Method for evaluating power supply cable dynamic thermal stability and evaluation system

Abstract

The application relates to the technical field, in particular to a power cable dynamic heat stability evaluation system and an evaluation method, which comprises the following steps: determining a short-circuit detection point of a power cable based on the state of the power cable; determining a loss maximum point of a buried power cable based on the soil thermal conductivity of the buried power cable within a preset time length, the buried depth change rate of the power cable within the preset time length, the dust accumulation thickness of an exposed power cable, and whether the exposed power cable has a crack; performing a short-circuit stability calibration test on the short-circuit detection point of the power cable; and determining whether the dynamic heat stability of the power cable is qualified based on whether a line damage or deformation phenomenon occurs at the short-circuit detection point of the power cable after the test. The application improves the accuracy of short-circuit detection point analysis, reduces energy waste, and improves energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of technology, and in particular to a method and system for evaluating the dynamic and thermal stability of power supply cables. Background Technology

[0002] In modern society, power cables are a critical infrastructure for power transmission. Whether in industrial production, commercial activities, or daily life, a stable and reliable power supply is indispensable. The performance of power cables directly affects the safe operation of the power system and the efficient transmission of electrical energy. During operation, power cables may suffer short-circuit faults. Short-circuit currents generate enormous heat and mechanical stress, posing a severe challenge to the dynamic and thermal stability of power cables. Good dynamic and thermal stability ensures that power cables maintain stable performance under normal operation and fault conditions, reducing energy loss and improving power transmission efficiency. Traditional evaluation methods only consider the physical parameters of the power cable itself, ignoring the influence of its environment. This leads to inaccurate determination of short-circuit detection points, resulting in unreliable evaluation results and energy loss.

[0003] A prior art method and apparatus for evaluating the influence of environmental thermal resistance on the core temperature of a three-core cable are disclosed. The method includes the following steps: obtaining the environmental thermal resistance under air laying and / or soil laying based on a thermal circuit model of the three-core cable; obtaining the core temperature of the three-core cable based on the thermal circuit model; if the three-core cable is air-laid, determining the sensitivity of the core temperature to the environmental thermal resistance under air laying based on the relationship between the environmental thermal resistance and the ambient temperature; if the three-core cable is soil-laid, determining the sensitivity of the core temperature to the environmental thermal resistance under soil laying. This invention can accurately analyze the degree of influence of environmental thermal resistance on the core temperature of a three-core cable; based on the sensitivity under air laying or soil laying, when the three-core cable has a large loaded current, especially when the three-core cable is laid under air radiation, the monitoring intensity of the ambient temperature is increased, thereby ensuring the safe and stable operation of power cables. It is evident that the prior art suffers from low accuracy in analyzing short-circuit detection points, leading to energy waste and reduced energy utilization efficiency. Summary of the Invention

[0004] To address this issue, the present invention provides a method and system for evaluating the dynamic and thermal stability of power cables, thereby overcoming the problem in the prior art where low accuracy in analyzing short-circuit detection points leads to energy waste and reduced energy utilization efficiency.

[0005] To achieve the above objectives, in one aspect, the present invention provides a method for evaluating the dynamic and thermal stability of power supply cables, comprising:

[0006] Acquire the physical parameters of the power supply cable itself, the electrical parameters related to the fault, and the environmental data of the power supply cable;

[0007] Based on whether the power supply cable is in the laying and use state or in the unlaid and waiting-to-use state, the point with the maximum short-circuit current or the point with the maximum loss of the power supply cable is determined as the short-circuit detection point for the dynamic and thermal stability of the power supply cable.

[0008] Based on the soil thermal conductivity of the buried power cables within a preset time period and the rate of change of the burial depth of the power cables within a preset time period, the point of maximum loss of the buried power cables is determined. Based on the dust accumulation thickness of the exposed power cables and whether there are cracks in the completely exposed power cables, the point of maximum loss of the exposed power cables is determined.

[0009] When determining the dust accumulation thickness of exposed power cables, the dust accumulation thickness of the exposed power cables can be directly determined based on the rainfall frequency of the environment where the exposed power cables are located within a preset period, or the dust accumulation thickness can be determined after rinsing the exposed power cables with water.

[0010] A short-circuit stability verification test is conducted on the short-circuit detection points of the power supply cable. Based on whether line damage or deformation occurs at the short-circuit detection points of the power supply cable after the test, it is determined whether the dynamic and thermal stability of the power supply cable is qualified.

[0011] Furthermore, the short-circuit detection points for determining the dynamic and thermal stability of power supply cables include:

[0012] If the power supply cable is in the laying and use state, the point with the greatest loss of the power supply cable is determined as the short circuit detection point for the dynamic and thermal stability of the power supply cable.

[0013] If the power supply cable is in an unlaid and unused state, the point with the maximum short-circuit current of the power supply cable is determined as the short-circuit detection point for the dynamic and thermal stability of the power supply cable.

[0014] Furthermore, determining the point of maximum loss for the buried power supply cable includes:

[0015] The point where the average soil thermal conductivity of the buried power cable is the lowest within a preset time period, and the point where the rate of change of the burial depth of the power cable is the highest within a preset time period, are used as loss detection points.

[0016] Fiber optic temperature sensors are installed on the surface of the power supply cable at the loss detection point to record the temperature changes of the power supply cable in real time during operation.

[0017] Based on the recorded temperature data and combined with the temperature coefficient of resistance of the power supply cable and the load current, the real-time loss at the loss detection point is calculated.

[0018] The point with the highest real-time loss is taken as the point of maximum loss.

[0019] Furthermore, determining the point of maximum loss in the exposed power supply cable includes:

[0020] The point where the dust accumulates thickest on the exposed power cable and the point where the number of cracks is greatest on the completely exposed power cable are used as loss detection points.

[0021] Fiber optic temperature sensors are installed on the surface of the power supply cable at the loss detection point to record the temperature changes of the power supply cable in real time during operation.

[0022] Based on the recorded temperature data and combined with the temperature coefficient of resistance of the power supply cable and the load current, the real-time loss at the loss detection point is calculated.

[0023] The point with the highest real-time loss is taken as the point of maximum loss.

[0024] Furthermore, determining the dust accumulation thickness of the exposed power supply cable includes:

[0025] If the rainfall frequency in the environment where the exposed power cable is located is less than the preset rainfall frequency within a preset period, the thickness of dust accumulation is determined after rinsing the exposed power cable with water.

[0026] If the rainfall frequency in the environment where the exposed power supply cable is located is greater than or equal to the preset rainfall frequency within a preset period, the dust accumulation thickness of the exposed power supply cable is directly determined.

[0027] Furthermore, determining the point of maximum short-circuit current for power supply cables includes the location where the maximum short-circuit current occurs in the cable loop, i.e., for a single cable not exceeding the manufacturing length, the point of maximum short-circuit current is determined at the end of the cable; for cables with intermediate joints, the point of maximum short-circuit current is determined at the beginning of each segment with reduced cable cross-section; when the cable segments have equal cross-sections, the point of maximum short-circuit current is determined at the beginning of the next cable segment, i.e., at the first intermediate joint; for parallel-connected cables without intermediate joints, the point of maximum short-circuit current is determined after the parallel connection point.

[0028] Furthermore, determining whether the dynamic and thermal stability of the power supply cable is qualified includes:

[0029] If, after the test, damage or deformation is found at the short-circuit test point of the power supply cable, the dynamic and thermal stability of the power supply cable is deemed unqualified.

[0030] If no line damage or deformation is found at the short-circuit test point of the power supply cable after the test, the dynamic and thermal stability of the power supply cable is deemed qualified.

[0031] Furthermore, it was determined that the short-circuit test points of the power supply cable after the test showed line damage or deformation, including insulation layer damage, insulation layer burning, insulation layer peeling, conductor shape change, conductor melting, and conductor strand breakage.

[0032] Furthermore, the short-circuit stability verification test of the power supply cable short-circuit detection point includes the short-circuit current of the power supply cable in the historical maximum short-circuit current when the power supply cable is laid and in use, or the short-circuit current of the power supply cable in the rated peak withstand current of the equipment connected to the power supply cable when the power supply cable is not laid and in use is not laid.

[0033] On the other hand, the present invention also provides an evaluation system for the evaluation method of the dynamic and thermal stability of the power supply cable, comprising:

[0034] The data acquisition module is used to acquire the physical parameter data of the power supply cable itself, the fault-related electrical parameter data, and the environmental data of the power supply cable.

[0035] The short-circuit detection point determination module, which is connected to the data acquisition module, includes a short-circuit detection point type determination unit for determining the short-circuit detection point of the power supply cable based on the state of the power supply cable, and a maximum loss point determination unit for determining the maximum loss point of the power supply cable based on the laying method of the power supply cable, the soil thermal conductivity of the power supply cable within a preset time period, the rate of change of the burial depth of the power supply cable within a preset time period, the dust accumulation thickness of the power supply cable, and whether there are cracks in the completely exposed power supply cable.

[0036] The test module, which is connected to the short-circuit detection point determination module, is used to perform short-circuit stability verification tests on the short-circuit detection points of the power supply cable.

[0037] The judgment module, which is connected to the test module, is used to determine whether the dynamic and thermal stability of the power supply cable is qualified based on whether line damage or deformation occurs at the short circuit detection point of the power supply cable after the test.

[0038] Compared with existing technologies, the beneficial effects of this invention are that it uses the point of maximum loss as the short-circuit detection point for power cables in the laying and use state. Because cable loss is one of the key factors affecting its dynamic and thermal stability during actual operation, by focusing on the point of maximum loss, the location where the cable is most prone to thermal stability problems under normal operating conditions can be accurately identified. When the cable is in the unlaid, unused state, the point of maximum short-circuit current is determined as the short-circuit detection point. Before being put into use, the main potential risk facing the cable is short-circuit fault. By pre-determining the point of maximum short-circuit current, the dynamic and thermal stability of the cable under the most unfavorable short-circuit conditions can be assessed in advance. Considering the two different states of the power cable and determining the short-circuit detection point according to their respective characteristics improves the accuracy of short-circuit detection point analysis, reduces energy waste, and thus improves energy utilization efficiency.

[0039] In particular, by identifying the location with the minimum average soil thermal conductivity and the location with the maximum rate of change in burial depth within a preset time period as loss detection points, this invention can accurately focus on the locations in buried cables most prone to significant losses. For example, in areas with complex soil composition and underground construction, changes in soil thermal conductivity and burial depth can significantly affect cable heat dissipation and operating status. This targeted identification of detection points avoids indiscriminate inspection of the entire cable, making subsequent monitoring and evaluation work more focused. The above method improves the accuracy of short-circuit detection point analysis, thereby reducing energy waste and improving energy utilization efficiency.

[0040] In particular, this invention uses the areas with the greatest dust accumulation and the largest number of cracks in exposed power cables as loss detection points. This allows for precise location of critical areas where significant losses are most likely to occur during cable operation. In actual open-air environments, dust accumulation and surface cracks are significant factors affecting cable heat dissipation and insulation performance, leading to increased losses. This method avoids a comprehensive and cumbersome inspection of the entire exposed cable section. The dust accumulation thickness is determined by comparing the rainfall frequency of the cable's environment within a preset period with a preset rainfall frequency, fully considering the impact of environmental factors on dust accumulation on the cable surface. Different rainfall frequencies result in varying degrees of dust washing away from the cable surface. This method of flexibly determining dust accumulation thickness based on actual environmental conditions makes the assessment of dust's impact on cable losses more closely aligned with actual operating conditions. By improving the accuracy of short-circuit detection point analysis, this reduces energy waste and improves energy efficiency.

[0041] In particular, this invention provides an intuitive and easy-to-understand criterion for determining whether the dynamic and thermal stability of power cables is up to standard by explicitly identifying whether line damage or deformation occurs at the short-circuit test point after the test. Both power system maintenance personnel and related testing technicians can quickly and accurately assess the dynamic and thermal stability of power cables based on this clear standard. This method improves the accuracy of short-circuit test point analysis, reduces energy waste, and ultimately improves energy efficiency. Attached Figure Description

[0042] Figure 1 This is a flowchart illustrating the process of evaluating the dynamic and thermal stability of power supply cables according to an embodiment of the present invention.

[0043] Figure 2 This is a flowchart illustrating the process of determining the point of maximum loss in a buried power supply cable in the method for evaluating the dynamic and thermal stability of power supply cables according to an embodiment of the present invention.

[0044] Figure 3 This is a flowchart illustrating the process of determining whether the dynamic and thermal stability of a power supply cable is qualified in the evaluation method for dynamic and thermal stability of power supply cables according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of the structure of the evaluation system for the evaluation method of the dynamic and thermal stability of power supply cables according to an embodiment of the present invention. Detailed Implementation

[0046] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0047] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0048] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0049] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0050] Please see Figures 1-3 As shown, Figure 1 This is a flowchart illustrating the process of evaluating the dynamic and thermal stability of power supply cables according to an embodiment of the present invention. Figure 2 This is a flowchart illustrating the process of determining the point of maximum loss in a buried power supply cable in the method for evaluating the dynamic and thermal stability of power supply cables according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating the process of determining whether the dynamic and thermal stability of a power supply cable is qualified in the evaluation method for dynamic and thermal stability of power supply cables according to an embodiment of the present invention.

[0051] Step S1: Obtain the physical parameter data of the power supply cable itself, the fault-related electrical parameter data, and the environmental data of the power supply cable.

[0052] Step S2: Based on whether the power supply cable is in the laying and use state or in the unlaid and waiting-to-use state, determine the point with the maximum short-circuit current of the power supply cable or the point with the maximum loss of the power supply cable as the short-circuit detection point for the dynamic and thermal stability of the power supply cable.

[0053] Step S3: Based on the soil thermal conductivity of the buried power supply cable within a preset time period and the rate of change of the burial depth of the power supply cable within a preset time period, determine the point of maximum loss of the buried power supply cable; and based on the dust accumulation thickness of the exposed power supply cable and whether there are cracks in the completely exposed power supply cable, determine the point of maximum loss of the exposed power supply cable.

[0054] Step S4: When determining the dust accumulation thickness of the exposed power supply cable, the dust accumulation thickness of the exposed power supply cable is directly determined based on the rainfall frequency of the environment where the exposed power supply cable is located within a preset period, or the dust accumulation thickness is determined after rinsing the exposed power supply cable with water.

[0055] Step S5: Perform a short-circuit stability verification test on the short-circuit detection point of the power supply cable. Based on whether line damage or deformation occurs at the short-circuit detection point of the power supply cable after the test, determine whether the dynamic and thermal stability of the power supply cable is qualified.

[0056] The physical parameter data of the power supply cable in this embodiment of the invention includes, but is not limited to, "power supply cable length, power supply cable outer diameter and power supply cable material resistivity". The fault-related electrical parameter data includes, but is not limited to, "short circuit current magnitude and duration data, voltage level and number of phases of the line before the fault and fault location data". The environmental data of the power supply cable includes, but is not limited to, "temperature data, humidity data and chemical substance data".

[0057] Specifically, in step S2, when determining the short-circuit detection point for the dynamic and thermal stability of the power supply cable, the short-circuit detection point for the dynamic and thermal stability of the power supply cable is determined according to the state of the power supply cable.

[0058] When the power supply cable is in the laying and use state, the point with the greatest loss of the power supply cable is determined as the short circuit detection point for the dynamic and thermal stability of the power supply cable.

[0059] When the power supply cable is in an unlaid and ready-to-use state, the point with the maximum short-circuit current of the power supply cable is determined as the short-circuit detection point for the dynamic and thermal stability of the power supply cable.

[0060] This invention uses the point of maximum loss as the short-circuit detection point for power cables in their laid and operational state. Because cable loss is a key factor affecting its dynamic and thermal stability during actual operation, focusing on the point of maximum loss allows for precise identification of the location most prone to thermal stability issues under normal operating conditions. When the cable is in its unlaid, unused state, the point of maximum short-circuit current is identified as the short-circuit detection point. Before being put into use, the main potential risk to the cable is short-circuit faults. By pre-determining the point of maximum short-circuit current, the dynamic and thermal stability of the cable under the most unfavorable short-circuit conditions can be assessed in advance. Considering the two different states of the power cable and determining the short-circuit detection point based on their respective characteristics improves the accuracy of short-circuit detection point analysis, reduces energy waste, and thus improves energy utilization efficiency.

[0061] Specifically, in step S3, the step of determining the point of maximum loss of the buried power supply cable includes:

[0062] Step S3301: The point where the average soil thermal conductivity of the buried power supply cable is the lowest within a preset time period, and the point where the rate of change of the burial depth of the power supply cable is the highest within a preset time period, are taken as loss detection points.

[0063] Step S3302: Install an optical fiber temperature sensor on the surface of the power supply cable at the loss detection point to record the temperature change of the power supply cable in real time during operation.

[0064] Step S3303: Calculate the real-time loss at the loss detection point based on the recorded temperature data and in combination with the temperature coefficient of resistance of the power supply cable and the load current.

[0065] Step S3304: The loss detection point with the largest real-time loss is taken as the point with the largest loss.

[0066] In this embodiment of the invention, the preset duration is set to 25 days, but the value is not limited to this. Those skilled in the art can adjust the value according to actual needs. For example, in the past 25 days, the soil around the power supply cable was periodically tested using professional soil thermal conductivity measuring equipment. Due to the complex soil composition in this area and the ongoing construction work such as underground pipeline laying in some areas, there are significant differences in soil thermal conductivity. After measurement and analysis, it was found that the average soil thermal conductivity was the lowest in a section of about 50 meters, at 0.8 W / (m·K). At the same time, the burial depth of the power supply cable was monitored during this period using high-precision measuring instruments. Due to the impact of construction activities, the burial depth in some areas changed. After measurement, it was found that the burial depth change rate was the largest at one location, changing from 1.5 meters to 1.2 meters in 25 days. These two locations were determined as loss detection points, and fiber optic temperature sensors were installed on the surface of the power supply cable at the two determined loss detection points. These sensors can record the temperature changes of power cables in real time and accurately during operation. They also have advantages such as resistance to electromagnetic interference and corrosion resistance, making them suitable for use in complex underground environments. First, the temperature coefficient of resistance (TCR) of the power cable is obtained, assuming it is 0.004 / ℃. Then, the load current of the power cable is acquired in real time through power monitoring equipment. Assuming the load current is 200A at a certain moment, and based on the temperature data recorded by the fiber optic temperature sensor, the temperature at the loss detection point is assumed to be 40℃. In the initial state (assuming an ambient temperature of 20℃), the resistance change of the cable is calculated based on the TCR. The real-time loss at two loss detection points at different times is continuously recorded and calculated. After a period of monitoring and comparison, it is found that one of the loss detection points has the maximum real-time loss at a certain moment. Assuming that on the 15th day of monitoring, the real-time loss at one of the loss detection points reaches its maximum value of 500W, this point is determined as the point of maximum loss for this buried power cable.

[0067] This invention identifies the locations with the lowest average soil thermal conductivity and the highest rate of change in burial depth within a preset time period as loss detection points. This allows for precise targeting of the locations in buried cables most prone to significant losses. For example, in areas with complex soil composition and underground construction, changes in soil thermal conductivity and burial depth can significantly impact cable heat dissipation and operational status. This targeted identification of detection points avoids indiscriminate inspection of the entire cable, making subsequent monitoring and evaluation more focused. By using this method, the accuracy of short-circuit detection point analysis is improved, thereby reducing energy waste and increasing energy efficiency.

[0068] Specifically, in step S3, the step of determining the point of maximum loss of the exposed power supply cable includes:

[0069] The point where the dust accumulates thickest on the exposed power cable and the point where the number of cracks is greatest on the completely exposed power cable are used as loss detection points.

[0070] Fiber optic temperature sensors are installed on the surface of the power supply cable at the loss detection point to record the temperature changes of the power supply cable in real time during operation.

[0071] Based on the recorded temperature data and combined with the temperature coefficient of resistance of the power supply cable and the load current, the real-time loss at the loss detection point is calculated.

[0072] The point with the highest real-time loss is taken as the point of maximum loss.

[0073] Specifically, in step S3, when determining the dust accumulation thickness of the exposed power supply cable, the dust accumulation thickness is determined based on the comparison between the rainfall frequency of the environment where the exposed power supply cable is located within a preset period and the preset rainfall frequency.

[0074] When the rainfall frequency of the environment where the exposed power cable is located is less than the preset rainfall frequency within a preset period, the thickness of dust accumulation is determined after rinsing the exposed power cable with water.

[0075] When the rainfall frequency of the environment where the exposed power supply cable is located within a preset period is greater than or equal to the preset rainfall frequency, the dust accumulation thickness of the exposed power supply cable is directly determined.

[0076] In this embodiment of the invention, the preset period is set to 30 days, and the preset rainfall frequency ranges from 0.2 to 0.5, with a preferred value of 0.3. However, these values ​​are not limited to these values, and those skilled in the art can adjust them according to actual needs. For example, during the 30-day period, staff inspected the power cable every 5 days, using professional dust detection equipment and manual observation to determine the dust accumulation thickness and crack conditions at different locations on the cable. After multiple inspections, it was found that the dust accumulation thickness was the greatest at 200 meters from the cable's starting point, reaching 3 millimeters. Simultaneously, the number of cracks was the greatest on a 10-meter section of cable 400 meters from the starting point, with a total of 5 cracks. Therefore, these two locations were designated as loss detection points. Fiber optic temperature sensors were installed on the surface of the power cable at the two identified loss detection points, ensuring that the sensors were securely installed and could accurately record the cable's temperature changes. Staff consulted local meteorological data to analyze the rainfall in the area over the 30 days, finding that it rained a total of 6 days during those 30 days, averaging once every 5 days. The rainfall frequency in this area over the next 30 days is 0.2, with a preset rainfall frequency range of 0.2-0.5 and a preferred value of 0.3. Since the actual rainfall frequency of 0.2 is less than the preset frequency, the dust accumulation thickness is determined after rinsing the exposed power cables with water. Under safe conditions, workers use professional rinsing equipment to rinse the power cable section. After rinsing, dust detection equipment is used again to measure the dust thickness at the point of maximum dust accumulation (200 meters from the starting point). The measurement confirms that the dust accumulation thickness after rinsing is 1 mm. The temperature coefficient of resistance of the power cable is known to be 0.004 / ℃. By connecting to a power monitoring system, the load current of the power cable is acquired in real time. Assuming that the load current is 180A at a certain moment, the resistance change and loss are calculated based on the temperature data. Temperature monitoring and real-time loss calculations are continuously performed at two loss detection points. After a period of comparison, it is assumed that the loss detection point with the maximum dust accumulation thickness has a large real-time loss in multiple calculations, and one of these calculations reaches a maximum value of 400W. The maximum real-time loss at the point with the largest number of cracks within the same time period is 350W. Therefore, the point with the largest dust accumulation thickness is determined as the point with the largest loss in this exposed power cable.

[0077] This invention uses the areas with the greatest dust accumulation and the largest number of cracks in exposed power cables as loss detection points. This allows for precise location of critical areas where significant losses are most likely to occur during cable operation. In actual open-air environments, dust accumulation and surface cracks are significant factors affecting cable heat dissipation and insulation, leading to increased losses. This method avoids a comprehensive and cumbersome inspection of the entire exposed cable section. The dust accumulation thickness is determined by comparing the rainfall frequency of the cable's environment within a preset period with a preset rainfall frequency, fully considering the impact of environmental factors on dust accumulation on the cable surface. Different rainfall frequencies result in varying degrees of dust washing away from the cable surface. This method of flexibly determining dust accumulation thickness based on actual environmental conditions makes the assessment of dust's impact on cable losses more closely aligned with actual operating conditions. This method improves the accuracy of short-circuit detection point analysis, reducing energy waste and improving energy efficiency.

[0078] Specifically, in step S2, determining the point of maximum short-circuit current for the power supply cable includes the location where the maximum short-circuit current occurs in the cable loop, i.e., for a single cable not exceeding the manufacturing length, the point of maximum short-circuit current is determined at the end of the cable; for cables with intermediate joints, the point of maximum short-circuit current is determined at the beginning of each segment with a reduced cable cross-section; when the cable segment has a uniform cross-section, the point of maximum short-circuit current is determined at the beginning of the next cable segment, i.e., at the first intermediate joint; for parallel-connected cables without intermediate joints, the point of maximum short-circuit current is determined after the parallel connection point.

[0079] In this embodiment of the invention, it is assumed that there is a 500-meter-long power supply cable used to supply power to a small factory workshop. This cable is led out from the factory's power distribution room, has no intermediate joints, and its length is within the manufacturing length range. According to the above rules, the point where the short-circuit current is maximum is determined to be at the end of the cable. This is because, in this case, the line impedance from the power distribution room to the end of the cable gradually increases. When a short circuit occurs, according to Ohm's law, the equivalent impedance is maximum when a short circuit occurs at the end of the cable, so the short-circuit current is maximum.

[0080] Specifically, in step S5, when determining whether the dynamic and thermal stability of the power supply cable is qualified, the dynamic and thermal stability of the power supply cable is determined based on whether line damage or deformation occurs at the short circuit detection point of the power supply cable after the test.

[0081] If, after the test, the power supply cable shows signs of damage or deformation at the short-circuit test point, the power supply cable is deemed to have failed the dynamic and thermal stability test.

[0082] If no line damage or deformation is found at the short-circuit test point of the power supply cable after the test, the dynamic and thermal stability of the power supply cable is deemed qualified.

[0083] In the embodiments of the present invention, the occurrence of line breakage or deformation at the short-circuit detection point of the power supply cable after the test includes insulation layer breakage, insulation layer charring, insulation layer shedding, conductor shape change, conductor fusing, and conductor strand breaking.

[0084] Specifically, in step S5, the short-circuit stability verification test on the short-circuit detection point of the power supply cable includes that when the short-circuit current during the short-circuit stability verification test on the power supply cable in the laid and used state is the historical maximum short-circuit current of the power supply cable, or when the short-circuit current during the short-circuit stability verification test on the power supply cable in the unlaid and to-be-used state is the rated peak withstand current of the equipment connected to the power supply cable.

[0085] In the embodiments of the present invention, it is assumed that through query, it is found that the maximum short-circuit current that has occurred in this power supply cable during past operation is 5000A. This historical maximum short-circuit current of 5000A is used as the short-circuit current for the short-circuit stability verification test on the power supply cable in the laid and used state. Connect test equipment at the short-circuit detection point of the power supply cable to simulate a 5000A short-circuit current passing through the cable, and observe and record the conditions at the short-circuit detection point of the power supply cable during the test, including whether there are phenomena such as line breakage, deformation, overheating, etc. For example, during the test, use a professional temperature sensor to monitor the temperature change at the short-circuit detection point, and use a high-definition camera to record the appearance change of the cable. For the power supply cable in the unlaid and to-be-used state, determine the rated peak withstand current of the equipment it is connected to. Assume that the rated peak withstand current of the equipment to which this power supply cable will be connected is 4000A, then this 4000A is used as the short-circuit current for the short-circuit stability verification test on the power supply cable in the unlaid and to-be-used state. Similarly, connect test equipment at the short-circuit detection point of the power supply cable to simulate a 4000A short-circuit current passing through the cable, and carefully observe and record various conditions at the short-circuit detection point of the power supply cable during the test. Similar to the test of the laid and used state, monitor temperature changes, appearance changes, etc. For the power supply cable in the laid and used state, if there is no line breakage or deformation at the short-circuit detection point after the test, it indicates that the dynamic and thermal stability of this power supply cable is qualified; otherwise, if there are situations such as line breakage and deformation, the dynamic and thermal stability is unqualified and repair or replacement is required. For the power supply cable in the unlaid and to-be-used state, similarly determine whether its dynamic and thermal stability is qualified based on whether there is line breakage or deformation at the short-circuit detection point after the test. If it is qualified, laying and installation can be carried out; if it is unqualified, the cable needs to be inspected or replaced to ensure the safe and stable operation of the power system after installation.

[0086] This invention provides an intuitive and easy-to-understand criterion for determining the dynamic and thermal stability of power cables by clearly defining whether line damage or deformation occurs at the short-circuit test point after testing. Both power system maintenance personnel and related testing technicians can quickly and accurately assess the dynamic and thermal stability of power cables based on this clear standard. This method improves the accuracy of short-circuit test point analysis, reduces energy waste, and ultimately improves energy utilization efficiency.

[0087] Please see Figure 4 As shown, Figure 4 This is a schematic diagram of the structure of the evaluation system for the evaluation method of the dynamic and thermal stability of power supply cables according to an embodiment of the present invention.

[0088] Specifically, an evaluation system for an evaluation method of the dynamic and thermal stability of the power supply cable includes:

[0089] The data acquisition module is used to acquire the physical parameter data of the power supply cable itself, the fault-related electrical parameter data, and the environmental data of the power supply cable.

[0090] The short-circuit detection point determination module, which is connected to the data acquisition module, includes a short-circuit detection point type determination unit for determining the short-circuit detection point of the power supply cable based on the state of the power supply cable, and a maximum loss point determination unit for determining the maximum loss point of the power supply cable based on the laying method of the power supply cable, the soil thermal conductivity of the power supply cable within a preset time period, the rate of change of the burial depth of the power supply cable within a preset time period, the dust accumulation thickness of the power supply cable, and whether there are cracks in the completely exposed power supply cable.

[0091] The test module, which is connected to the short-circuit detection point determination module, is used to perform short-circuit stability verification tests on the short-circuit detection points of the power supply cable.

[0092] The judgment module, which is connected to the test module, is used to determine whether the dynamic and thermal stability of the power supply cable is qualified based on whether line damage or deformation occurs at the short circuit detection point of the power supply cable after the test.

[0093] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for evaluating the dynamic and thermal stability of power supply cables, characterized in that, include: Acquire the physical parameters of the power supply cable itself, the electrical parameters related to the fault, and the environmental data of the power supply cable; Based on whether the power supply cable is in the laying and use state or in the unlaid and waiting-to-use state, the point with the maximum short-circuit current or the point with the maximum loss of the power supply cable is determined as the short-circuit detection point for the dynamic and thermal stability of the power supply cable. Based on the soil thermal conductivity of the buried power cables within a preset time period and the rate of change of the burial depth of the power cables within a preset time period, the point of maximum loss of the buried power cables is determined. Based on the dust accumulation thickness of the exposed power cables and whether there are cracks in the completely exposed power cables, the point of maximum loss of the exposed power cables is determined. When determining the dust accumulation thickness of exposed power cables, the dust accumulation thickness of the exposed power cables can be directly determined based on the rainfall frequency of the environment where the exposed power cables are located within a preset period, or the dust accumulation thickness can be determined after rinsing the exposed power cables with water. A short-circuit stability verification test is conducted on the short-circuit detection points of the power supply cable. Based on whether line damage or deformation occurs at the short-circuit detection points of the power supply cable after the test, it is determined whether the dynamic and thermal stability of the power supply cable is qualified.

2. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 1, characterized in that, Short-circuit detection points for determining the dynamic and thermal stability of power cables include: If the power supply cable is in the laying and use state, the point with the greatest loss of the power supply cable is determined as the short circuit detection point for the dynamic and thermal stability of the power supply cable. If the power supply cable is in an unlaid and unused state, the point with the maximum short-circuit current of the power supply cable is determined as the short-circuit detection point for the dynamic and thermal stability of the power supply cable.

3. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 2, characterized in that, The point at which the buried power cable experiences the greatest loss includes: The point where the average soil thermal conductivity of the buried power cable is the lowest within a preset time period, and the point where the rate of change of the burial depth of the power cable is the highest within a preset time period, are used as loss detection points. Fiber optic temperature sensors are installed on the surface of the power supply cable at the loss detection point to record the temperature changes of the power supply cable in real time during operation. Based on the recorded temperature data and combined with the temperature coefficient of resistance of the power supply cable and the load current, the real-time loss at the loss detection point is calculated. The point with the highest real-time loss is taken as the point of maximum loss.

4. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 3, characterized in that, The point at which the exposed power supply cable experiences the greatest loss includes: The point where the dust accumulates thickest on the exposed power cable and the point where the number of cracks is greatest on the completely exposed power cable are used as loss detection points. Fiber optic temperature sensors are installed on the surface of the power supply cable at the loss detection point to record the temperature changes of the power supply cable in real time during operation. Based on the recorded temperature data and combined with the temperature coefficient of resistance of the power supply cable and the load current, the real-time loss at the loss detection point is calculated. The point with the highest real-time loss is taken as the point of maximum loss.

5. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 4, characterized in that, The determination of the dust accumulation thickness of exposed power cables includes: If the rainfall frequency in the environment where the exposed power cable is located is less than the preset rainfall frequency within a preset period, the thickness of dust accumulation is determined after rinsing the exposed power cable with water. If the rainfall frequency in the environment where the exposed power supply cable is located is greater than or equal to the preset rainfall frequency within a preset period, the dust accumulation thickness of the exposed power supply cable is directly determined.

6. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 1, characterized in that, The point of maximum short-circuit current for power cables includes the location where the maximum short-circuit current occurs in the cable loop. For a single cable not exceeding the manufacturing length, the point of maximum short-circuit current is determined at the end of the cable. For cables with intermediate joints, the point of maximum short-circuit current is determined at the beginning of each segment with a reduced cable cross-section. When the cable segments have equal cross-sections, the point of maximum short-circuit current is determined at the beginning of the next cable segment, i.e., at the first intermediate joint. For parallel-connected cables without intermediate joints, the point of maximum short-circuit current is determined after the point of connection.

7. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 1, characterized in that, Determining whether the dynamic and thermal stability of the power supply cable is qualified includes: If, after the test, damage or deformation is found at the short-circuit test point of the power supply cable, the dynamic and thermal stability of the power supply cable is deemed unqualified. If no line damage or deformation is found at the short-circuit test point of the power supply cable after the test, the dynamic and thermal stability of the power supply cable is deemed qualified.

8. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 7, characterized in that, After the test, the short-circuit detection point of the power supply cable was found to show line damage or deformation, including insulation layer damage, insulation layer burning, insulation layer peeling, conductor shape change, conductor melting, and conductor strand breakage.

9. The method for evaluating the dynamic and thermal stability of power supply cables according to claim 1, characterized in that, The short-circuit stability verification test of the power supply cable short-circuit detection point includes the short-circuit current of the power supply cable in the laying and use state being the historical maximum short-circuit current of the power supply cable, or the short-circuit current of the power supply cable in the unlaid and unused state being the rated peak withstand current of the equipment connected to the power supply cable.

10. An evaluation system for the evaluation method of the dynamic and thermal stability of power supply cables according to any one of claims 1-9, characterized in that, include: The data acquisition module is used to acquire the physical parameter data of the power supply cable itself, the fault-related electrical parameter data, and the environmental data of the power supply cable. The short-circuit detection point determination module, which is connected to the data acquisition module, includes a short-circuit detection point type determination unit for determining the short-circuit detection point of the power supply cable based on the state of the power supply cable, and a maximum loss point determination unit for determining the maximum loss point of the power supply cable based on the laying method of the power supply cable, the soil thermal conductivity of the power supply cable within a preset time period, the rate of change of the burial depth of the power supply cable within a preset time period, the dust accumulation thickness of the power supply cable, and whether there are cracks in the completely exposed power supply cable. The test module, which is connected to the short-circuit detection point determination module, is used to perform short-circuit stability verification tests on the short-circuit detection points of the power supply cable. The judgment module, which is connected to the test module, is used to determine whether the dynamic and thermal stability of the power supply cable is qualified based on whether line damage or deformation occurs at the short circuit detection point of the power supply cable after the test.

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