A method, device and medium for evaluating the overall aging state of a medium-voltage cable

Abstract

A method, device and medium for evaluating the overall aging status of a medium-voltage cable, characterized in that the method comprises the following steps: Step 1, collecting relevant data of the medium-voltage cable to be tested, and pre-simulating and analyzing the medium-voltage cable to be tested to obtain a standard impedance spectrum of the medium-voltage cable to be tested; Step 2, measuring the open-circuit impedance spectrum of the head end of the medium-voltage cable to be tested, and comparing it with the standard impedance spectrum to obtain an offset weight curve of the medium-voltage cable to be tested; Step 3, extracting the local minimum in the offset weight curve, and determining the aging status of the medium-voltage cable to be tested based on the local minimum. The method of the present invention is concise and has a clear concept, avoids errors in manual inspections, improves the extraction accuracy and efficiency of local extreme values in the impedance spectrum curve, and accurately and effectively analyzes the aging status of the cable.

Description

Technical Field

[0001] The present invention relates to the field of cable equipment, and more specifically, to a method, device and medium for evaluating the overall aging status of a medium-voltage cable. Background Art

[0002] As power loads continue to rise in the power system, power cables, as the main arteries of urban power transmission, play a vital role in energy transmission. However, the complex structure of urban underground cable lines, the diverse operating environments, and the increasing density of equipment all increase the risk of failure in distribution cable lines. Once a distribution cable line fails, it will seriously affect the safe operation of the urban power grid.

[0003] Currently, the aging status of medium-voltage distribution network cables is primarily assessed by testing the physical condition of cable insulation specimens. As cable insulation specimens age, their physical properties, such as the color and hardness of the cross-linked polyethylene (XLPE) material, undergo significant changes. However, this testing method relies on disconnecting the cable from normal operation, hindering widespread adoption.

[0004] In addition, the background technology literature: Location of moisture defects in distribution cable bodies and analysis of moisture characteristics, Li Rong et al., School of Electrical Engineering, Sichuan University, and the Proceedings of the Chinese Society of Electrical Engineering disclose a method for locating moisture defects in cables using cable input impedance spectrum. However, this method can only diagnose and locate defects at local moisture points in the cable, and cannot be used to accurately and effectively determine the comprehensive aging conditions of long-distance, large-scale power lines.

[0005] In addition, various manual inspection methods are also difficult to make an accurate assessment of the aging status of cables.

[0006] In response to the above problems, the present invention provides a new method, device and medium for evaluating the overall aging status of medium-voltage cables. Summary of the Invention

[0007] To address the deficiencies in the prior art, the present invention provides a method, device, and medium for evaluating the overall aging status of a medium-voltage cable. The method establishes a simulation model library, calculates the standard impedance spectrum of the medium-voltage cable to be tested, and performs normalized analysis on the actual impedance spectrum of the test cable based on the standard impedance spectrum, thereby accurately extracting the local extreme values of the normalized impedance spectrum and accurately determining the aging status of the medium-voltage cable.

[0008] The present invention adopts the following technical solutions.

[0009] A first aspect of the present invention relates to a method for evaluating the overall aging status of a medium-voltage cable, the method comprising the following steps: step 1, collecting relevant data of the medium-voltage cable to be tested, and performing simulation analysis on the medium-voltage cable to be tested in advance to obtain a standard impedance spectrum of the medium-voltage cable to be tested; step 2, measuring the open-circuit impedance spectrum of the head end of the medium-voltage cable to be tested, and comparing it with the standard impedance spectrum to obtain an offset weight curve of the medium-voltage cable to be tested; step 3, extracting a local minimum in the offset weight curve, and determining the aging status of the medium-voltage cable to be tested based on the local minimum.

[0010] Preferably, step 1 also includes: step 1.1, collecting the voltage level, cross-sectional area, and structural parameters of the medium-voltage cable to be tested, and using electromagnetic transient simulation software to construct a cable model for the medium-voltage cable to be tested; step 1.2, using the electromagnetic transient simulation software to inject an electrical signal into the cable model to obtain the attenuation coefficient, channel wave velocity, and characteristic impedance of the cable model; step 1.3, setting the load end of the cable model to an open-circuit state, and solving the open-circuit impedance of the first end of the cable model to generate a standard impedance spectrum of the medium-voltage cable to be tested.

[0011] Preferably, the open-circuit impedance of the head end of the single-conductor cable in the cable model is solved when the electrical signal is at different frequencies, so as to obtain a standard impedance spectrum of the cable model within a preset frequency range.

[0012] Preferably, the value of the standard impedance spectrum changes with the change of the cable length parameter in the cable model.

[0013] Preferably, a standard impedance spectrum is used to perform normalization processing on the open-circuit impedance spectrum of the first end of the medium voltage cable to be tested to generate an offset weight curve.

[0014] Preferably, a local minimum is extracted from the offset weight curve, and the aging state of the medium voltage cable to be tested is determined based on the medium voltage cable aging state range in which the local minimum falls.

[0015] Preferably, an average value is calculated for a plurality of local minimum values, and the average value is compared with the aging state range of the medium voltage cable.

[0016] Preferably, the aging state range of the medium voltage cable includes a slightly aging range [0, 0.3], a moderately aging range [0.3, 0.7], and a severely aging range [0.7, 1].

[0017] The second aspect of the present invention relates to an overall aging status assessment device for a medium-voltage cable, comprising a processor and a storage medium; the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method in the first aspect of the present invention.

[0018] The third aspect of the present invention relates to a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method of the first aspect of the present invention.

[0019] The beneficial effect of the present invention is that, compared with the prior art, the overall aging status assessment method, device, and medium of a medium-voltage cable of the present invention calculates a standard impedance spectrum of the medium-voltage cable to be tested by establishing a simulation model library, and normalizes and analyzes the actual impedance spectrum of the test cable based on the standard impedance spectrum, thereby accurately extracting the local extreme values of the normalized impedance spectrum, thereby accurately determining the aging status of the medium-voltage cable. The method of the present invention is concise, clear in concept, and highly objective, and can avoid errors in manual inspections, effectively improve the extraction accuracy and efficiency of local extreme values in the impedance spectrum curve, and accurately and effectively analyze the aging status of the cable by comprehensively evaluating the aging conditions at different locations of the cable to be tested.

[0020] The beneficial effects of the present invention also include:

[0021] 1. The present invention fully analyzes the structural parameters of the cable to be tested, and selects the relevant quantities that are most suitable for calculating the standard impedance spectrum of the cable for the multiple different structures and multiple different cabling methods in the cable to be tested. On the one hand, the method of the present invention can comprehensively solve the comprehensive impedance spectrum of multiple different cable cores, and use the comprehensive impedance spectrum as a higher confidence level to determine the offset weight of the medium-voltage cable, thereby improving the accuracy of the detection results of the present invention. On the other hand, the present invention can also generate a standard impedance spectrum by selecting only the optimal single-conductor cable-related parameters in the simplest way, thereby simplifying the calculation to the greatest extent. According to different judgment requirements, the method of the present invention can also flexibly select different standard impedance spectrum acquisition methods.

[0022] 2. In the prior art, since only the impedance spectrum is needed to determine the anomaly at a local position in the cable, fault detection and anomaly analysis can be achieved based on whether the normalized values of the impedance spectrum at different positions of the cable can smoothly transition. In the present invention, since it is necessary to determine the comprehensive aging status of the entire cable, not only the open-circuit impedance spectrum of the first end of the cable is collected, but also the local extreme point is extracted through a new normalization method, and the aging level of the entire cable is determined based on this local extreme point. Therefore, although similar to the prior art, the present invention also uses the impedance spectrum, but the present invention also reasonably combines mathematical methods to further extract valid data from the impedance spectrum to determine the aging status of the entire cable.

[0023] 3. The method of the present invention takes into account the problem of different cable lengths during the calculation of the standard impedance spectrum. It can simulate the open-end standard impedance spectrum of cables of different lengths based on the position of the cable when the impedance spectrum is actually measured, thereby making the normalization method more reliable. On the other hand, the method of the present invention does not require an assessment of the specific state of the cable, and therefore omits algorithms such as Fourier transform and mapping the impedance spectrum to the cable position. This greatly simplifies the method's calculation steps, reduces the method's requirements for data processing capabilities, simplifies equipment, saves costs, and obtains evaluation results more quickly and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the steps of a method for evaluating the overall aging condition of a medium voltage cable according to the present invention;

[0025] Figure 2 A schematic cross-sectional view of a medium-voltage cable in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention;

[0026] Figure 3 A schematic diagram of the structural division of a cross section of a medium-voltage cable in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention;

[0027] Figure 4 A schematic diagram of the open-circuit impedance amplitude spectrum of the head end of a medium-voltage cable with different structures in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention;

[0028] Figure 5 A schematic diagram of actual impedance spectra of a medium-voltage cable under different aging conditions in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention;

[0029] Figure 6 Schematic diagram of actual differential impedance spectra of a medium voltage cable under different aging conditions in a method for evaluating the overall aging condition of a medium voltage cable according to the present invention;

[0030] Figure 7 Schematic diagram of actual differential impedance spectra of cables of different models in two aging states in a method for evaluating the overall aging state of a medium-voltage cable according to the present invention;

[0031] Figure 8 Schematic diagram of offset weight curves of cables of different models in two aging states in a method for evaluating the overall aging state of a medium-voltage cable according to the present invention;

[0032] Figure 9 This is a schematic diagram of local extreme value fitting of an offset weight curve in a method for evaluating the overall aging status of a medium-voltage cable according to the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without making creative efforts are all within the scope of protection of the present invention.

[0034] Figure 1 Schematic diagram of the steps of the overall aging status evaluation method of a medium voltage cable according to the present invention. Figure 1 As shown, the first aspect of the present invention relates to a method for evaluating the overall aging status of a medium voltage cable, and the method includes steps 1 to 3.

[0035] Step 1: collect relevant data of the medium voltage cable to be tested, and perform simulation analysis on the medium voltage cable to be tested in advance to obtain a standard impedance spectrum of the medium voltage cable to be tested.

[0036] It is understandable that the model of the medium voltage cable to be tested in the present invention is not limited. If different medium voltage cables to be tested need to be measured, the specific structures and parameters of the cables of different models can be analyzed first to obtain a standard impedance spectrum.

[0037] Existing medium-voltage cables typically operate in the 3.6kV to 36kV range. Due to this limited voltage range, their internal structure is more complex than that of low-voltage cables. Typically, medium-voltage cables are constructed with multiple layers of insulation material forming the insulation shield, produced using the CCV catenary cross-linking process.

[0038] In the present invention, in order to evaluate the aging conditions of different medium-voltage cables, a simulation database can be pre-set to store the models and structural parameters of various mainstream medium-voltage cables. At the same time, the standard impedance spectrum of the medium-voltage cable can be pre-calculated based on the content stored in the database.

[0039] The medium-voltage cable used in one embodiment of the present invention is a YJV22 series power cable. Because the model of the cable to be tested may not be known in advance before evaluation, the present invention also utilizes a simulation database to pre-store information about mainstream cables. Furthermore, the simulation database can be updated at any time based on cable testing needs or the actual cable installation process, thereby adding data for more cable models to the simulation database. This allows the simulation database to meet the needs of ongoing testing and cable aging assessment methods.

[0040] Since the parameter of the standard impedance spectrum is mainly related to the length parameter of the medium voltage cable to be tested, in this process, it is also necessary to measure the length of the medium voltage cable to be tested in advance and calculate the size of the standard impedance spectrum of the cable accordingly.

[0041] Preferably, step 1 also includes: step 1.1, collecting the voltage level, cross-sectional area, and structural parameters of the medium-voltage cable to be tested, and using electromagnetic transient simulation software to construct a cable model for the medium-voltage cable to be tested; step 1.2, using the electromagnetic transient simulation software to inject an electrical signal into the cable model to obtain the attenuation coefficient, channel wave velocity, and characteristic impedance of the cable model; step 1.3, setting the load end of the cable model to an open-circuit state, and solving the open-circuit impedance of the first end of the cable model to generate a standard impedance spectrum of the medium-voltage cable to be tested.

[0042] It is understood that in the process of obtaining the standard impedance spectrum of the cable to be tested, relevant data of the cable can be collected first. The relevant data may include the voltage level carried by the cable, cross-sectional area, and structural parameters. The structural parameters may also specifically include the cable length.

[0043] Figure 2 This is a schematic cross-sectional view of a medium-voltage cable in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention. Figure 3 Schematic diagram of the structural division of the cross section of a medium voltage cable in a method for evaluating the overall aging status of a medium voltage cable according to the present invention. Figure 2-3 As shown in the figure, in one embodiment of the present invention, the voltage level of the cable is between 3.6 kV and 36 kV. The cross-sectional area is calculated from the cross-sectional area of three 120 mm² cables after cross-linking. The cable comprises, from the inside out, a metal conductor 1, an insulating layer 2, a metal shielding layer 3, a shielded insulating layer 4, an inner lining layer 5, an armor 6, and an outer sheath 7. The metal conductor 1 and the insulating layer 2 located outside it together constitute a single-conductor cable.

[0044] In addition, the selection method and common parameters of the materials of each layer can refer to the relevant provisions of the "National Standard of the People's Republic of China GB / T12706.1-2008" jointly issued by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China and the Standardization Administration of China. In the above standard, the first to fourth parts of the rated voltage 1kV (=1.2kV) to 35kV (=40.5kV) extruded insulated power cables and accessories list the relevant standard parameters of cable materials. These parameters can be borrowed in the present invention and applied to the cable model constructed by the cable to be tested. For example, the resistivity of the metal conductor in the cable is defined as 1.75×10 -8Ω·m, the conductor radius is 0.0062m, the outer diameter of the insulation layer is 0.0087m, the relative dielectric constant of the insulation layer is 2.3, the outer diameter of the shielding layer is 0.009m, and the resistivity of the steel armor is 9.1×10 -7 Ω·m, the inner diameter of the steel armor is 0.02338m, the outer diameter of the steel armor is 0.02388m, the outer diameter of the sheath is 0.02655m, the relative dielectric constant of the outer sheath is 2.7, and the cabling radius of the three-core cable is 0.0105m. Since the cable must meet the requirements of the relevant parameters in the above standards during the design and manufacturing process, these parameters can also be calculated based on the indicators already specified in the standards. This will not significantly affect the simulation results and can fully meet the requirements of the cable aging status assessment in the present invention and the accuracy of the assessment results.

[0045] Using the above parameters, the electromagnetic transient simulation software can construct the overall model of the cable in layers and solve the standard impedance spectrum of the medium voltage cable to be tested. Since the signal frequency range of the cable in the working state is usually predetermined by the power grid in which it is located, the present invention can pre-set the corresponding frequency range, select multiple frequency points spaced apart from each other in the frequency range, and inject electrical signals at different frequency points into the cable to simulate and solve the open-circuit impedance spectrum of the cable head end at that frequency. For example, the present invention can use a swept frequency signal to enable the input signal to achieve periodic changes in signal frequency, thereby achieving the acquisition of the open-circuit impedance spectrum of the head end at different frequencies.

[0046] Specifically, the electromagnetic transient simulation software in this invention can use the Berelon model of transmission lines to calculate cable channel characteristics. This model can use the relevant parameters described above to solve the propagation mode and state of electromagnetic waves within the cable line. This state can be used to solve the attenuation coefficient, channel wave velocity, and characteristic impedance of the cable model.

[0047] In addition, the present invention can not only simulate the overall state of the cable, but also decouple the channel transmission characteristics of different cable materials, that is, different material layers. In one embodiment of the present invention, by treating a single-conductor cable as an independent transmission channel, it is decoupled from the transmission channels composed of other directly or indirectly adjacent materials, and based on the decoupling, the calculation of the characteristics of the single-conductor cable channel is realized. The decoupling process of multiple channels in the present invention can be implemented using the simulation software mentioned above, or it can be implemented using other methods in the prior art.

[0048] Since single-conductor cable is the most important material for medium-voltage cables to transmit electrical signals, the present invention achieves accurate extraction of the single-channel characteristics of the single-conductor cable through decoupling, thereby making the determination result of the present invention more accurate.

[0049] Table 1 shows the calculation results of the decoupling of the YJV22 medium voltage cable channel characteristics when a 1MHz electrical signal is injected in one embodiment of the present invention. As shown in Table 1, moduli 1 to 7 are used to characterize the outer steel armor, three conductor shielding layers, and three-phase metal conductors, respectively. After the coupling between the materials caused by the current skin effect is eliminated through calculation, the calculation results of the 7 moduli are obtained respectively. Among them, moduli 5, 6, and 7 are the transmission characteristics of the three-phase conductors, respectively. When the electrical signal is at a higher frequency, the spectral lines of the three conductors coincide, and all have good periodicity, rapidity, and standard attenuation that meets the channel requirements. Therefore, the present invention uses the characteristics of a single metal conductor as the calculation index of the cable standard impedance spectrum.

[0050]

[0051] Table 1 Calculation results after decoupling of 1MHz electrical signal injection into YJV22 medium voltage cable channel characteristics

[0052] Preferably, the open-circuit impedance of the head end of the single-conductor cable in the cable model is solved when the electrical signal is at different frequencies, so as to obtain a standard impedance spectrum of the cable model within a preset frequency range.

[0053] It is understood that the present invention can employ existing impedance spectrum calculation formulas to solve the open-circuit impedance spectrum of the cable's headend. The parameters required in the solution formula include the transmission line's characteristic impedance, attenuation coefficient, cable length, signal frequency, and channel wave velocity, all of which are determined by the method described above. Furthermore, the circuit's characteristic impedance can be pre-solved using the Berelon model.

[0054] During the calculation process, the other end of the cable, that is, the load end, can be designed to be in an open circuit state, so the reflection coefficient at the load end can be taken as 1. Therefore, according to the transmission line theory, the line impedance spectrum formula is further deduced to obtain the open circuit impedance Z of the cable head end. l The value of

[0055]

[0056] Among them, Z c is the characteristic impedance of the transmission line, that is, the characteristic impedance of the single-conductor cable, Γ L is the reflection coefficient at the load end, γ is the propagation coefficient of the transmission line, l is the cable length, α is the attenuation coefficient, β is the phase constant, f is the signal frequency, and ν is the channel wave velocity.

[0057] Preferably, the value of the standard impedance spectrum changes with the change of the cable length parameter in the cable model. According to the content in the above formula, the cable length will affect the value of the standard impedance spectrum. Therefore, if an accurate standard impedance spectrum is required, the actual length of the cable to be tested also needs to be determined.

[0058] Step 2: measuring the open-circuit impedance spectrum of the first end of the medium voltage cable to be tested, and comparing it with the standard impedance spectrum to obtain the offset weight curve of the medium voltage cable to be tested.

[0059] It is understood that the present invention can consider using data analysis and processing software to calculate and plot the values of the head-end open-circuit impedance spectrum corresponding to different frequencies of the sweep signal, so as to obtain the following: Figure 4 The magnitude spectrum is shown. Figure 4 This is a schematic diagram of the head-end open-circuit impedance amplitude spectrum of medium-voltage cables with different structures in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention.

[0060] The actual impedance spectrum in the present invention can be obtained by measuring with an impedance spectrum instrument or other equipment. During the measurement process, the position of the measurement point in the cable can be recorded, so as to select a corresponding standard impedance spectrum for comparison.

[0061] Preferably, a standard impedance spectrum is used to perform normalization processing on the impedance spectra at different positions of the medium voltage cable to be tested to generate an offset weight curve.

[0062] It is understood that the normalization method of the present invention can first solve the difference between the modulus values of the actual impedance spectrum and the standard impedance spectrum. This difference is also called the differential impedance spectrum. After obtaining the differential impedance spectrum, the differential impedance spectrum is divided by the modulus value of the actual impedance spectrum to obtain the offset weight.

[0063] Figure 5 This is a schematic diagram of actual impedance spectra of a medium-voltage cable under different aging conditions in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention. Figure 6 This is a schematic diagram of actual differential impedance spectra of a medium-voltage cable under different aging conditions in a method for evaluating the overall aging condition of a medium-voltage cable according to the present invention. Figure 7 Schematic diagram of actual differential impedance spectra of different types of cables in two aging states in a method for evaluating the overall aging state of a medium voltage cable according to the present invention. Figure 5-7 As shown, the present invention compares the actual impedance spectra and differential impedance spectra of medium voltage cables under different aging conditions. Under different aging conditions and different voltage levels, the differences between the impedance spectra are not very large. It can be seen that it is actually difficult to grasp the aging status of a medium voltage cable from a holistic perspective using the existing methods.

[0064] It should be noted that, in order to initially compare the impedance spectra of multiple cables with significantly different aging conditions, the present invention selected cables with different relative dielectric constants for testing. Based on experience, when there are certain differences in the relative dielectric constants of the cable insulation layers, a preliminary assessment of the cable's aging state can be made. Therefore, in the present invention, cables with relative dielectric constants of 2.35, 2.4, and 2.5 were selected to characterize the cable conditions of slight, moderate, and severe aging, respectively.

[0065] Figure 8 Schematic diagram of the offset weight curves of different types of cables in two aging states in a method for evaluating the overall aging state of a medium voltage cable according to the present invention. Figure 8 As shown in the figure, when the offset weight curve is generated by the normalization method, the offset weights of cables with different dielectric constants show significant differences. This shows that compared to the differential impedance spectrum, the offset weight curve can better distinguish the two aging states.

[0066] Step 3: extract the local minimum value in the offset weight curve, and determine the aging state of the medium voltage cable to be tested based on the local minimum value.

[0067] Figure 9 Schematic diagram of local extreme value fitting of the offset weight curve in the overall aging status assessment method of a medium voltage cable according to the present invention. Figure 9 As shown, preferably, a local minimum value is extracted from the offset weight curve, and the aging state of the medium voltage cable to be tested is determined based on the medium voltage cable aging state range in which the local minimum value falls.

[0068] In order to analyze the differences between cables under different aging conditions, the present invention collects multiple local extreme values in the offset weight curve. This collection method can be implemented by referring to various algorithms in the prior art.

[0069] Preferably, an average value is calculated for a plurality of local minimum values, and the average value is compared with the aging state range of the medium voltage cable.

[0070] The present invention can collect the amplitude values of multiple local minimum values in the curve spectrum, calculate the average value, and define the aging state of the cable based on the value range of the average value.

[0071] Preferably, the aging state range of the medium voltage cable includes a slightly aging range [0, 0.3], a moderately aging range [0.3, 0.7], and a severely aging range [0.7, 1].

[0072] The selection of different aging ranges in the present invention is based on empirical judgment. Due to the high accuracy of the assessment method in the present invention, the number of aging ranges can be appropriately increased. In the present invention, if the calculated average amplitude value is 0.2, the cable can be judged to be in a lightly aged state according to the above aging range. If the value is 0.5, it can be judged to be in a moderately aged state, and so on.

[0073] The method of the present invention can not only determine the aging status of a cable at a specific location, but also comprehensively assess the overall aging status of the cable at multiple locations. In addition, when the method of the present invention detects cable aging, the aging of the cable can be monitored in real time by increasing the number of sensor data collection times of the detection equipment, thereby providing reasonable and appropriate current maintenance.

[0074] The second aspect of the present invention relates to an overall aging status assessment device for a medium-voltage cable, comprising a processor and a storage medium; characterized in that: the storage medium is used to store instructions; the processor is used to operate according to the instructions to execute the steps of the method according to the first aspect of the present invention.

[0075] It is understandable that the overall aging status assessment device for medium-voltage cables includes hardware structures and / or software modules that perform the corresponding functions in order to implement the various functions of the method provided in the above-mentioned embodiment of the present application. Those skilled in the art should easily realize that, in combination with the algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0076] The embodiment of the present application can divide the functional modules of the overall aging status assessment device of the medium voltage cable according to the above-mentioned method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. In actual implementation, there may be other division methods.

[0077] The device includes at least one processor, a bus system and at least one communication interface.

[0078] The processor can be a central processing unit (CPU), and can also be replaced by a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC) or other hardware, or the FPGA or other hardware can be used together with the CPU as a processor.

[0079] The memory may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited to these. The memory may exist independently and be connected to the processor via a bus. The memory may also be integrated with the processor.

[0080] The hard disk can be a mechanical disk or a solid-state drive (SSD). The interface card can be a host bus adapter (HBA), a redundant array of independent disks (RID), an expander card, or a network interface controller (NIC), etc., which is not limited in the embodiments of the present invention. The interface card in the hard disk module communicates with the hard disk. The storage node communicates with the interface card of the hard disk module to access the hard disk in the hard disk module.

[0081] The interface of the hard disk can be Serial Attached Small Computer System Interface (SAS), Serial Advanced Technology Attachment (SATA), or Peripheral Component Interconnect express (PCIe).

[0082] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using a software program, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more media integrated therein. The available media may be magnetic media (eg, floppy disks, hard disks, magnetic tapes), optical media (eg, DVDs), or semiconductor media (eg, solid state disks (SSDs)).

[0083] The third aspect of the present invention relates to a computer-readable storage medium having a computer program stored thereon, wherein the program implements the steps of the method of the first aspect of the present invention when executed by a processor.

[0084] The computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages such as Smalltalk, C++, and conventional procedural programming languages such as "C" language or similar programming languages. Computer-readable program instructions may be executed entirely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., utilizing an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be personalized by utilizing the state information of the computer-readable program instructions. The electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0085] Various aspects of the present disclosure are described herein with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present disclosure. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer-readable program instructions.

[0086] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processor of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, where these instructions cause the computer, programmable data processing device, and / or other device to operate in a specific manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0087] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0088] The beneficial effect of the present invention is that, compared with the prior art, the overall aging status assessment method, device, and medium of a medium-voltage cable of the present invention calculates a standard impedance spectrum of the medium-voltage cable to be tested by establishing a simulation model library, and normalizes and analyzes the actual impedance spectrum of the test cable based on the standard impedance spectrum, thereby accurately extracting the local extreme values of the normalized impedance spectrum, thereby accurately determining the aging status of the medium-voltage cable. The method of the present invention is concise, clear in concept, and highly objective, and can avoid errors in manual inspections, effectively improve the extraction accuracy and efficiency of local extreme values in the impedance spectrum curve, and accurately and effectively analyze the aging status of the cable by comprehensively evaluating the aging conditions at different locations of the cable to be tested.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for evaluating the overall aging status of a medium voltage cable, characterized in that: The method comprises the following steps: Step 1: Collect relevant data of the medium voltage cable to be tested, and perform simulation analysis on the medium voltage cable to be tested in advance to obtain a standard impedance spectrum of the medium voltage cable to be tested; The step 1 further comprises: The voltage level, cross-sectional area, and structural parameters of the medium-voltage cable to be tested are collected to construct a cable model for the medium-voltage cable to be tested using electromagnetic transient simulation software: Electromagnetic transient simulation software is used to inject electrical signals into the cable model to obtain the cable model's attenuation coefficient, channel wave velocity, and characteristic impedance. A frequency sweep signal is used to enable the input signal to achieve periodic changes in signal frequency, thereby obtaining the first-end open-circuit impedance spectrum at different frequencies. Using a single-conductor cable as an independent transmission channel, the single-conductor cable is decoupled from the transmission channels formed by other directly or indirectly adjacent materials, and the coupling between materials caused by the current skin effect is eliminated through calculation; The impedance spectrum calculation formula is used to solve the open-circuit impedance of the first end of the cable model to obtain the standard impedance spectrum; the characteristic impedance of the circuit is pre-solved according to the Berelon model; The impedance spectrum calculation formula is: Among them, Z l is the open-circuit impedance at the beginning of the cable, Z c is the characteristic impedance of the transmission line, that is, the characteristic impedance of the single-conductor cable, Γ L is the reflection coefficient at the load end, γ is the propagation coefficient of the transmission line, l is the cable length, α is the attenuation coefficient, β is the phase constant, f is the signal frequency, and ν is the channel wave velocity; Step 2: measuring the open-circuit impedance spectrum of the first end of the medium-voltage cable to be tested, and comparing it with a standard impedance spectrum to obtain an offset weight curve of the medium-voltage cable to be tested; Step 3: extracting a local minimum value from the offset weight curve, and determining the aging state of the medium voltage cable to be tested based on the medium voltage cable aging state range in which the local minimum value falls.

2. The method for evaluating the overall aging status of a medium voltage cable according to claim 1, characterized in that: The open-circuit impedance of the head end of the single-conductor cable in the cable model when the electrical signal is at different frequencies is solved to obtain a standard impedance spectrum of the cable model within a preset frequency range.

3. The method for evaluating the overall aging status of a medium voltage cable according to claim 2, wherein: The value of the standard impedance spectrum changes with the change of the cable length parameter in the cable model.

4. The method for evaluating the overall aging status of a medium voltage cable according to claim 3, wherein: The standard impedance spectrum is used to perform normalization processing on the open-circuit impedance spectrum of the first end of the medium voltage cable to be tested to generate an offset weight curve.

5. The method for evaluating the overall aging status of a medium voltage cable according to claim 4, characterized in that: An average value is calculated for a plurality of the local minimum values, and the average value is compared with the aging state range of the medium voltage cable.

6. The method for evaluating the overall aging status of a medium voltage cable according to claim 5, characterized in that: The aging state range of the medium voltage cable includes a slight aging range [0, 0.3], a moderate aging range [0.3, 0.7), severe aging range [0.7, 1].

7. A device for evaluating the overall aging status of a medium-voltage cable, 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 execute the steps of the method for evaluating the overall aging condition of a medium voltage cable according to any one of claims 1 to 6.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the method for evaluating the overall aging status of a medium voltage cable according to any one of claims 1 to 6 are implemented.

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