Submarine cable anchor smashing fault assessment early warning method and diagnosis method

Abstract

The invention discloses a submarine cable anchor smashing fault evaluation and early warning method and a diagnosis method, and belongs to the technical field of electrics.The evaluation and early warning method comprises the steps that the stress deformation value, the operation state and the temperature of an optical fiber and currents of all layers of a submarine cable are monitored; the optical fiber stress deformation value refers to a stress value and a deformation value of the optical fiber; according to the optical fiber operation state, the optical fiber temperature and the current of each metal layer of the submarine cable, whether the submarine cable breaks down is evaluated; and if the submarine cable does not have a fault, the early warning degree is judged according to the monitored optical fiber stress deformation value. According to the invention, guidance can be provided for analysis and evaluation of submarine cable operation and maintenance personnel after submarine cable faults occur.

Description

Technical Field

[0001] The invention belongs to the field of electrical technology and relates to a submarine cable fault monitoring method, in particular to a submarine cable anchor failure assessment and early warning method and a diagnosis method. Background Art

[0002] With the development and utilization of marine resources and the development of offshore wind farms and other projects, submarine cables have been increasingly widely used in recent years, becoming an important channel for offshore wind farm booster stations to transmit electricity from sea to land. However, submarine cable failures often cause offshore wind farms to be unable to transmit electricity to the grid, resulting in direct economic losses and requiring a lot of time and money for repairs.

[0003] Real-time understanding of the operation status of submarine cables can reveal many potential problems. At present, there is a large gap in the evaluation of submarine cable status. Due to the special operating environment of submarine cables, they cannot be inspected routinely like land cables. There is a lack of effective safety management measures. In addition, when analyzing the operating status of submarine cables, the monitoring information is too single and the temperature, strain, disturbance and other information cannot be combined to comprehensively judge the status of submarine cables. In particular, when an anchor failure occurs in a submarine cable, there is a lack of correspondence between the degree of fault development and the optical fiber monitoring data, especially quantitative research based on the changes in fault-related characteristic quantities and the establishment of fault thresholds. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a submarine cable anchor failure assessment and early warning method and a diagnosis method, establishes a quantitative research and diagnostic analysis method for anchor failure, and helps to improve the operation and maintenance capabilities of the submarine cable operation status.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for evaluating and warning of anchor failure of a submarine cable: monitoring optical fiber stress and deformation values, optical fiber operating status, optical fiber temperature and current of each layer of the submarine cable; optical fiber stress and deformation values ​​refer to stress values ​​and deformation values ​​of the optical fiber; based on the optical fiber operating status, optical fiber temperature and current of each metal layer of the submarine cable, evaluating whether a submarine cable has a fault; if the submarine cable has not a fault, judging the degree of warning based on the monitored optical fiber stress and deformation values.

[0007] Furthermore, the method for evaluating whether a submarine cable has a fault is as follows: if the optical fiber fails, the optical fiber temperature is greater than 90°C, or the currents of all metal layers of the submarine cable are 0A, then the submarine cable has a fault. Among them, optical fiber failure means that the optical fiber signal disappears; and the currents of all layers of the submarine cable are 0A, which means that the steel wire armor current, lead sheath current, and conductor current measured at both ends of the submarine cable are all 0A.

[0008] Furthermore, the warning degree is divided based on whether plastic deformation occurs in each metal layer of the submarine cable as a warning threshold, and the optical fiber stress deformation value is used as the warning threshold value for judgment.

[0009] Furthermore, the warning degree is divided into three levels of damage warning: if the metal layers of the submarine cable do not undergo plastic deformation, it is a level one damage warning; if the steel wire armor layer and lead sheath of the submarine cable undergo plastic deformation, it is a level two damage warning; if the core transmission conductor of the submarine cable undergoes plastic deformation, it is a level three damage warning.

[0010] Furthermore, the method for determining the warning degree is as follows: determining the warning threshold value of each level of damage warning level; and determining the damage warning level according to the relationship between the monitored optical fiber stress deformation value and the warning threshold value of each level of damage warning level.

[0011] Furthermore, the method for determining the warning threshold value of each level of damage warning level is as follows: calculating the falling speed of anchors of different masses at the sea water depth in the sea area where the submarine cable is laid; using anchors of different masses and the corresponding falling speeds as the boundary conditions of the mechanical analysis model of the submarine cable anchor failure, analyzing the plastic deformation of each metal layer of the submarine cable, and obtaining the minimum mass anchor that causes plastic deformation of the steel wire armor layer and lead sheath of the submarine cable and plastic deformation of the core transmission conductor; extracting the optical fiber stress deformation values ​​when two minimum mass anchors hit the submarine cable as the warning threshold values ​​for judging each level of damage warning level.

[0012] That is, if the monitored optical fiber stress deformation value is less than the optical fiber stress deformation value when the steel wire armor layer and the lead sheath are hit by the minimum mass anchor, it is a first-level damage warning; if the monitored optical fiber stress deformation value is greater than or equal to the optical fiber stress deformation value when the steel wire armor layer and the lead sheath are hit by the minimum mass anchor, and less than the optical fiber stress deformation value when the core power transmission conductor is hit by the minimum mass anchor, it is a second-level damage warning; if the monitored optical fiber stress deformation value is greater than or equal to the optical fiber stress deformation value when the core power transmission conductor is hit by the minimum mass anchor, it is a third-level damage warning.

[0013] Furthermore, the optical fiber stress deformation value is the optical fiber stress deformation value when the optical fiber is relatively far from the anchor position.

[0014] In a second aspect, the present invention provides a method for diagnosing a submarine cable anchor failure: evaluating whether a submarine cable failure occurs according to a submarine cable anchor failure assessment and early warning method; if a submarine cable failure occurs, diagnosing the type of ship anchor that caused the anchor failure based on the monitored optical fiber stress deformation value and maritime information.

[0015] Furthermore, the diagnosis method of the ship anchor type is: determining the diagnostic threshold value of each ship anchor type; preliminarily judging the ship anchor type based on the relationship between the monitored optical fiber stress deformation value and the diagnostic threshold value of each ship anchor type; combining maritime information to determine whether there is a ship of this type in the sea area where the anchor is located at the time of anchoring, and finally determining the anchored ship.

[0016] Furthermore, the method for determining the diagnostic threshold value of each ship anchor type is: taking the depth of sea water in the sea area where the submarine cable is laid as the boundary condition, and using the submarine cable anchor failure mechanics analysis model, the optical fiber stress deformation value when the submarine cable is damaged by the anchor of each ship is calculated respectively, as the diagnostic threshold value of each ship anchor type.

[0017] That is, if the monitored optical fiber stress deformation value is equal to a certain diagnostic threshold value, then the ship anchor type corresponding to the diagnostic threshold value is the ship anchor type preliminarily determined; or, if the minimum diagnostic threshold value greater than the monitored optical fiber stress deformation value is determined, then the ship anchor type corresponding to the diagnostic threshold value is the ship anchor type preliminarily determined. If the maritime information shows that there is a ship of this type in the sea area where the optical fiber stress deformation value is generated, it is ultimately determined to be an anchor-smashed ship; if the maritime information shows that there is no ship of this type in the sea area where the optical fiber stress deformation value is generated, then it is determined that the submarine cable optical fiber stress deformation value is abnormal due to other fault reasons.

[0018] The beneficial effects of the present invention are as follows: the present invention provides a submarine cable anchor failure assessment and early warning method and a diagnostic method, and obtains the optical fiber stress deformation values ​​when the metal layers inside the submarine cable are plastically deformed when different mass anchors hit the submarine cable in the standard based on the anchor failure simulation model, and proposes a three-level damage early warning level early warning threshold value when the submarine cable anchor failure occurs based on this; with a representative ship anchor configuration, the optical fiber stress deformation characteristics when the submarine cable is anchored are obtained by using the submarine cable anchor model, and a submarine cable anchor failure diagnosis method is proposed in combination with maritime information; the non-electrical optical fiber stress strain and temperature, electrical quantity steel wire armor, lead sheath and conductor end current and maritime information are integrated to evaluate the operating state of the submarine cable after being damaged by the anchor, and provide guidance for submarine cable operation and maintenance personnel to analyze and evaluate after the submarine cable failure occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a mechanical analysis model of submarine cable anchor failure;

[0020] Figure 2 It is the relative position of the optical fiber when taking the value under the anchor damage warning threshold;

[0021] Figure 3 It is the area where the submarine cable deformation is most serious;

[0022] Figure 4 It is the temperature distribution cloud map after the submarine cable is deformed;

[0023] Figure 5 It is the conductor temperature and optical fiber strain curve under different energy impacts;

[0024] Figure 6 It is a flow chart of the evaluation and early warning method of submarine cable anchor failure;

[0025] Figure 7 It is a flowchart for diagnosing submarine cable anchor failure. DETAILED DESCRIPTION

[0026] The specific implementation of the present invention is described below with reference to the accompanying drawings.

[0027] Based on the finite element simulation method, the following Figure 1 The mechanical analysis model of submarine cable anchor failure shown in the figure analyzes the stress and deformation changes of each layer in the submarine cable when the anchor hits the submarine cable, so as to obtain the mechanism of submarine cable anchor damage; the elastic-plastic mechanics general equation of the submarine cable is constructed through equilibrium equations, geometric equations and constitutive equations. There are mainly two types of boundary conditions in the elastic-plastic deformation process: stress boundary conditions and displacement boundary conditions.

[0028] (1) Stress boundary condition: σ ij l j =F i Where l j is the direction cosine of the out-of-plane normal n. The surface force of the submarine cable during the anchoring process mainly acts in the z direction (space rectangular coordinate system), so the stress boundary condition of the submarine cable under the anchoring action is σ z =F z , where F z The impact force applied to the anchor.

[0029] (2) Displacement boundary condition: u i =u i When a submarine cable with a length of L is subjected to the action of an anchor, the displacement boundary conditions at both ends of its axial direction are: at x = 0, u = 0, v = 0, w = 0; at x = L, u = 0, v = 0, w = 0.

[0030] After given boundary conditions, the deformation characteristic data of the submarine cable during the anchoring process can be solved by the universal equation. The elastic-plastic mechanics of the anchor falling mechanics and the submarine cable after being stressed during the anchoring process are analyzed. The elastic deformation will not temporarily cause the submarine cable structure to be damaged. As the impact energy increases, the metal layer of the submarine cable will enter plastic deformation, and the metal layer will produce permanent deformation that cannot disappear and destroy the submarine cable structure. Therefore, for the submarine cable anchoring fault warning, the warning threshold can be formulated based on whether the metal layers of the submarine cable undergo plastic deformation under the impact of the anchor.

[0031] In particular, since the occurrence time of anchor strike on submarine cables is short, generally in milliseconds, the stress deformation change of the built-in optical fiber, which is more sensitive to external force disturbance, is used as the warning threshold. The built-in optical fiber of the submarine cable is a torsional structure, and its relative position in the axial direction of the submarine cable is variable. The stress deformation value of the optical fiber is greatly affected by the relative position of the optical fiber and the anchor in the radial direction. In order to avoid missing reports, the warning value should be selected when the optical fiber is relatively far from the impact position, such as Figure 2 shown.

[0032] Different mass anchors and falling speeds are used as boundary conditions for the mechanical analysis model of submarine cable anchor failure. The differences in the plastic deformation stage of each metal layer of the submarine cable with different impact energies are obtained, the plastic deformation of each layer in the submarine cable is analyzed, and the equivalent plastic deformation cloud map of each metal layer under different anchor weights is obtained.

[0033] The anchor failure is divided into three damage warning levels, and the stress deformation value of the optical fiber under the corresponding impact energy is extracted as the warning threshold value of the submarine cable anchor failure.

[0034] Among them, the first-level damage warning means that the submarine cable is disturbed, but the metal layers of the submarine cable are not damaged; the second-level damage warning means that the submarine cable is hit by an anchor, and the external protective steel wire armor layer and lead sheath undergo irreversible plastic deformation, but the internal transmission conductor of the submarine cable is not damaged. At this time, the submarine cable can still operate normally, but the operation and maintenance personnel should be notified to arrange underwater inspections during subsequent routine maintenance to further determine the damage status; the third-level damage warning means that the transmission conductor of the submarine cable core undergoes plastic deformation.

[0035] Taking the representative ships in the offshore area as the analysis object, and the anchors configured by each ship falling at a specific water depth as the boundary condition, the mechanical analysis model of submarine cable anchor failure is used to calculate the internal optical fiber stress deformation distribution cloud map when the submarine cable is damaged by anchor. After obtaining the corresponding optical fiber monitoring quantity information characteristics, combined with maritime information, diagnostic analysis is performed to determine which type of ship anchored and caused the failure.

[0036] After the submarine cable is deformed by the impact of the anchor, the metal layer loss increases and the non-metal layer thermal resistance decreases, or the operating temperature of the submarine cable changes. Therefore, the status assessment of the submarine cable after the submarine cable anchor failure can be analyzed from the optical fiber temperature monitoring characteristic quantity, and a comprehensive assessment can be performed based on the current monitoring quantity of the built-in optical fiber and the end of the submarine cable.

[0037] In particular, the optical fiber temperature monitoring characteristic quantity is to calculate the temperature field distribution of the submarine cable after the anchor failure occurs, based on the deformation of each layer in the submarine cable. In the process of calculating the temperature field in the submarine cable with anchor failure, the most severely deformed area in the submarine cable after the anchor failure occurs is extracted, that is, Figure 3 The dotted line position, Figure 4 The internal temperature field distribution of the submarine cable after the anchor is deformed by the impact, and the conductor temperature and optical fiber strain curves of the submarine cable are drawn under different energy impacts, showing a trend of first increasing and then decreasing, such as Figure 5 shown.

[0038] Therefore, the present invention proposes a submarine cable anchor failure assessment early warning / diagnosis method:

[0039] First, the anchor failure is evaluated, such as Figure 6 As shown: monitor the stress deformation value of the optical fiber, the operating status of the optical fiber, the temperature of the optical fiber and the current of each layer of the submarine cable. According to the operating status of the optical fiber, the temperature of the optical fiber and the current of each metal layer of the submarine cable, evaluate whether the submarine cable has a fault. The evaluation method is: if the optical fiber fails, the optical fiber temperature is greater than 90°C or the current of each metal layer of the submarine cable is 0A, the submarine cable has a fault.

[0040] Specifically, for submarine cable anchor failures, when the impact energy is large, it will cause the optical fiber to break, making the existing submarine cable optical fiber monitoring methods ineffective, and the submarine cable needs to be repaired. This also includes the most serious situation, that is, the metal layer in the submarine cable is broken, and the current monitoring value of each metal layer is also invalid and the measurement value is 0, and power should be shut down immediately for emergency repairs. If the optical fiber does not break after the submarine cable anchor failure occurs, the temperature change of the optical fiber can be used as the basis for evaluating the operating status of the submarine cable, that is, when the temperature is greater than 90°C, the power should be shut down for maintenance.

[0041] Then, if the submarine cable has not failed, an early warning of the anchor failure is issued, that is, the damage warning level is determined based on the monitored optical fiber stress deformation value. If the submarine cable has failed, the anchor failure is diagnosed, that is, the type of ship anchor that caused the anchor failure is diagnosed based on the monitored optical fiber stress deformation value and maritime information.

[0042] In a specific embodiment, taking the submarine cable of Jiangsu Rudong offshore wind farm with model HYJQF41-F-127 / 2203×500+1×36B1+1×(34B4+2A1b) as an example, early warning and diagnosis are specifically described.

[0043] Regarding early warning, it is first necessary to determine the warning threshold values ​​for each level of damage warning, and then judge the damage warning level accordingly.

[0044] The anchors of coastal ships in my country are mainly Hall anchors. The falling speeds of Hall anchors of different masses at a water depth of 10m are calculated according to the speed-resistance balance condition as shown in Table 1.

[0045] Table 1. Standard Hall anchor mass and falling speed at 10m water depth

[0046] Anchor weight (kg) Falling speed at 10m water depth (m / s) 35 2.052 40 3.336 60 3.571 100 3.873 125 4.034 150 4.148 180 4.284 240 4.478

[0047] Using the different mass anchors and falling speeds in Table 1 as the boundary conditions of the mechanical analysis model of submarine cable anchor failure, the plastic deformation of each layer in the submarine cable is analyzed, as shown in Table 2. It can be seen that under the impact of different mass anchors, the metal layers enter the plastic deformation stage with different impact energies, and there are obvious differences. When the submarine cable is hit by a 35kg anchor falling at a depth of 10 meters, the steel wire armor layer and lead sheath inside the submarine cable undergo plastic deformation, while the conductor is protected by the external insulation layer and does not undergo plastic deformation; with the increase of the mass of the anchor, the impact energy is also increasing. Under the impact of a 180kg anchor falling at a depth of 10 meters, the internal conductor of the submarine cable begins to undergo plastic deformation.

[0048] Table 2 Plastic deformation of each metal layer under different anchor weight impact

[0049]

[0050] The stress and deformation values ​​of the optical fiber under the impact of two types of anchors with different masses are extracted as the warning thresholds of this type of submarine cable, as shown in Table 3. That is, when the steel wire armor undergoes plastic deformation, the stress of the optical fiber is 3.14MPa and the deformation is 3.46mm; when the lead sheath undergoes plastic deformation, the stress of the optical fiber is 11.98MPa and the deformation is 4.16mm; when the conductor undergoes plastic deformation, the stress of the optical fiber is 17.15MPa and the deformation is 6.45mm.

[0051] Table 3 Optical fiber stress deformation values ​​under plastic deformation of each metal layer of submarine cable

[0052]

[0053] For the composite optical fiber three-core 220kV submarine cable, the warning of its anchor failure is divided into three levels of damage warning, as shown in Table 4. Among them, the first level damage warning means that the submarine cable is disturbed, but the metal layers of the submarine cable are not damaged; the second level damage warning means that the submarine cable is hit by the anchor, and the external protective steel wire armor layer and lead sheath have irreversible plastic deformation, but the internal transmission conductor of the submarine cable is not damaged. At this time, the submarine cable can still operate normally, but the operation and maintenance personnel should be notified to arrange underwater inspections during subsequent routine maintenance to further determine the damage status of the location; the third level damage warning means that the transmission conductor of the submarine cable core undergoes plastic deformation. At this time, the fault needs to be evaluated in combination with the subsequent submarine cable anchor failure assessment method.

[0054] Table 4 Composite optical fiber three-core 220kV submarine cable warning

[0055]

[0056] Therefore, if the submarine cable has not failed, but the monitored optical fiber stress deformation value reaches the warning threshold of the third-level damage warning, the conductor in the submarine cable has entered plastic deformation and the core is damaged. However, the submarine cable can also operate with damage for a short time. The operation and maintenance personnel should be reminded in time to carry out subsequent submarine cable salvage and repair to avoid greater damage during long-term operation.

[0057] Regarding diagnosis, it is first necessary to determine the diagnostic threshold value of each ship anchor type, and then diagnose the ship anchor type that caused the anchor failure based on this and combined with maritime information.

[0058] The representative small and medium-sized ships (fishing boats, passenger ships and cargo ships) in the offshore area are taken as the analysis objects. The specific ship parameters and anchor weights are shown in Table 5 below.

[0059] Table 5 Related parameters of different types of ships

[0060] Vessel Type Length / m Width / m Draft / m Displacement / t Anchor weight / kg Fishing boats 32 7.3 1.9 100 360 Passenger Ship 48 9.7 2.5 1000 1020 cargo ship 85 15.5 4.8 5000 2100

[0061] The anchors configured by the above three typical ships fall at a water depth of 10m as the boundary condition. The mechanical analysis model of submarine cable anchor failure is used to calculate the internal optical fiber stress deformation distribution cloud map when the transmission submarine cable is damaged by the three types of ship anchors, and the corresponding optical fiber monitoring quantity information characteristics are obtained as shown in Table 6.

[0062] Table 6 Fiber optic characteristic monitoring quantities of three typical ship anchor failures

[0063]

[0064] For submarine cables that are hit by three types of ship anchors and cause failures, optical fiber stress strain and maritime information (AIS) can be used for diagnosis and analysis. The diagnostic analysis flow chart is as follows: Figure 7 shown.

[0065] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art.

[0066] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A submarine cable anchor failure assessment and early warning method, characterized by: Monitor optical fiber stress deformation value, optical fiber operation status, optical fiber temperature and current of each layer of submarine cable; Evaluate whether the submarine cable has a fault based on the optical fiber operating status, optical fiber temperature and the current of each metal layer of the submarine cable; If there is no failure in the submarine cable, the warning level is determined based on the monitored optical fiber stress deformation value.

2. The method for evaluating and warning of submarine cable anchor failure according to claim 1 is characterized in that: The method for evaluating whether a submarine cable fails is as follows: if the optical fiber fails, the optical fiber temperature is greater than 90° C., or the currents of all metal layers of the submarine cable are 0A, the submarine cable fails.

3. The method for evaluating and warning of submarine cable anchor failure according to claim 1 is characterized in that: The warning degree is divided based on whether plastic deformation occurs in each metal layer of the submarine cable as the warning threshold, and the optical fiber stress deformation value is used as the warning threshold value for judgment.

4. The method for evaluating and warning of submarine cable anchor failure according to claim 3 is characterized in that: The warning level is divided into three levels of damage warning: If no plastic deformation occurs in the metal layers of the submarine cable, it is a first-level damage warning; If the steel wire armor layer and lead sheath of the submarine cable undergo plastic deformation, it is a secondary damage warning; If the core transmission conductor of the submarine cable undergoes plastic deformation, it will be a level 3 damage warning.

5. The method for evaluating and warning of submarine cable anchor failure according to claim 4 is characterized in that: The method for determining the warning degree is as follows: Determine the warning thresholds for each level of damage warning; The damage warning level is determined based on the relationship between the monitored optical fiber stress deformation value and the warning threshold value of each damage warning level.

6. The method for evaluating and warning of submarine cable anchor failure according to claim 5 is characterized in that: The method for determining the warning threshold value of each level of damage warning level is as follows: Calculate the falling speed of anchors of different masses at the depth of seawater in the sea area where submarine cables are laid; Using anchors of different masses and corresponding falling speeds as the boundary conditions of the mechanical analysis model of anchor failure of submarine cables, the plastic deformation of each metal layer of the submarine cable is analyzed, and the minimum mass anchor that causes plastic deformation of the steel wire armor layer and lead sheath of the submarine cable and plastic deformation of the core transmission conductor is obtained; The optical fiber stress deformation values ​​when two minimum mass anchors hit the submarine cable are extracted as the warning thresholds for judging the damage warning levels.

7. The method for evaluating and warning of submarine cable anchor failure according to claim 1 is characterized in that: The optical fiber stress deformation value is the optical fiber stress deformation value when the optical fiber is relatively far from the anchor position.

8. A method for diagnosing a submarine cable anchor failure, characterized in that: According to the submarine cable anchor failure assessment and early warning method according to any one of claims 1 to 7, assess whether a submarine cable fails; If a submarine cable fails, the type of ship anchor that caused the anchor failure can be diagnosed based on the monitored optical fiber stress deformation value and maritime information.

9. The method for diagnosing a submarine cable anchor failure according to claim 8, characterized in that: The diagnosis method of the ship anchor type is: Determine diagnostic threshold quantities for each ship anchor type; The type of ship anchor is preliminarily determined based on the relationship between the monitored optical fiber stress deformation value and the diagnostic threshold value of each ship anchor type. The anchor-smashing ship is finally determined by combining maritime information to determine whether there is a ship of this type in the sea area where the anchor was struck.

10. The method for diagnosing submarine cable anchor failure according to claim 9, characterized in that: The method for determining the diagnostic threshold value of each ship anchor type is as follows: taking the depth of sea water in the sea area where the submarine cable is laid as the boundary condition, and using the submarine cable anchor failure mechanics analysis model to calculate the optical fiber stress deformation value when the submarine cable is damaged by the anchor of each ship, as the diagnostic threshold value of each ship anchor type.

Images