Power cable on-line monitoring system and positioning method thereof

Abstract

The invention discloses a power cable on-line monitoring system and a positioning method thereof, and particularly relates to the technical field of cable fault positioning, the power cable on-line monitoring system comprises a signal acquisition module, a signal processing module, a signal positioning analysis module, a signal communication module and a signal display module, the signal acquisition module is provided with high-frequency current sensors according to specific intervals to acquire current traveling wave signals; the signal processing module carries out filtering, amplification and analog-to-digital conversion on the signal and extracts time domain and frequency domain features; the positioning analysis module calculates the position of a fault point based on the time domain reflected wave time difference and the frequency domain attenuation coefficient; the communication module transmits the coordinates of the fault point to a remote monitoring terminal; and the display module marks fault points and plans a maintenance path. The system can efficiently collect signals, accurately position fault points, adapt to various communication environments, facilitate maintenance planning and monitor the state of the sensor in real time, and effectively improve the fault monitoring and maintenance efficiency of the power cable.

Description

Technical Field

[0001] The present invention relates to the technical field of cable fault location, and more specifically, to an on-line monitoring system for power cables and a positioning method thereof. Background Art

[0002] In today's power supply system, power cables, as key facilities for transmitting electric energy, are widely used in various fields such as urban power grids and industrial plants. With the acceleration of urbanization and the continuous expansion of industrial production scale, the power demand continues to grow, which poses higher requirements for the stable operation of power cables. However, during the long-term operation of power cables, they face many challenges and faults occur from time to time.

[0003] From the perspective of internal factors, the cable insulation material will gradually age over time, its insulation performance will decline, and it is easy to cause short-circuit faults. At the same time, defects that may exist in the manufacturing process of the cable, such as uneven insulation layer thickness and insecure conductor connection, will also lead to faults after long-term operation. Considering external environmental factors, the intrusion of moisture in the natural environment, the corrosion of chemical substances in the soil, and the external damage caused by human factors such as construction excavation and vehicle rolling will all pose threats to the normal operation of the cable.

[0004] When a power cable fails, quickly and accurately locating the fault point and repairing it in time are crucial for ensuring the stability and reliability of power supply. If the fault location is inaccurate or the repair is not timely, it may cause large-scale power outages, bringing huge economic losses to industrial production, such as production line shutdown and product scrapping; it will also seriously affect the daily life of residents and reduce the quality of life.

[0005] Although the existing cable fault location technologies can meet some requirements to a certain extent, there are still obvious limitations. For example, some traditional off-line detection methods require the cable to be powered off for detection, which not only affects the continuity of power supply, but also has low detection efficiency and is difficult to meet the requirements of modern power systems for power supply reliability. Some on-line monitoring technologies based on the traveling wave method can locate faults while the cable is running, but in a complex cable network environment, the propagation of traveling waves will be interfered by various factors, resulting in a decrease in positioning accuracy and being unable to accurately determine the fault point location. In addition, the current monitoring systems also have deficiencies in sensor layout and status monitoring. Unreasonable sensor layout may lead to omission of fault signals, and there is a lack of real-time and effective monitoring of the working status of the sensors themselves. Once a sensor fails, the accuracy and reliability of the entire monitoring system will be greatly reduced. Therefore, it is of great practical significance to develop a more efficient, accurate and complex operating environment-adaptable on-line monitoring system for power cables and a positioning method thereof. Summary of the Invention

[0006] To overcome the above-mentioned defects of the prior art, the present invention provides an on-line monitoring system for power cables and a positioning method thereof to solve the problems raised in the above-mentioned background art.

[0007] To achieve the above object, the present invention provides the following technical solutions: An on-line monitoring system for power cables, comprising:

[0008] A signal acquisition module, which is provided with a plurality of high-frequency current sensors at intervals along the cable length direction for real-time acquisition of the current traveling wave signal of the cable;

[0009] A signal processing module, which filters, amplifies and performs analog-to-digital conversion on the acquired current traveling wave signal to extract time-domain and frequency-domain features;

[0010] A positioning analysis module, which establishes a positioning algorithm based on the time difference of the time-domain reflected wave and the frequency-domain attenuation coefficient to calculate the position of the fault point;

[0011] A communication module, which transmits the fault point coordinates to a remote monitoring terminal;

[0012] A display module, which marks the position of the fault point on the terminal map and provides a maintenance path plan.

[0013] Preferably, in the signal acquisition module, the arrangement interval of the high-frequency current sensors satisfies the formula:

[0014]

[0015] where D is the sensor interval, v is the traveling wave propagation speed in the cable, and Δt min is the minimum time resolution recognizable by the system.

[0016] Preferably, the signal processing module uses wavelet transform for noise suppression, and the filtered signal satisfies:

[0017]

[0018] where is the Morlet wavelet basis function, a is the scale factor, and b is the translation factor.

[0019] Preferably, the time-domain positioning formula of the positioning analysis module is:

[0020]

[0021] where L is the distance between the fault point and the nearest sensor, t1 is the arrival time of the initial traveling wave, and t2 is the arrival time of the reflected wave.

[0022] Preferably, the frequency-domain positioning formula of the positioning analysis module is:

[0023]

[0024] Among them, A1 and A2 are the amplitudes of adjacent sensor signals, is the phase, and d is the sensor spacing.

[0025] Preferably, the frequency-domain positioning result is optimized by a weighted fusion algorithm:

[0026] L final = w1L time + w2L freq

[0027] Among them, w1 and w2 are the weight coefficients of the time-domain and frequency-domain results, satisfying w1 + w2 = 1.

[0028] A positioning method based on the above-mentioned on-line monitoring system for power cables includes the following steps:

[0029] Step 1: Real-time collect the current traveling wave signals of the cable through a plurality of high-frequency current sensors arranged at intervals along the cable length direction;

[0030] Step 2: Filter, amplify, and perform analog-to-digital conversion on the current traveling wave signals to extract time-domain waveform and frequency-domain spectrum characteristics;

[0031] Step 3: Calculate the initial distance between the fault point and the nearest sensor based on the time difference of the time-domain reflected wave;

[0032] Step 4: Combine the frequency-domain attenuation coefficient and phase difference, and inversely deduce and correct the distance in combination with the propagation model;

[0033] Step 5: Output the final positioning result by using the weighted fusion algorithm;

[0034] Step 6: Upload the positioning result to the remote monitoring terminal through the dual-mode communication module;

[0035] Step 7: Mark the fault point coordinates on the terminal map and generate a maintenance path that avoids obstacles;

[0036] Step 8: Periodically send test pulses to verify the sensor status through the integrity of the reflected wave.

[0037] Preferably, in the above Step 4, the propagation model is:

[0038]

[0039] Among them, n is the number of full cycles of the phase, which is determined by multi-band joint solution.

[0040] The technical effects and advantages of the present invention:

[0041] 1. The signal acquisition module reasonably sets the spacing of high-frequency current sensors through its formula to ensure that current traveling wave signals can be accurately captured, avoiding missing fault information due to excessive spacing and preventing cost increase due to too small spacing, thus ensuring the high efficiency and economy of the monitoring system.

[0042] 2. The signal processing module uses wavelet transform to suppress noise and can adjust the scale factor and translation factor according to the characteristics of signals and noise, effectively filtering out noise, improving signal quality, reducing interference in fault feature extraction, and thus improving the fault location accuracy.

[0043] 3. The positioning analysis module combines time-domain and frequency-domain positioning algorithms. The time-domain positioning quickly and preliminarily determines the approximate location of the fault point, and the frequency-domain positioning calculates relevant parameters and inversely deduces and corrects the distance in combination with the propagation model. The two complement each other and are further optimized by the weighted fusion algorithm to combine their advantages and further improve the positioning accuracy.

[0044] 4. The communication module adopts a dual-mode communication method combining 4G / 5G and LoRa. In areas with good signals, 4G / 5G is used to achieve high-speed and stable transmission; in areas with weak signals or high power consumption requirements, it switches to LoRa to ensure the reliability of data transmission with low power consumption and long-distance transmission, adapting to different communication environments and ensuring the stable upload of positioning results.

[0045] 5. The display module marks the coordinates of the fault point on the map of the remote monitoring terminal and uses map software to plan a maintenance path to avoid obstacles, facilitating maintenance personnel to quickly reach the fault point, reducing maintenance time, and improving the recovery efficiency of the power system.

[0046] 6. By periodically sending test pulses and analyzing the integrity characteristics such as the amplitude and phase of the reflected waves of the sensors, the working state of the sensors is monitored in real time. Once the reflected waves are abnormal, an alarm is sent in time to notify the maintenance personnel for repair, ensuring the stable and reliable operation of the monitoring system and avoiding monitoring and positioning errors caused by sensor failures. Brief Description of the Drawings

[0047] Figure 1 It is a schematic flow diagram of the on-line monitoring and positioning method for power cables of the present invention. Detailed Embodiment

[0048] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0049] As shown in the attached Figure 1 When implementing using a positioning method of a power cable on-line monitoring system as shown, along the length direction of the power cable, according to the formula Determine a certain spacing and arrange multiple high-frequency current sensors at intervals. In actual operation, first, determine the traveling wave propagation speed v in the cable, which can be obtained from the material parameters of the cable and relevant technical manuals; at the same time, clarify the minimum time resolution Δt that the system can recognize. min , which is jointly determined by the hardware performance and software algorithm of the monitoring system. Suppose the traveling wave propagation speed v of a certain section of cable is 150 m / μs, and the minimum time resolution Δt that the system can recognize min . Then, according to the formula, calculate that the sensor spacing D ≤ 7.5 m, and D = 7 m can be selected during actual installation. These high-frequency current sensors collect the current traveling wave signals of the cable in real time, providing raw data for subsequent fault analysis. The beneficial effect of such a setting is that it ensures that the sensors can accurately capture the current traveling wave signals, and through reasonable spacing settings, it will not miss fault information due to too large a spacing, nor will it cause cost increase due to too small a spacing, ensuring the efficiency and economy of the monitoring system.

[0050] Then, the signal processing module uses wavelet transform for noise suppression and processes the collected current traveling wave signals according to the formula for processing, where is the Morlet wavelet basis function, a is the scale factor, and b is the translation factor for processing. In actual applications, select appropriate scale factor a and translation factor b according to the characteristics of the signal and the characteristics of the noise. For example, for current traveling wave signals containing high-frequency noise, the value of a can be appropriately adjusted to make the wavelet basis function have better resolution in the high-frequency band, so as to more effectively filter out the noise. After filtering the signal, it is amplified and analog-to-digital converted to extract time-domain and frequency-domain characteristics. The beneficial effect of this processing method is that it can significantly improve the signal quality, reduce the interference of noise on the extraction of fault characteristics, make the subsequent positioning analysis more accurate and reliable, and improve the accuracy of fault location.

[0051] Then, use the positioning analysis module for positioning. Specifically, first, perform time-domain positioning calculation. According to the time-domain positioning formula calculate the distance between the fault point and the nearest sensor. In actual operation, collect the initial traveling wave arrival time t1 and the reflected wave arrival time t2 through the sensor, and calculate in combination with the known traveling wave propagation speed. Suppose at a certain moment, a sensor collects the initial traveling wave arrival time t1 = 10 μs, the reflected wave arrival time t2 = 15 μs, and the traveling wave propagation speed v = 150 m / μs, then calculate that the distance between the fault point and this sensor is This step can quickly and preliminarily determine the approximate location of the fault point, providing a basis for subsequent precise analysis.

[0052] Then, perform frequency-domain positioning calculation, using the frequency-domain positioning formula and Calculate the frequency-domain attenuation coefficient and phase difference. Among them, A1(f) and A2(f) are the amplitudes of adjacent sensor signals, is the phase, and d is the sensor spacing. Through these parameters, combined with the propagation model (n is the number of full cycles of the phase, determined by multi-band joint solution) to inversely deduce and correct the distance. For example, given that the adjacent sensor spacing d = 10m, at a certain frequency f = 50Hz, it is measured that A1(50) = 2V and A2(50) = 1.5V, By calculating the frequency-domain attenuation coefficient α(50) and the phase difference Then, combined with the number of full cycles of the phase n determined by multi-band joint solution, substitute it into the propagation model to calculate the frequency-domain positioning distance L freq . Frequency-domain positioning can analyze the location of the fault point from another angle, complement the time-domain positioning result, and improve the accuracy of positioning.

[0053] With the fusion of positioning results, the weighted fusion algorithm L final = w1L time + w2L freq

[0054] Among them, w1 and w2 are the weight coefficients of the time-domain and frequency-domain results, satisfying w1 + w2 = 1. In practical applications, according to different environments and cable characteristics, appropriate weight coefficients are determined through a large amount of experimental data. For example, in an area with a relatively complex electromagnetic environment, the frequency-domain positioning is more affected by interference. At this time, the weight w2 of the frequency-domain result can be appropriately reduced, and the weight w1 of the time-domain result can be increased. This fusion algorithm combines the advantages of time-domain and frequency-domain positioning, further improves the accuracy of fault point positioning, and is more reliable than single time-domain or frequency-domain positioning.

[0055] Implementation of the communication module: Upload the positioning result to the remote monitoring terminal through a dual-mode communication module. In practical applications, a dual-mode communication method combining a 4G / 5G communication module and a LoRa communication module can be selected. In an area with good signal, the 4G / 5G communication module is preferentially used to achieve high-speed and stable data transmission, ensuring that the positioning result can be transmitted to the remote monitoring terminal in a timely and accurate manner; in an area with weak signal or high power consumption requirements, switch to the LoRa communication module to ensure the reliability of data transmission with the advantages of low power consumption and long-distance transmission. The beneficial effect of this dual-mode communication method is to adapt to different communication environments, ensure that the positioning result can be stably uploaded to the remote monitoring terminal, and improve the applicability and reliability of the system.

[0056] Implementation of the display module: Mark the coordinates of the fault point on the map of the remote monitoring terminal, and use the path planning function of the map software to generate a repair path that avoids obstacles in combination with the actual geographical environment and obstacle information. For example, when the fault point is located in the underground cable of a city street, the system will avoid obstacles such as buildings and rivers according to the map data and plan the most convenient repair path for the maintenance personnel. This function greatly facilitates the maintenance personnel to quickly reach the fault point for repair, reduces the repair time, and improves the recovery efficiency of the power system.

[0057] Implementation of sensor status verification: Periodically send test pulses to verify the sensor status through the integrity of the reflected wave. Set to send a test pulse every certain period (such as 1 hour). After receiving the test pulse, the sensor will generate a reflected wave. By analyzing the integrity of the reflected wave, such as whether the characteristics of the amplitude, phase, etc. of the reflected wave are within the normal range, to determine whether the sensor is working properly. If the reflected wave is abnormal, it indicates that the sensor may be faulty, and the system will promptly issue an alarm to notify the maintenance personnel for inspection. This method can monitor the working status of the sensor in real time, ensure the stability and reliability of the entire monitoring system, and avoid inaccurate fault monitoring and positioning caused by sensor failures.

[0058] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An on-line monitoring system for power cables, characterized in that, Including: A signal acquisition module, which is provided with a plurality of high-frequency current sensors at intervals along the cable length direction for real-time acquisition of the current traveling wave signals of the cable; A signal processing module, which filters, amplifies and performs analog-to-digital conversion on the acquired current traveling wave signals to extract time-domain and frequency-domain features; A positioning analysis module, which establishes a positioning algorithm based on the time difference of the time-domain reflected wave and the frequency-domain attenuation coefficient to calculate the position of the fault point; A communication module, which transmits the coordinates of the fault point to a remote monitoring terminal; A display module, which marks the position of the fault point on the terminal map and provides a maintenance path planning.

2. The on-line monitoring system for power cables according to claim 1, characterized in that, In the signal acquisition module, the layout interval of the high-frequency current sensors satisfies the formula: where D is the sensor spacing, v is the traveling wave propagation speed in the cable, and Δt min is the minimum time resolution recognizable by the system.

3. The on-line monitoring system for power cables according to claim 1, characterized in that, The signal processing module uses wavelet transform for noise suppression, and the filtered signal satisfies: Among them, is the Morlet wavelet basis function, a is the scale factor, and b is the translation factor.

4. An on-line monitoring system for power cables according to claim 1, characterized in that, The time-domain positioning formula of the positioning analysis module is: Wherein, L is the distance between the fault point and the nearest sensor, t1 is the arrival time of the initial traveling wave, and t2 is the arrival time of the reflected wave.

5. An on-line monitoring system for power cables according to claim 4, characterized in that, The frequency-domain positioning formula of the positioning analysis module is: where A1 and A2 are the amplitudes of adjacent sensor signals, is the phase, and d is the sensor spacing.

6. The on-line monitoring system for power cables according to claim 5, characterized in that, The frequency-domain positioning result is optimized by a weighted fusion algorithm: L final = w1L time + w2L freq Wherein, w1 and w2 are the weight coefficients of the time-domain and frequency-domain results, and satisfy w1 + w2 = 1.

7. A positioning method for an on-line monitoring system of a power cable according to any one of claims 1-6, characterized in that Including the following steps: Step 1: Real-time acquisition of the current traveling wave signals of the cable through a plurality of high-frequency current sensors arranged at intervals along the cable length direction; Step 2: Filter, amplify and perform analog-to-digital conversion on the current traveling wave signals to extract time-domain waveform and frequency-domain spectrum features; Step 3: Calculate the initial distance between the fault point and the nearest sensor based on the time difference of the time-domain reflected wave; Step 4: Through the frequency-domain attenuation coefficient and phase difference, combine the propagation model to inversely deduce and correct the distance; Step 5: Use a weighted fusion algorithm to output the final positioning result; Step 6: Upload the positioning result to a remote monitoring terminal through a dual-mode communication module; Step 7: Mark the coordinates of the fault point on the terminal map and generate a maintenance path to avoid obstacles; Step 8: Periodically send test pulses to verify the sensor status through the integrity of the reflected wave.

8. A method for on-line monitoring and positioning of a power cable according to claim 7, characterized in that In the step 4, the propagation model is: Wherein, n is the number of full cycles of the phase, which is determined by multi-band joint solution.

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