Cable channel fire monitoring method and system based on ultrasonic infrared thermography temperature measurement

Abstract

The invention discloses a cable channel fire monitoring method and system based on ultrasonic infrared thermal image temperature measurement. The method comprises the steps of obtaining a visible light image and a first infrared thermal image in a channel; if an abnormal temperature point appears in the infrared thermogram, positioning the cable position by using an identification algorithm, and judging the position of the abnormal temperature point; if the abnormal temperature point is located on the cable body, an ultrasonic generator is started, and a second infrared thermal image is obtained; comparing the temperature of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image, if the cable has a heating defect, constructing a three-dimensional temperature field model of the cable, outputting simulation temperature distribution of the inner side and the outer side of a cable insulation layer, and correcting the three-dimensional temperature field model of the cable; and based on the corrected simulated temperature distribution on the inner side of the cable insulation layer, judging the type of the cable insulation defect, and performing fire early warning. According to the invention, the core temperature of the inner side of the insulating layer can be obtained, defect types are subdivided, and accurate grading early warning of cable channel fire risks is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fire monitoring of cable channel, and particularly relates to a cable channel fire monitoring method and system based on ultrasonic infrared thermal imaging temperature measurement. BACKGROUND

[0002] With the continuous development of the electric power industry and the acceleration of urbanization, the number of cables is increasing, and the safety and stability of cable operation are very important. The cable is usually laid in the cable channel and is located underground, so it is difficult to monitor the signs of fire occurrence by artificial means. In order to ensure the stable supply of electricity, a non-contact temperature monitoring method for the cable channel is needed to determine the location of the abnormally high temperature point and improve the speed and accuracy of fire judgment. Uploading data to the cloud is also conducive to the unified management of the responsible department.

[0003] Existing temperature measurement methods usually use distributed optical fibers, manual temperature measurement, and robot temperature measurement, etc. However, distributed optical fibers need to be pre-set in the cable, and manual temperature measurement is inconvenient. For example, the patent document with publication number CN111273130A provides a cable fire monitoring and investigation emergency disposal integrated system and method. In the early stage of fire, a fire monitoring device arranged near the joint is used to carry out fire monitoring. When the fire monitoring device sends an alarm signal, a self-walking investigation robot group in the same interval is started to carry out emergency investigation of the fire, obtain fire positioning and fire scene picture data, and determine the location of the fire point. The fire-fighting system is linked to quickly start the fire-fighting mechanism. However, the robot is difficult to operate flexibly in the cable channel. For example, the patent document with publication number CN113689651A provides a cable channel early fire warning method, device, warning monitoring platform, and storage medium, which comprehensively uses cable electrical, temperature, and gas characteristic parameters to complete system identification and trend judgment to realize fire warning and alarm, and provides active safety protection for the cable channel. However, this method cannot and is not easy to determine whether the high temperature point in the channel is located in the cable body or the channel environment, which brings obstacles to the temperature monitoring of the cable and the cable channel. SUMMARY

[0004] The main purpose of the present application is to provide a cable channel fire monitoring method and system based on ultrasonic infrared thermal imaging temperature measurement, which is convenient for determining the location of the high temperature point and distinguishing the type, and overcoming the shortcomings of the prior art.

[0005] The present application adopts the following technical solutions.

[0006] The cable channel fire monitoring method based on ultrasonic infrared thermal imaging temperature measurement comprises: S1, arranging an infrared camera and an ultrasonic generator in the cable channel, monitoring in all angles through the infrared camera, and obtaining visible light images and first infrared thermal images in the channel; S2, if an abnormal temperature point appears in the infrared thermal image, compare the visible light image and the first infrared thermal image, and use a recognition algorithm to locate the cable position; combine the cable location to determine the position of the abnormal temperature point; S3, if the abnormal temperature point is located on the cable body, then turn on the ultrasonic generator and use the infrared camera to take pictures again to obtain a second infrared thermal image; compare the temperature of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image to determine whether the cable has a heating defect. S4. When the cable has a heating defect, construct a three-dimensional temperature field model of the cable and output the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, determine whether to correct the three-dimensional temperature field model of the cable. S5. Based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, determine the type of cable insulation defect, obtain a judgment report, and issue a fire warning based on the judgment report.

[0007] Further preferably, in S3, the temperature values ​​of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image are extracted and recorded as follows: and ;when minus If the deviation exceeds the set standard deviation threshold, the cable is deemed to have a heating defect; if minus If the temperature rise is not greater than the set standard deviation threshold, it indicates that the temperature rise is due to normal load or measurement deviation.

[0008] More preferably, by using the cable's basic parameters, including conductor cross-section, insulation layer thickness, material thermal conductivity, and collected current and ambient temperature data, a three-dimensional temperature field model of the cable is constructed through finite element simulation, and the simulated temperature distribution of the inner and outer sides of the cable insulation layer is output.

[0009] More preferably, in S4, multiple temperature sensors are arranged on the cable surface at different locations in the cable area detected by the infrared camera and ultrasonic generator to detect the cable surface temperature; the average value of the cable surface temperature detected by the sensors within a set distance from the abnormal temperature point is calculated, and the average value is recorded as the reference temperature of the three-dimensional temperature field model of the cable. When the absolute value of the deviation between the simulated temperature on the outside of the cable insulation layer and the reference temperature is greater than a set threshold, the simulation calculation parameters of the three-dimensional temperature field model of the cable are adjusted according to the reference temperature so that the absolute value of the deviation is not greater than the set threshold.

[0010] More preferably, the simulation calculation parameters include the convective heat transfer coefficient and the conductor contact resistance; Regarding the convective heat transfer coefficient, if the simulated temperature on the outside of the cable insulation layer is greater than the reference temperature, the initial convective heat transfer coefficient is increased by a certain percentage; if the simulated temperature on the outside of the cable insulation layer is not greater than the reference temperature, the initial convective heat transfer coefficient is decreased by a certain percentage; the certain percentage is set according to the actual situation. After each adjustment of the convective heat transfer coefficient, the simulated temperature of the outside of the cable insulation layer is re-simulated until the absolute value of the deviation between the simulated temperature of the outside of the cable insulation layer and the reference temperature is not greater than a set threshold. If the number of times the convective heat transfer coefficient is adjusted exceeds the set adjustment number threshold, the conductor contact resistance is adjusted again until the condition that the absolute value of the deviation is not greater than the set threshold is met. The adjusted convective heat transfer coefficient and conductor contact resistance, which meet the conditions, are used as calibration parameters to obtain the corrected three-dimensional temperature field model of the cable.

[0011] More preferably, the specific steps of supplementing and adjusting the conductor contact resistance until the absolute value of the deviation is not greater than a set threshold include: Based on the theoretical resistance value of the cable conductor, the contact resistance of the conductor is adjusted by adjusting the step size according to the set compensation ratio; the set compensation ratio is set according to the actual situation. After each adjustment, the simulation is repeated to obtain the simulated temperature of the outer side of the cable insulation layer until the absolute value of its deviation from the reference temperature is no greater than the set threshold.

[0012] More preferably, in S5, based on the calibrated three-dimensional temperature field model of the cable, the simulated temperature inside the insulation layer is extracted, the temperature difference ΔT between the simulated temperature T_inner and the reference temperature is calculated, and the heating rate v_sim of the simulated temperature inside the insulation layer is calculated. Combined with the heating rate v_ref of the reference temperature, the cable insulation defect type and fire induction risk are determined as a judgment report. The types of cable insulation defects include mild insulation aging defects, insulation deterioration defects, severe insulation defects, and major insulation defects; the insulation deterioration defects include cracks / early stage of electrical treeing; the severe insulation defects include the development stage of electrical treeing / poor joint contact; the major insulation defects include precursors of insulation breakdown / early stage of internal short circuit.

[0013] More preferably, in the determination of each type of cable insulation defect, the difference between the heating rate of the reference temperature and the heating rate of the simulated temperature inside the insulation layer, the temperature difference of the reference temperature, and the calculated simulated temperature inside the insulation layer are compared with the corresponding set determination conditions. When the determination conditions of any type of cable insulation defect are met, a determination report is generated and a corresponding fire warning is issued.

[0014] This invention also proposes a cable channel fire monitoring system based on ultrasonic infrared thermal imaging temperature measurement, comprising: The image acquisition module arranges an infrared camera and an ultrasonic generator in the cable channel. The infrared camera performs all-angle monitoring to acquire visible light images and a first infrared thermal image within the channel. The abnormal temperature point location determination module, if an abnormal temperature point appears in the infrared thermal image, compares the visible light image and the first infrared thermal image, and uses a recognition algorithm to locate the cable position; combined with the cable location, it determines the position of the abnormal temperature point. The cable heating detection module activates the ultrasonic generator and takes another infrared camera image if the abnormal temperature point is located on the cable body. The module then compares the temperatures of the same abnormal temperature point in the first and second infrared thermal images to determine if the cable has a heating defect. The cable 3D temperature field model construction module constructs a 3D temperature field model of the cable when there is a heating defect, and outputs the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, it determines whether to correct the cable 3D temperature field model. The fire early warning module determines the type of cable insulation defect based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, generates a judgment report, and issues a fire early warning based on the judgment report.

[0015] The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions; The processor is used to perform the steps of the above method according to the instructions.

[0016] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention simultaneously acquires visible light images and a first infrared thermal image using an infrared camera, and combines this with the YOLO recognition algorithm to perform pixel-level positioning of the cable, clearly distinguishing whether abnormal temperature points are located within the cable itself or in the cable channel environment. This design solves the problem of traditional monitoring technologies being unable to identify the source of high temperatures, avoiding misjudging heating from debris in the channel environment as cable faults. It also prevents cable defects from being masked by ambient temperature, thus improving the basic accuracy of fire precursor monitoring.

[0018] 2. This invention uses an ultrasonic generator to excite the suspected area and compares the temperature changes in the infrared thermal images before and after excitation. This allows for accurate determination of whether the temperature anomaly is caused by normal load or defects such as insulation cracks or electrical trees. The core principle is that the defective area generates additional Joule heat under the action of ultrasonic waves. This method overcomes the limitation of single infrared thermometry in distinguishing between "load-induced temperature rise" and "defect-induced temperature rise," significantly improving the accuracy of identifying early-stage heating defects in cables.

[0019] 3. Based on a calibrated temperature field model, this invention extracts core indicators such as the inner temperature and heating rate of the insulation layer, and subdivides cable insulation defects into four categories: mild aging, deterioration, severe defects, and major defects. Differentiated early warning and handling measures are configured for each type of defect. From "mere record-keeping" to a tiered response of "power cut-off + fire alarm linkage," a closed-loop process of "defect identification - risk assessment - emergency response" is achieved. This avoids resource waste caused by excessive early warnings and enables rapid response to major fire hazards, ensuring the operational safety of cable channels. Attached Figure Description

[0020] Figure 1 This is a flowchart of the cable channel fire monitoring method based on ultrasonic infrared thermography of the present invention. Figure 2 This is a flowchart of the method according to Embodiment 1 of the present invention; Figure 3 This is a system structure diagram of the cable channel fire monitoring system based on ultrasonic infrared thermal imaging temperature measurement according to the present invention; Figure 4 This is a cable channel layout diagram of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0022] The present invention proposes the following technical solution: like Figure 1 As shown, this invention proposes a method for monitoring cable channel fires based on ultrasonic infrared thermography, comprising: S1, An infrared camera and an ultrasonic generator are arranged in the cable channel. The infrared camera is used to perform all-angle monitoring and acquire visible light images and a first infrared thermal image in the channel. S2, if an abnormal temperature point appears in the infrared thermal image, compare the visible light image and the first infrared thermal image, and use a recognition algorithm to locate the cable position; combine the cable location to determine the position of the abnormal temperature point; S3, if the abnormal temperature point is located on the cable body, then turn on the ultrasonic generator and use the infrared camera to take pictures again to obtain a second infrared thermal image; compare the temperature of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image to determine whether the cable has a heating defect. In S3, the temperature values ​​of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image are extracted and recorded as follows: and ;when minus If the deviation exceeds the set standard deviation threshold, the cable is deemed to have a heating defect; if minus If the temperature rise is not greater than the set standard deviation threshold, it indicates that the temperature rise is due to normal load or measurement deviation.

[0023] S4. When the cable has a heating defect, construct a three-dimensional temperature field model of the cable and output the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, determine whether to correct the three-dimensional temperature field model of the cable. In S4, using cable basic parameters including conductor cross-section, insulation layer thickness, material thermal conductivity, and collected current and ambient temperature data, a three-dimensional temperature field model of the cable is constructed through finite element simulation, and the simulated temperature distribution of the inner and outer sides of the cable insulation layer is output.

[0024] In S4, multiple temperature sensors are placed on the cable surface at different locations in the cable area detected by the infrared camera and ultrasonic generator to detect the cable surface temperature; the average value of the cable surface temperature detected by the sensors within a set distance from the abnormal temperature point is calculated, and the average value is recorded as the reference temperature of the three-dimensional temperature field model of the cable. When the absolute value of the deviation between the simulated temperature on the outside of the cable insulation layer and the reference temperature is greater than a set threshold, the simulation calculation parameters of the three-dimensional temperature field model of the cable are adjusted according to the reference temperature so that the absolute value of the deviation is not greater than the set threshold.

[0025] 5. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 4, characterized in that: The simulation calculation parameters include the convective heat transfer coefficient and the conductor contact resistance; Regarding the convective heat transfer coefficient, if the simulated temperature on the outside of the cable insulation layer is greater than the reference temperature, the initial convective heat transfer coefficient is increased by a certain percentage; if the simulated temperature on the outside of the cable insulation layer is not greater than the reference temperature, the initial convective heat transfer coefficient is decreased by a certain percentage; the certain percentage is set according to the actual situation. After each adjustment of the convective heat transfer coefficient, the simulated temperature of the outside of the cable insulation layer is re-simulated until the absolute value of the deviation between the simulated temperature of the outside of the cable insulation layer and the reference temperature is not greater than a set threshold. If the number of times the convective heat transfer coefficient is adjusted exceeds the set adjustment number threshold, the conductor contact resistance is adjusted again until the condition that the absolute value of the deviation is not greater than the set threshold is met. The adjusted convective heat transfer coefficient and conductor contact resistance, which meet the conditions, are used as calibration parameters to obtain the corrected three-dimensional temperature field model of the cable.

[0026] The specific steps for supplementing and adjusting the conductor contact resistance until the absolute value of the deviation is not greater than a set threshold include: Based on the theoretical resistance value of the cable conductor, the contact resistance of the conductor is adjusted by adjusting the step size according to the set compensation ratio; the set compensation ratio is set according to the actual situation. After each adjustment, the simulation is repeated to obtain the simulated temperature of the outer side of the cable insulation layer until the absolute value of its deviation from the reference temperature is no greater than the set threshold.

[0027] S5. Based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, determine the type of cable insulation defect, obtain a judgment report, and issue a fire warning based on the judgment report.

[0028] In S5, based on the calibrated three-dimensional temperature field model of the cable, the simulated temperature inside the insulation layer is extracted. The temperature difference ΔT between the simulated temperature T_inner and the reference temperature, and the heating rate v_sim of the simulated temperature inside the insulation layer are calculated. Combined with the heating rate v_ref of the reference temperature, the cable insulation defect type and fire induction risk are determined, and a judgment report is generated. The types of cable insulation defects include mild insulation aging defects, insulation deterioration defects, severe insulation defects, and major insulation defects; the insulation deterioration defects include cracks / early stage of electrical treeing; the severe insulation defects include the development stage of electrical treeing / poor joint contact; the major insulation defects include precursors of insulation breakdown / early stage of internal short circuit.

[0029] In the determination of each type of cable insulation defect, the difference between the heating rate of the reference temperature and the heating rate of the simulated temperature inside the insulation layer, the temperature difference of the reference temperature, and the calculated simulated temperature inside the insulation layer are compared with the corresponding set judgment conditions. When the judgment conditions of any type of cable insulation defect are met, a judgment report is generated and a corresponding fire warning is issued.

[0030] This invention also proposes a cable channel fire monitoring system based on ultrasonic infrared thermal imaging temperature measurement, comprising: The image acquisition module arranges an infrared camera and an ultrasonic generator in the cable channel. The infrared camera performs all-angle monitoring to acquire visible light images and a first infrared thermal image within the channel. The abnormal temperature point location determination module, if an abnormal temperature point appears in the infrared thermal image, compares the visible light image and the first infrared thermal image, and uses a recognition algorithm to locate the cable position; combined with the cable location, it determines the position of the abnormal temperature point. The cable heating detection module activates the ultrasonic generator and takes another infrared camera image if the abnormal temperature point is located on the cable body. The module then compares the temperatures of the same abnormal temperature point in the first and second infrared thermal images to determine if the cable has a heating defect. The cable 3D temperature field model construction module constructs a 3D temperature field model of the cable when there is a heating defect, and outputs the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, it determines whether to correct the cable 3D temperature field model. The fire early warning module determines the type of cable insulation defect based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, generates a judgment report, and issues a fire early warning based on the judgment report.

[0031] The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions; The processor is used to perform the steps of the above method according to the instructions.

[0032] The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0033] Example 1 This invention proposes a method for monitoring cable channel fires based on ultrasonic infrared thermography, such as... Figure 2 As shown, the specific steps are as follows.

[0034] S1, An infrared camera and an ultrasonic generator are arranged in the cable channel. The infrared camera performs all-angle monitoring and acquires visible light images and first infrared thermal images in the channel. Preferably, the infrared camera can monitor the entire cable channel from all angles.

[0035] S2. Compare the visible light image and the first infrared thermal image to locate the cable position; if an abnormal temperature point appears in the infrared thermal image, determine whether the abnormal temperature point is located in the cable body or in the cable channel environment based on the cable location.

[0036] Preferably, the cable in the visible light image is identified and compared using methods such as the YOLO algorithm, the cable is located, the position of the cable is marked in the first infrared thermal image, and it is determined whether the abnormal temperature point is located in the cable body or in the cable channel environment.

[0037] S3. If the abnormal temperature point is located on the cable body, the ultrasonic generator is turned on and the infrared camera is used again to take a picture to obtain a second infrared thermal image. The temperature of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image is compared to determine whether the cable has a heating defect.

[0038] Preferably, the ultrasonic generator can cause the temperature of the cable defect to rise further. After continuous excitation for several seconds, an infrared camera is used to capture the image, obtaining a second infrared thermal image. Combining the infrared thermal image information can help determine if the defect is abnormal.

[0039] The temperature values ​​of the same anomalous temperature point are extracted from the first and second infrared thermal images and denoted as follows: and .when minus If the temperature exceeds the set standard deviation threshold, it indicates that the ultrasonic excitation caused an abnormal temperature rise at the abnormal temperature point, which is determined to be a heating defect in the cable. The heating principle is that defects such as internal insulation cracks and electrical trees in the cable generate additional Joule heat under the action of ultrasound, exacerbating the temperature rise; if minus If the temperature rise is not greater than the set standard deviation threshold, it indicates that the temperature increase is due to normal load or measurement deviation. As a preferred embodiment of the present invention, considering that the temperature error of conventionally used infrared imagers is mostly within ±2℃, the set standard deviation threshold is set to 2℃.

[0040] S4. When the cable has a heating defect, construct a three-dimensional temperature field model of the cable and output the simulated temperature distribution inside and outside the cable insulation layer; based on the simulated temperature distribution outside the cable insulation layer, determine whether to correct the three-dimensional temperature field model of the cable.

[0041] Specifically, when it is determined that the cable has a heating defect, the cable's basic parameters (conductor cross-section, insulation layer thickness, material thermal conductivity) and the collected current and ambient temperature data are used to construct a three-dimensional temperature field model of the cable through finite element simulation, and output the simulated temperature distribution inside and outside the cable insulation layer.

[0042] Multiple temperature sensors are placed on the cable surface at different locations within the cable area detected by the infrared camera and ultrasonic generator to detect the cable surface temperature. The average cable surface temperature detected by the sensors within a set distance from the abnormal temperature point is calculated, and the average value is recorded as the reference temperature for the cable's three-dimensional temperature field model. The set distance is adjusted according to actual conditions. In a preferred embodiment of the invention, the average cable surface temperature detected by two sensors is selected as the reference temperature.

[0043] When the absolute value of the deviation between the simulated temperature on the outer side of the cable insulation layer and the reference temperature exceeds a set threshold, the simulation calculation parameters of the cable's three-dimensional temperature field model are adjusted according to the reference temperature to ensure that the absolute value of the deviation does not exceed the set threshold. In a preferred embodiment of this invention, the set threshold is 2°C.

[0044] Specifically, to make the finite element simulation results more accurate, this invention combines the channel ambient temperature and real-time current from infrared testing to dynamically assign values ​​to the finite element calculations [zs1], calibrates the three-dimensional temperature field model of the cable, and compares the simulated temperature on the outside of the cable insulation layer with the reference temperature. The temperature inside the cable insulation layer is the highest temperature in the cable insulation, which determines the cable's allowable current and thermal aging. Therefore, accurately obtaining this temperature is the core of cable temperature monitoring, but the temperature inside the insulation layer cannot be accurately measured by adding sensors. This invention corrects the simulation results based on the reference temperature from on-site temperature testing, ensuring that the simulation model can accurately reflect the overall temperature distribution of the cable during operation. It can obtain the temperature inside the cable insulation layer, which cannot be directly detected, with high precision, and can also obtain the cable's temperature distribution under different current carrying capacity, fault current, and external temperatures.

[0045] Specifically, the convective heat transfer coefficient and conductor contact resistance in the three-dimensional temperature field model of the cable are adjusted.

[0046] Regarding the convective heat transfer coefficient, the airflow state within the channel (such as natural convection or forced ventilation) directly affects the cable's heat dissipation efficiency. The smaller the convective heat transfer coefficient, the higher the simulated temperature of the cable surface; conversely, the higher the coefficient, the lower the simulated temperature. If the initial value of the convective heat transfer coefficient is set too low, the simulated temperature of the outer insulation layer / outer sheath will be too high; if it is set too high, the temperature will be too low, directly affecting the simulation results of the temperature of the outer insulation layer.

[0047] If the simulated temperature on the outside of the cable insulation layer is greater than the reference temperature, the initial convective heat transfer coefficient is increased by a certain percentage; if the simulated temperature on the outside of the cable insulation layer is not greater than the reference temperature, the initial convective heat transfer coefficient is decreased by a certain percentage.

[0048] After each adjustment, the steady-state thermal analysis is run again to obtain the new simulated temperature of the outer side of the cable insulation layer, until the absolute value of the deviation between the simulated temperature of the outer side of the cable insulation layer and the reference temperature is not greater than the set threshold.

[0049] If the number of adjustments to the convective heat transfer coefficient exceeds the set threshold, then the conductor contact resistance needs to be adjusted as a supplement: Based on the theoretical resistance value of the cable conductor, the step size is adjusted according to the set compensation ratio to adjust the conductor contact resistance (e.g., R0=0.07Ω / km, adjusted to 0.0707Ω / km); after each adjustment, the simulation is repeated to obtain the simulated temperature of the outer side of the cable insulation layer until the absolute value of its deviation from the reference temperature is not greater than the set threshold.

[0050] The adjusted convective heat transfer coefficient and conductor contact resistance, which meet the conditions, are used as calibration parameters to obtain the corrected three-dimensional temperature field model of the cable.

[0051] S5, based on the output of the corrected three-dimensional temperature field model of the cable, determines the type of cable insulation defect, obtains a judgment report, and issues a fire warning based on the judgment report.

[0052] Specifically, based on the calibrated three-dimensional temperature field model of the cable, the simulated temperature inside the insulation layer is extracted, the temperature difference ΔT between the simulated temperature T_inner inside the insulation layer and the reference temperature is calculated, and the heating rate v_sim of the simulated temperature inside the insulation layer is calculated. Combined with the heating rate v_ref of the reference temperature, the cable insulation defect type and fire induction risk are determined as a judgment report, and fire warning is issued based on the judgment report.

[0053] Cable insulation defects include: Mild insulation aging defects: When v_ref-v_sim is in the range of 0.05~0.1℃ / s, and ΔT≤5℃ and T_inner≤80℃, the fire risk is judged to be extremely low. It will not cause a fire in the short term, but long-term operation will accelerate aging and pose a potential fire hazard. The fire warning method is: only record, without triggering audible and visual alarms.

[0054] Insulation deterioration defects (cracks / early stage of electrical treeing): v_ref-v_sim is in the range of 0.1~0.5℃ / s, and 5℃<ΔT≤10℃, 80℃<T_inner≤90℃; the fire risk is moderate, and partial discharge is likely to occur at the defect. If there is continuous overload or the ambient temperature and humidity increase, it may cause insulation breakdown and thus induce a fire.

[0055] The fire warning methods are as follows: audible and visual alarms, on-site ultrasonic partial discharge retesting and infrared thermal imaging retesting to confirm the defect range; load current limiting for the cable section; preparation of insulation repair materials and spare parts, and formulation of a weekly repair plan.

[0056] Severe insulation defects (electric tree development stage / poor joint contact): v_ref-v_sim is in the range of 0.5~1℃ / s, and 10℃<ΔT≤15℃, 90℃<T_inner≤100℃; then the fire risk is high, the defective area has shown significant overheating, the carbonization rate of the insulation layer is accelerated, and insulation breakdown may occur within 24~48h, igniting the cable sheath.

[0057] The fire warning methods are as follows: sound and light alarms are issued and risk warnings are pushed out; on-site inspection is carried out immediately, and the defective section is temporarily disconnected and isolated (if it is a non-critical load); if it is a critical load, the backup cable circuit is switched on; emergency repairs or cable replacement are carried out.

[0058] Major insulation defects (precursors to insulation breakdown / initial stage of internal short circuit): v_ref-v_sim>1℃ / s, and ΔT>15℃, T_inner>100℃; then the fire risk is judged to be extremely high, a local high temperature channel has been formed at the defect, and complete insulation breakdown will occur within minutes to hours, causing the cable body to catch fire and spread to the channel.

[0059] The fire warning method is as follows: activate the highest level audible and visual alarm, immediately cut off the power supply to the cable section and adjacent sections, and activate the emergency plan; confirm the fire situation on site and organize initial firefighting to prevent the fire from spreading to other cables and passage facilities; before the fault is resolved, it is strictly forbidden to restore power to the area.

[0060] Immediately cut off the power supply to the affected cable section and adjacent sections, and activate the emergency response plan; maintenance personnel should confirm the fire situation on-site and organize initial firefighting efforts; fire brigades should arrive at the scene simultaneously and stand by to prevent the fire from spreading to other cables and access facilities; power supply to the area must not be restored until the fault is resolved.

[0061] Example 2 This invention also proposes a cable channel fire monitoring system based on ultrasonic infrared thermal imaging temperature measurement, comprising: The image acquisition module arranges an infrared camera and an ultrasonic generator in the cable channel. The infrared camera performs all-angle monitoring to acquire visible light images and a first infrared thermal image within the channel. The abnormal temperature point location determination module, if an abnormal temperature point appears in the infrared thermal image, compares the visible light image and the first infrared thermal image, and uses a recognition algorithm to locate the cable position; combined with the cable location, it determines the position of the abnormal temperature point. The cable heating detection module activates the ultrasonic generator and takes another infrared camera image if the abnormal temperature point is located on the cable body. The module then compares the temperatures of the same abnormal temperature point in the first and second infrared thermal images to determine if the cable has a heating defect. The cable 3D temperature field model construction module constructs a 3D temperature field model of the cable when there is a heating defect, and outputs the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, it determines whether to correct the cable 3D temperature field model. The fire early warning module determines the type of cable insulation defect based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, generates a judgment report, and issues a fire early warning based on the judgment report.

[0062] like Figure 3 and Figure 4 The diagrams shown depict the system structure and cable channel layout of a cable channel fire monitoring system based on ultrasonic infrared thermography. Example 3 The present invention also proposes a terminal, including a processor and a storage medium: The storage medium is used to store instructions; The processor is used to perform the steps of the above method according to the instructions.

[0063] Example 4 The present invention also proposes a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for monitoring cable channel fires based on ultrasonic infrared thermography, characterized in that, include: S1, An infrared camera and an ultrasonic generator are arranged in the cable channel. The infrared camera is used to perform all-angle monitoring and acquire visible light images and a first infrared thermal image in the channel. S2, if an abnormal temperature point appears in the infrared thermal image, compare the visible light image and the first infrared thermal image, and use a recognition algorithm to locate the cable position; combine the cable location to determine the position of the abnormal temperature point; S3, if the abnormal temperature point is located on the cable body, then turn on the ultrasonic generator and use the infrared camera to take pictures again to obtain a second infrared thermal image; compare the temperature of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image to determine whether the cable has a heating defect. S4. When the cable has a heating defect, construct a three-dimensional temperature field model of the cable and output the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, determine whether to correct the three-dimensional temperature field model of the cable. S5. Based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, determine the type of cable insulation defect, obtain a judgment report, and issue a fire warning based on the judgment report.

2. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 1, characterized in that: In S3, the temperature values ​​of the same abnormal temperature point in the first infrared thermal image and the second infrared thermal image are extracted and recorded as follows: and ;when minus If the deviation exceeds the set standard deviation threshold, the cable is deemed to have a heating defect; if minus If the temperature rise is not greater than the set standard deviation threshold, it indicates that the temperature rise is due to normal load or measurement deviation.

3. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 1, characterized in that: In S4, using cable basic parameters including conductor cross-section, insulation layer thickness, material thermal conductivity, and collected current and ambient temperature data, a three-dimensional temperature field model of the cable is constructed through finite element simulation, and the simulated temperature distribution of the inner and outer sides of the cable insulation layer is output.

4. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 1, characterized in that: In S4, multiple temperature sensors are placed on the cable surface at different locations in the cable area detected by the infrared camera and ultrasonic generator to detect the cable surface temperature; the average value of the cable surface temperature detected by the sensors within a set distance from the abnormal temperature point is calculated, and the average value is recorded as the reference temperature of the three-dimensional temperature field model of the cable. When the absolute value of the deviation between the simulated temperature on the outside of the cable insulation layer and the reference temperature is greater than a set threshold, the simulation calculation parameters of the three-dimensional temperature field model of the cable are adjusted according to the reference temperature so that the absolute value of the deviation is not greater than the set threshold.

5. The cable channel fire monitoring method based on ultrasonic infrared thermal imaging temperature measurement a according to claim 4, characterized in that: The simulation calculation parameters include the convective heat transfer coefficient and the conductor contact resistance; Regarding the convective heat transfer coefficient, if the simulated temperature on the outside of the cable insulation layer is greater than the reference temperature, the initial convective heat transfer coefficient is increased by a certain percentage; if the simulated temperature on the outside of the cable insulation layer is not greater than the reference temperature, the initial convective heat transfer coefficient is decreased by a certain percentage. The specified ratio is set according to the actual situation; After each adjustment of the convective heat transfer coefficient, the simulated temperature of the outside of the cable insulation layer is re-simulated until the absolute value of the deviation between the simulated temperature of the outside of the cable insulation layer and the reference temperature is not greater than a set threshold. If the number of times the convective heat transfer coefficient is adjusted exceeds the set adjustment number threshold, the conductor contact resistance is adjusted again until the condition that the absolute value of the deviation is not greater than the set threshold is met. The adjusted convective heat transfer coefficient and conductor contact resistance, which meet the conditions, are used as calibration parameters to obtain the corrected three-dimensional temperature field model of the cable.

6. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 5, characterized in that: The specific steps for supplementing and adjusting the conductor contact resistance until the absolute value of the deviation is not greater than a set threshold include: Based on the theoretical resistance value of the cable conductor, the contact resistance of the conductor is adjusted by adjusting the step size according to the set compensation ratio; the set compensation ratio is set according to the actual situation. After each adjustment, the simulation is repeated to obtain the simulated temperature of the outer side of the cable insulation layer until the absolute value of its deviation from the reference temperature is no greater than the set threshold.

7. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 6, characterized in that: In S5, based on the calibrated three-dimensional temperature field model of the cable, the simulated temperature inside the insulation layer is extracted. The temperature difference ΔT between the simulated temperature T_inner and the reference temperature, and the heating rate v_sim of the simulated temperature inside the insulation layer are calculated. Combined with the heating rate v_ref of the reference temperature, the cable insulation defect type and fire induction risk are determined, and a judgment report is generated. The types of cable insulation defects include mild insulation aging defects, insulation deterioration defects, severe insulation defects, and major insulation defects; the insulation deterioration defects include cracks / early stage of electrical treeing; the severe insulation defects include the development stage of electrical treeing / poor joint contact; the major insulation defects include precursors of insulation breakdown / early stage of internal short circuit.

8. The cable channel fire monitoring method based on ultrasonic infrared thermography according to claim 7, characterized in that: In the determination of each type of cable insulation defect, the difference between the heating rate of the reference temperature and the heating rate of the simulated temperature inside the insulation layer, the temperature difference of the reference temperature, and the calculated simulated temperature inside the insulation layer are compared with the corresponding set judgment conditions. When the judgment conditions of any type of cable insulation defect are met, a judgment report is generated and a corresponding fire warning is issued.

9. A cable channel fire monitoring system based on ultrasonic infrared thermography using the method described in any one of claims 1-8. Includes, characterized in that: The image acquisition module arranges an infrared camera and an ultrasonic generator in the cable channel. The infrared camera performs all-angle monitoring to acquire visible light images and a first infrared thermal image within the channel. The abnormal temperature point location determination module, if an abnormal temperature point appears in the infrared thermal image, compares the visible light image and the first infrared thermal image, and uses a recognition algorithm to locate the cable position; combined with the cable location, it determines the position of the abnormal temperature point. The cable heating detection module activates the ultrasonic generator and takes another infrared camera image if the abnormal temperature point is located on the cable body. The second infrared thermal image is obtained by comparing the temperature of the same abnormal temperature point in the first and second infrared thermal images to determine whether the cable has a heating defect. The cable 3D temperature field model construction module constructs a 3D temperature field model of the cable when there is a heating defect, and outputs the simulated temperature distribution of the inner and outer sides of the cable insulation layer; based on the simulated temperature distribution of the outer side of the cable insulation layer, it determines whether to correct the cable 3D temperature field model. The fire early warning module determines the type of cable insulation defect based on the simulated temperature distribution inside the cable insulation layer output by the corrected three-dimensional temperature field model of the cable, generates a judgment report, and issues a fire early warning based on the judgment report.

10. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-8.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-8.

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