A method for identifying and locating the moisture intrusion fault of an underwater cable

Abstract

The present invention discloses a method for identifying and locating the moisture ingress fault of underwater cables. The method for identifying and locating the moisture ingress fault of underwater cables can achieve the detection purpose of identifying and locating the moisture ingress faults of DC transmission cables in offshore wind farms, submarine observation networks, offshore drilling platforms, offshore power generation platforms and underwater combat systems, including steps such as acquisition of test data, establishment of moisture ingress fault diagnosis functions, identification and location of moisture ingress faults of underwater cables, etc., and can effectively judge the location where the moisture ingress fault of the underwater cable occurs and the degree of cable fault. The beneficial effects of the present invention are that it can efficiently, accurately, real-timely and conveniently identify and locate the moisture ingress and aging phenomena of cross-linked polyethylene cables used in submarine observation networks, offshore drilling platforms, offshore power generation platforms and underwater combat systems, etc., and discover potential hidden dangers of the power supply system in advance, so as to realize the reliable operation of the underwater cable power supply system.

Description

Technical Field

[0001] The present invention relates to the field of underwater cable fault assessment, and particularly to a method for identifying and locating the moisture ingress fault of underwater cables. Background Art

[0002] With the development of various fields such as deep - sea scientific research, resource development, combat deployment, and information observation, deep - sea development projects including offshore wind farms, subsea observatory networks, offshore drilling platforms, offshore power generation platforms, and underwater combat systems are booming. Since the deep - sea area is generally more than 100 km away from the land, and the distribution of various marine resources is extremely uneven, the distance between the power - consuming load units and the power - generation / supply units is generally far. Therefore, long - distance underwater cables have become the key to maintaining the power supply stability of various platforms and systems. However, the complex terrain and frequent seabed geological activities in the deep - sea area cause the transmission cables laid underwater to be easily damaged by external forces, resulting in water intrusion. Furthermore, moisture - affected areas of different areas and shapes appear between the multiple interfaces of the cable, causing changes in impedance parameters in some areas, leading to problems such as electric - field concentration, water / electric tree growth, and abnormal hot - spot generation in some areas. In severe cases, the leakage current at this part increases, greatly accelerating the deterioration process of the underwater cable and significantly reducing the power supply reliability of various deep - sea operation platforms.

[0003] Currently, the technology for identifying and locating the moisture ingress fault of underwater cables is still a difficult problem. Methods commonly used in land cables, such as AC / DC oscillating waves, ultra - low - frequency dielectric spectroscopy, and frequency - domain impedance spectroscopy, still cannot be well applied in the identification and location of moisture ingress faults of deep - sea underwater cables due to problems such as large equipment volume, severe signal attenuation, and strong external interference. Therefore, it is necessary to conduct research on the difficult problem of identifying and locating the moisture ingress fault of underwater cables and propose a technical method that can efficiently, safely, and conveniently identify and locate the moisture ingress fault of underwater cables. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for identifying and locating the moisture ingress fault of underwater cables.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] A method for identifying and locating the moisture ingress fault of underwater cables, used for identifying and locating the moisture ingress fault of the DC transmission cables of offshore wind farms, is characterized by including the following steps:

[0007] The first step: Acquisition of test data

[0008] 1.1 Using spread spectrum modulation technology, a high-frequency test signal is injected into the head end of the underwater cable to be tested. The high-frequency test signal is generated by a detection data processing background (13), a test signal port (14), a test signal sequence module (15), a sine modulation module (16), a test signal coupling channel (17), a test signal output terminal (18), a reflection signal input terminal (8), a feedback signal coupling channel (9), a modulation module (10), a reflection signal processing module (11), and a feedback signal port (12), and is connected to the corresponding test cable through a twisted pair. The underwater cable 1 (1), the underwater cable 2 (2), and the underwater cable 3 (3) are all powered by a DC power supply (4), and choke coils (5 - 7) are connected in series in the lines connecting the DC power supply and the underwater cable to reduce the interference of the power supply part on the high-frequency test signal and the feedback signal;

[0009] 1.2 The modulated high-frequency test signal can be loaded into the corresponding underwater cable through different coupling channels, and different numbers of channels can be selected according to actual needs; the high-frequency test signal is a sine-modulated pseudo-random sequence wave with frequencies of 50 kHz, 500 kHz, 10 MHz, and 30 MHz in sequence, and is represented by i x (t), where x = 1, 2, 3, 4, corresponding to different signal frequencies f x ;

[0010] 1.3 The corresponding reflection signal is obtained through the feedback loop, and is represented by k x (t), where x = 1, 2, 3, 4;

[0011] 1.4 Repeat the above test 3 times, and take the average value of the tests as the data source for fault identification and location calculation;

[0012] The second step: Establishment of the moisture fault diagnosis function

[0013] Record the time when the test channel starts to generate the high-frequency test signal as t1, and the time when the feedback channel receives the reflection signal as t2, then the delay time τ is τ = t2 - t1;

[0014] 2.1 Calculate the correlation relationship between the high-frequency test signal and the reflection signal, as follows

[0015] R x (t) = k x (t - τ) - i x (t) (1)

[0016] In the formula, k x (t - τ) is the test signal after delay processing, and x represents different test frequencies;

[0017] 2.2 Determine the moisture diagnosis function, as follows

[0018]

[0019] In the formula, t in represents the time at the start of the test, and t out represents the time at the end of the test. y represents the abscissa value related to the cable position, and M(t, y) is the integral transform kernel function, and its expression form is

[0020] M(t, y) = e -2νy (3)

[0021] In the formula, ν represents the propagation speed of the test signal in the cable, and is taken as 1.68e8 m / s;

[0022] 2.3 Compare the diagnostic function F x (y) calculated at different test frequencies as follows

[0023] A x (y) = F x (y) - F x+1 (y) (4)

[0024] Among them, x = 1, 3; at the same time, plot the comparison function A x (y) of the diagnostic function, with the ordinate being the value of the comparison function and the abscissa being y, analyze the distribution of the peaks in the function A x (y), and record the abscissas corresponding to the peaks as y1,

[0025] y2,... y n , where the abscissa of the rightmost side of the comparison function A x (y) is recorded as y L ;

[0026] Step 3: Identification and location method for underwater cable moisture damage faults

[0027] 3.1 Based on the calculation results of step 2.3, make a preliminary judgment on whether there is a moisture damage fault as follows

[0028] If there are peaks in A x (y), and there are points where the peak is greater than 0.5e4, it indicates that there is a moisture damage fault in the cable, and the number of moisture damage positions is related to the number of peaks that meet the requirements;

[0029] If there are peaks in A x (y), but all peaks are less than 0.5e4, it indicates that there is no moisture damage fault in the cable, but inspection and maintenance need to be strengthened;

[0030] If there are no peaks in A x (y), it indicates that there is no moisture damage fault in the cable and the operating state of the cable is good;

[0031] 3.2 Based on the judgment result in 3.1, locate the possible moisture-damaged fault points, and the location method is as follows

[0032]

[0033] In the formula, L is the total length of the cable line to be tested, i = 1, 2,..., n, and n is an even number;

[0034] 3.3 According to the above calculation steps, the moisture-damaged faults of the underwater cable can be finally identified and located, that is: the distributions of the moisture-damaged faults are [l1, l2], [l3, l4]... [l n-1 , l n .

[0035] Furthermore, it also includes the following steps:

[0036] The method for identifying and locating the moisture-damaged faults of an underwater cable can perform on-line fault tests on multiple cables simultaneously according to the number of cable lines to be tested, making it more suitable for the moisture-damaged fault location requirements of offshore power transmission cables under different operation requirements.

[0037] The beneficial effects of the present invention are as follows:

[0038] The method for identifying and locating the moisture-damaged faults of the underwater cable of the present invention can efficiently, accurately, real-timely and conveniently identify and locate the moisture-damaged and aging phenomena of the cross-linked polyethylene cables used in the subsea observation network, offshore drilling platform, offshore power generation platform and underwater combat system, etc., and discover the potential hidden dangers of the power supply system in advance to realize the reliable operation of the underwater cable power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the principle of the method for identifying and locating the moisture-damaged faults of the underwater cable of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The following further describes the present invention with reference to the drawings.

[0041] Figure 1 It is a schematic diagram of the principle of the method for identifying and locating the moisture-damaged faults of the underwater cable of the present invention, used for realizing the detection purpose of identifying and locating the moisture-damaged faults of the DC transmission cables of the offshore wind farm, subsea observation network, offshore drilling platform, offshore power generation platform and underwater combat system. Its structure and usage mode include the following contents:

[0042] The first step: Acquisition of test data

[0043] 1.1 Using the spread spectrum modulation technology, a high-frequency test signal is injected into the head end of the underwater cable to be tested. The high-frequency test signal is generated by the detection data processing background (13), the test signal port (14), the test signal sequence module (15), the sine modulation module (16), the test signal coupling channel (17), the test signal output end (18), the reflection signal input end (8), the feedback signal coupling channel (9), the modulation module (10), the reflection signal processing module (11) and the feedback signal port (12), and is connected to the corresponding test cable through a twisted pair. The underwater cable 1 (1), the underwater cable 2 (2), and the underwater cable 3 (3) are all powered by a DC power supply (4), and choke coils (5 - 7) are connected in series in the lines connecting the DC power supply and the underwater cables to reduce the interference of the power supply part on the high-frequency test signal and the feedback signal;

[0044] 1.2 The modulated high-frequency test signal can be loaded into the corresponding underwater cable through different coupling channels, and different numbers of channels can be selected according to actual needs; the high-frequency test signal is a sine-modulated pseudo-random sequence wave with frequencies of 50 kHz, 500 kHz, 10 MHz, and 30 MHz in sequence, and is represented by i x (t), where x = 1, 2, 3, 4, corresponding to different signal frequencies f x ;

[0045] 1.3 The corresponding reflection signal is obtained through the feedback loop and is represented by k x (t), where x = 1, 2, 3, 4;

[0046] 1.4 Repeat the above test 3 times, and take the average value of the tests as the data source for fault identification and location calculation;

[0047] The second step: Establishment of the moisture fault diagnosis function

[0048] Record the time when the test channel starts to generate the high-frequency test signal as t1, and the time when the feedback channel receives the reflection signal as t2, then the delay time τ is τ = t2 - t1;

[0049] 2.1 Calculate the correlation between the high-frequency test signal and the reflection signal as follows

[0050] R x (t) = k x (t - τ) - i x (t) (1)

[0051] In the formula, k x (t - τ) is the test signal after delay processing, and x represents different test frequencies;

[0052] 2.2 Determine the moisture diagnosis function as follows

[0053]

[0054] wherein, t in represents the time at the start of the test, and t out represents the time at the end of the test. y represents the abscissa value related to the cable position, and M(t, y) is the integral transform kernel function, and its expression is

[0055] M(t, y) = e -2νy (3)

[0056] wherein, ν represents the propagation speed of the test signal in the cable, which is taken as 1.68e8 m / s;

[0057] 2.3 Compare the diagnostic function F x (y) obtained at different test frequencies as follows

[0058] A x (y) = F x (y) - F x+1 (y) (4)

[0059] where x = 1, 3; meanwhile, plot the comparison function A x (y) of the diagnostic function, with the ordinate being the value of the comparison function and the abscissa being y, analyze the distribution of the peaks in the function A x (y), and record the abscissas corresponding to the peaks as y1,

[0060] y2,... y n , where the abscissa of the rightmost side of the comparison function A x (y) is recorded as y L ;

[0061] Step 3: Method for identifying and locating the moisture intrusion fault of the underwater cable

[0062] 3.1 Based on the calculation results of Step 2.3, make a preliminary judgment on whether there is a moisture intrusion fault as follows

[0063] If there are peaks in A x (y), and there are points where the peak is greater than 0.5e4, it indicates that there is a moisture intrusion fault in the cable, and the number of moisture intrusion positions is related to the number of peaks that meet the requirements;

[0064] If there are peaks in A x (y), but all the peaks are less than 0.5e4, it indicates that there is no moisture intrusion fault in the cable, but the inspection and maintenance need to be strengthened;

[0065] If there are no peaks in A x (y), it indicates that there is no moisture intrusion fault in the cable, and the operating state of the cable is good;

[0066] 3.2 Based on the judgment result in 3.1, locate the possible moisture-damaged fault points. The location method is as follows

[0067]

[0068] In the formula, L is the total length of the cable line to be tested, i = 1, 2,..., n, and n is an even number;

[0069] 3.3 According to the above calculation steps, the moisture-damaged fault of the underwater cable can be finally identified and located, that is: the distribution of the moisture-damaged fault is [l1, l2], [l3, l4]... [l n-1 , l n .

[0070] In addition, the present invention can also achieve the following test functions:

[0071] A method for identifying and locating the moisture-damaged fault of an underwater cable can perform on-line fault tests on multiple cables simultaneously according to the number of cable lines to be tested, making it more suitable for the moisture-damaged fault location requirements of offshore transmission cables under different operation requirements.

Claims

1. A method for identifying and locating the moisture fault of underwater cables, which is used to identify and locate the moisture faults of power transmission cables in offshore wind farms, subsea observation networks, offshore drilling platforms, offshore power generation platforms and underwater combat systems. It is characterized by the following steps: The first step: Acquisition of test data 1.1 Using spread spectrum modulation technology, a high-frequency test signal is injected into the head end of the underwater cable to be tested. The high-frequency test signal is generated by a detection data processing background (13), a test signal port (14), a test signal sequence module (15), a sine modulation module (16), a test signal coupling channel (17), a test signal output terminal (18), a reflection signal input terminal (8), a feedback signal coupling channel (9), a modulation module (10), a reflection signal processing module (11) and a feedback signal port (12), and is connected to the corresponding test cable through a twisted pair. The underwater cable 1 (1), the underwater cable 2 (2), and the underwater cable 3 (3) are all powered by a DC power supply (4), and choke coils (5 - 7) are connected in series in the lines connecting the DC power supply and the underwater cable to reduce the interference of the power supply part on the high-frequency test signal and the feedback signal; 1.2 The modulated high-frequency test signal can be loaded into the corresponding underwater cable through different coupling channels, and different numbers of channels can be selected according to actual needs; the high-frequency test signal is a sine-modulated pseudo-random sequence wave with frequencies of 50 kHz, 500 kHz, 10 MHz, and 30 MHz in sequence, and is represented by i x (t), where x = 1, 2, 3, 4, corresponding to different signal frequencies f x ; 1.3 Obtain the corresponding reflected signal through a feedback loop, denoted by k x (t), where x = 1, 2, 3, 4; 1.4 Repeat the above test 3 times, and take the average value of the tests as the data source for fault identification and location calculation; The second step: Establishment of a moisture ingress fault diagnosis function Record the time when the high-frequency test signal starts to be generated in the test channel as t1, and the time when the reflection signal is received in the feedback channel as t2. Then the delay time τ is τ = t2 - t1; 2.1 Calculate the correlation between the high-frequency test signal and the reflection signal as follows R x r(t) = k x r(t - τ) - i x r(t)(1) where k x (t - τ) is the test signal after delay processing, and x represents different test frequencies; 2.2 Determine the moisture ingress diagnosis function as follows where t in represents the time at the start of the test, and t out represents the time at the end of the test. y represents the abscissa value related to the cable position, and M(t, y) is the integral transform kernel function, and its expression is M(t,y) = e -2νy (3) In the formula, ν represents the propagation speed of the test signal in the cable, which is taken as 1.68e8 m / s; 2.3 Compare the diagnostic function F x (y) obtained at different test frequencies as follows A x (y) = F x (y) - F x+1 (y) (4) Among them, x = 1, 3; At the same time, plot the comparison function A x (y), where the vertical axis is the comparison function value and the horizontal axis is y, and analyze the distribution of the peaks in the function A x (y), and sequentially record the abscissas corresponding to the peaks as y1, y2,... y n , where the abscissa of the rightmost side of the comparison function A x (y) is recorded as y L ; The third step: Method for identifying and locating moisture ingress faults in underwater cables 3.1 Make a preliminary judgment on whether there is a moisture ingress fault according to the calculation result in step 2.3 as follows If A x (y) has a peak value, and there are points where the peak value is greater than 0.5e4, it indicates that there is a moisture ingress fault in the cable, and the number of moisture ingress positions is related to the number of peak values that meet the requirements; If A x If there are peaks in (y), but all peaks are less than 0.5e4, it indicates that there is no moisture ingress fault in the cable, but inspection and maintenance need to be strengthened; If A x (y) has no peak value, it indicates that there is no moisture ingress fault in the cable and the cable is in good operating condition; 3.2 According to the judgment result in 3.1, locate the possible moisture ingress fault points. The location method is as follows In the formula, L is the total length of the tested cable line, i = 1, 2,..., n, and n is an even number; 3.3 According to the above calculation steps, the moisture fault of the underwater cable can be finally identified and located, that is: the distributions of the moisture faults are [l1, l2], [l3, l4]…[l n-1 ,l n .

2. For a method for identifying and locating moisture ingress faults in an underwater cable as described in claim 1, online fault tests of multiple cables can be carried out simultaneously according to the number of cable lines to be tested, making it more suitable for the moisture ingress fault location requirements of offshore power transmission cables under different operation requirements.

Images