CN114486581A - Dynamic submarine cable fatigue monitoring method for floating type fan - Google Patents
Dynamic submarine cable fatigue monitoring method for floating type fan Download PDFInfo
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Abstract
The invention provides a dynamic submarine cable fatigue monitoring method of a floating fan, which comprises the steps of connecting distributed optical fiber vibration measuring equipment, distributed optical fiber strain measuring equipment and distributed optical fiber attenuation measuring equipment to optical fibers in a dynamic submarine cable, and synchronously starting the optical fibers, and jointly analyzing the fatigue state of the dynamic submarine cable by using the vibration quantity measured by the distributed optical fiber vibration measuring equipment, the optical fiber strain quantity measured by the distributed optical fiber strain measuring equipment and the optical fiber attenuation quantity measured by the distributed optical fiber attenuation measuring equipment, so that the problems of strain and attenuation measurement in the shaking state of the dynamic submarine cable are effectively solved.
Description
Technical Field
The invention relates to the technical field of submarine dynamic submarine cable monitoring, in particular to a dynamic submarine cable fatigue monitoring method of a floating fan.
Background
The floating type fan is different from the fixed type offshore fan in that the fixed type fan is fixed on the seabed by means of a pile foundation, the part of the floating type fan under the seawater is arranged on a buoy and fixed on the seabed through a plurality of anchor cables, and the floating type fan can move along with the wind waves and generate electricity by facing the wind. The submarine cable connected between the floating wind turbine and the fixed platform (offshore booster station) is called a dynamic submarine cable (dynamic submarine cable for short), and the dynamic submarine cable is not buried under the seabed but is suspended in the sea water through a buoyancy device. Due to the scouring of ocean currents and sea waves, the dynamic submarine cable is always in a shaking state and is influenced by the irregular power generation time of the fan, and the power load and the thermal expansion of the dynamic submarine cable are also in a changing process. These characteristics all make the dynamic submarine cable more susceptible to mechanical fatigue and aging.
The submarine cable on-line monitoring means based on optical fiber sensing comprises a distributed optical fiber strain monitoring technology (BOTDA for short) based on Brillouin optical time domain analysis technology, a distributed optical fiber vibration monitoring technology (DVS for short) based on phase sensitive optical time domain analysis and a distributed optical fiber attenuation monitoring technology (OTDR for short) based on backward Rayleigh scattering, and the distributed optical fiber strain monitoring technology, the distributed optical fiber vibration monitoring technology (DVS for short) and the distributed optical fiber attenuation monitoring technology (OTDR for short) based on optical fiber sensing realize strain parameter measurement, vibration parameter measurement and attenuation parameter measurement of optical fibers in the dynamic submarine cable respectively. The traditional submarine cable on-line monitoring assumes that the submarine cable is in a static laying state, and strain, vibration and attenuation monitoring are mutually independent to operate and model analysis can also achieve a good monitoring effect. For a dynamic submarine cable, when the submarine cable shakes to cause local stress on the optical fiber to generate strain and transmission attenuation, the strain and attenuation of the optical fiber in the part are usually unstable dynamically, and the shaking causes the cable to have an alternately stressed, stretched and relaxed state. This creates a new problem: and how to extract reliable strain and attenuation parameters from the dynamic change data and analyze the fatigue state of the dynamic submarine cable. In contrast, the BOTDA and OTDR devices employ a method of transmitting laser pulses multiple times to perform measurement and averaging, the single measurement period of the BOTDA is not equal to 60 seconds to 600 seconds, the single measurement period of the OTDR is not equal to ten seconds to 60 seconds, and the single measurement period of the DVS is 1 millisecond. If the strain parameter of the optical fiber changes dynamically in the measurement period of the BOTDA, the measurement data can not reflect the true strain quantity. If the attenuation parameters of the optical fiber are dynamically changed during the measurement period of the OTDR, the measurement data is the average value of the attenuation during the measurement period.
Disclosure of Invention
In view of the above drawbacks of the prior art, the present invention provides a dynamic submarine cable fatigue monitoring method for a floating wind turbine, which is used to solve the problems of poor accuracy of dynamic submarine cable fatigue monitoring in the prior art.
To achieve the above and other related objects, the present invention provides a dynamic submarine cable fatigue monitoring method for a floating wind turbine, comprising: accessing distributed optical fiber vibration measuring equipment, distributed optical fiber strain measuring equipment and distributed optical fiber attenuation measuring equipment to optical fibers in the dynamic submarine cable, and synchronously starting the optical fibers to obtain measuring data of each preset position of the optical fibers; for the measurement data at each of the preset positions, performing the following steps: the distributed optical fiber vibration measuring equipment demodulates shaking parameters from the measuring data and respectively transmits the shaking parameters to the distributed optical fiber strain measuring equipment and the distributed optical fiber attenuation measuring equipment; the distributed optical fiber strain measurement equipment calculates the optical fiber strain of the dynamic submarine cable in a shaking state according to the shaking parameters so as to form an optical fiber strain time sequence of the preset position; and the distributed optical fiber attenuation measuring equipment calculates an optical fiber attenuation value of the dynamic submarine cable in a shaking state according to the shaking parameters so as to form an optical fiber attenuation time sequence of the preset position.
In an embodiment of the present invention, the synchronously turning on the distributed optical fiber vibration measurement device, the distributed optical fiber strain measurement device, and the distributed optical fiber attenuation measurement device includes: and a time synchronizer is respectively in communication connection with the optical fiber and distributed optical fiber vibration measuring equipment, the distributed optical fiber strain measuring equipment and the distributed optical fiber attenuation measuring equipment so as to realize synchronous starting.
In an embodiment of the present invention, the distributed optical fiber vibration measurement device demodulates a shaking parameter from the measurement data, and transmits the shaking parameter to the distributed optical fiber strain measurement device and the distributed optical fiber attenuation measurement device, respectively, including: the shaking parameters demodulated by the distributed optical fiber vibration measuring equipment comprise shaking intensity A and shaking frequency F to form a characteristic sequence [ A ]1,F1,A2,F2,A3,F3,……,An,Fn,……]And according to
Conversion to AF-signature sequence [ AF1,AF2,AF3,……,AFn,……]Extracting and establishing A characteristic vector, wherein A is [ A ═ A1,A2,A3,An,…]And continuously transmitting the AF characteristic sequence to the distributed optical fiber strain measurement equipment through a network, and transmitting the A characteristic vector to the distributed optical fiber attenuation measurement equipment.
In an embodiment of the present invention, the calculating to obtain the optical fiber strain amount of the dynamic submarine cable in a swaying state includes: the distributed optical fiber strain measurement equipment performs sequencing fitting on the received shaking parameter sequence, re-maps the Brillouin frequency offset data acquired by the distributed optical fiber strain measurement equipment, and calculates to obtain the optical fiber strain of the dynamic submarine cable in a shaking state.
In an embodiment of the present invention, the calculating to obtain the optical fiber attenuation of the dynamic submarine cable in a swaying state includes: the distributed optical fiber attenuation measuring equipment sequences the received shaking parameter sequences, re-maps the Rayleigh scattering intensity data acquired by the distributed optical fiber attenuation measuring equipment, and calculates to obtain the optical fiber attenuation of the dynamic submarine cable in a shaking state.
In an embodiment of the present invention, the method further includes: obtaining the optical fiber strain time sequence of each preset position; calculating the mean value of the optical fiber strain time series of each preset position to generate a first vector; calculating a first cross-correlation value of the optical fiber strain time sequence and the first vector at each preset position; and comparing the first cross-correlation value corresponding to each preset position with a first preset fatigue alarm threshold value respectively, and judging whether the optical fiber has strain fatigue at the corresponding preset position according to the comparison result.
In an embodiment of the present invention, the calculation formula of the first preset fatigue alarm threshold is: a first preset fatigue alarm threshold value ═ a × mean value of each of the first cross correlation values + b × mean square error of each of the first cross correlation values; wherein a and b are coefficients.
In an embodiment of the present invention, the method further includes: obtaining the optical fiber attenuation time sequence of each preset position; calculating the mean value of the optical fiber attenuation time sequence of each preset position to generate a second vector; calculating a second cross-correlation value between the optical fiber attenuation time sequence of each preset position and the second vector; and comparing the second cross-correlation values corresponding to the preset positions with a second preset fatigue alarm threshold respectively, and judging whether the optical fiber has attenuation fatigue at the corresponding preset positions according to the comparison result.
In an embodiment of the present invention, the calculation formula of the second preset fatigue alarm threshold is: a second preset fatigue alarm threshold value ═ c × mean value of each second cross-correlation value + d × mean square deviation of each second cross-correlation value; wherein c and d are coefficients.
In an embodiment of the present invention, the method further includes: if strain fatigue and attenuation fatigue exist at one preset position of the optical fiber at the same time, judging the fatigue grade of the preset position to be first grade; if strain fatigue or attenuation fatigue exists at one of the preset positions of the optical fiber, judging the fatigue grade of the preset position to be two grades; and if the strain fatigue and the attenuation fatigue do not exist at one preset position of the optical fiber, judging that the preset position is fatigue-free.
As described above, the dynamic submarine cable fatigue monitoring method for a floating wind turbine according to the present invention specifically uses an optical fiber sensing technology to collect strain, attenuation, and vibration information of a submarine cable, and fuses multi-source sensing data through an accurate clock synchronization technology, so as to extract and analyze strain and attenuation parameter signals under the submarine cable shaking background, and the method has the following main beneficial effects: the strain monitoring, the optical fiber attenuation monitoring and the optical fiber vibration monitoring parameters are comprehensively applied, original data of the strain and attenuation monitoring are processed by taking the vibration monitoring parameters as characteristic vectors aiming at the submarine cable in a shaking state, prepared optical fiber strain and attenuation parameters are obtained, fatigue point detection is carried out by utilizing a cross-correlation function, and the problem of strain and attenuation measurement in the shaking state of the dynamic submarine cable is solved.
Drawings
Fig. 1 is a schematic view of an application scenario of a dynamic submarine cable fatigue monitoring method for a floating wind turbine according to an embodiment of the present invention.
Fig. 2 is a schematic flow chart of a dynamic submarine cable fatigue monitoring method for a floating wind turbine according to an embodiment of the present invention.
Fig. 3 is a schematic flow chart of a dynamic submarine cable fatigue monitoring method for a floating wind turbine according to another embodiment of the present invention.
Fig. 4 is a schematic flow chart of a dynamic submarine cable fatigue monitoring method for a floating wind turbine according to another embodiment of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Fig. 1 shows an application scenario of the dynamic submarine cable fatigue monitoring method for floating wind turbine according to the present invention, wherein 1 is a wind turbine, 2 is a head buoy, 3 is a bending limiter, 4 is a buoyancy device, 5 is ballast, and 6 is a dynamic submarine cable.
In an embodiment, the dynamic submarine cable fatigue monitoring method of the floating wind turbine mainly includes the following steps:
firstly, accessing distributed optical fiber vibration measuring equipment, distributed optical fiber strain measuring equipment and distributed optical fiber attenuation measuring equipment to optical fibers in the dynamic submarine cable, and synchronously starting the optical fibers to obtain measuring data of each preset position of the optical fibers.
In detail, distributed optical fiber strain measurement equipment (BOTDA), distributed optical fiber vibration measurement equipment (DVS), and distributed optical fiber attenuation measurement equipment (OTDR) are selected as sensing equipment, and the three equipment are cooperatively used for measurement and analysis. The strain parameter measurement, the vibration parameter measurement and the attenuation parameter measurement of the optical fiber in the dynamic submarine cable are respectively realized by a distributed optical fiber strain monitoring technology (BOTDA) based on a Brillouin optical time domain analysis technology, a distributed optical fiber vibration monitoring technology (DVS) based on phase-sensitive optical time domain analysis and a distributed optical fiber attenuation monitoring technology (OTDR) based on backward Rayleigh scattering.
In an embodiment, a high-precision time synchronization device, for example, with a precision of 1 μ s, is connected to the BOTDA, the OTDR, and the DVS, respectively, to implement time synchronization of the three measurement devices, i.e., the BOTDA, the OTDR, and the DVS, at a level of 1 μ s. In addition, the three devices of BOTDA, OTDR, and DVS are respectively connected to a high-speed internet, such as a gigabit ethernet, thereby realizing mutual high-speed communication between the devices. Respectively connecting optical fibers in the dynamic submarine cable into BOTDA, OTDR and DVS equipment at T0And at the moment, the three devices start to collect and store original spectral data at each preset position on the optical fiber after being synchronously started.
Next, as shown in fig. 2, for the measurement data at each of the preset positions, the following steps are performed:
s10, the distributed optical fiber vibration measuring equipment demodulates shaking parameters from the measured data and respectively transmits the shaking parameters to the distributed optical fiber strain measuring equipment and the distributed optical fiber attenuation measuring equipment;
specifically, after receiving the data, the DVS performs a phase coherent demodulation calculation analysis. For example, the distributed optical fiber vibration measurement device takes Δ t as 10ms as an interval, the demodulated oscillation parameters include oscillation intensity a and oscillation frequency F, and a characteristic sequence [ a ] is formed1,F1,A2,F2,A3,F3,……,An,Fn,……]And according to
Conversion to AF-signature sequence [ AF1,AF2,AF3,……,AFn,……]Extracting and establishing A characteristic vector, wherein A is [ A ═ A1,A2,A3,An,…]And continuously transmitting the AF characteristic sequence to the distributed optical fiber strain measurement equipment through a network, and transmitting the A characteristic vector to the distributed optical fiber attenuation measurement equipment.
S20, calculating the optical fiber strain quantity of the dynamic submarine cable in the shaking state by the distributed optical fiber strain measuring equipment according to the shaking parameters to form the optical fiber strain time of the preset positionA sequence; for example, for fiber position z, the sequence ξ of the fiber strain at z position as a function of time can be foundtSequence of z-position optical fiber attenuation values with time ηt；
The BOTDA performs sequencing fitting on the eigenvectors received from the DVS, re-maps the collected Brillouin frequency offset data, and finally calculates to obtain the accurate optical fiber strain quantity in the sea cable shaking state. In detail, after the BOTDA receives the AF feature sequence continuously for N × Δ t, for example, 100 × 10ms, the AF feature sequence is formed by arranging N features in the AF sequence from small to large2Setting the position index of a certain characteristic quantity in the original AF sequence as p, and setting the position index in the new AF sequence as p2The position in the sequence is q, and the mapping relationship is described as q ═ f (p). The BOTDA stores raw spectrum data at intervals of Δ t-10 ms, and the BOTDA stores brillouin frequency offset data as B1, that is, B1-BΔt1,BΔt2,BΔt3…, respectively; changing B1 to BΔt1,BΔt2,BΔt3… is mapped into a new Brillouin frequency deviation sequence B2 according to the formula q ═ f (p), Lorenz curve fitting is carried out according to the B2 sequence, and the central position frequency deviation of the Lorenz curve is fbThe optical fiber strain ξ ═ (f)b-f0)*λ，f0The fundamental frequency offset of the optical fiber in a relaxed state can be scaled to 10874MHz at room temperature of 20 ℃, wherein the value of lambda is 18.9, and the like.
S30, calculating an optical fiber attenuation value of the dynamic submarine cable in a shaking state by the distributed optical fiber attenuation measuring equipment according to the shaking parameters to form an optical fiber attenuation time sequence of the preset position;
the OTDR sequences the eigenvectors received from the DVS, re-maps the eigenvectors into the Rayleigh scattering intensity data acquired by the OTDR, and finally calculates to obtain an accurate optical fiber attenuation value in the shaking state of the submarine cable. In detail, after the OTDR receives the a-feature sequence continuously for N × Δ t, e.g. 100 × 10ms, N features in the a-sequence are arranged in descending order to form a2Setting the position index of a certain characteristic quantity in the original A sequence as s, and setting the position index in the new A sequence as s2The position in the sequence is t, and the mapping relationship is described as t ═ f(s). OTDR with Δ t being 10msStoring raw spectrum data by recording, storing Rayleigh scattering intensity data by OTDR (optical time Domain reflectometer) as R1 ═ RΔt1,RΔt2,RΔt3…, respectively; r1 ═ RΔt1,RΔt2,RΔt3… is mapped into a new Rayleigh scattering intensity sequence R2 according to the formula of t ═ f(s), the R2 sequence is solved with the mean value eta according to the statistical theorem of large numbers, and eta is the optical fiber attenuation value.
Note that the sequence of step S20 and step S30 may be changed or synchronized with each other, and the present application is not limited thereto.
As shown in fig. 3, in an embodiment, the dynamic submarine cable fatigue monitoring method for a floating wind turbine of the present application further includes the following steps:
s40, obtaining the optical fiber strain time sequence of each preset position;
s50, calculating the mean value of the optical fiber strain time series of each preset position to generate a first vector;
s60, calculating a first cross correlation value between the optical fiber strain time sequence and the first vector at each preset position;
s70, comparing the first cross correlation values corresponding to the preset positions with first preset fatigue alarm thresholds respectively, and judging whether the optical fiber has strain fatigue at the corresponding preset positions according to the comparison result.
Steps S40 to S70 will be described in detail below.
The steps S10-S30 described above can obtain the time series xi of the optical fiber strain at each preset position of the optical fibertz1,ξtz2,ξtz3,.... For xi of different positionstz1,ξtz2,ξtz3,., averaging to obtain a first vector
Xi is reducedtz1,ξtz2,ξtz3,.. are respectively connected with
Calculating a first cross-correlation value to obtain a first cross-correlation value xi R at different positionszThe cross-correlation formula is R (N) ((1/N) ∑ [ x (m) y (m + N))]. Further, ξ R is solvedzIs μ ξ, the mean square error is σ ξ, and the first fatigue alarm threshold value Thd ξ +3 σ ξ is set as 1.5 μ ξ +3 σ ξ (the coefficient is not limited to this example); for position z1, if ξ Rz1And the position z1 is judged to have strain fatigue.
As shown in fig. 4, in an embodiment, the dynamic submarine cable fatigue monitoring method for a floating wind turbine of the present application further includes the following steps:
s80, obtaining the optical fiber attenuation time sequence of each preset position;
s90, calculating the mean value of the optical fiber attenuation time sequence of each preset position to generate a second vector;
s100, calculating a second cross-correlation value between the optical fiber attenuation time sequence of each preset position and the second vector;
s110, comparing the second cross correlation values corresponding to the preset positions with a second preset fatigue alarm threshold respectively, and judging whether the optical fiber is subjected to attenuation fatigue at the corresponding preset positions according to the comparison result.
The following describes steps S80 to S110 in detail.
The above-described steps S10-S30 can obtain the time series η of the optical fiber attenuation at each predetermined position of the optical fibertz1,ηtz2,ηtz3,.... Eta for different positionstz1,ηtz2,ηtz3,., averaging to obtain a second vector
Will etatz1,ηtz2,ηtz3,.. and
calculating a second cross-correlation value to obtain a second cross-correlation value eta R at different positionszThe cross-correlation formula is R (N) ((1/N) ∑ [ x (m) y (m + N))]. Further, η R is obtainedzIs μ η, the mean square error is σ η, and the second fatigue alarm threshold value Thd η is set to 1.5 μ η +3 σ η (the coefficients are not limited to these values)Example); for position z1, if η Rz1And the damping fatigue is judged to occur at the position z 1.
The sequence of steps S40 to S70 and steps S80 to S110 may be changed or synchronized with each other, but the present application is not limited thereto. Step S40-S70 innovatively uses the distributed optical fiber strain quantity as the dynamic fatigue evaluation of the basic data, and uses the cross-correlation function value as the parameter value for evaluating the strain fatigue; steps S80-S110 are dynamic fatigue evaluation based on distributed optical fiber attenuation as basic data, and the cross-correlation function value is used as the parameter value for evaluating the attenuation fatigue, that is, the average value of the feature vectors at different positions is taken as the reference, and the cross-correlation function is calculated by the feature vectors at different positions and the reference, and the discrimination threshold mode is extracted.
Further, after steps S40 to S110 are executed, the dynamic submarine cable fatigue monitoring method for a floating wind turbine of the present application further includes the following determination steps:
a. if strain fatigue and attenuation fatigue exist at one preset position of the optical fiber at the same time, judging the fatigue grade of the preset position to be first grade;
b. if strain fatigue or attenuation fatigue exists at one of the preset positions of the optical fiber, judging the fatigue grade of the preset position to be two grades;
c. and if the strain fatigue and the attenuation fatigue do not exist at one preset position of the optical fiber, judging that the preset position is fatigue-free.
For example, for position z1, if both strain fatigue and attenuation fatigue occur, then the fatigue at position z1 is determined to be ranked 1, if only one of them occurs, then the fatigue at position z1 is determined to be ranked 2, the rank 1 severity is greater than rank 2, otherwise no fatigue is determined.
In summary, according to the dynamic submarine cable fatigue monitoring method for the floating fan, the distributed optical fiber vibration measuring device, the distributed optical fiber strain measuring device and the distributed optical fiber attenuation measuring device are connected to the optical fibers in the dynamic submarine cable and are synchronously started, and the fatigue state of the dynamic submarine cable is jointly analyzed according to the vibration quantity measured by the distributed optical fiber vibration measuring device, the optical fiber strain quantity measured by the distributed optical fiber strain measuring device and the optical fiber attenuation quantity measured by the distributed optical fiber attenuation measuring device, so that the strain and attenuation measuring problems in the shaking state of the dynamic submarine cable are effectively solved, various defects in the prior art are effectively overcome, and the dynamic submarine cable fatigue monitoring method has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A dynamic submarine cable fatigue monitoring method of a floating wind turbine is characterized by comprising the following steps:
accessing distributed optical fiber vibration measuring equipment, distributed optical fiber strain measuring equipment and distributed optical fiber attenuation measuring equipment to optical fibers in the dynamic submarine cable, and synchronously starting the optical fibers to obtain measuring data of each preset position of the optical fibers;
for the measurement data at each of the preset positions, performing the following steps:
the distributed optical fiber vibration measuring equipment demodulates shaking parameters from the measuring data and respectively transmits the shaking parameters to the distributed optical fiber strain measuring equipment and the distributed optical fiber attenuation measuring equipment;
the distributed optical fiber strain measurement equipment calculates the optical fiber strain of the dynamic submarine cable in a shaking state according to the shaking parameters so as to form an optical fiber strain time sequence of the preset position; and the number of the first and second groups,
and the distributed optical fiber attenuation measuring equipment calculates an optical fiber attenuation value of the dynamic submarine cable in a shaking state according to the shaking parameters so as to form an optical fiber attenuation time sequence of the preset position.
2. The method of claim 1, wherein the synchronously activating the distributed optical fiber vibration measurement device, the distributed optical fiber strain measurement device, and the distributed optical fiber attenuation measurement device comprises:
and a time synchronizer is respectively in communication connection with the optical fiber and distributed optical fiber vibration measuring equipment, the distributed optical fiber strain measuring equipment and the distributed optical fiber attenuation measuring equipment so as to realize synchronous starting.
3. The method of claim 1, wherein the distributed fiber vibration measurement device demodulates a jitter parameter from the measurement data for transmission to the distributed fiber strain measurement device and the distributed fiber attenuation measurement device, respectively, comprising:
the shaking parameters demodulated by the distributed optical fiber vibration measuring equipment comprise shaking intensity A and shaking frequency F to form a characteristic sequence [ A ]1,F1,A2,F2,A3,F3,……,An,Fn,……]And according to
Conversion to AF-signature sequence [ AF1,AF2,AF3,……,AFn,……]Extracting and establishing A characteristic vector, wherein A is [ A ═ A1,A2,A3,An,…]And continuously transmitting the AF characteristic sequence to the distributed optical fiber strain measurement equipment through a network, and transmitting the A characteristic vector to the distributed optical fiber attenuation measurement equipment.
4. The method of claim 1, wherein the calculating to derive the fiber strain amount of the dynamic submarine cable in a sloshing state comprises:
the distributed optical fiber strain measurement equipment performs sequencing fitting on the received shaking parameter sequence, re-maps the Brillouin frequency offset data acquired by the distributed optical fiber strain measurement equipment, and calculates to obtain the optical fiber strain of the dynamic submarine cable in a shaking state.
5. The method of claim 1, wherein the calculating the fiber attenuation of the dynamic submarine cable in a sloshing state comprises:
the distributed optical fiber attenuation measuring equipment sequences the received shaking parameter sequences, re-maps the Rayleigh scattering intensity data acquired by the distributed optical fiber attenuation measuring equipment, and calculates to obtain the optical fiber attenuation of the dynamic submarine cable in a shaking state.
6. The method of claim 1, further comprising:
obtaining the optical fiber strain time sequence of each preset position;
calculating the mean value of the optical fiber strain time series of each preset position to generate a first vector;
calculating a first cross-correlation value of the optical fiber strain time sequence and the first vector at each preset position;
and comparing the first cross-correlation value corresponding to each preset position with a first preset fatigue alarm threshold value respectively, and judging whether the optical fiber has strain fatigue at the corresponding preset position according to the comparison result.
7. The method of claim 6, wherein the first preset fatigue warning threshold is calculated by the formula:
a first preset fatigue alarm threshold value a is the mean value of each first cross correlation value + b is the mean square error of each first cross correlation value; wherein a and b are coefficients.
8. The method of claim 1 or 6, further comprising:
obtaining the optical fiber attenuation time sequence of each preset position;
calculating the mean value of the optical fiber attenuation time sequence of each preset position to generate a second vector;
calculating a second cross-correlation value between the optical fiber attenuation time sequence of each preset position and the second vector;
and comparing the second cross-correlation values corresponding to the preset positions with a second preset fatigue alarm threshold respectively, and judging whether the optical fiber has attenuation fatigue at the corresponding preset positions according to the comparison result.
9. The method of claim 8, wherein the second predetermined fatigue warning threshold is calculated by the formula:
a second preset fatigue alarm threshold value ═ c × mean value of each second cross-correlation value + d × mean square deviation of each second cross-correlation value; wherein c and d are coefficients.
10. The method of claim 8, further comprising:
if strain fatigue and attenuation fatigue exist at one preset position of the optical fiber at the same time, judging the fatigue grade of the preset position to be first grade;
if strain fatigue or attenuation fatigue exists at one of the preset positions of the optical fiber, judging the fatigue grade of the preset position to be two grades;
and if the strain fatigue and the attenuation fatigue do not exist at one preset position of the optical fiber, judging that the preset position is fatigue-free.
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