Cable water tree aging positioning method based on dielectric spectrum diagnosis technology

Abstract

The invention discloses a cable water tree aging positioning method based on a dielectric spectrum diagnosis technology, and the analysis method comprises the following steps: 1), carrying out the dielectric spectrum test of a to-be-detected cable, and analyzing a detection result; 2) if the detection data has a layering phenomenon, the cable to be detected has an aging phenomenon; 3) performing low-voltage-high-voltage-low-voltage detection on the cable to be detected, and analyzing a detection result; 4) if the hysteresis reaction exists, determining that the water tree is aged, and if the hysteresis reaction does not exist, determining that the water tree is thermally aged; and 5) if water tree aging occurs, applying direct current voltage to two ends of the cable, performing dielectric spectrum testing again, analyzing detection data, and obtaining a conclusion. According to the method, aging types are classified according to the hysteresis response of water tree aging in the dielectric spectrum testing, water tree aging phenomenon fault points are positioned, and meanwhile, the integrity of the cable structure is ensured.

Description

Technical Field

[0001] The invention relates to a cable water tree aging positioning method based on dielectric spectrum diagnostic technology. Background Art

[0002] In today's power systems, high-voltage cross-linked polyethylene (XLPE) cables are widely used in power transmission and distribution due to their simple structure, excellent insulation performance, and superior heat resistance. However, over time and under the influence of various external factors, XLPE cables can face numerous problems during use, with water treeing being a critical and common issue.

[0003] Water tree aging can have a serious negative impact on cable performance and service life. This is primarily due to changes in the electric field distribution within the cable, leading to electric field concentration. This significantly reduces the cable's withstand capacity, potentially causing electrical dendrites and insulation defects, ultimately leading to irreversible functional degradation of the cable's insulation. In severe cases, this can even cause insulation breakdown, posing a significant threat to the safe and stable operation of power systems. Therefore, timely and accurate detection and diagnosis of water tree aging in XLPE cables is crucial. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for locating cable water tree aging based on dielectric spectrum diagnostic technology, which is practical and widely used, by utilizing the hysteresis reaction of water tree aging in dielectric spectrum testing to classify aging types and locate the fault points of water tree aging phenomena, while ensuring the integrity of the cable structure.

[0005] In order to solve the above problems, the present invention adopts the following technical solutions: The present invention discloses a method for locating cable water tree aging based on dielectric spectrum diagnostic technology, comprising the following steps: 1) Perform dielectric spectrum test on the cable to be tested and analyze the test results; 2) If the test data shows stratification, it means that the cable under test is aging; 3) Perform low voltage-high voltage-low voltage test on the cable to be tested and analyze the test results; 4) If there is a hysteresis reaction, it is water tree aging; if not, it is thermal aging; 5) If it is water tree aging, apply DC voltage to both ends of the cable, perform dielectric spectrum test again, analyze the test data and draw conclusions.

[0006] Preferably, the test in step 1) adopts a high-voltage, low-frequency dielectric spectrum test, which includes a signal generator, a power amplifier, two measurement fixtures, an oscilloscope, and a data acquisition system. The measurement fixture clamps the conductor at one end of the cable, and the other clamps the outside of the cable and is grounded. The test frequency is 0.01-0.1 Hz, and 50 sampling points are evenly set within this range. The test voltage is an AC power supply with the working voltage high voltage UT of the cable to be tested as the reference, and the voltage amplitude is set according to the cable length. The collected data is processed and analyzed to extract the dielectric spectrum data.

[0007] Preferably, the coefficient referenced in the delamination phenomenon in step 2) is the dielectric constant of the cable insulation layer: ; Where U is the measured current, I is the measured voltage, Phase difference; The corresponding value is measured at each frequency sampling point in a non-aged cable with the same specifications as the cable to be tested. , forming the original dielectric spectrum T0, each frequency sampling point obtained after the test cable is tested measures the corresponding , forming the original dielectric spectrum Tn, at each frequency sampling point, like: , then the count is 1, otherwise it is 0; If the system counter J 40, it means that delamination occurs and the cable under test is aging; otherwise, it does not occur.

[0008] Preferably, the steps of performing low voltage-high voltage-low voltage testing on the cable to be tested in steps 3) and 4) are as follows: A. The test voltage is 0.3UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D1; B. The test voltage is UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed without recording data; C. Within 1 minute after the end, the test voltage is 0.3UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D2; , then the count is 1, otherwise it is 0; If the system counter J 15, it means that hysteresis occurs and the cable under test has water tree aging, otherwise it has thermal aging.

[0009] Preferably, the step of locating the water tree aging of the cable to be tested in step 5) is: 1) Assume the length of the cable to be tested is L, the DC test voltage is Us, and the cable is divided into n test intervals. The cable length of a single test interval is , the voltage difference between the two ends of a single detection interval is ; 2) For length The test voltage for cables of the same specification is UT, and the test frequency is 0.01~0.1Hz. 50 sampling points are evenly set within this range to perform low-frequency dielectric spectrum testing and obtain test data frequency- Data F0; 3) First, the length is The same specification cables are added with 0 at both ends. , 2 , 3 ,...,n DC voltage, within 1 minute after the end, the test voltage is UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain test data frequency- Data F1, frequency- Data F2, ..., frequency-data Fn; 4) Calculate the coefficient for each voltage level , get the data matrix K; 5) Test the cable to be tested and the cable of the same specification (without aging) with a test voltage of UT and a test frequency of 0.01~0.1Hz. Set 50 sampling points evenly within this range and perform low-frequency dielectric spectrum testing to obtain the frequency- Data Z0 and frequency- Data Zw; 6) First, measure the DC voltage Us at both ends of the cable to be tested. Within 1 minute, the test voltage is UT and the test frequency is 0.01~0.1Hz. Set 50 sampling points evenly within this range to perform low-frequency dielectric spectrum test and obtain the test data frequency- Data Zt; 7) Calculate the coefficient of each sampling point ; 8) Calculate the average ; 9) Find the value in the data matrix that matches The closest value is obtained, and the number a corresponding to the value is obtained. Then the water tree aging position is X=a* nearby.

[0010] The beneficial effects of the present invention are: utilizing the hysteresis reaction of water tree aging in dielectric spectrum testing to classify aging types, locating the fault point of the water tree aging phenomenon, and ensuring the integrity of the cable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art, but this does not limit the scope of protection of the present invention.

[0012] Figure 1 is a flow chart of the method of the present invention; DETAILED DESCRIPTION

[0013] See Figure 1 A cable water tree aging location method based on dielectric spectrum diagnostic technology is shown, comprising the following steps: 1) Perform dielectric spectrum test on the cable to be tested and analyze the test results; 2) If the test data shows stratification, it means that the cable under test is aging; 3) Perform low voltage-high voltage-low voltage test on the cable to be tested and analyze the test results; 4) If there is a hysteresis reaction, it is water tree aging; if not, it is thermal aging; 5) If it is water tree aging, apply DC voltage to both ends of the cable, perform dielectric spectrum test again, analyze the test data and draw conclusions.

[0014] In step 1), the test uses a high-voltage, low-frequency dielectric spectrum test. The test includes a signal generator, a power amplifier, two measurement fixtures, an oscilloscope, and a data acquisition system. The measurement fixture clamps the conductor at one end of the cable, and the other clamps the outside of the cable and is grounded. The test frequency is 0.01-0.1 Hz, and 50 sampling points are evenly set within this range. The test voltage is the working voltage of the cable under test, high voltage U T The AC power supply is used as the benchmark, the voltage amplitude is set according to the cable length, the collected data is processed and analyzed, and the dielectric spectrum data is extracted.

[0015] The coefficient referenced in the delamination phenomenon described in step 2) is the dielectric constant of the cable insulation layer: ; Where U is the measured current, I is the measured voltage, Phase difference.

[0016] The corresponding value is measured at each frequency sampling point in a non-aged cable with the same specifications as the cable to be tested. , forming the original dielectric spectrum T0, each frequency sampling point obtained after the test cable is tested measures the corresponding , which constitutes the original dielectric spectrum T n , at each frequency sampling point; like: , then the count is 1, otherwise it is 0.

[0017] If the system counter J If the value is 40, it means that delamination has occurred and the cable under test has aged. Otherwise, it does not appear.

[0018] Furthermore, the steps of performing low voltage-high voltage-low voltage testing on the cable to be tested in steps 3) and 4) are as follows: 1. The test voltage is 0.3U T , the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D1.

[0019] 2. Test voltage is U T ,The test frequency is 0.01~0.1Hz. 50 sampling points are evenly set within this range to perform low-frequency dielectric spectrum test without recording data.

[0020] 3. Within 1 minute after step 2, the test voltage is 0.3U T , the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D2.

[0021] , then the count is 1, otherwise it is 0.

[0022] If the system counter J 15, it means that hysteresis occurs and the cable under test has water tree aging, otherwise it has thermal aging.

[0023] Furthermore, the step of locating the water tree aging of the cable to be tested in step 5) is as follows: A. Assume the length of the cable to be tested is L, the DC test voltage is Us, and the cable is divided into n test intervals. The cable length of a single test interval is , the voltage difference between the two ends of a single detection interval is .

[0024] B、For length The test voltage for cables of the same specification is U T , test frequency 0.01~0.1Hz, evenly set 50 sampling points within this range, perform low-frequency dielectric spectrum test, and obtain test data frequency- Data F0.

[0025] C. First, the length is The same specification cables are added with 0 at both ends. , 2 ,3,...,n DC voltage, within 1 minute after the test, the test voltage is U T，The test frequency is 0.01~0.1Hz. 50 sampling points are evenly set within this range to perform low-frequency dielectric spectrum testing. The test data frequency- Data F 1， frequency- Data F2, ..., frequency- Data F n .

[0026] D. Calculate the coefficient for each voltage level , and get the data matrix K.

[0027] E. Test the cable to be tested and the cable of the same specification (without aging) with a test voltage of U T , the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain the frequency- Data Z0 and frequency- Data Z w .

[0028] F. First, measure the DC voltage Us at both ends of the cable to be tested. Within 1 minute, the test voltage is T , test frequency 0.01~0.1Hz, evenly set 50 sampling points within this range, perform low-frequency dielectric spectrum test, and obtain test data frequency- Data Zt.

[0029] G. Calculate the coefficient of each sampling point ; H. Calculate the average ; Find the value in the data matrix that matches The closest value is obtained, and the number a corresponding to the value is obtained. Then the water tree aging position is near X=a*.

[0030] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

[0031] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that are not conceived through creative work should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined in the claims.

Claims

1. The present invention discloses a method for locating cable water tree aging based on dielectric spectrum diagnostic technology, which is characterized by: The following steps are involved: 1) Perform dielectric spectrum test on the cable to be tested and analyze the test results; 2) If the test data shows stratification, it means that the cable under test is aging; 3) Perform low voltage-high voltage-low voltage test on the cable to be tested and analyze the test results; 4) If there is a hysteresis reaction, it is water tree aging; if not, it is thermal aging; 5) If it is water tree aging, apply DC voltage to both ends of the cable, perform dielectric spectrum test again, analyze the test data and draw conclusions.

2. The cable water tree aging location method based on dielectric spectrum diagnostic technology according to claim 1 is characterized by: In step 1), a high-voltage, low-frequency dielectric spectrum test is used. The test includes a signal generator, a power amplifier, two measurement fixtures, an oscilloscope, and a data acquisition system. The measurement fixture clamps the conductor at one end of the cable, and the other clamps the outside of the cable, and the fixture is grounded. The test frequency is 0.01 to 0.1 Hz, with 50 sampling points evenly spaced within this range. The test voltage is an AC power supply based on the working voltage (high voltage UT) of the cable under test. The voltage amplitude is set according to the cable length. The collected data is processed and analyzed to extract the dielectric spectrum data.

3. The cable water tree aging location method based on dielectric spectrum diagnostic technology according to claim 1 is characterized by: The coefficient referenced in the delamination phenomenon in step 2) is the dielectric constant of the cable insulation layer: ; Where U is the measured current, I is the measured voltage, Phase difference; The corresponding value is measured at each frequency sampling point in a non-aged cable with the same specifications as the cable to be tested. , forming the original dielectric spectrum T0, each frequency sampling point obtained after the test cable is tested measures the corresponding , forming the original dielectric spectrum Tn, at each frequency sampling point, like: , then the count is 1, otherwise it is 0; If the system counter J40, it means that delamination occurs and the cable under test is aging. Otherwise, it does not occur.

4. The method for locating cable water tree aging based on dielectric spectrum diagnostic technology according to claim 1, characterized in that: The steps for performing low-voltage-high-voltage-low-voltage testing on the cable to be tested in steps 3) and 4) are as follows: A. The test voltage is 0.3UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D1; B. The test voltage is UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed without recording data; C. Within 1 minute after the end, the test voltage is 0.3UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain frequency- Data D2; , then the count is 1, otherwise it is 0; If the system counter J 15, it means that hysteresis occurs and the cable under test has water tree aging, otherwise it has thermal aging.

5. The method for locating cable water tree aging based on dielectric spectrum diagnostic technology according to claim 1, characterized in that: In step 5), the steps for locating the water tree aging of the cable to be tested are: 1) Assume the length of the cable to be tested is L, the DC test voltage is Us, and the cable is divided into n test intervals. The cable length of a single test interval is , the voltage difference between the two ends of a single detection interval is ; 2) For length The test voltage for cables of the same specification is UT, and the test frequency is 0.01~0.1Hz. 50 sampling points are evenly set within this range to perform low-frequency dielectric spectrum testing and obtain test data frequency- Data F0; 3) First, the length is The same specification cables are added with 0 at both ends. , 2, 3, ..., n DC voltage, within 1 minute after the end, the test voltage is UT, the test frequency is 0.01~0.1Hz, 50 sampling points are evenly set within this range, and low-frequency dielectric spectrum test is performed to obtain test data frequency- Data F1, frequency- Data F2, ..., frequency- Data Fn; 4) Calculate the coefficient for each voltage level , get the data matrix K; 5) Test the cable to be tested and the cable of the same specification (without aging) at a voltage of UT and a test frequency of 0.01-0.1 Hz. Set 50 sampling points evenly within this range and perform low-frequency dielectric spectrum testing to obtain frequency-data Z0 and frequency-data Zw. 6) First, measure the DC voltage Us at both ends of the cable to be tested. Within 1 minute, the test voltage is UT, the test frequency is 0.01~0.1Hz, and 50 sampling points are evenly set within this range to perform low-frequency dielectric spectrum test to obtain the test data frequency-data Zt; 7) Calculate the coefficient of each sampling point ; 8) Calculate the average ; 9) Find the value in the data matrix that matches The closest value is obtained, and the number a corresponding to the value is obtained. Then the water tree aging position is X=a* nearby.

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