1839 results about "Submarine cable" patented technology

The invention discloses a submarine cable risk dynamic assessment method and system based on multi-modal deep learning, and belongs to the field of marine infrastructure operation and maintenance. Aiming at the problems of incomplete data coverage, unreal generated scene, low evaluation reliability and the like in the prior art, the method comprises the following steps of: 1) constructing a multi-source heterogeneous data set containing six types of data including geology, ocean, ships, biology and the like, and realizing data alignment by adopting space-time grid coding; 2) designing a physical constraint generative adversarial network, and generating risk scene data conforming to a fluid mechanics law through a Navier-Stokes equation constraint; 3) creating a hierarchical space-time fusion network (HST-Transform), and combining CNN spatial feature extraction, a time sequence attention mechanism and a dynamic memory module to realize multi-modal fusion; according to the method, the detection rate of rare risk events is increased by 62%, the evaluation accuracy rate reaches 91.7%, the false alarm rate is reduced by 34% compared with a traditional method, and submarine cable breakage accidents can be effectively prevented.

The invention discloses a cable insulation life prediction method and system based on LSTM accelerated aging mapping, and relates to the technical field of submarine cable insulation life prediction. The existing method has the defects of insufficient multi-stress nonlinear modeling, laboratory and field data separation, difficulty in small sample modeling and the like, and the insulation life of the submarine cable is difficult to accurately predict. The method comprises the following steps: data acquisition: acquiring parameters of insulation electrical performance, physical and chemical performance and mechanical performance under an accelerated aging condition; carrying out data preprocessing: carrying out homodromous processing on the inverse indexes, improving box plot denoising, filling missing data with a space-time K nearest neighbor algorithm, and carrying out normalization; constructing an LSTM model: embedding a dielectric constant differential equation as a physical constraint, and introducing an index weight; and model training and evaluation: adopting five-fold cross validation, and quantizing prediction precision through mean square errors and decision coefficients. According to the technical scheme, the prediction precision is improved, the fault risk caused by insulation aging is reduced, the maintenance cost is reduced, and the reliability of the ocean energy transmission system is improved.

The invention discloses a submarine cable pipeline detection method based on underwater acousto-optic fusion, and relates to the related field of underwater detection.The method comprises the steps that underwater sonar image data and underwater optical image data are acquired through underwater sensor equipment; carrying out preprocessing extraction to obtain sonar rectangular image data and standard optical image data; performing feature extraction by using a parallel double-branch convolution-Transform network to obtain an acoustic mode embedded feature set and an optical mode embedded feature set; carrying out attention perception and weighted fusion to obtain acousto-optic multi-modal fusion level features; decoding is carried out through a multi-mode decoder structure, and acousto-optic fusion pixel-level features are obtained; and carrying out detection classification by using a detection regression head and a classification head to obtain a submarine cable pipeline detection result. The technical problem that existing submarine cable pipeline detection is insufficient in detection precision and robustness is solved, and the technical effects of improving the detection precision and enhancing the detection robustness are achieved.

The invention discloses a submarine cable fault online diagnosis and positioning method and system based on an optical fiber sensing technology, and relates to the technical field of optical fiber sensing, and the method comprises the steps: obtaining a real-time strain data flow of a submarine cable through a distributed optical fiber strain measurement device; carrying out space-time alignment and abnormal value correction processing on the original data set, and constructing a target data set; coordinate mapping is carried out on the target data set and a geographic information system of a submarine cable laying line, and a fault diagnosis layer with multi-dimensional visualization features is generated; an interactive fault analysis panel is generated on a geographic information system interface, and the deviation ratio between the strain theoretical threshold value and the actual measurement value of each monitoring point in the target data set is calculated; according to the submarine cable fault online diagnosis and positioning method and system based on the optical fiber sensing technology, rapid positioning of fault features is achieved, the fault response efficiency is improved, and long-term stable operation of a submarine communication network is ensured.

The invention discloses a submarine cable insulation multi-field aging prediction method and system, and relates to the technical field of material science and engineering. An existing model has the problems that parameter interaction effect analysis is insufficient, feature weight distribution is not scientific, a data standardization method is insufficient, and the capacity of capturing dynamic response and nonlinear aging behaviors is weak. The method comprises the steps of multi-physics field accelerated aging experiment design and data acquisition, key characteristic parameter screening through grey correlation analysis, support vector machine modeling and optimization, dynamic aging behavior evaluation and service life prediction and feedback adjustment. According to the technical scheme, aging behaviors are comprehensively captured through a multi-physics field cooperation experiment, key parameters are scientifically screened in combination with grey correlation analysis, a nonlinear relation is optimized through support vector machine modeling, long-term prediction precision is improved through dynamic feedback adjustment, and reliability is enhanced through quantitative life evaluation; the aging characteristics of the submarine cable insulating material in multiple physical fields are comprehensively and accurately reflected, and a scientific basis is provided for multi-dimensional evaluation of the aging performance of a high polymer material.

The invention provides a submarine cable with a large cross section and high heat dissipation performance. The submarine cable comprises an inner protection layer, a center assembly, a plurality of electric units, a plurality of power assemblies and a first heat dissipation assembly. An accommodating cavity is formed in the inner protective layer; the central component is positioned in the accommodating cavity; the plurality of electric units are located in the accommodating cavity, and the plurality of electric units are arranged around the central assembly; the multiple power assemblies are located in the containing cavity, the multiple power assemblies and the multiple electric units are correspondingly arranged, and the power assemblies are configured to enable the electric units to move towards or away from the inner protection layer; the first heat dissipation assembly is arranged around the periphery of the inner protection layer, and the first heat dissipation assembly is configured to dissipate heat of the electric units making contact with the inner protection layer through the inner protection layer.

The invention discloses an underwater robot submarine cable inspection method and system based on two-dimensional image sonar, and relates to the field of submarine cable inspection. The existing submarine cable inspection method has the problems of insufficient detection precision, lack of autonomy, dynamic obstacle avoidance defect and the like. The method comprises the steps of submarine cable feature recognition model construction, underwater robot sensing system configuration, image processing, path planning, obstacle avoidance path generation and detouring. According to the technical scheme, the underwater robot carries the electromagnetic induction sensor, the two-dimensional image sonar and the ultra-short baseline positioning device, and an image processing technology and a path planning algorithm are combined, so that efficient inspection of the submarine cable is realized; when the robot encounters an obstacle, the robot can generate an obstacle point cloud through image processing in combination with prior obstacle information, and performs obstacle avoidance in combination with a local path planning algorithm, so that safe and smooth proceeding of an inspection task is ensured; the detection precision is effectively improved, automatic and efficient inspection is realized, and a powerful guarantee is provided for long-term stable operation of the submarine cable.

The present application relates to the technical field of submarine cable simulation, and particularly relates to a vortex-induced vibration simulation method. The method comprises: on the basis of physical parameters and dimension parameters of a submarine cable and physical parameters of seawater, determining a three-dimensional finite element model, wherein the three-dimensional finite element model comprises a target fluid domain and a target solid domain; in a fluid module corresponding to the target fluid domain, configuring a first physical field boundary condition corresponding to the target fluid domain, and in a transient structure module corresponding to the target solid domain, configuring a second physical field boundary condition corresponding to the target solid domain; and on the basis of a target simulation control strategy, the first physical field boundary condition and the second physical field boundary condition, and by means of the fluid module, the transient structure module and a coupling module, performing simulation to obtain a vortex-induced vibration feature of the submarine cable, wherein the coupling module is used for connecting the fluid module to the transient structure module.

The invention discloses a submarine cable shape monitoring method based on an ultra-weak fiber bragg grating, which comprises the following steps of: obtaining curvatures # imgabs0 #, # imgabs1 # and # imgabs2 # in X-axis and Y-axis directions from curvatures in two orthogonal directions of curvatures calculated by three uniformly distributed optical fibers, representing angle offset from an ith sensing unit to an X-axis positive direction, and obtaining a bending curvature, an arc angle and a direction angle; and coordinate information in the space is further obtained by combining rotation and translation matrix iterative calculation of a shape reconstruction algorithm, namely, three-dimensional space coordinates of the measured curve can be determined point by point, and finally, complete shape reconstruction and other steps are realized. According to the invention, high-precision large-scale three-dimensional deformation monitoring can be realized. By optimizing the eccentric distance and the strain transmission efficiency of the optical fiber, the tiny deformation of the submarine cable is accurately captured, and by combining an innovative three-dimensional curve reconstruction algorithm, the bending, inclination and other deformation states of the cable can be accurately reflected in different environments. Therefore, the method has obvious advantages in a monitoring task with a high-precision requirement, especially in a complex marine environment.

The invention discloses a submarine cable detection method and device and a nonvolatile storage medium. The method comprises the following steps: acquiring the position of a fault point under the condition that a submarine cable is detected to have a fault; determining a first target search range corresponding to the position of the fault point based on the fault positioning response time, the submarine cable routing information processing time and the ocean current speed; determining a fault probability of each routing section of the submarine cable in the first target search range based on the submarine cable depth data, the water depth data and the environment data in the first target search range; and sorting the fault probabilities of the routing segments to obtain a routing segment sequence, and scheduling the patrol ship to perform fault detection based on the routing segment sequence. According to the method and the device, the technical problems of low response speed and low processing efficiency caused by inaccurate positioning and large range of the fault range propagated by the fault point when the submarine cable is identified to have a fault when the submarine cable is monitored in the related technology are solved.

The invention relates to the technical field of submarine engineering and information processing, in particular to a submarine cable positioning method and system, and the method comprises the steps: synchronously collecting magnetic field, structured light and underwater acoustic signal data, and fusing inertial navigation information to construct a unified space-time reference system; precise registration of heterogeneous data is realized by adopting sliding time window screening, multi-modal noise reduction and rigid body transformation; constructing a graph structure model for expressing cable space-signal features based on the fused data, and reasoning cable path topology by using a graph convolutional network; reconstructing a cable center line through three-dimensional visualization, embedding the cable center line into submarine topography, and realizing risk area dynamic clustering by combining signal integrity score and burial depth estimation; historical time sequence data are fused, a long short-term memory network is adopted to predict cable drift, detectable attenuation and burial depth change trends, risk levels are divided based on prediction results, and spatial distribution early warning and disposal suggestions are output. According to the invention, the cable positioning precision and the risk assessment intelligent level in a complex seabed environment are improved.

The invention discloses a submarine cable detection method and device based on quantum magnetometers, the device comprises a multi-frequency signal generating device and a quantum magnetic field sensing device, and the quantum magnetic field sensing device comprises a first quantum magnetometer, a second quantum magnetometer and a signal processing module; according to the method, two quantum magnetometers which are horizontally installed are used for detecting the ratio of amplitude values of alternating magnetic fields generated by two equal-amplitude alternating currents with different frequencies in a submarine cable, and the distance relation between the two quantum magnetometers and the submarine cable is judged by comparing the ratio values detected by the two quantum magnetometers. And when the ratios detected by the two quantum magnetometers are equal, the position of the motion platform is the position of the submarine cable. The quantum magnetometer is used as a core sensor, so that the influence of posture change of the motion platform on detection data jitter is reduced, and the detection precision is improved; and a multi-frequency signal detection mode is adopted, so that the difficulty of extracting the characteristic magnetic field signal generated by the submarine cable to be detected from the total magnetic field is reduced.

The invention provides a submarine cable bending limiting structure with a damage early warning device, and particularly relates to the technical field of ocean engineering. The structure wraps the outer surface of a submarine cable to be protected and comprises a plurality of unit limiters which are sequentially connected end to end. Each unit limiter is formed by splicing two limiting single bodies which are internally provided with cable through holes and are symmetrical about the central axis; each limiting single body comprises a female head part, a male head part and a neck locking part; the female head part and the male head part are positioned at two ends of the neck locking part; the outer surface of the female head part is of a semicircular convex surface structure; a semicircular concave surface structure is arranged on the inner surface of the male head part, the concave surface structure of the male head part wraps the convex surface structure of the adjacent female head part, and a gap exists between the concave surface structure and the convex surface structure, so that the female head part can rotate in the male head part; the neck locking part of each limiting single body is provided with an injury early warning device. The submarine cable damage early warning device is compact in structure and convenient to install, the position of the damage limiter can be found in time through the damage early warning device, and possible damage risks of the submarine cable can be found in time.

The invention relates to the technical field of submarine cable fault positioning, in particular to a submarine cable fault positioning system based on underwater beacons. The method comprises the steps that an underwater acoustic beacon array unit monitors and collects submarine cable fault sound wave signals in real time based on underwater acoustic beacons; the fault signal processing analysis unit extracts submarine cable fault sound wave signal parameters based on a non-point source space sound source waveform analysis model, and generates multi-parameter fault sound source feature vectors; the sound source positioning analysis algorithm unit performs three-dimensional inversion positioning based on the multi-parameter fault sound source feature vector and the arrival time difference of the submarine cable fault sound wave signal to the underwater acoustic beacon, and obtains the spatial position information of the submarine cable fault point; and the data communication alarm management unit sends the spatial position information of the submarine cable fault point to a shore-based operation and maintenance system. The submarine cable fault positioning method is used for realizing a submarine cable fault positioning technology for quickly and accurately positioning and identifying spatial extension characteristics in a complex submarine environment.

A corrugated copper submarine cable and a submarine cable production device. The submarine cable production device comprises a worktable, and further comprises: a fixing compartment arranged in the middle of the upper surface of the worktable, wherein a fixing pipe penetrates the interior of the fixing compartment, a winding assembly is arranged on the circumferential surface of one end of the fixing pipe, and the winding assembly comprises a rotating ring rotatably arranged on the circumferential surface of the fixing pipe; and a welding compartment arranged on one side of the fixing compartment, wherein two support frames are arranged in the welding compartment, the top ends of the two support frames are both fixedly connected to limiting rings, a positioning ring is rotatably arranged between the two limiting rings, the inner wall of the positioning ring is fixedly connected to a plurality of arc welding heads, and the plurality of arc welding heads are distributed in a circumferential array along the inner wall of the positioning ring. By providing a welding assembly, the present invention solves the problem of reduced production efficiency of corrugated copper submarine cables caused by a relatively slow welding speed and low efficiency during normal welding in which welding is performed by a large number of technicians to generate corrugated textures.

The invention relates to a minimum bending radius multi-point turning action control method and system, and relates to the technical field of submarine cable laying, and the method comprises the steps: obtaining cable parameters of a cable, cable laying ship parameters of a cable laying ship, and marine environment parameters; analyzing the cable parameters, the cable laying ship parameters and the marine environment parameters to generate a predicted bending radius; analyzing the cable parameters to determine the minimum bending radius; judging whether the predicted bending radius meets the requirement of the minimum bending radius or not; if yes, the cable parameters of the cable, the cable laying ship parameters of the cable laying ship and the marine environment parameters are continuously obtained for cyclic judgment; if not, analyzing the predicted bending radius and the minimum bending radius to generate a bending radius error; analyzing the bending radius error to generate a speed adjustment amount; and the cable laying ship is adjusted according to the speed adjustment amount so that the predicted bending radius can meet the requirement of the minimum bending radius. The method has the effect of improving the timeliness of adjusting the bending radius.

The invention discloses a submarine cable insulation performance online monitoring and fault positioning method, a medium and equipment. The method comprises the following steps: S1, synchronously acquiring multi-source sensing data in real time; s2, multi-modal noise cooperative suppression and feature extraction; s3, insulation state degradation evaluation based on multi-feature fusion; s4, double-end traveling wave accurate fault positioning is carried out; and S5, carrying out data visualization and alarm linkage. According to the invention, marine complex environmental noise interference can be effectively suppressed, key parameters representing the insulation state of the submarine cable are monitored in real time in a multi-dimensional manner, and early warning of insulation degradation and preliminary judgment of a fault mode are realized through an intelligent fusion evaluation model. And the improved traveling wave accurate capture and wave velocity dynamic correction technology is utilized to realize accurate positioning of a fault point, so that the accuracy and sensitivity of submarine cable state monitoring and the fault positioning precision can be remarkably improved, and powerful technical support is provided for safe and economical operation of submarine cables.

The invention discloses a submarine cable laying path planning method and system capable of avoiding risks in the whole course, and the method comprises the steps: carrying out the rasterization of submarine elevation information, deleting a risk grid unit, and obtaining the grid unit data of a to-be-laid submarine cable region; determining a submarine cable laying starting point grating unit according to the submarine cable laying starting point coordinate, determining a submarine cable laying terminal point grating unit according to the submarine cable laying starting point coordinate, and representing a submarine cable laying path by a continuous grating unit sequence comprising the submarine cable laying starting point grating unit and the submarine cable laying terminal point grating unit; the submarine cable laying path is iteratively optimized by adopting a multi-objective optimization algorithm, and the optimized submarine cable laying path with low laying cost is obtained while the laying risk is controlled. According to the method, the comprehensive objective function considering the whole-course topographic relief and the local slope risk is combined, the whole-course risk and cost of the submarine cable laying path are subjected to multi-objective optimization, and the problem that the submarine cable laying cost is greatly increased or the whole-course reliability is reduced due to the fact that a local risk area is directly avoided is solved.

The invention belongs to the technical field of submarine cables, and provides a high-voltage three-core submarine cable. Comprising a cable core, a waterproof layer, an inner sheath, an armor layer and an outer sheath, the cable core comprises at least one conductive core, the conductive core comprises a conductor and an insulation system arranged outside the conductor, the insulation system comprises a conductor shielding layer, an insulation layer and an insulation shielding layer, and the conductivity of the conductor shielding layer is gradually reduced from inside to outside in the radial direction of the conductive core; the conductivity of the insulation shielding layer is gradually reduced from outside to inside in the radial direction of the conductive core. The contact interface of the conductor shielding layer and the insulating layer prevents charge from gathering at the interface, and the electric field distribution between the conductor shielding layer and the insulating shielding layer is greatly optimized; similarly, the electric conductivity of the insulation shielding layer is set to be gradually increased in the direction away from the insulation layer, the interface electric field between the insulation layer and the insulation shielding layer is optimized, electric charges on the interface of the insulation layer can be rapidly led to the insulation shielding layer, and the partial discharge phenomenon is prevented.

A submarine cable for ultra-deep water. The submarine cable comprises: a plurality of cable cores, a plurality of pre-formed filler strips and an outer protective structure, wherein the plurality of cable cores are tightly twisted together; the plurality of pre-formed filler strips are arranged in gaps between the plurality of cable cores; the outer protective structure is wrapped around the peripheries of the plurality of cable cores and the plurality of pre-formed filler strips. Each pre-formed filler strip is provided with a cavity, which extends in the direction of length of the pre-formed filler strip, and through holes, which are arranged at intervals in the direction of length of the pre-formed filler strip and penetrate into the cavity in a radial direction; and the outer protective structure is provided with flow holes. When a submarine cable for ultra-deep water is laid and placed into a deep sea, seawater can enter gaps between a plurality of cable cores and cavities of pre-formed filler strips by means of flow holes, which allows the air inside the submarine cable to be completely discharged, so that the pressure inside and outside the submarine cable keeps balanced, thereby avoiding an internal structure of the submarine cable being crushed, and thus prolonging the service life of the submarine cable.

The invention discloses an anti-ocean-current trajectory tracking control method and system for a jet-arm submarine cable laying robot. The method comprises the steps that an anti-ocean-current motion model of the jet-arm submarine cable laying robot is constructed; acquiring a position error and a course tracking error according to a given reference trajectory based on the ocean current resistance motion model, and constructing a preset time controller; according to the preset time, the controller obtains a virtual controller of the jet arm seabed cable laying robot so as to define a longitudinal speed error and an angular speed error; constructing a parameter adaptive law according to the longitudinal velocity error and the angular velocity error; and constructing a disturbance observer based on the virtual controller and the parameter adaptive law to obtain an actual controller for ocean current trajectory tracking of the jet arm submarine cable laying robot. Aiming at the problem that an existing submarine cable laying robot cannot realize accurate trajectory tracking in a complex submarine environment, a more perfect ocean current resistance motion model is established, and a disturbance observer is introduced to estimate disturbance in real time so as to realize accurate control; a preset time theory is adopted, so that the system can be converged to a preset time, and the robustness is better; the disturbance observer is used to more accurately compensate the interference of ocean current of the seabed, and the anti-interference capability of the submarine cable laying robot is improved.

The invention relates to the technical field of cable monitoring, in particular to a power cable damage monitoring system and method based on a digital twin model, and the system comprises a data collection module, an optical calculation processing module, a terahertz radar detection module, a digital twin modeling module and an underwater communication module. The optical calculation processing module performs high-frequency parallel processing on the acquired environmental data to generate a three-dimensional damage map of the submarine cable; the terahertz radar detection module obtains echo signals of a submarine cable insulation layer and extracts insulation aging state information. The digital twinborn modeling module constructs a cable digital twinborn model based on the three-dimensional damage map and the aging information, and predicts a fault diffusion path; and the underwater communication module transmits the model data to a target receiving end. According to the system, the insulation aging detection precision and the real-time prediction capability of the submarine cable are improved, and the intelligence and the engineering applicability of the system are enhanced.

The submarine cable laying robot comprises a main body frame, a buoyancy adjusting device is arranged at the top of the main body frame, spiral propellers are arranged on the two sides of the main body frame respectively, a cable pressing device and two spraying devices are arranged at the bottom of the main body frame, and the two spraying devices are symmetrically arranged at the bottom of the main body frame. The cable pressing device is arranged corresponding to the two spraying devices; the spiral propeller is used for driving the submarine cable laying robot to walk on the seabed, the buoyancy adjusting device is used for adjusting the buoyancy of the submarine cable laying robot on the seabed, and the two spraying devices are used for digging cable burying grooves with the corresponding depths in the corresponding positions of submarine cables in the mode of spraying high-pressure liquid. And the cable pressing device is used for pressing the cable into the cable burying groove. The device has the universality of different cable burying depth operations and the universality of different seabed geological operations, the operation efficiency and safety are improved, and the cost and the risk are reduced.

The invention discloses a deep-sea photoelectric separator with a liquid leakage identification function and an assembly process thereof, and the separator comprises a photoelectric separator cylinder, a sealing injection molding part, a submarine cable penetration part, a first end cover, a second end cover, a sensor, an optical connector, an electric connector, an electric connection box, and a fiber coiling box. The sensor, the electric connection box and the fiber coiling box are respectively arranged in the photoelectric separator cylinder, an insulating layer at one end of the submarine cable extends into the photoelectric separator cylinder through the submarine cable cabin-penetrating piece, and the sealing injection molding piece wraps the outer wall of the submarine cable cabin-penetrating piece and the insulating layer of a section of submarine cable in front of the outer end of the submarine cable cabin-penetrating piece, so that the sealing effect is improved; the submarine cable is divided into an electric wire part and an optical fiber part at one end in the photoelectric separator barrel, the electric wire part is connected with a tail cable of the electric connector in the electric connection box, the optical fiber part is connected with a tail cable of the optical connector in the fiber coiling box, the sensor is connected to one optical fiber in series, optical power detection is carried out through the sensor, and liquid leakage identification and alarm are achieved.

The utility model relates to the technical field of submarine cable production, and discloses a water-tree-resistant cross-linked polyethylene insulated optical fiber composite wet-type submarine cable, which comprises a main body mechanism and an auxiliary mechanism, the auxiliary mechanism is positioned on the inner side of the main body mechanism, and the main body mechanism comprises a water-blocking conductor, a conductor shield and an insulating layer. According to the water-tree-resistant cross-linked polyethylene insulated optical fiber composite wet-type submarine cable and the production equipment, through installation of a main body mechanism, the elongation of copper monofilaments is controlled to be 30-35%, the resistivity is smaller than or equal to 0.017241 omega.mm / m, a layer of semi-conductive seawater-resistant water-blocking tape is longitudinally wrapped between every two layers of conductors, a layer of water-blocking yarn is bound outside the water-blocking tape, and the water-tree-resistant cross-linked polyethylene insulated optical fiber composite wet-type submarine cable is formed. The outer layer of the stranded conductor is wrapped by a layer of reverse semi-conductive water-blocking binding tape and a layer of semi-conductive tetoron tape, the water-blocking layer of the semi-conductive water-blocking binding tape faces the conductor, the overlapping positions of the two layers of semi-conductive tapes are not overlapped at the same position, the semi-conductive tapes are required to be flatly wrapped and uniformly overlapped, the overlapping rate is controlled to be 20-35%, and the insulating layer is made of an XLPE insulating material and has the thickness of 24.0 mm.

The invention discloses a bidirectional hybrid output direct-current transformer and a fault current limiting design method thereof, and the medium-voltage side and the high-voltage side of the bidirectional hybrid output direct-current transformer are respectively composed of three thyristor valve groups and three sub-module bridge arms, and are connected through a medium-frequency transformer. The thyristor valve group is formed by reversely connecting two groups of series thyristors in parallel, and the medium-voltage side sub-module bridge arm and the high-voltage side sub-module bridge arm are respectively composed of NM half-bridge sub-modules and NH half-bridge sub-modules. According to the invention, the sub-module bridge arms with strong control capability are combined with the thyristors and the diode valve groups which are low in cost, low in loss and high in power density, bidirectional power transmission and reliable turn-off of the thyristors can be realized through coordination and cooperation of the middle-voltage side bridge arms and the high-voltage side bridge arms, smooth direct current is ensured, and a filter does not need to be installed. When a short-circuit fault occurs in the outgoing submarine cable, a fault current active suppression strategy is provided, and the scheme can effectively reduce the peak value of the fault current and eliminate the current-limiting inductance.

The invention discloses an offshore wind power collecting and sending-out system and method based on a multi-port multi-frequency alternating current and direct current hybrid integrated platform, and belongs to the field of power transmission and distribution of power systems. The system comprises an intermediate-frequency, power-frequency and low-frequency wind power collection subsystem, an offshore integrated platform, a direct-current sending-out submarine cable, a low-frequency sending-out submarine cable, an onshore converter station and an onshore frequency conversion station. The various wind power collection subsystems respectively collect wind turbine generator group outputs with corresponding frequencies and send the wind turbine generator group outputs to the offshore integrated platform; the offshore integrated platform converts intermediate-frequency, power-frequency and partial low-frequency electric energy into direct current and then transmits the direct current to the onshore converter station through the direct-current sending-out submarine cable, and the converter station converts the direct current into power-frequency alternating current; and after being boosted, the other low-frequency electric energy is sent to a land frequency conversion station through a low-frequency sending-out submarine cable to be converted into power-frequency alternating current, so that efficient collection and grid-connected sending-out of multi-frequency wind power resources are realized. According to the invention, the problem that a plurality of independent platforms need to be built in a complex multi-point grid-connected scene in the prior art can be solved.

The invention discloses a high-voltage direct-current submarine cable test system and method, and relates to the field of high-voltage direct-current submarine cable test, and the method comprises the steps: constructing a simulated seabed test space with a multidirectional water flow impact device, and arranging a curvature adjustment mechanism capable of actively changing the bending form of a submarine cable sample; collecting submarine cable insulation layer temperature and bending form data in real time in a test process under a simulated seabed test space condition, dynamically establishing an association relationship between the two data, and tracking the association relationship to a limit state; through collaborative analysis of temperature gradient distribution and charge peak-to-valley ratio characteristics, the safety boundary and the limit failure state of the submarine cable are judged through continuous growth of the temperature gradient and synchronous deterioration of the charge peak-to-valley ratio in combination with indexes such as outer sheath carbonization and temperature difference sudden change. The comprehensive evaluation of the performance of the submarine cable under the extreme condition is realized, and a powerful technical guarantee is provided for improving the reliability and the safety of a cable system.

The invention discloses an offshore wind power harmonic transmission quantification method and system considering submarine cable insulation aging, and relates to the field of harmonic transmission characteristic analysis. The method comprises the following steps: dividing the insulation aging severity level of the submarine cable, and determining an insulation capacitance gain coefficient corresponding to each level of submarine cable; determining an actual capacitance gain coefficient of the insulation state of the submarine cable based on cable aging detection results regularly acquired by a power grid company; correcting the capacitance value of the submarine cable based on the actual capacitance gain coefficient; and establishing an equivalent circuit of an offshore wind power grid-connected system through the submarine cable line, estimating a grid-connected system harmonic resonant frequency causing harmonic current amplification according to the corrected submarine cable capacitance value, and estimating a harmonic current amplification coefficient of a grid-connected point under the harmonic resonant frequency of the grid-connected system. According to the method, the evaluation accuracy of the resonant frequency and harmonic amplification severity of the offshore wind power grid-connected system is remarkably improved, so that effective suppression of harmonic resonance amplification can be guided.

A submarine cable core comprising a conductor which is surrounded by at least an inner semiconductive layer, an insulation layer and an outer semiconductive layer in that order; wherein said insulation layer comprises: a low density polyethylene homopolymer or low density polyethylene copolymer with at least one polyunsaturated comonomer and optionally one or more further comonomers; and, a copolymer comprising at least one polar comonomer selected from the group consisting of an alkyl acrylate, an alkyl methacrylate or vinyl acetate, wherein the amount of polar monomer units in the insulation layer is from 1 to 150 micromol per gram based on the total amount of polymer components in the insulation layer.