A method, arrangement and system for locating a fault on an electric cable

Abstract

The present invention relates to a method for locating a fault (2) on an electrically conductive cable (1), and a cable tracker arrangement for locating such a fault.

Description

[0001] A method, arrangement and system for locating a fault on an electric cable

[0002] Technical Field

[0003]

[0001] The present invention relates to the field of detection of faults in electric cables. In particular, the invention relates to a method, arrangement and system for detecting a fault on submarine cables.

[0004] Background

[0005]

[0002] There is an ever-increasing demand for green and clean energy, in order to solve the environmental challenges facing the world. This means that the reliance on electric energy is bound to accelerate drastically in the coming years. Since the production of electric energy is not evenly distributed across geographic regions, it is necessary to improve the infrastructure facilitating transfer of electric energy. At the same time, the demand for high-speed and high-capacity communication is increasing.

[0006]

[0003] Therefore, the requirement for cables capable of transferring large amounts of energy and / or information is set to increase. These cables are often required to cross large expanses of water, where they can be buried in the seabed. For example, there are numerous submarine electric cables connecting Norway, which is rich in clean hydroelectric energy, to neighbouring countries across the sea. To meet the demand for high-speed information transfer, the number of submarine fibre optic cables are also increasing between countries and to regions separated by water. Naturally, the detection of faults and maintenance in such submarine cables is complicated due to restricted access.

[0007]

[0004] Although submarine cables are typically buried in the seabed to protect them from external forces, they may yet be damaged. For example, ships dropping and dredging anchors may cause breakages or indentations on the cable. Trawlers dragging nets across the sea bottom may cause similar damages. A shifting seabed can expose parts of the cable to the elements. Malignant actors may attempt to disrupt the flow of electric energy by destroying parts of a cable. Apart from these external events, a cable may also acquire damage leading to a fault due to substandard production or cable-laying.

[0005] Once a fault occurs in a cable, it may be difficult to pinpoint the exact location of the fault. At present the location may be estimated by generating a voltage pulse at one end of the cable and measuring a relative change in the cable wave impedance, the distance to the fault is then calculated by the cable impedance and time for the pulse to return. In power cables, this pulse may be generated in the conductor. For other types of cables, such as a fibre optic cable, an optical pulse is sent down the fibre optic cable. When the optical pulse encounters a fault (such as a break or damage), it scatters back. By measuring the time delay and intensity of the scattered signal, the the spatial location of the fault can be determined.

[0008]

[0006] However, the prior art solutions do not provide accurate results, resulting in long lengths of cable being replaced in order to make sure that the faulty part of the cable has been removed. Since each cable is typically tailor-made for a distance, and there is a limited amount of spare cable, this can become a significant problem once enough damage has been sustained.

[0009]

[0007] In the prior art, various different solutions have been proposed to overcome this issue. Korean patents, KR101468033B1, KR101692469B1 and KR101468033B1 propose towing an unmanned underwater vehicle along a length of submarine cable, providing a pulse in the cable, detecting an acoustic sound caused by an electric arc emanating from the fault on the cable and thereby estimating the position of the fault on the cable. US8474320B2 discloses a stationary solution for the identification of the acoustic signal by the use of a comparison unit, which is able to identify the acoustic signal created by a fault in a cable.

[0010]

[0008] It is an object of the present invention to improve upon, mitigate or significantly alleviate the shortcomings of the prior art.

[0011] Summary of the Invention

[0012]

[0009] According to a first aspect, the present invention relates to a method for locating a fault on an electrically conductive cable, wherein the method comprises the steps of: providing a cable tracker arrangement along the cable arranged on a single propelled or towed unit, where the cable tracker arrangement comprises: at least four means for measuring electromagnetic energy, each arranged at a distance to each other in a plane;

[0013] - at least two means for measuring acoustic energy separated by a baseline distance; and processing means for processing signals from the means for measuring electromagnetic energy, and from the means for measuring acoustic energy; measuring, with the means for measuring electromagnetic energy, electromagnetic energy from the cable; calculating a heading of the cable based on input from the means for measuring electromagnetic energy; providing an electric pulse in an electrically conductive material of the cable, measuring said electric pulse with the means for measuring electromagnetic energy, and transmitting a corresponding signal to the processing means; detecting and identifying the electric pulse with the processing means;

[0014] - counting the time elapsed from the detection of said electric pulse; measuring, with each of the two means for measuring acoustic energy, an acoustic sound caused by the electric pulse forming an arc from the fault on the cable, and each transmitting a corresponding signal to the processing means;

[0015] - detecting and identifying the acoustic sound;

[0016] - calculating the distance to the fault on the cable by using the elapsed time difference between detection of the electric pulse and detection of the acoustic sound; counting the time difference between detection of the acoustic sound in each of the two means for measuring acoustic energy; and calculating the distance and / or bearing to the fault on the cable by using the time difference between the two detections of the acoustic sound.

[0017]

[0010] Thus, by providing a method that detects the time difference between detection of an electric pulse, moving at the speed of light, and an acoustic sound, moving at the speed of sound, it is possible to pinpoint the location of a fault more accurately than the prior art solutions. The present invention thereby reduces the need to replace long lengths of cable due to uncertainty as to the precise location of a fault, and significantly reduces the time spent searching for the exact location of a fault. Thus, costs in repairing a cable can be reduced and the environmental footprint is improved due to less waste of replaced cable lengths.

[0018] [Oil] An electrically conductive cable may be any cable comprising a material that is capable of conducting an electric current, such as, but not limited to: power cables comprising conductors and communications cables. Power cables may typically comprise a copper or aluminium conductor, these elements may be considered the electrically conductive materials in such cables. Communications cables may typically comprise fibre optic cables surrounded by a sheath comprising an electrically conductive material such as stainless steel. In certain cables, the sheath may be designed with the intent of being electrically conductive in order to facilitate fault detection.

[0019]

[0012] A fault on an electrically conductive cable may comprise any of: a clean breakage of the cable, a partial breakage of the cable, and damage to the insulation or other internal components. Such faults may be detectable by monitoring changes in the transfer of electricity or signals in the cable.

[0020]

[0013] Preferably, the electric pulse may be measured as the cable arrangement moves along, adjacent or in the vicinity of the cable. The electric pulse may therefore be measure as it passes along the cable in the vicinity of the cable tracker arrangement. It will be understood in the context of the invention that cable tracker arrangements may also be placed at a distance to the cable, depending on the sensitivity and configuration of the means for measuring electromagnetic energy.

[0021]

[0014] The electric pulse may be provided at a first end of the cable. Wherein the first end of the cable may be defined as the length of cable starting from the fault on the cable and extending in the direction where the cable tracker arrangement is moving toward an estimated location of a fault on the cable.

[0022]

[0015] In other embodiments, the electric pulse may be provided at a second end of the cable. A second end of the cable may be defined as the length of cable starting from the fault on the cable and extending in the opposite direction to where the cable tracker arrangement is moving toward an estimated location of a fault on the cable. Preferably for these embodiments, the cable may be at least partially intact thereby allowing the pulse to extend past the fault and thereby past the cable tracker arrangement.

[0023]

[0016] The electric pulse may be provided at a land-based end-station of a cable. The end-station may be provided with means for generating a pulse, or such means may be provided to the end-station. In other embodiments, the electric pulse may be provided at any point of the cable, where pulse generating means are configured to conductively provide electric energy to the cable. Preferably, any pulse generating means that is conductively connected to the cable may be performed on land.

[0024]

[0017] The electric pulse may be provided inductively. Typically for these embodiments, an electromagnetic coil is provided in the vicinity of the cable and current is induced. Such embodiments may typically be advantageous when used for submarine cables and / or in cases where there may be multiple faults on a cable, where conductive connections may be harder to facilitate.

[0025]

[0018] The intensity of the electric pulse may be dependent on the type of fault in the cable, and the type of electrically conductive material through which the pulse is to be passed. In embodiments where there is a partial breakage, or inner damage to the cable, it may be necessary to create a pulse strong enough to burn through the isolation of the cable. For cables having a full breakage, or a breakage with electrically conductive material exposed from the insulation of the cable, a somewhat weaker pulse may be sufficient to create the necessary arc and acoustic sound at the fault.

[0026]

[0019] The processing means may comprise a processing unit, or an arrangement of processing units. The processing means may comprise a sensor processor configured to process raw data signals from the means for measuring electromagnetic energy, and from the means for measuring acoustic energy.

[0020] Preferably, the sensor processor may be arranged in proximity to the means for measuring electromagnetic energy, and from the means for measuring acoustic energy. The sensor processor may be arranged as part of said single towed or propelled unit and may be signally connected to processing means arranged externally to said single unit. Such embodiments may be advantageous where the signals from the sensors are exposed to noise from the environment or from other components on the cable tracker arrangement, and thus shorter cable lengths from the sensors are beneficial.

[0027]

[0021] The processing means may comprise a computing unit configured for processing, analysis, detection, identification and / or calculation of data received from a sensor processor. The computing unit may be arranged on the single towed or propelled unit,. Advantageously, such embodiments may allow for lower bandwidth connections to be utilised as computations are performed on the single towed or propelled unit.

[0028]

[0022] In other embodiments, the computing unit may be arranged externally to said single unit. For example, a propelled or towed unit may be tethered to a floating vessel such that a sensor processing unit may be arranged on the single propelled or towed unit forming the cable tracker arrangement, and may be signally connected via a tether to a computing unit arranged on a floating vessel. In certain embodiments, an acoustic link may be employed instead of, or in addition to, a physical tether.

[0029]

[0023] The processing means may additionally comprise electronics for controlling and steering motion of the cable tracker arrangement. These electronics may include steering and propulsion control.

[0030]

[0024] In certain embodiments, at least one of the following steps of:

[0031] - detecting and identifying the electric pulse;

[0032] - counting the time elapsed from the detection of said electric pulse;

[0033] - detecting and identifying the acoustic sound; and calculating the distance to the fault on the cable by using the elapsed time difference between detection of the electric pulse and detection of the acoustic sound, may be performed in the processing means. Preferably, for embodiments comprising a computing unit, these steps may be performed in the computing unit. Any steps not performed in the processing means may be performed manually by a human. In other embodiments, at least one of the aforementioned steps may be performed manually, and the remainder may be performed in the processing means.

[0034]

[0025] For embodiments where at least one step is performed manually by a human, a human machine interface may be provided. The human machine interface may typically be provided on a floating vessel, where the human machine interface may be signally connected to the cable tracking arrangement and the processing means. Thus, the human machine interface may provide means for displaying signals from the cable tracker arrangement allowing an operator to perform any of the aforementioned steps.

[0035]

[0026] The elapsed time difference from the detection of the electric pulse, to the detection of the acoustic sound and thus the calculation of the distance may be dependent on the medium of travel of the acoustic sound. For example, the speed of sound differs from air to water. Furthermore, the speed of sound is dependent on temperature, pressure and salinity. Thus, the calculation of distance may be dependent on these factors.

[0036]

[0027] In embodiments of the invention, the electrically conductive cable may be a submarine cable. The submarine cable may be any of: a submarine communications cable and a submarine power cable. A submarine communications cable may typically comprise a fibre optic cable. A submarine power cable may typically comprise a High Voltage Direct Current cable. Alternatively, the submarine power cable may comprise an Alternating Current cable.

[0037]

[0028] In embodiments of the invention, the cable tracker arrangement may be provided on a floating or submerged vessel. A floating vessel may typically comprise a manned ship or boat. Floating vessels may also comprise unmanned surface vehicles (USV), such as drones operating either autonomously and / or remotely piloted on the surface of the water. Submerged vessels may include Remotely Operated Vehicles (ROV), that may typically be tethered with a communications and power cable to a floating vessel on the surface of the water. Other submerged vessels may include Autonomous Underwater Vehicles (AUV), that in contrast to ROVs may typically not comprise any physical connection to a unit above the surface of the water. Untethered AUV's may comprise means for transmitting information acoustically to floating units. However, certain AUV's may comprise a tether for transmitting information to buoys or floating unit that are towed by the AUV.

[0038]

[0029] In embodiments of the invention, the method may include the steps of: moving the cable tracker arrangement along the cable in a direction of the fault; providing an electric current in an electrically conductive material of the cable; measuring, with the means for measuring electromagnetic energy, a change in electric current in the cable along a length of the cable, and transmitting a corresponding signal to the processing means; detecting said change in the electric current and thereby identifying the location of the fault.

[0039]

[0030] An electric pulse may be defined as a brief, transient flow of electrical energy. It may be characterized by its short duration and may be a sudden burst or spike of electrical activity. In contrast an electric current may be a continuous flow of charged particles through a conductor.

[0040]

[0031] In the context of the invention the cable tracker arrangement being arranged on a single propelled or towed unit may be understood as at least the means for measuring electromagnetic energy, means for measuring acoustic energy and the part of the processing means comprising a sensor processor, may all be arranged on a single rigid unit such as an ROV, AUV, floating vessel or similar. A single rigid unit contrasts to units connected by tethers or towing lines. Preferably also a computing unit may be arranged on the single propelled or towed unit.

[0041]

[0032] In embodiments of the invention, the means for measuring electromagnetic energy may comprise at least one magnetometer. Preferably, the magnetometer may be a vector magnetometer configured to measure the X-Y-Z components of a magnetic field. Thus, it may be possible to accurately measure the depth and position of a cable.

[0033] In embodiments of the invention, the means for measuring acoustic energy may comprise at least one of: a microphone or a hydrophone. Typically, for embodiments where a fault is being located on a submarine cable, a hydrophone may be preferable, wherein the hydrophone may be provided in the same body of water as the submarine cable.

[0042]

[0034] At least one of these aforementioned steps may be performed in the processing means.

[0043]

[0035] The baseline distance may be defined as the distance between the active sensing elements, i.e. each of the means for measuring acoustic energy.

[0044]

[0036] According to a second aspect, the present invention relates to a cable tracker arrangement for locating a fault on an electrically conductive cable, wherein the arrangement is provided on a single propelled or towed unit and comprises: at least four means for measuring electromagnetic energy; means for measuring acoustic energy each arranged at a distance to the other in a plane, and processing means, signally connected to the means for measuring electromagnetic energy and the means for measuring acoustic energy, wherein the processing means are configured for: processing signals from the means for measuring electromagnetic energy and the means for measuring acoustic energy;

[0045] - detecting and identifying an electric pulse and an acoustic sound from said signals;

[0046] - calculating a distance to a fault on an electrically conductive cable by counting the elapsed time between a pulse in the cable and an acoustic sound discharged from the fault on the cable which is caused by the electric pulse forming an arc from the fault on the cable; counting the time difference between detection of the acoustic sound in each of the two means for measuring acoustic energy;

[0047] - calculating the distance and / or bearing to the fault on the cable by using the time difference between the two detections of the acoustic sound; and, calculating a heading of the cable based on input from the means for measuring electromagnetic energy.

[0048]

[0037] Any of the aforementioned embodiments of the first aspect may be equally applied to the second aspect.

[0049]

[0038] In embodiments of the invention:

[0050] - the means for measuring electromagnetic energy;

[0051] - the means for measuring acoustic energy; and

[0052] - the processing means, may be configured for underwater use.

[0053]

[0039] In certain alternative embodiments, the processing means, or parts of the processing means, preferably the sensor processor may be configured for underwater use. Other components of the processing means, such as the computing unit, may be arranged external to the cable tracker arrangement and may not be required to be configured for underwater use.

[0054]

[0040] According to a third aspect, the present invention relates a system for locating a fault in a submarine electrically conductive cable, comprising: an arrangement according to any of the aforementioned aspects or embodiments, wherein the arrangement is provided on a submerged or floating vessel.

[0055]

[0041] In embodiments of the invention, the vessel may be any of: a remotely operated vehicle (ROV), a ship, a towed vessel, an unmanned surface vehicle (USV) and an autonomous underwater vehicle (AUV).

[0056]

[0042] In the following description, numerous specific details are introduced by way of example only to provide a thorough understanding of embodiments of the claimed method, arrangement and system. One skilled in the relevant art, however, will recognize that these embodiments can be practiced without one or more of the specific details, or with other components, arrangements, methods, systems, etc. In other instances, well-known structures or operations are not shown, or are not described in detail, to avoid obscuring aspects of the disclosed embodiments. Brief Description of the Figures

[0057]

[0043] The following drawings are appended to facilitate the understanding of the invention. The drawings show embodiments of the invention, which will now be described by way of example only, where:

[0058]

[0044] Fig. 1 is a schematic illustration of the method, arrangement and system in use on an AUV.

[0059]

[0045] Fig. 2 is a schematic illustration of the method, arrangement and system in use on a tethered ROV.

[0060]

[0046] Fig. 3 is a flow diagram illustrating the steps of the method.

[0061] Detailed Description of the Figures

[0062]

[0047] In the following, general embodiments as well as particular exemplary embodiments of the invention will be described. References will be made to the accompanying drawings. It shall be noted, however, that the drawings are exemplary embodiments only, and that other features and embodiments may well be within the scope of the invention as claimed. Further, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality.

[0063]

[0048] Unless otherwise defined, all terms of art, notations and other scientific terms or terminology used herein are intended to have the meanings commonly understood by those of skill in the art to which this invention pertains. Certain terms of art, notations, and other scientific terms or terminology may, however, be defined specifically as indicated below.

[0064]

[0049] Fig. 1 illustrates the invention according to an embodiment where the cable tracker arrangement 10 is provided on a submerged AUV travelling through a body of water 4, thus forming a system 100 for locating a fault on a submarine electrically conductive cable 1. The submarine cable 1 has been buried in the seabed 5 and the AUV is shown travelling in a direction C at a height B above and along the cable 1. The AUV is exemplified as a single self-propelled unit 100 comprising a cable tracker arrangement 10.

[0050] The cable tracker arrangement 10 is illustrated as comprising a means for measuring magnetic energy 11, and a means for measuring acoustic energy 12 placed on rods 9 extending out from the body 7 of the AUV. Furthermore, processing means 13 are exemplified as being arranged in the AUV body 7.

[0065]

[0051] In the submarine cable 1 a dashed line 23 is provided in order to represent an electric pulse 23 being provided at a first end la of the cable 1. The dashed line 23 extends to a location of a fault 2 on the cable 1, where an arc 25 is formed from the cable 1 and into the surrounding environment. The second end lb of the cable 1 is shown as not having an electric pulse 23, and the fault 2 on the cable 1 in Fig.

[0066] 1 may thus be considered an example of a full breakage of the conductor thereby causing electricity to be led out from the cable 1.

[0067]

[0052] At the fault point 2 on the cable in Fig. 1, curved lines 22 are shown emanating from the fault 2 and the arc 25 caused by the electric pulse 23 exiting the cable 1. These curved lines 22 represent acoustic waves 22 moving through the seabed 5 and the body of water 4. The acoustic waves 22 stem from the loud and distinct noise created by the arc 25 at the fault 2. As will be understood, the acoustic waves 22 will travel through the body of water 4 towards the AUV at the speed of sound.

[0068]

[0053] Another set of elliptical lines 21 are seen encircling the submarine cable 1 in Fig. 1 at a point below the AUV. These elliptical lines 21 represent electromagnetic radiation 21 emanating from the cable 1 as the pulse 23 passes through said cable 1. The means 11 for measuring electromagnetic energy 21 can therefore pick up the electromagnetic energy 21 in the cable 1 caused by the pulse 23 passing below the AUV.

[0069]

[0054] Thus, for the exemplary fault 2 in Fig. 1, the AUV is configured to measure an electric pulse 23 being provided at a first end la of the submarine cable 1. Once said pulse 23 has passed the AUV, a signal is sent to the processing means 13 which identifies the pulse 23 and starts counting the time that passes from after the pulse 23 has passed. The pulse 23 passes the location of the AUV with the speed of light to the fault 2 where it creates an arc 25 and a loud acoustic sound. 22. The acoustic sound 22 propagates through the body of water 4 and is picked up by the acoustic measuring means 12 on the AUV. A signal is thus sent from the acoustic measuring 12 means to the processing means 13, where the acoustic sound 22 is identified as being caused by the arc 25. The elapsed time difference D from registration of the electric pulse 23 and the acoustic sound 24 is recorded, and this is used to calculate the distance L to the fault 2.

[0070]

[0055] The calculation of the distance L to the fault 2 will include parameters such as: the pressure, temperature and salinity of the water; the placement of the various means 11 for measuring electromagnetic energy 21 and means 12 for measuring acoustic energy 22 on the AUV; and any other parameters that the skilled person will understand are relevant in the context of the invention.

[0071]

[0056] The system 100 illustrated in Fig. 1 is furthermore capable of moving along the cable 1 and continuously measuring electromagnetic energy 21. Thus, once an approximate point of a fault 2 has been calculated, an electric current may be continuously provided to the cable 1. The means 11 for measuring electromagnetic energy 21 can measure the electromagnetic energy 21 from the electric current in the cable 1 as the AUV moves along the cable 1. At the point of a fault 2, a change in the electromagnetic energy 21 will be noticeable and the processing means 13 is configured to detect that the change is caused by a fault 2 on the cable 1. Thus, the position of a fault 2 may be verified by these additional steps.

[0072]

[0057] Although not explicitly illustrated in the Figures, the skilled person will understand in the context of the invention that the embodiment of Fig. 1, and in particular the configuration of the AUV and cable tracker arrangement 10 may vary. For example, the system 100 may be tethered to a floating vessel operating on the surface of the body of water 4 thus forming an ROV. Furthermore, the skilled person will understand that the exemplary embodiment of Fig. 1 may be applied to flying drones or cable tracker arrangements 10 arranged above or on a body of water or land.

[0073]

[0058] Turning to Fig. 2, another embodiment is illustrated where a cable tracker arrangement 10 is provided on a ROV. The ROV is shown in a perspective view moving in a body of water 4 in a direction C along a submarine cable 1 buried in the seabed 5. The submarine cable 1 is exemplified as a high-voltage electrically conductive cable 1. A tether 6 connects the ROV to a floating vessel, arranged on the surface of the body of water 4 and thus not shown in the figure. The ROV may be self-propelled and thus the tether 6 may provide electric and / or hydraulic energy and a communications link between the floating vessel and the ROV. However, the skilled person will understand in the context of the invention that the exemplary embodiment in Fig. 2 could be amended to not include a tether 6 and instead function as an AUV with the requisite amendments.

[0074]

[0059] The ROV is furthermore exemplified in Fig. 2 as comprising a main body 7 and a frame 8 arranged below the main body 7. The frame 8 is exemplified as a truss structure 8 comprising several outlying sensor rods 9. At the distal end of each rod 9, various sensors 11,12 are provided. At the back-end of the ROV, two rods 9 are illustrated extending orthogonally to the travelling direction C and each rod 9 in opposing directions. At the end of each of these two back-end rods 9 a means 11 for measuring electromagnetic energy 21 is exemplified as a magnetometer 11.

[0075]

[0060] At the forward-end of the ROV, two rods 9 are arranged extending parallel to the travelling direction C. At the end of each of these two forward-end rods 9 a magnetometer 11 is provided. Furthermore, each of the forward-end rods 9 has a hydrophone 12 collocated with the magnetometer 11 at the distal end of the rod 9. Thus, each magnetometer 11 and each hydrophone 12 is separated by the other sensors 11,12 of the same category by a baseline distance. The baseline distance is exemplified as varying between the back and front rods 9 in Fig. 1. As the skilled person will understand, the example in Fig. 1 of collocating hydrophones 12 and magnetometer 11 may be preferable, but variations are envisaged within the scope of the invention where the hydrophones 12 and magnetometers 11 have different locations or are placed on different rods 9.

[0076]

[0061] Similar to Fig. 1, the exemplary embodiment in Fig. 2 illustrates that in the submarine cable 1 a dashed line 23 is provided in order to represent an electric pulse 23 being provided at a first end la of the cable 1. The dashed line 23 extends to a location of a fault 2 on the cable 1, where an arc 25 is formed from the cable 1 and into the surrounding environment. The second end lb of the cable is shown as not having an electric pulse 23, and the fault 2 on the cable in Fig. 2 may thus also be considered an example of a full breakage of the conductor thereby causing electricity to be led out from the cable 1.

[0077]

[0062] At the fault 2 point on the cable in Fig. 1, curved lines 22 are shown emanating from the fault 2 and the arc 25 caused by the electric pulse 23 exiting the cable 1. These curved lines 22 represent acoustic waves 22 moving through the seabed 5 and the body of water 4. The acoustic waves 22 stem from the loud and distinct noise created by the arc 25 at the fault 2. The acoustic waves are shown travelling through the body of water 4 towards and passing the AUV at the speed of sound.

[0078]

[0063] As will be seen in Fig. 2, the frontmost curved line 22 heading in the direction of the ROV is illustrated as passing a first hydrophone 12a on one side of the ROV, at a time interval A before it passes the second hydrophone 12b on the opposing side of the ROV. The time interval A in the passing of the acoustic sound 22 past the first 12a and second hydrophone 12b can be used to calculate the distance to the fault L by the use of trigonometry, as will be apparent to the skilled person in the context of the invention. Thus, these steps may be used to provide additional verification of the distance to a fault 2 on the cable 1.

[0079]

[0064] At each magnetometer Il a dotted line 21 is illustrated in Fig. 2, the dotted line 21 extends to the dashed line 23 representing the pulse 23 in the cable 1. The dotted line 21 represents the electromagnetic energy 21 emanating from the cable 1. Each magnetometer 11 is configured to measure this strength and variation in the electromagnetic energy 21. Thus, by employing four magnetometers 11 as exemplified in Fig. 2 it is possible to use the measurements from each sensor 9 to triangulate distance L to the cable 1 and heading of the cable 1.

[0080]

[0065] Although not illustrated in Fig. 2, the ROV may typically be provided with a processing means 13 comprising at least one sensor processor and a computing unit. Each of the hydrophones 12 and magnetometers 11 may be signally connected to an individual sensor processor, or they may share connections to one or more sensor processors. The sensor processors are signally connected to a computing unit, which in the exemplary embodiment of Fig. 2, and Fig. 1, may be on board the AUV / ROV. Thus, the need for a high bandwidth connection to a floating vessel above sea level may not be necessary.

[0081]

[0066] As explained in relation to the embodiment of Fig. 1, the ROV in Fig. 2 may also be used to continuously measure electromagnetic energy 21 emanating from a continuous electric current provided to the cable 1 and thereby verifying the position of a fault 2.

[0082]

[0067] Turning to Fig. 3, a flow diagram is illustrated to represent the various steps of the method according to the invention. These steps have been described in relation to the embodiments of Fig. 1 and Fig. 2. In relation to Fig. 3, an embodiment of a method will be explained which pertains to the embodiments of Fig. 1 and Fig. 2.

[0083]

[0068] The first step in Fig. 3 relates to the provision of a cable tracker arrangement 10. The embodiments in Fig. 1 and Fig. 2 exemplified this as an AUV and an ROV, respectively. It will however be understood that other variations and embodiments are possible, such as the provision of flying, floating or land-based vessels comprising a cable tracker arrangement 10.

[0084]

[0069] The second step in Fig. 3 relates to the measurement of electromagnetic energy 21 from the cable 1. The cable tracker arrangement 10 typically starts measuring before an electric pulse 23 is provided in the third step.

[0085]

[0070] The fourth step of detecting an electric pulse 23 may typically occur in the processing means 13. Thus, the cable tracker arrangement 10 has transmitted measurements from the means 11 for measuring electromagnetic energy 21, and the processing means 13 is configured to detect the electric pulse 23 based on these transmitted measurements and predetermined parameters.

[0086]

[0071] Once an electric pulse 23 has been detected by the processing means 13, the fifth step of counting the time elapsed from detection commences.

[0087] Simultaneously as, or before, the detection of the electric pulse 23, the measurement of acoustic sound 22 commences. Thus, the counting continues until the acoustic sound 22 is detected in the sixth step. At which point, the elapsed time D difference is recorded and processed in the seventh step.

[0088]

[0072] The seventh step of processing the elapsed time difference D includes using parameters such as the location and orientation of the various means 11,12 for measuring electromagnetic 21 and acoustic energy 22 in relation to each other, environmental factors related to the body of water 4 and pre-determined values relating to these environmental factors such as the speed of sound in water at a given salinity, temperature and pressure.

[0089]

[0073] In the preceding description, various aspects of the method, arrangement and system according to the invention have been described with reference to the illustrative embodiments. For purposes of explanation, specific numbers, systems and configurations were set forth in order to provide a thorough understanding of the method, arrangement, system and their workings. However, this description is not intended to be construed in a limiting sense. Various modifications and variations of the illustrative embodiment, as well as other embodiments of the method, arrangement and system, which are apparent to persons skilled in the art to which the disclosed subject matter pertains, are deemed to lie within the scope of the present invention.

[0090] Clauses

[0091] 1. A method for locating a fault (2) on an electrically conductive cable (1), wherein the method comprises the steps of: providing a cable tracker arrangement (10) along the cable (1), where the cable tracker arrangement (10) comprises: means (11) for measuring electromagnetic energy (21); means (12) for measuring acoustic energy (22); and processing means (13) for processing signals from the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22); measuring, with the means (11) for measuring electromagnetic energy (21), electromagnetic energy (21) from the cable (1); providing an electric pulse (23) in an electrically conductive material of the cable (1), measuring said electric pulse (23) with the means (11) for measuring electromagnetic energy (21), and transmitting a corresponding signal to the processing means (13);

[0092] - detecting and identifying the electric pulse (23);

[0093] - counting the time elapsed from the detection of said electric pulse (23); measuring, with the means (12) for measuring acoustic energy (22), an acoustic sound (24) caused by the electric pulse (23) forming an arc (25) from the fault (2) on the cable (1), and transmitting a corresponding signal to the processing means (13);

[0094] - detecting and identifying the acoustic sound (24); and

[0095] - calculating the distance (L) to the fault (2) on the cable (1) by using the elapsed time difference (D) between detection of the electric pulse (23) and detection of the acoustic sound (24). The method according to claim 1, wherein the electrically conductive cable (1) is a submarine cable (1). The method according to claim 2, wherein the cable tracker arrangement

[0096] (10) is provided on a floating or submerged vessel (3). The method according to any of the preceding claims, wherein the method includes the steps of: moving the cable tracker arrangement (10) along the cable in a direction of the fault (2); providing an electric current in an electrically conductive material of the cable (1); measuring, with the means (11) for measuring electromagnetic energy (21), a change in electric current in the cable (1) along a length of the cable, and transmitting a corresponding signal to the processing means (13); detecting said change in the electric current and thereby identifying the location of the fault (2). The method according to any of the preceding claims, wherein the cable tracker arrangement (10) is arranged on a single propelled or towed unit (3). The method according to any of the preceding claims, wherein the means

[0097] (11) for measuring electromagnetic energy (21) comprises at least one magnetometer. The method according to any of the preceding claims, wherein the means

[0098] (12) for measuring acoustic energy (22) comprises at least one of: a microphone or a hydrophone. The method according to any of the preceding claims, wherein the cable tracking arrangement (10) comprises two means (12) for measuring acoustic energy (22) separated by a baseline distance, wherein the method includes:

[0099] - measuring, with each of the two means (12) for measuring acoustic energy (22), the acoustic sound (24) caused by the electric pulse (23), and each transmitting corresponding signals to the processing means (13); - detecting and identifying the acoustic sound (24);

[0100] - counting the elapsed time difference (A) between detection of the acoustic sound in each of the two means (12) for measuring acoustic energy (22),

[0101] - calculating the distance (L) and / or bearing to the fault (2) on the cable (1) by using the elapsed time difference (A) between the two detections of the acoustic sound (24). A cable tracker arrangement (10) for locating a fault (2) on an electrically conductive cable (1), wherein the arrangement (10) comprises: means (11) for measuring electromagnetic energy (21); means (12) for measuring acoustic energy (22), and processing means (13), signally connected to the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22), wherein the processing means are configured for: processing signals from the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22),

[0102] - detecting and identifying an electric pulse (23) and an acoustic sound (24) from said signals,

[0103] - calculating a distance (L) to a fault (2) on an electrically conductive cable (1) by counting the elapsed time (D) between a pulse (23) in the cable (1) and an acoustic sound (24) discharged from the fault (2) on the cable (1) which is caused by the electric pulse (23) forming an arc (25) from the fault (2) on the cable (1). The cable tracker arrangement (10) according to claim 9, wherein the arrangement (10) is provided on a single propelled or towed unit (3). The cable tracker arrangement (10) according to any of claims 9-10, comprising at least two means (11) for measuring electromagnetic energy (21), each arranged at a distance (A) to the other, and wherein the processing means (13) is configured to calculate a distance (B) of the arrangement (10) to a cable (1) from input of the means (11) for measuring electromagnetic energy (21). The cable tracker arrangement according to claim 11, comprising at least three means (11) for measuring electromagnetic energy (21), each arranged at distance (A) to each other in a plane, and wherein the processing means (13) is configured to calculate a position of the cable (1) based on input from the means (11) for measuring electromagnetic energy (21). The cable tracker arrangement (10) according to any of claims 9-12, wherein:

[0104] - the means (11) for measuring electromagnetic energy (21);

[0105] - the means (12) for measuring acoustic energy (22); and

[0106] - the processing means (13), are all configured for underwater use. The cable tracker arrangement (10) according to any of claims 9-13, wherein arrangement (10) comprises two means (12) for measuring acoustic energy (22) separated by a baseline distance. A system (100) for locating a fault in a submarine electrically conductive cable (1), comprising: an arrangement (10) according to any of claims 9-14, wherein the arrangement (10) is provided on a submerged or floating vessel (3). The system according to claim 15, wherein the vessel (3) is any of: a remotely operated vehicle (ROV), a ship, a towed vessel, an unmanned surface vehicle (USV) and an autonomous underwater vehicle (AUV).

[0107] List of Reference Numbers

Claims

Claims1. A method for locating a fault (2) on an electrically conductive cable (1), wherein the method comprises the steps of: providing a cable tracker arrangement (10) arranged on a single propelled or towed unit (3), along the cable (1), where the cable tracker arrangement (10) comprises: at least four means (11) for measuring electromagnetic energy (21), each arranged at a distance to each other in a plane;- at least two means (12) for measuring acoustic energy (22) separated by a baseline distance; and processing means (13) for processing signals from the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22); measuring, with the means (11) for measuring electromagnetic energy (21), electromagnetic energy (21) from the cable (1); calculating a heading of the cable (1) based on input from the means (11) for measuring electromagnetic energy (21); providing an electric pulse (23) in an electrically conductive material of the cable (1); measuring said electric pulse (23) with the means (11) for measuring electromagnetic energy (21), and transmitting a corresponding signal to the processing means (13);- detecting and identifying the electric pulse (23);- counting the time (D) elapsed from the detection of said electric pulse (23); measuring, with each of the two means (12) for measuring acoustic energy (22), an acoustic sound (24) caused by the electric pulse (23) forming an arc (25) from the fault (2) on the cable (1), and each transmitting a corresponding signal to the processing means (13);- detecting and identifying the acoustic sound (24);- calculating the distance (L) to the fault (2) on the cable (1) by using the time elapsed (D) between detection of the electric pulse (23) and detection of the acoustic sound (24)- counting the time difference (A) between detection of the acoustic sound in each of the two means (12) for measuring acoustic energy (22); andcalculating the distance (L) and / or bearing to the fault (2) on the cable (1) by using the elapsed time difference between the two detections of the acoustic sound (24).

2. The method according to claim 1, wherein the electrically conductive cable(I) is a submarine cable (1).

3. The method according to claim 2, wherein the cable tracker arrangement(10) is provided on a floating or submerged vessel (3).

4. The method according to any of the preceding claims, wherein the method includes the steps of: moving the cable tracker arrangement (10) along the cable in a direction of the fault (2); providing an electric current in an electrically conductive material of the cable (1); measuring, with the means (11) for measuring electromagnetic energy (21), a change in electric current in the cable (1) along a length of the cable, and transmitting a corresponding signal to the processing means (13); detecting said change in the electric current and thereby identifying the location of the fault (2).

5. The method according to any of the preceding claims, wherein the means(II) for measuring electromagnetic energy (21) comprises at least one magnetometer.

6. The method according to any of the preceding claims, wherein the means(12) for measuring acoustic energy (22) comprises at least one of: a microphone or a hydrophone.

7. A cable tracker arrangement (10) for locating a fault (2) on an electrically conductive cable (1), wherein the arrangement (10) is provided on a single propelled or towed unit and comprises: at least four means (11) for measuring electromagnetic energy (21) each arranged at a distance (A) to the other in a plane;- two means (12) for measuring acoustic energy (22) separated by a baseline distance, andprocessing means (13), signally connected to the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22), wherein the processing means are configured for: processing signals from the means (11) for measuring electromagnetic energy (21) and the means (12) for measuring acoustic energy (22),- detecting and identifying an electric pulse (23) and an acoustic sound (24) from said signals,- calculating a distance (L) to a fault (2) on an electrically conductive cable (1) by counting the elapsed time (D) between a pulse (23) in the cable (1) and an acoustic sound (24) discharged from the fault (2) on the cable (1) which is caused by the electric pulse (23) forming an arc (25) from the fault (2) on the cable (1), counting the time difference (A) between detection of the acoustic sound in each of the two means (12) for measuring acoustic energy (22);- calculating the distance (L) and / or bearing to the fault (2) on the cable (1) by using the time difference between the two detections of the acoustic sound (24); and,- calculating a heading of the cable (1) based on input from the means (11) for measuring electromagnetic energy (21).

8. The cable tracker arrangement (10) according to claim 7, wherein:- the means (11) for measuring electromagnetic energy (21);- the means (12) for measuring acoustic energy (22); and- the processing means (13), are all configured for underwater use.

9. A system (100) for locating a fault in a submarine electrically conductive cable (1), comprising: an arrangement (10) according to any of claims 7 or 8, wherein the arrangement (10) is provided on a submerged or floating vessel (3).

10. The system according to claim 9, wherein the vessel (3) is any of: a remotely operated vehicle (ROV), a ship, a towed vessel, an unmanned surface vehicle (USV) and an autonomous underwater vehicle (AUV).

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