Patent Application
20230411939
This application claims the benefit of priority from European Patent Application No. 22 305 614.4, filed on Apr. 26, 2022, the entirety of which is incorporated by reference.
The present invention relates to high voltage and medium voltage cables, in particular to a system and method for inspecting damages to high voltage and/or medium voltage cables or cable assemblies.
A high voltage (HV) and medium voltage (MV) cable is used for electric power transmission at medium and high voltage, e.g. above 1 000 V. Such cables include a conductor and an insulation. The insulation may consist of polymers or polyethylene, including ethylene propylene rubber (EPR) and cross-linked polyethylene (XLPE). At inner and outer sides of the insulation semiconducting layers are fused to the insulation. The semiconducting layers prevent air-filled cavities between the metal conductors and the dielectric so that small electric discharges cannot arise and endanger the insulation material. The insulation is usually also covered by a copper or aluminum wire screen, or a lead or aluminium or copper jacket, or combinations thereof. This metallic screen or jacket is followed by a polymeric (e.g. PE or PVC) outer sheath.
The cables are manufactured in cable manufacturing lines using extrusion. The quality control and meeting product specifications are very important in cable production. A failure due to dielectric breakdown in the HV-cable may cause a break to power supply. For instance, high voltage cables are used for long length connections for power distribution and power transmission. The manufacturing quality is monitored during the operation of the cable manufacturing line to assure the quality of the final product. The final product is usually a assembly comprising cable lengths connected together as well as connected accessories such as terminations joints, GIS terminations, asymmetric joints, MV joints, MV terminations, MV plugin terminations, etc.
Physical damages can occur to HV cables, or MV cables, or MV/HV cable products, where the long term performance of the product can be seriously jeopardized. When such damages occur, during production, transportation, installation, or service of these products, it is necessary to evaluate the extend of the damage. One means of assessing the damage is do measure the degree of geometrical deviation in the defect region, and in other cases to remove layers or parts bit by bit until the remainder of the cable or assembly can be confirmed to be undamaged. Another example is to cut away polymeric or other materials until no further damage is observed on the object.
The main problem in such operations is the lack of a good three-dimensional (3D) assessment of the damage before starting the dissection/disassembly, during this process, as well as an assessment of the dimensions of the healthy parts remaining of the assembly. Also, upon repairing the assemblies/cables with new parts and/or substituting new layers in place, there is no good three-dimensional assessment of whether the repaired product meets the acceptance criteria defining a healthy product.
Today assessment of the external damages, the internally damaged parts, and the remaining healthy components within is carried out by means of manual measurement tools, photographic evidence, and other methods that rely on manual use of digital tools.
EP3901571 discloses a system and a method for determining a quality of a surface of a high voltage cable end using a 3D scanner. The method comprises moving a non-contact surface scanner about the cable end, measuring distance to the surface over the area of the surface by sequentially measuring a plurality of sub-areas of the area of the surface, creating a continuous 3D surface geometry measurement of the surface of the cable end and comparing, using the continuous 3D surface geometry measurement with at least one surface geometry acceptance threshold determining the quality of the surface of the high voltage cable end.
The object of the invention is to provide a system and a method for assessment of damages of HV and/or MV cables that solves or at least mitigate the problems of prior art.
The object of the invention is achieved by means of the patent claims.
In the exemplary embodiments, various features and details are shown in combination. The fact that several features are described with reference to a particular example should not be construed as implying that those features be necessity have to be included together in all the embodiments of the invention.
Conversely, features that are described with reference to different embodiments should not be construed as mutually exclusive. As those skilled in the art will readily understand, embodiments that incorporate any subset of features described herein and that are not expressly interdependent have been contemplated by the inventor and are part of the intended disclosure. However, explicit descriptions of all such embodiments would not contribute to the understanding of the principles of the invention, and consequently some permutations have been omitted for the sake of simplicity.
The invention provides an inspection method that can generate a go/no go criteria on the performed repair on-site. This provides the capability of tracking the geometries in 3D of each damage and subsequent repair of the product. The data can be stored and accessed during the full lifetime of the cable system. The generated data is feasible for use in future physics based digital twin models.
The 3D data can also be easily transferred to an external expert which can evaluate the extend of the damage and the quality of repair, and provide the go/no go criteria remotely. These measurement results will also add value to the cable systems in that the data can be stored and provided to for future reference and health checks of the cable system.
In one embodiment, a method for inspecting damages to high voltage and/or medium voltage cables or cable components, comprises:
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. A data point cloud is a set of data points in space. The points may represent a 3D shape or object. Each point position has its set of Cartesian coordinates (X, Y, Z). Point clouds are generally produced by 3D scanners or by photogrammetry software, which measure many points on the external surfaces of objects around them. As the output of 3D scanning processes, point clouds are used for many purposes, including to create 3D CAD models for manufactured parts, for metrology and quality inspection, and for a multitude of visualization, animation, rendering and mass customization applications.
While point clouds can be directly rendered and inspected, point clouds are often converted to polygon mesh or triangle mesh models, NURBS surface models, or CAD models through a process commonly referred to as surface reconstruction.
There are many techniques for converting a point cloud to a 3D surface. Some approaches, like Delaunay triangulation, alpha shapes, and ball pivoting, build a network of triangles over the existing vertices of the point cloud, while other approaches convert the point cloud into a volumetric distance field and reconstruct the implicit surface so defined through a marching cubes algorithm.
In one embodiment is the sets of 3D surface geometry measurements from each repeated step merged to obtain a full 3D map of the damaged section of the cable.
In order to get a full 3D map, there may be attached at least one marker device on the cable near the area of interest. The marker device may then be identified in the 3D data and used to align the sets of surface geometry measurement data during merging.
The inspection may comprise measuring the insulation thickness of the cable or cable component.
The method may further comprise steps of repairing the cable after a damage has been identified. Such repair may comprise at least some of the following steps:
In one embodiment, a system for inspecting damages to high voltage and/or medium voltage cables, the system comprises:
The invention will now be described in more detail by means of examples and with reference to the figures.
The illustrated system also comprises an analysis part 42. The analysis part 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 part 42 may be comprised in the non-contact surface scanner 40. The analysis part 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 damage 41. The continuous 3D surface geometry measurement is processed to evaluate if there is a damage in the area of interest, and can also create an image of the damage when a damage is present in the scanned surface.
In one embodiment, the analysis part can provide a go/no go evaluation. 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. The criterium for providing go/no go may be based on at least one of 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.
In one embodiment, the analysis part 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 part 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.
In step 33 the captured 3D surface from step 32 is inspected to evaluate if any damages are present.
If the inspection reveals a damage, the operator can remove a section of the cable body, and repeat steps 31-33. This cycle can be repeated until no damage is revealed during the inspection step 33, ie. when an undamaged part of the cable is revealed.
After this procedure, the cable/accessory can be repaired by adding layers until the cable or accessory is complete and undamaged. An example of this process is described in
If all scans reveal a damage, the cable part may be deemed rejected and the cable may need to be repaired by cutting out the damaged part and splicing the remaining cable or making a joint for inserting a cable part.
The scans may be stored for later proof of repair and as evidence that a full repair with cutting and joining was necessary.
Based on the provided knowledge, one layer of the cable/cable accessory is repaired in step 51.
In step 52, the outer layer of the repaired area is scanned by moving a 3D surface scanner about the cable over the area of interest, and a set of 3-dimensional (3D) surface geometry measurement data of the area of interest is captured and stored.
In some embodiments, there may also be added a step of inspecting the scan of the repaired layer before proceeding with the next layer. This can be performed manually or automatically and can provide feedback to the operator on the quality of each repaired layer. This will improve the quality of the repair.
The repair and scanning process in steps 51 and 52 are repeated until all damaged layers have been repaired. The scans made during this process can be used to create a 3D surface geometry of the repaired cable in step 53. The 3D geometry of the cable can be stored for later use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22305614.4 | Apr 2022 | EP | regional |
