, and is connected by tether 22 to a computer 24 (for example a microcomputer or a portable computer) of ground station 25, said computer being programmed for controlling the path followed by the ROV and the camera(s) and/or for sending instructions to perform the appropriate inspection steps. The tether 22 can comprise one or more cable(s) and/or wire(s) to allow data exchange between the ground station 25 and the ROV, for example to control the ROV 20, and/or to provide the electric power to the ROV and/or to control the probe 26.

[0118] Alternatively, a tether-less or wireless ROV is also possible, see for example https://www.hydromea.com/exray-wireless-underwater-drone/; it operates autonomously with wireless connection. The ROV can be controlled from the ground station by wireless means (for example optical means) or by such wireless means combined with a tether. For example, a ground station generates control data of the ROV and/or of the probe 26 which are sent (for example through a tether and/or one or more optical fiber(s)) to an optical component (emitter and/or receiver) and said control data are then sent by said emitter to said ROV.

[0119] In such case, the ROV can for example carry the probe (including for example one of more thruster(s) and/or batteries) and possibly any device that is too big to enter a particular location of a hydraulic machine, for example between blades of a runner; the probe is released for inspection when the ROV has reached a position under the hydraulic machine, for example under runner, and is guided, for example with at least one thruster to inspect at least part of the hydraulic machine, for example part of the runner.

[0120] The thruster(s) and/or one or more probe(s) and/or one or more lighting device(s) can be controlled either from the ROV or from the ground station, via a tether or wireless. For example, data or the image data from the probe can be wireless transmitted from the probe to the ROV and/or to the ground station 25. For example, an optical receiver receives data or images which are optically sent by the probe and the optical receiver is connected to the ground station, for example by one or more tether(s) and/or one or more optical fibre(s).

[0121] FIG. 3A represents a tether 29 between the ground station 25 and the probe 26. This tether is for example for data transmission between the probe and the ground station 25 and/or for supplying the probe with power. If the tether 29 is both for exchanging data between the ground station 25 and the probe 26 and for supplying the probe with power, then tether 28 may not be implemented. As illustrated on FIG. 3B (see below), tether 29 can be fixed on the ROV or a specific cable can attach the probe to the ROV.

[0122] Data exchange between the probe 26 and the ground station 25 via tether 29 can be advantageous when the tether 28 has a limited bandwidth.

[0123] Both power supply of the probe 26 by the ground station 25 and data exchange between the probe 26 and the ground station 25 via tether 29 can be advantageous when the tether 28 has a limited bandwidth and is limited in power.

[0124] FIGS. 3B-3E are schematic presentations of different possible configurations of a system according to the invention. On these figures, the same reference numbers identify the same technical features as on the other figures and the corresponding explanations are not be repeated for the sake of clarity. In particular:

[0125] FIG. 3B shows a configuration where the probe is connected to the ground station via a tether 29, so that data can be exchanged between the probe 26 and the ground station 25 and the ground station 25 can supply the probe 26 with power; tether 29 can be fixed to the ROV or a specific cable 33 can attach the probe 26 to the ROV 20;

[0126] FIG. 3C shows a configuration where the probe 26 is connected to the ROV 20 via tether 28, so that data can be exchanged between the probe 26 and the ROV 20 and the ROV 20 can supply the probe 26 with power; communication between the ROV 20 and the ground station 25 is partly wireless: optical communication is established between the ROV and an optical component 40 which is itself connected to the ground station via a tether 42 and/or one or more optical fibre(s);

[0127] FIG. 3D shows a configuration where the probe 26 is wireless connected to an optical component 40 (receiver and/or emitter) and to the ROV via tether 28 (for power supply), so that data can be exchanged between the probe 26 and the optical component 40; control data can be exchanged between the ROV 20 and the optical component 40, which is itself connected to the ground station via a tether 42 and/or one or more optical fibre(s); tether 42 and/or one or more optical fibre(s) transmit(s) control data from the ground station 25 to the component 40 and transmit(s) data or images from the component 40 to the ground station;

[0128] FIG. 3E shows a configuration where the probe 26 is powered with batteries and is connected to an optical component 40 (receiver and/or emitter), so that data can be exchanged between the probe 26 and the optical component 40; control data can be exchanged between the ROV 20 and the optical component 40, which is itself connected to the ground station via a tether 42 and/or one or more optical fibre(s); tether 42 and/or one or more optical fibre(s) transmit(s) control data of the ROV and/or of the probe from the ground station to the component 40 and also transmit(s) data or images from the component 40 to the ground station 25. In configurations like on FIGS. 3C-3E where the ROV 20 is connected at least partly tether-less to the ground station 25, the ROV is attached to tether 42 and goes to an appropriate location while being connected to the tether 42; it is then detached from tether 42 to continue travelling to an appropriate location from which it communicates wireless with the optical component 40.

[0129] In a particular embodiment, the communication between the probe 26 (for example an imaging device, for example a camera) and the ground station 25, for example through tether 29 and/or wireless, is bidirectional: the probe sends data and/or images to the ground station 25 and the ground station 25 controls the probe (for example the ground station switches the probe on/off, and/or adjusts a focus or any optical parameter of an imaging device, for example a camera, and/or a resolution and/or a frame rate). When the inspection is finished, the probe returns to the ROV.

[0130] Powering of the probe, for example of an imaging device, for example of a camera, can be done by batteries in the probe, or from the ROV or from a ground station (via a tether).

[0131] Data, in particular images from the probe can be processed (in real time or not) by a processor or by programmable means adequately programmed, in the ROV and/or can be transmitted to computer 24 of ground station 25, said computer 24 being programmed for processing said data and/or images, for example to generate a 3D representation or view; an image can be displayed on one or more display or screen 27a, 27b so that an operator can decide whether the hydraulic machine should be repaired. It is also possible to make measurements and generate a map of the defects detected on a blade or on any portion of a hydro turbine; such a map, giving information about the location of the defects, can be generated by computer 24 and possibly displayed.

[0132] The illustrated system can be adapted to several devices according to the invention ROVs performing inspection of different parts at the same time.

[0133] A device according to the invention performing inspection of blades 32, 34, 36 of a runner of a hydro turbine is shown on FIG. 3A. It comprises a ROV 20 which either propels itself up the draft tube; it is piloted remotely from the ground station 25 by an operator that uses the camera image to locate the ROV. Alternatively, the ROV is able to find its way to the runner and performs the inspection autonomously. It can have access to the draft tube through the man hole (depending on the watered or dewatered situation). It can be seen on FIG. 3A that the probe 26 can inspect the runner between two neighbouring blades, although the distance between two blades is limited to between 50 mm or 100 mm and 300 mm or even 500 mm.

[0134] The invention can be implemented for inspecting blades 32, 34, 36 (see for example FIG. 3A) of a runner, however other parts of a hydro-turbine or of a hydraulic machine can be inspected according to the invention, for example stay vanes or wicket gates or the draft tube of said hydro-turbine or any other part of a hydraulic machine.

[0135] More generally, the invention allows inspection of any submerged area of a hydraulic machine and/or of a hydroelectric installation provided that such area is accessible from the draft tube where the underwater ROV or the AUV is located: for example blade(s), stay vanes, wicket gates and the draft tube itself.