Laser scanning of cable and cable accessory components subjected to mechanical loads and elastic or inelastic deformation

Abstract

A method for detecting deformations of high voltage and/or medium voltage cables and/or cable components, include at a first point of time, capturing and storing (302) a first set of 3-dimensional, 3D, surface geometry measurement data of an area of interest of a surface of the cable or cable component. The method also incudes, at a second point of time, capturing and storing (304) a second set of 3-dimensional, 3D, surface geometry measurement data of an area of interest of a surface of the cable or cable component by moving a 3D surface scanner about the cable over the area of interest. The first and second sets of captured 3D surface geometry measurement data is compared to determine changes that have occurred in the cables or cable components between the first and second points of time, where changes indicate a deformation of the cable or cable component.

Claims

1. A method for detecting deformations of high voltage and/or medium voltage cables and/or cable components, comprising following steps: a) at a first point of time, capture and store a first set of 3-dimensional, 3D, surface geometry measurement data of an area of interest of a surface of the cable or cable component, b) at a second point of time, capture and store a second set of 3-dimensional, 3D, surface geometry measurement data of said area of interest of said surface of the cable or cable component by moving a 3D surface scanner about the cable over the area of interest, and c) compare the first and second sets of captured 3D surface geometry measurement data to determine changes that have occurred in the cable or cable component between the first and second points of time, where changes indicate a deformation of the cable or cable component.

2. The method according to claim 1, wherein the first set of 3D surface geometry measurement data is captured by moving a 3D surface scanner about the cable over the area of interest.

3. The method according to claim 1, wherein the first set of 3D surface geometry measurement data is captured by inspecting a data file representing the geometry of the cable or cable component in the area of interest.

4. The method according to claim 1, wherein the 3D surface geometry measurement data are represented by a data point cloud, where data points in the data point cloud can be further processed to provide a representation of the cable or cable component.

5. The method according to claim 1, further comprising following steps: at a n.sup.th point of time, capture and store a n.sup.th set of 3-dimensional, 3D, surface geometry measurement data of said area of interest of said surface of the cable or cable component by moving a 3D surface scanner about the cable over the area of interest, and comparing the n sets of captured 3D surface geometry measurement data to determine changes that have occurred in the cable or cable component between the first, second and n.sup.th points of time.

6. The method according to claim 1, further comprising generating a quality report for the area of interest.

7. The method according to claim 5, further comprising generating a quality report for the area of interest, where the quality report comprises a representation of changes over time from the first to the n.sup.th point of time.

8. The method according to claim 5, further comprising generating a quality report for the area of interest, where the quality report comprises a representation of changes over time from the first to the n.sup.th point of time and/or a go/no go notification allowing or disallowing the cable or cable component to proceed operation at the second or n.sup.th point of time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an example of a 3D surface geometry measurement of a of a cable.

(2) FIG. 2 illustrates a high volt cable end.

(3) FIG. 3 is a flow chart illustrating steps of a method for detecting deformations of high voltage and/or medium voltage cables and/or cable components.

DETAILED DESCRIPTION

(4) FIG. 1 is a schematic illustration of a system according for scanning the surface 5 and/or interfaces of high voltage and/or medium voltage cable components, in this example a cable end 1. The sizes of various object of the illustration are not in scale. The system comprises a non-contact surface scanner 40. The non-contact surface scanner 40 is directable to an area of interest 45.

(5) In one embodiment, the non-contact surface scanner 40 may be a 3D laser scanner. The scanner may also be other types of non-contact surface scanners, for example white line scanners using projected white lines able to project up to 1,500,000 measurements/s and/or 99 white light scanning lines, or other kinds of suitable scanners.

(6) Other examples of scanners that can be used are structured light scanner, a lidar based scanner, photogrammetry means that captures a number of images which can be merged into a 3D model, etc.

(7) The non-contact surface scanner 40 is arranged to measure the distance to the surface 5 of the area of interest. In the example in the figure, the field-of-view of the non-contact surface scanner corresponds to the area of interest, but the area of interest 45 on the surface 5 may be larger or smaller than the field-of-view or scanning area of the non-contact surface scanner 40. The field-of-view may be round, rectangular, linear or any other shape as determined by the non-contact surface scanner. The non-contact surface scanner 40 is movable around the cable 1 such that the surface 5 of the cable 1 is covered by a plurality of sub-areas in order to ensure that the entire area of interest is scanned. The size of plurality of sub-areas may vary, for example by varying the distance between the non-contact surface scanner 40 and the cable 1. In one embodiment the non-contact surface scanner 40 is freely movable in any direction around the cable 1, such as a handheld 3D laser scanner.

(8) The non-contact surface scanner 40 should know its position and direction in 3D space, for example by recognizing a plurality of markers (not shown) positioned on the surface 5. The markers may be stickers or sterile clamps with specific patterns or markers thereon. The markers will result in NaN (not a number=empty) areas underneath them, however, the scan can be paused, markers/clamps relocated and then the measurement can also scan the area under the markers. In another embodiment the non-contact surface scanner 40 may be mounted to a fixture or jig, e.g. mountable to the HV-cable, such that the non-contact surface scanner 40 may be moved up/down and around the surface 5 to completely fill the area of interest 45 with sub-areas. In this way, using markers may be avoided. In other embodiments, the non-contact surface scanner 40 can be arranged in a fixture or jig, and the cable may be moved relative to the scanner 40.

(9) In some embodiments, the geometry of the scanned surface itself may be used as reference for the position of the non-contact surface scanner 40 itself in 3D space.

(10) The illustrated system also comprises an analysis unit 42. The analysis unit 42 is in communication with the non-contact surface scanner 40 over a wired or wireless communication link. In one embodiment, at least parts of the analysis unit 42 may be comprised in the non-contact surface scanner 40. The analysis unit 42 comprises a processor 43 adapted to process measurement data from the non-contact surface scanner 40 for each of the plurality of sub-areas to create a continuous 3D surface geometry measurement of the area of interest 45, and thus the surface to be evaluated. The continuous 3D surface geometry measurement can be processed to evaluate the characteristics of the surface and can also create an image of the surface for evaluation and for later reference.

(11) In one embodiment, the analysis unit 42 is adapted to transmit the continuous 3D surface geometry measurement to a storage device 44 as a 3D topographic map of the area of interest 45. The analysis unit 42 is in communication with the storage device 44 over a wired or wireless communication link. The storage device 44 may be on on-premise server or cloud server. The 3D topographic map of the surface 5 of the cable 1 on the server 44 may be accessible to users and clients for future reference of the cable system.

(12) FIG. 2 illustrates a detailed view of a high voltage cable end. As shown an exemplary high voltage cable end 1. The outer sheath 9, the lead sheath 8, swelling tapes 7 and the outer semiconducting screen 6 have been removed, leaving the conductor 2, the inner semiconducting screen 3 and the insulation 4. The surface 5 of the insulation 4 is inspected to ensure that there are no irregularities, before a high voltage cable accessory component, such as high voltage joint, termination for the cable, a rubber joint, is slipped over it.

(13) FIG. 3 illustrates an embodiment of a method for detecting deformations of high voltage and/or medium voltage cables, and/or cable components.

(14) The method is in this example used to detect deformations in a cable, but as described above, it may be used for different types of cables, cable parts, cable accessory, part assemblies, etc.

(15) In the first step 301, a cable is provided which have an area of interest that is expected or suspected to be subjected to mechanical loads or stress, for example cable armor, weldings, accessory parts, flanges, etc.

(16) Then, in 302, at a first point of time, a first set of 3-dimensional, (3D), surface geometry measurement data of an area of interest of a surface of the cable or cable component is captured and the data is stored in a memory for later processing. The 3D surface geometry measurement data can be obtained by moving a 3D surface scanner about the cable over the area of interest as described above.

(17) Alternatively or additionally, the 3D surface geometry measurement data can be obtained by inspecting a data file representing the geometry of the cable or cable component in the area of interest. Such a data file can for example be a 3D drawing and/or specifications of the cable or cable component provided by the manufacturer, a CAD file provided for manufacturing the cable, etc.

(18) The 3D surface geometry measurement data can be represented by a data point cloud, where the data points in the data point cloud can be further processed to provide a representation of the cable, for example a topographic map of the area of interest, the cable or the cable component.

(19) The cable/cable component will then be put to use, for example submarine cables being deployed from a vessel, used for land applications etc., as earlier described, where it is exposed to one or more mechanical loads, see 306 in FIG. 3. After a period of time 303, at a second point of time, in step 304, a second set of 3D surface geometry measurement data of the same area of interest of a surface of the cable or cable component is captured by moving a 3D surface scanner about the cable over the area of interest. The second set of 3D surface geometry measurement data is also stored in a memory. The period of time between the first and second point of time can vary according to the kind of area of interest on the cable, the application of the cable, environmental factors at the location of the cable etc. In some instances, it is important to discover at an early time when a change has occurred, and in these instances a shorter period of time is preferred.

(20) After capturing the second set of measurement data, the first and second sets of captured 3D surface geometry measurement data are compared at step 305 to determine changes that have occurred in the cables or cable components between the first and second points of time. This comparison may be performed by an operator visually inspecting the captured data, or this may be performed by a computer processor. The captured data may in any embodiment be processed to evaluate the characteristics of the surface and can also be processed to create an image of the surface for evaluation and for later reference.

(21) The process may be repeated so that at a third and n subsequent points of time, a third to a n.sub.th set of 3-dimensional, (3D), surface geometry measurement data of the area of interest of a surface of the cable or cable component is captured and stored by moving a 3D surface scanner about the cable over the area of interest.

(22) The third to the n.sub.th set of captured 3D surface geometry measurement data is then compared to the first and/or to all the previous sets of data to determine changes that have occurred in the cables or cable components between the first, second and n.sub.th point of time.

(23) In one embodiment, the analysis unit can provide a go/no go evaluation of the scanned cable/cable part at the second or later point of time. In this way an operator may receive a go or a no go after the scan is performed, allowing or disallowing the operator to proceed with the cable part or marking the cable for repair or replacement.

(24) The criterium for providing go/no go may be based on a selection of criterions. The criterions can be selected depending on the type of cable part to be scanned, the type of non-contact scanner used and the purpose of the scan. Examples of criterions are: a height variation threshold, a surface derivative threshold, a peeling wave threshold and/or at least one of an area of a cut, a depth of a cut, and a slope of a cut.

(25) Further criterions may be employed after further processing of the 3D surface geometry measurement data. Further processing can for example be levelling and sorting the data. Examples of further criterions are local derivatives, local indentation and noise level.

(26) The analysis unit can use the above to identify the worst regions of the area of interest, such as deeper cuts, nicks, scratches, steps, for example by means of finite element method (FEM). The method can calculate local computed FEF and local computed partial discharge inception voltage (PDIV).

(27) The result of the comparisons and analysis can be used in a step 307 to generate a quality report or a monitoring report.