A simulation design method for detecting submarine buried submarine cable based on transient electromagnetic method

Abstract

The application relates to a seabed buried submarine cable detection simulation design method based on transient electromagnetic method, a three-layer marine layered electromagnetic simulation model of air-seawater-seabed sediment layer is first constructed, a double-transmitting single-receiving coil structure arranged by equivalent counter-flux is set in the model, and a submarine cable target model containing a copper core conductor layer and other multilayer structures is established in the seabed sediment layer; a transient electromagnetic field is generated by applying a pulse current excitation to the transmitting coil, secondary electromagnetic response signals under different detection coil heights from the seabed are simulated and calculated; a signal-to-noise ratio model is constructed based on the signal response data, an optimal transmitting power calculation formula is derived by combining magnetic dipole approximation and the relationship between power and current, and the determination of the optimal transmitting power of the transient electromagnetic device under different detection heights is realized. The application considers the marine layered electromagnetic propagation characteristics and the water surface reflection effect, can scientifically configure the power parameters of the detection system, reduces energy consumption under the premise of ensuring signal quality, and improves seabed submarine cable detection efficiency.

Description

Technical Field

[0001] This invention relates to a simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic methods. It is applicable to the optimization design of the transmission power of transient electromagnetic devices in submarine cable detection systems, and can accurately determine the optimal transmission power at different detection heights. It belongs to the field of marine electromagnetic detection and seabed target recognition technology. Background Technology

[0002] With the rapid development of marine resources and the construction of submarine engineering projects, submarine cables, as core facilities for marine communication, power transmission, marine observation, and submarine engineering monitoring, are widely laid on the seabed surface or buried in seabed sedimentary layers such as silt and sand. Due to long-term marine environmental erosion and seabed topographic changes, the actual location, burial depth, and structural condition of submarine cables are difficult to accurately detect using traditional methods. Therefore, efficient and reliable submarine cable detection technology has become an urgent need in the field of marine engineering.

[0003] Currently, seabed target detection technologies are mainly divided into three categories: acoustic detection, magnetic anomaly detection, and electromagnetic detection. Acoustic detection technologies (side-scan sonar, shallow seismic profilers, etc.) rely on the propagation and reflection of sound waves to achieve detection. They have advantages in seabed topographic surveying, but sound waves attenuate significantly in seabed sediment layers and are easily affected by complex seabed topography, sediment properties, and noise interference, resulting in lower detection accuracy for buried submarine cables. Magnetic anomaly detection technologies identify targets through magnetic field anomalies. They only have good detection effects on ferromagnetic structures, and their ability to detect non-magnetic / weakly magnetic submarine cables is limited. Furthermore, they are easily affected by changes in the ocean geomagnetic background field and interference from other metallic structures.

[0004] Transient electromagnetic method (TEM), a typical time-domain electromagnetic detection method, uses the transient magnetic field induced by the pulse current turn-off of the transmitting coil to generate eddy currents. The receiving coil then collects the attenuation characteristics of the secondary electromagnetic field of conductive targets to achieve target identification and location. It has advantages such as large detection depth, high sensitivity to conductive targets, and adaptability to complex geological environments, and has been widely used in land exploration. In recent years, its application has gradually expanded to the detection of targets such as submarine pipelines and cables. However, the electromagnetic propagation characteristics of marine and terrestrial environments are fundamentally different. Seawater has a high conductivity of 3-5 S / m, causing electromagnetic fields to attenuate rapidly. Furthermore, the layered structure of the air-seawater-seabed sediment layer significantly affects electromagnetic field propagation. Simultaneously, the water surface, as the interface between air and seawater, reflects the electromagnetic field. The superposition of the reflected field and the directly propagated field alters the characteristics of the received signal, increasing the complexity of signal interpretation.

[0005] Furthermore, transient electromagnetic devices are typically mounted on underwater platforms or towed equipment. The height of the detection coil above the seabed changes in real time with the movement of the equipment. This height directly affects the propagation path of the electromagnetic field and the energy reaching the submarine cable target, thus determining the strength of the target's response signal: too low a transmission power will make the target signal difficult to identify, while too high a power will result in energy waste and increased equipment load. However, the transmission power and operating parameters of existing submarine electromagnetic detection systems largely rely on empirical parameters or simple theoretical models, resulting in the following technical shortcomings:

[0006] 1. There is a lack of detailed simulation analysis for the marine stratified environment, and the electromagnetic coupling effect of air, seawater, seabed sediment layer and the water surface reflection effect are not fully considered on the detection signal;

[0007] 2. The inherent relationship between detection altitude and transmission power was not systematically analyzed, making it impossible to dynamically match the optimal transmission power based on real-time detection altitude;

[0008] 3. The lack of a power design method that combines numerical simulation and optimization algorithms results in a lack of scientific rigor in power configuration, making it difficult to balance energy consumption and detection efficiency in the detection system.

[0009] Therefore, it is urgent to propose a transient electromagnetic detection simulation design method based on a multi-layered marine environment model to accurately calculate the optimal transmission power at different detection altitudes, and provide a scientific and reliable technical solution for the design of submarine cable detection systems. Summary of the Invention

[0010] To address the aforementioned shortcomings of existing transient electromagnetic detection technologies for submarine cables, this invention provides a simulation design method for submarine cable detection based on transient electromagnetic methods. By constructing a layered electromagnetic model that closely matches the real marine environment, and combining numerical simulation and power optimization algorithms, the method systematically analyzes the impact of detection altitude on the target response signal, derives the optimal transmission power calculation formula for different detection altitudes, and solves the problems of existing technologies such as power configuration relying on experience, low detection efficiency, and high energy consumption, thereby achieving scientific configuration of the detection system's power parameters.

[0011] A simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic methods is proposed. This method constructs a multi-layered electromagnetic model of the ocean and combines electromagnetic numerical simulation with power optimization algorithms to determine the optimal transmission power of the transient electromagnetic detection device. The method includes the following steps:

[0012] S1: Constructing a layered electromagnetic simulation model of the ocean: Establishing a three-layered structure model from top to bottom, consisting of an air layer, a seawater layer, and a seabed sediment layer, to simulate the environment above the sea surface, the water environment where the electromagnetic detection device is located, and the seabed sediment / silt structure, respectively, reflecting the characteristics of conductivity changes with depth in the marine environment, and providing a basis for the calculation of transient electromagnetic field propagation.

[0013] S2: Deployment of detection coil structure: A coil structure consisting of two transmitting coils and one receiving coil is set up in the seawater layer. The two transmitting coils are arranged vertically, and the receiving coil is placed between the two transmitting coils. The two transmitting coils are arranged in an equal and opposite magnetic flux configuration, and currents with the same amplitude and opposite direction are passed through them to cancel each other out of the far-field magnetic flux, thereby reducing the interference of the ambient background magnetic field on the detection signal.

[0014] S3: Establish a target model for submarine cables: Construct a layered simulation model of submarine cables within the seabed sediment layer. The submarine cable model consists of a copper core conductor layer, a rubber insulation layer, a lead shielding layer, an outer rubber insulation layer, and a steel armor layer from the inside out, which realistically reflects the conductivity and magnetic characteristics of submarine cables and ensures the rationality of transient electromagnetic response simulation.

[0015] S4: Transient Electromagnetic Response Simulation Calculation: A pulsed current signal is applied to the transmitting coil and then quickly turned off to simulate the generation of a transient electromagnetic field and induced eddy currents in seawater and seabed sediment layers. The receiving coil collects and records the time decay response signal of the secondary electromagnetic field generated by the submarine cable target. Electromagnetic simulation software is used to assign electromagnetic parameters such as conductivity and permeability to each layer of material, and transient current excitation is set for the transmitting coil. A pulsed current signal is applied to the transmitting coil and then quickly turned off to cause a sudden change in the magnetic field around the transmitting coil and generate eddy currents in seawater and seabed sediment layers. The eddy currents are distorted near the conductive submarine cable and generate a secondary electromagnetic field. The receiving coil collects and records the time decay response signal (transient voltage response signal) of the secondary electromagnetic field.

[0016] S5: Acquisition of multi-height response data: Change the height parameter of the detection coil above the seabed, repeat S4, and simulate to obtain transient electromagnetic response signal data under different height conditions. Calculate and acquire transient electromagnetic response signal data under different height conditions, and establish the correlation between detection height and signal strength.

[0017] S6: Construct a power optimization model and calculate the optimal transmission power: Based on signal response data at different altitudes, construct a signal-to-noise ratio model. Combining the magnetic field strength and distance relationship of the magnetic dipole approximation, and the electric power and current relationship of the transmitting coil, derive the formula for calculating the optimal transmission power. Substitute the detection altitude and submarine cable burial depth parameters to calculate the optimal transmission power at the corresponding altitude.

[0018] S4 and S5 use electromagnetic simulation software to establish a three-dimensional electromagnetic model, assign conductivity and permeability parameters to each layer of material, and set transient current excitation for the transmitting coil.

[0019] The electromagnetic simulation software used is ANSYS Maxwell. During the simulation, specialized curved surface meshes are set for the coil structure and submarine cable structure, and internal coarse meshes are set for the air layer, seawater layer, and seabed sediment layer. The simulation time is 40ms and the simulation step size is 0.25ms, which realizes the fine acquisition of transient electromagnetic response.

[0020] The distance from the detection coil to the submarine cable target in S6 satisfy ,in To detect the height of the coil above the seabed surface, This refers to the depth at which submarine cables are buried in the seabed sediment layer.

[0021] The formula for calculating the optimal transmission power in S6 is as follows: ,in For optimal transmission power, These are constants related to system parameters, including the number of coil turns, effective coil area, coil resistance, and system preset signal-to-noise ratio.

[0022] The transmitting coil has a diameter of 400mm, the receiving coil has a diameter of 250mm, and the vertical distance between the two transmitting coils is 100mm. The coil parameters are adapted to the spatial constraints of seabed exploration, taking into account both magnetic field transmission strength and signal reception sensitivity.

[0023] The response signal collected by the receiving coil in S4 is a transient voltage response signal, and the secondary electromagnetic field is generated by distorted induced eddy currents near the submarine cable.

[0024] Compared with existing technologies, by establishing a realistic marine stratified environment model and combining simulation and optimization algorithms, the beneficial effects of this invention are as follows:

[0025] This invention establishes a multi-layer electromagnetic simulation model that includes the submarine cable structure and the marine environment to simulate the propagation process of transient electromagnetic fields in air, seawater, and seabed sediment layers. Based on this, it analyzes the impact of changes in the height of the detection coil above the seabed on the target response signal and further constructs a transmission power optimization algorithm to obtain the optimal transmission power under different detection height conditions.

[0026] This invention constructs a three-layered electromagnetic model and a multi-layered submarine cable structure model that closely resemble the real marine environment. It fully considers the electromagnetic coupling effect of air-seawater-seabed sediment layer, the water surface reflection effect, and the conductivity and magnetic characteristics of the submarine cable itself. This solves the problems of simplified simulation models and large deviations from the actual marine environment in existing technologies, and significantly improves the accuracy of transient electromagnetic response simulation.

[0027] This invention systematically analyzes the influence of the probe coil's height above the seabed on the target response signal. By obtaining complete signal response data through multi-height simulation, it establishes a quantitative correlation between probe height and signal strength, thus solving the technical deficiency of existing technologies that do not finely analyze the relationship between probe height and transmission power.

[0028] This invention combines numerical simulation and power optimization algorithms to derive a universal formula for calculating the optimal transmit power. It can quickly calculate the optimal transmission power based on the real-time detection height and the burial depth of the submarine cable, replacing the traditional empirical parameter configuration method and realizing the scientific and precise configuration of the detection system's power parameters.

[0029] This invention is based on optimal transmission power configuration. Under the premise of ensuring that the system signal-to-noise ratio reaches the preset value and the target signal is clearly identifiable, the transmission power is reduced to the maximum extent, thereby reducing system energy consumption and equipment load. At the same time, it improves the detection efficiency of submarine cables and provides a standardized and replicable technical solution for the design and optimization of submarine electromagnetic detection systems.

[0030] The simulation and calculation processes of this invention are both implemented numerically, which can quickly evaluate the electromagnetic response at different detection heights and automatically calculate the optimal transmission power, greatly improving the design efficiency of the submarine cable detection system and reducing the system development and debugging costs. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating a specific implementation method of the simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic method according to the present invention.

[0033] Figure 2 This is a schematic diagram of the multi-layered electromagnetic model structure of the seabed for the simulation design method of seabed cable laying detection based on transient electromagnetic method of the present invention.

[0034] Figure 3 This is a schematic diagram of a submarine cable structure buried in silt, based on a simulation design method for detecting submarine cables buried in the seabed using transient electromagnetic methods, according to the present invention.

[0035] Figure 4 This is a schematic diagram of the arrangement of transient electromagnetic transmitting and receiving coils in a simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic method according to the present invention.

[0036] Figure 5 This is a schematic diagram of the instantaneous excitation of the transient electromagnetic transmitting coil in the simulation design method for detecting submarine cables buried on the seabed based on the transient electromagnetic method of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Reference Figure 1 - Figure 5 The specific steps of the simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic method of the present invention are as follows:

[0039] S1: Constructing a layered electromagnetic simulation model of the ocean: Establishing a three-layered structure model from top to bottom, consisting of an air layer, a seawater layer, and a seabed sediment layer, to simulate the environment above the sea surface, the water environment where the electromagnetic detection device is located, and the seabed sediment / silt structure, respectively, reflecting the characteristics of conductivity changes with depth in the marine environment, and providing a basis for the calculation of transient electromagnetic field propagation.

[0040] S2: Deployment of the detection coil structure: A coil structure consisting of two transmitting coils and one receiving coil is set up in the seawater layer. The two transmitting coils are arranged vertically, and the receiving coil is located between the two transmitting coils. The two transmitting coils are arranged in an equal and opposite magnetic flux configuration, and currents with the same amplitude but opposite directions are passed through them to cancel each other out of the far-field magnetic flux, reducing the interference of the ambient background magnetic field on the detection signal. The receiving coil is located between the two transmitting coils and is used to receive the secondary electromagnetic response signal generated by the underground conductive target.

[0041] S3: Establishing the Submarine Cable Target Model: To ensure the rationality of the simulation model, this invention simplifies the layered modeling of the submarine cable. The cable, from the inside out, includes a copper core conductor layer, a rubber insulation layer, a lead shielding layer, an outer rubber insulation layer, and a steel armor layer. This layered structure reflects the conductivity and magnetism characteristics of the submarine cable in an electromagnetic field, thus more realistically simulating its transient electromagnetic response. The electromagnetic simulation software used is ANSYS Maxwell. During the simulation, specialized curved surface meshes are set for the coil structure and the submarine cable structure, and internal coarse meshes are set for the air layer, seawater layer, and seabed sediment layer. The simulation time is 40ms, and the simulation step size is 0.25ms, achieving refined acquisition of the transient electromagnetic response.

[0042] S4: Transient Electromagnetic Response Simulation: A transient electromagnetic field is generated by applying a pulsed current signal to the transmitting coil. When the transmitting current is rapidly turned off, the magnetic field around the transmitting coil changes, thereby inducing eddy currents in the seawater and seabed sediment. These eddy currents are distorted near the conductive cable, generating a secondary electromagnetic field. This secondary electromagnetic field is received by the receiving coil, and its time-decay response is recorded. The conductive cable affects the eddy current distribution, thus forming a secondary electromagnetic field. This secondary electromagnetic field is received by the receiving coil, and the transient voltage response signal of the receiving coil is recorded. The response curve of the received voltage changing with time is obtained through simulation calculation.

[0043] S5: Acquisition of multi-height response data: Change the height parameter of the detection coil above the seabed, repeat S4, and simulate to obtain transient electromagnetic response signal data under different height conditions. Calculate and acquire transient electromagnetic response signal data under different height conditions, and establish the correlation between detection height and signal strength.

[0044] S6: Construct a power optimization model and calculate the optimal transmission power: Based on signal response data at different altitudes, construct a signal-to-noise ratio model. Combining the magnetic field strength and distance relationship of the magnetic dipole approximation, and the electric power and current relationship of the transmitting coil, derive the formula for calculating the optimal transmission power. Substitute the detection altitude and submarine cable burial depth parameters to calculate the optimal transmission power at the corresponding altitude.

[0045] In the simulation model, the transient electromagnetic response under different height conditions is studied by changing the height parameter of the coil system above the seabed. Let the height of the detection coil above the seabed be... The submarine cable is buried at a depth of The distance between the coil and the cable target is:

[0046]

[0047] in: The distance between the transmitting coil and the submarine cable target. To detect the height of the coil system above the seabed surface,

[0048] This refers to the depth at which submarine cables are buried in the seabed sediment layer.

[0049] When the transmitting coil is energized, it generates a magnetic field, the magnetic moment of which can be expressed as:

[0050]

[0051] in: The magnetic moment of the transmitting coil; This refers to the number of coil turns. The current in the transmitting coil; This represents the effective area of ​​the coil.

[0052] Under the magnetic dipole approximation, the magnetic field strength generated by the transmitting coil and the target distance satisfy an anticubic relationship:

[0053]

[0054] in: The relationship between and magnetic field strength indicates that the magnetic field strength decreases rapidly as the probe coil's height above the seabed increases.

[0055] The transient electromagnetic response voltage received by the receiving coil can be expressed as:

[0056]

[0057] in: For the receiving coil in time The induced voltage at any given time This is the decay function of the transient electromagnetic response as a function of time.

[0058] The electrical power of the transmitting coil can be expressed as:

[0059]

[0060] in: For the power of the transmitting coil, This is the resistance of the transmitting coil.

[0061] Since the received signal strength is proportional to the transmitted current, the relationship between the signal amplitude and the transmitted power can be obtained as follows:

[0062]

[0063] To ensure the system signal-to-noise ratio reaches the preset value, the optimal transmit power expression under different detection altitude conditions can be obtained:

[0064]

[0065] in: For optimal transmission power, Constants related to system parameters

[0066] This invention first establishes a three-dimensional electromagnetic simulation model including an air layer, a seawater layer, a seabed sediment layer, and the submarine cable structure. Then, transient current excitation is applied to the simulation model, and the transient electromagnetic response of the receiving coil is calculated. Subsequently, the height parameter of the detection coil above the seabed is changed, and signal response data under different height conditions are obtained. A signal-to-noise ratio model is constructed based on the relationship between received signal strength and height. Finally, the optimal transmission power under different height conditions is calculated using a power optimization formula. Through the above simulation and optimization methods, the power parameters of the submarine cable transient electromagnetic detection system can be rationally configured, thereby reducing system energy consumption and improving submarine cable detection efficiency while ensuring signal quality.

[0067] S4 and S5 use electromagnetic simulation software to establish a three-dimensional electromagnetic model, assign conductivity and permeability parameters to each layer of material, and set transient current excitation for the transmitting coil.

[0068] Distance from the detection coil to the submarine cable target in S6 satisfy ,in To detect the height of the coil above the seabed surface, This refers to the depth at which submarine cables are buried in the seabed sediment layer.

[0069] The formula for calculating the optimal transmit power in S6 is: ,in For optimal transmission power, These are constants related to system parameters, including the number of coil turns, effective coil area, coil resistance, and system preset signal-to-noise ratio.

[0070] The transmitting coil has a diameter of 400mm, the receiving coil has a diameter of 250mm, and the vertical distance between the two transmitting coils is 100mm. The coil parameters are adapted to the spatial constraints of seabed exploration, taking into account both magnetic field transmission strength and signal reception sensitivity.

[0071] The response signal collected by the receiving coil in S4 is a transient voltage response signal, and the secondary electromagnetic field is generated by distorted induced eddy currents near the submarine cable.

[0072] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A simulation design method for detecting a submarine buried submarine cable based on transient electromagnetic method, characterized in that: Includes the following steps: S1: Constructing a layered electromagnetic simulation model of the ocean: Establishing a three-layered structure model from top to bottom, consisting of an air layer, a seawater layer, and a seabed sediment layer, to simulate the environment above the sea surface, the water environment where the electromagnetic detection device is located, and the seabed sediment / silt structure, respectively. S2: Deployment of detection coil structure: A coil structure is set up in the seawater layer. The coil structure includes two transmitting coils arranged in a vertical direction and a receiving coil located between the two transmitting coils. The two transmitting coils are arranged with equal and opposite magnetic flux and are supplied with currents of the same amplitude but opposite directions. S3: Establish a target model for submarine cables: Construct a layered simulation model of submarine cables within the seabed sediment layer. The layered simulation model of submarine cables consists of, from the inside out, a copper core conductor layer, a rubber insulation layer, a lead shielding layer, an outer rubber insulation layer, and a steel armor layer. S4: Transient electromagnetic response simulation calculation: Apply a pulse current signal to the transmitting coil and quickly turn it off to simulate the generation of transient electromagnetic fields and induced eddy currents in seawater and seabed sediments. Collect and record the time decay response signal of the secondary electromagnetic field generated by the submarine cable target through the receiving coil. S5: Acquisition of multi-height response data: Change the height parameter of the probe coil above the seabed, repeat S4, and simulate to obtain transient electromagnetic response signal data under different height conditions; S6: Construct a power optimization model and calculate the optimal transmission power: Based on signal response data at different altitudes, construct a signal-to-noise ratio model. Combining the magnetic field strength and distance relationship of the magnetic dipole approximation, and the electric power and current relationship of the transmitting coil, derive the optimal transmission power calculation formula. Substitute the detection altitude and submarine cable burial depth parameters to calculate the optimal transmission power at the corresponding altitude; the optimal transmission power calculation formula in S6 is as follows: ,in For optimal transmission power, These are constants related to system parameters, including the number of coil turns, effective coil area, coil resistance, and system preset signal-to-noise ratio. To detect the height of the coil above the seabed surface, This refers to the depth at which submarine cables are buried in the seabed sediment layer.

2. The simulation design method for submarine cable detection based on transient electromagnetic method according to claim 1, characterized in that: S4 and S5 use electromagnetic simulation software to establish a three-dimensional electromagnetic model, assign conductivity and permeability parameters to each layer of material, and set transient current excitation for the transmitting coil.

3. The simulation design method for submarine cable detection based on transient electromagnetic method according to claim 2, characterized in that: The electromagnetic simulation software used was ANSYS Maxwell. During the simulation, specialized curved surface meshes were set for the coil structure and the submarine cable structure, and internal coarse meshes were set for the air layer, seawater layer, and seabed sediment layer. The simulation time was 40ms and the simulation step size was 0.25ms.

4. The simulation design method for detecting submarine cables buried on the seabed based on transient electromagnetic method according to claim 3, characterized in that: The distance from the detection coil to the submarine cable target in S6 satisfy .

5. The simulation design method for submarine cable detection based on transient electromagnetic method according to claim 1, characterized in that: The transmitting coil has a diameter of 400mm, the receiving coil has a diameter of 250mm, and the vertical distance between the two transmitting coils is 100mm.

6. The simulation design method for submarine cable detection based on transient electromagnetic method according to claim 1, characterized in that: The response signal collected by the receiving coil in S4 is a transient voltage response signal, and the secondary electromagnetic field is generated by distorted induced eddy currents near the submarine cable.

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