A damage detection method for underwater long-distance power transmission cables

Abstract

The present invention discloses a method for detecting the degree of damage of underwater long-distance power transmission cables. The method for detecting the degree of damage of underwater long-distance power transmission cables can achieve the purpose of rapid detection and identification of underwater long-distance power transmission cables when insulation damage occurs. The method for detecting the degree of damage includes power transmission cable detection mode and data acquisition, establishment of a damage model of long-distance power transmission cables and calculation of damage factors, and judgment of the degree of damage of long-distance power transmission cables, thereby judging the service performance of underwater cables. The beneficial effect of the present invention is that it can safely, efficiently and accurately monitor and warn the insulation damage and line faults of underwater long-distance power transmission cables online, thereby improving their underwater operation reliability.

Description

Technical Field

[0001] The invention relates to the field of underwater cable fault detection and diagnosis, and in particular to a method for detecting the damage degree of underwater long-distance power transmission cables. Background Art

[0002] Underwater long-distance power transmission cables are currently the main form of power supply for islands, and are also the main way to transmit offshore renewable energy power generation. Compared with the land, the most prominent features of the underwater operating environment are the many uncertain factors, the high risk of insulation corrosion, and the high probability of external force damage. In addition, the complex seabed terrain and the significant effect of ocean currents can easily cause insulation damage to underwater power transmission cables. As the country continues to develop deep and deep sea areas, the total length of underwater power transmission cables continues to grow, and their working water depth continues to increase, resulting in a sharp increase in the difficulty of maintenance. In addition, storms are frequent in some sea areas, and it is very difficult for robots and maintenance personnel to dive, which makes the current operation and maintenance of underwater long-distance power transmission cables face great difficulties. Therefore, the present invention proposes a method for online detection of the degree of damage to underwater long-distance power transmission cables, avoiding the diving of maintenance personnel or equipment. It only needs to be detected at the end where the underwater cable is connected to the land, so that the damage in the entire line of the underwater cable can be detected in real time, which improves the efficiency of operation and maintenance operations and the safety of underwater power transmission cable detection.

[0003] At present, in actual testing, there is no very effective method for detecting damage to underwater long-distance power transmission cables. The main methods used in onshore cable testing are traveling wave method, time domain reflection method and optical fiber ranging, and the application effect still needs to be improved. Therefore, in order to reduce the workload of on-site testing and improve the efficiency and accuracy of testing, it is necessary to conduct research on the damage detection method of underwater long-distance power transmission cables and propose an intelligent method that can monitor the operating status of power transmission cables online in real time. Summary of the invention

[0004] The purpose of the present invention is to provide a method for detecting the damage degree of underwater long-distance power transmission cables.

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

[0006] 1. A method for detecting the damage degree of underwater long-distance power transmission cables, which is used to achieve the purpose of rapid detection and identification of insulation damage in underwater long-distance power transmission cables, and is characterized in that it comprises the following steps:

[0007] Step 1: Transmission cable detection and data acquisition

[0008] 1.1 Use the spread spectrum time domain reflectometry technique to modulate the high-frequency test signal s(t). The modulated test signal frequency f x50kHz, 500kHz, 10MHz, 30MHz, 200MHz respectively; wherein x = 1, 2, 3, ..., 5; and the modulated high frequency test signal is s x (t), x = 1, 2, 3, ..., 5;

[0009] 1.2 Connect the relevant test instrument to the terminal of the underwater long-distance power transmission cable, which is located at the end close to the power-consuming equipment or the end close to the power generation equipment. Use the connector to closely connect the test instrument to the underwater cable to be tested.

[0010] 1.3 Carry out the traveling wave test at each test frequency modulated in 1.1 in turn, and collect the corresponding reflected traveling wave signal at the cable terminal position in turn, and use r x (t), x = 1, 2, 3, ..., 5;

[0011] 1.4 According to steps 1.1 to 1.3, repeat the test several times to ensure that the reflected signal obtained remains stable. Take the average value of multiple tests to obtain the test frequency f x The corresponding transmission signal s x (t) and the reflected signal r x (t);

[0012] Step 2: Establishment of damage model for long-distance transmission cables and calculation of damage factor

[0013] According to the different test frequencies, the signal s is transmitted x (t) and the reflected signal r x (t), and establish the damage model of underwater long-distance transmission cables:

[0014] 2.1 Reflection signal r x (t) Perform mixed signal isolation processing as follows:

[0015] re x (t) = w x *r x (t)-n x *s x (t)-l x (t) (1)

[0016]

[0017] In the formula, w x 、n x are respectively the reflection signal proportional factor and the transmission signal mixing coefficient, l x is the background noise signal;

[0018] 2.2 Obtain the transmitted signal s under different test frequency signals respectivelyx (t) and the reflected signal re after isolation x The mutual similarity function G of (t) d (t), as shown below:

[0019]

[0020] Where λ is the first transmitted signal s during the test process x (t) and the received reflected signal r x The time difference between (t), that is, the delay time, the value range of λ is [0,63 / f x ];

[0021] 2.3 According to the calculated mutual similarity function value, draw the corresponding mutual similarity function curve, denoted as g x (λ), by the curve g x (λ) is analyzed to obtain the damage factor g' of underwater transmission cables.

[0022]

[0023] Step 3: Determine the damage degree of long-distance transmission cables

[0024] According to the range of the damage factor g' obtained in the above steps, the degree of damage to the transmission cable is judged. When g'=0, it is determined that the tested transmission cable is not damaged as a whole and is in good condition.

[0025] When g'=1, it is preliminarily determined that the transmission cable has slight insulation damage in a local location and can continue to be used, but requires enhanced monitoring;

[0026] When g'=2, it is judged that the transmission cable has moderate insulation damage in a large area, and the damage depth is small. It is necessary to further detect the damage location and damage type, and perform maintenance according to the situation;

[0027] When g'=3, it is determined that the tested transmission cable has serious insulation damage, and the damage area is large and there are many damage points. It is necessary to immediately detect the damage location and type, and carry out power outage maintenance as soon as possible;

[0028] When g'=4, it indicates that part of the insulation of the transmission cable has been penetratingly damaged. The operating status of the cable is at a dangerous level. The damage should be located immediately, and the power should be shut down for maintenance or replacement of the damaged part.

[0029] Furthermore, the method further comprises the following steps:

[0030] The damage degree detection method for underwater long-distance power transmission cables is described. According to the overall length of the underwater long-distance power transmission cables, the frequency of the modulated high-frequency test signal s(t) is changed. The test signal frequency f x Appropriate reduction or increase is made among 50kHz, 500kHz, 10MHz, 30MHz and 200MHz to make it more suitable for intelligent evaluation of different types of underwater power transmission systems.

[0031] The beneficial effects of the present invention are:

[0032] 1. The damage degree detection method for underwater long-distance power transmission cables of the present invention can efficiently, accurately, real-time and conveniently judge and evaluate the operating status and damage problems of long-distance underwater cables, avoid power outages caused by underwater cable insulation failures or line failures, and improve the reliability of offshore new energy power plants and island power supply.

[0033] 2. The damage degree detection method for underwater long-distance power transmission cables of the present invention can timely discover potential dangers and faults of underwater power transmission cables, and provide a basis for on-site operation and maintenance personnel to accurately judge the service performance and maintenance necessity of underwater cables through comparison and analysis of historical data. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the method for detecting the damage degree of underwater long-distance power transmission cables of the present invention; DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] Figure 1 This is a flow chart of the method for detecting the damage degree of underwater long-distance power transmission cables of the present invention, which is used to achieve the purpose of rapid detection and identification of insulation damage in underwater long-distance power transmission cables. The method of using the method includes the following contents:

[0037] Step 1: Transmission cable detection and data acquisition

[0038] 1.1 Use the spread spectrum time domain reflectometry technique to modulate a high-frequency test signal s(t), the modulated test signal frequencies fx are 50kHz, 500kHz, 10MHz, 30MHz, 200MHz, respectively; where x = 1, 2, 3, ..., 5; and modulate the high-frequency test signal at s x (t), x = 1, 2, 3, ..., 5;

[0039] 1.2 Connect the relevant test instrument to the terminal of the underwater long-distance power transmission cable, which is set at the end close to the power-consuming equipment or at the end close to the power generation equipment. Use the connector to closely connect the test instrument to the underwater cable to be tested;

[0040] 1.3 Carry out the traveling wave test at each test frequency modulated in 1.1 in turn, and collect the corresponding reflected traveling wave signal at the cable terminal position in turn, and use r x (t), x = 1, 2, 3, ..., 5;

[0041] 1.4 According to steps 1.1 to 1.3, repeat the test several times to ensure that the reflected signal obtained remains stable. Take the average value of multiple tests to obtain the test frequency f x The corresponding transmission signal s x (t) and the reflected signal r x (t);

[0042] Step 2: Establishment of damage model for long-distance transmission cables and calculation of damage factor

[0043] According to the different test frequencies, the signal s is transmitted x (t) and the reflected signal r x (t), and establish the damage model of underwater long-distance transmission cables:

[0044] 2.1 Reflection signal r x (t) Perform mixed signal isolation processing as follows:

[0045] re x (t) = w x *r x (t)-n x *s x (t)-l x (t) (1)

[0046]

[0047] In the formula, w x 、n x are respectively the reflection signal proportional factor and the transmission signal mixing coefficient, l x is the background noise signal;

[0048] 2.2 Obtain the transmitted signal s under different test frequency signals respectively x (t) and the reflected signal re after isolation x The mutual similarity function G of (t) d (t), as shown below:

[0049]

[0050] Where λ is the first transmitted signal s during the test process x (t) and the received reflected signal r x The time difference between (t), i.e., the delay time, the value range of λ is [0,63 / f x ];

[0051] 2.3 According to the calculated mutual similarity function value, draw the corresponding mutual similarity function curve, denoted as g x (λ), by the curve g x (λ) is analyzed to obtain the damage factor g' of underwater transmission cables.

[0052]

[0053] Step 3: Determine the damage degree of long-distance transmission cables

[0054] According to the range of the damage factor g' value obtained in the above steps, the degree of damage to the transmission cable is judged.

[0055] When g'=0, it is determined that the tested transmission cable is not damaged as a whole and is in good condition;

[0056] When g'=1, it is preliminarily determined that the transmission cable has slight insulation damage in a local location and can continue to be used, but requires enhanced monitoring;

[0057] When g'=2, it is judged that the transmission cable has moderate insulation damage in a large area, and the damage depth is small. It is necessary to further detect the damage location and damage type, and perform maintenance according to the situation;

[0058] When g'=3, it is determined that the tested transmission cable has serious insulation damage, and the damage area is large and there are many damage points. It is necessary to immediately detect the damage location and type, and carry out power outage maintenance as soon as possible;

[0059] When g'=4, it indicates that part of the insulation of the transmission cable has been penetratingly damaged. The operating status of the cable is at a dangerous level. The damage should be located immediately, and the power should be shut down for maintenance or replacement of the damaged part.

[0060] In addition, the present invention also realizes the following test functions:

[0061] The damage degree detection method for underwater long-distance power transmission cables is described. According to the overall length of the underwater long-distance power transmission cables, the frequency of the modulated high-frequency test signal s(t) is changed. The test signal frequency f xAppropriate reduction or increase is made among 50kHz, 500kHz, 10MHz, 30MHz and 200MHz to make it more suitable for intelligent evaluation of different types of underwater power transmission systems.

Claims

1. A method for detecting the degree of damage of underwater long-distance power transmission cables, used for monitoring the operation status of submarine power transmission cables, characterized in that it comprises the following steps: Step 1: Transmission cable detection and data acquisition 1.1 Use the spread spectrum time domain reflectometry technique to modulate the high-frequency test signal s(t). The modulated test signal frequency f x They are 50kHz, 500kHz, 10MHz, 30MHz, and 200MHz respectively; in, x＝1,2,3，…，5； The modulated high frequency test signal is s x (t), x = 1, 2, 3, ..., 5; 1.2 Connect the relevant test instrument to the terminal of the underwater long-distance power transmission cable, which is located at the end close to the power-consuming equipment or the end close to the power generation equipment. Use the connector to closely connect the test instrument to the underwater cable to be tested. 1.3 Carry out the traveling wave test at each test frequency modulated in 1.1 in turn, and collect the corresponding reflected traveling wave signal at the cable terminal position in turn, and use r x (t), x = 1, 2, 3, ..., 5; 1.4 According to steps 1.1 to 1.3, repeat the test several times to ensure that the reflected signal obtained remains stable. Take the average value of multiple tests to obtain the test frequency f x The corresponding transmission signal s x (t) and the reflected signal r x (t); Step 2: Establishment of damage model for long-distance transmission cables and calculation of damage factor According to the different test frequencies, the signal s is transmitted x (t) and the reflected signal r x (t), and establish the damage model of underwater long-distance transmission cables: 2.1 Reflection signal r x (t) Perform mixed signal isolation processing as follows: re x (t)=w x *r x (t)-n x *s x (t)-l x (t) (1) In the formula, w x 、n x are respectively the reflection signal proportional factor and the transmission signal mixing coefficient, l x is the background noise signal; 2.2 Obtain the transmitted signal s under different test frequency signals respectively x (t) and the reflected signal re after isolation x The mutual similarity function G of (t) d (t), as shown below: Where λ is the first transmitted signal s during the test process x (t) and the received reflected signal r x The time difference between (t), that is, the delay time, the value range of λ is [0,63 / f x ]; 2.3 According to the calculated mutual similarity function value, draw the corresponding mutual similarity function curve, denoted as g x (λ), by the curve g x (λ) is analyzed to obtain the damage factor g' of underwater transmission cables. Step 3: Determine the damage degree of long-distance transmission cables According to the range of the damage factor g' value obtained in the above steps, the degree of damage to the transmission cable is judged. When g'=0, it is determined that the tested transmission cable is not damaged as a whole and is in good condition; When g'=1, it is preliminarily determined that the transmission cable has slight insulation damage in a local location and can continue to be used, but requires enhanced monitoring; When g'=2, it is judged that the transmission cable has moderate insulation damage in a large area, and the damage depth is small. It is necessary to further detect the damage location and damage type, and perform maintenance according to the situation; When g'=3, it is determined that the tested transmission cable has serious insulation damage, and the damage area is large and there are many damage points. It is necessary to immediately detect the damage location and type, and carry out power outage maintenance as soon as possible; When g'=4, it indicates that part of the insulation of the transmission cable has been penetratingly damaged. The operating status of the cable is at a dangerous level. The damage should be located immediately, and the power should be shut down for maintenance or replacement of the damaged part.

2. The method for detecting the degree of damage of underwater long-distance power transmission cables as claimed in claim 1, wherein the frequency of the modulated high-frequency test signal s(t) is changed according to the overall length of the underwater long-distance power transmission cable, and the test signal frequency f x Appropriate reduction or increase is made among 50kHz, 500kHz, 10MHz, 30MHz and 200MHz to make it more suitable for intelligent evaluation of different types of underwater power transmission systems.

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