Cable early fault positioning method and device based on metal sheath parameters

Abstract

The embodiment of the invention provides a cable early-stage fault positioning method and device based on metal sheath parameters. The cable early-stage fault positioning method based on the metal sheath parameters comprises the steps that a cable electrical model is established based on electrical parameters; obtaining a key electrical quantity, comparing the key electrical quantity with a preset threshold value, and determining a comparison result; determining fault feature information based on the comparison result; and determining a fault point based on the fault feature information and the fault positioning equation. According to the scheme, the impedance characteristic of the cable metal sheath is utilized, and the parameters of the metal sheath are introduced into a fault positioning algorithm. According to the method, the positioning error is effectively reduced, the accuracy of the early fault positioning process is remarkably improved, and a more efficient and more accurate solution is provided for solving the detection and positioning problems of the power system in the early stage of the fault.

Description

TECHNICAL FIELD

[0001] Embodiments of the present specification relate to the technical field of cable fault detection, in particular to a cable early fault positioning method based on metal sheath parameters. BACKGROUND

[0002] Underground cables have become an important part of modern power grid infrastructure due to their high reliability, low environmental impact, and good safety. However, the insulation layer of the cable gradually deteriorates due to mechanical stress, electrical load, chemical corrosion, and thermal aging during long-term operation. This aging process often leads to serious phase-to-ground faults, causing system interruption. Since such faults cannot be directly detected by the human eye, professional tools are needed for accurate identification, often causing inconvenience and long service interruption. It is worth noting that phase-to-ground faults are the main cause of power outages, accounting for about 70%, posing a serious challenge to the stable operation of the power system.

[0003] Current mainstream fault positioning technologies, such as impedance methods, have obvious limitations: synchronous measurement of cable voltage and current at both ends is required, which is complex and costly; they are easily affected by line parameter fluctuations and load current, resulting in large positioning errors; especially for single-ended grounded cables, their short length and low impedance characteristics make it difficult for conventional methods to achieve high-precision positioning; in addition, existing technologies respond slowly to early faults (such as transient discharge), and cannot provide effective early warning before the fault worsens, lacking real-time performance. These limitations make it difficult for existing systems to meet the urgent need for early warning and high-precision positioning of latent faults in modern power grids.

[0004] Therefore, a better solution is needed. SUMMARY

[0005] In view of the above, the embodiments of the present specification provide a cable early fault positioning method based on metal sheath parameters. One or more embodiments of the present specification also relate to a cable early fault positioning device based on metal sheath parameters, a computing device, a computer-readable storage medium, and a computer program to solve the technical defects in the prior art.

[0006] According to a first aspect of the embodiments of the present specification, a cable early fault positioning method based on metal sheath parameters is provided, comprising: establishing a cable electrical model based on electrical parameters; obtaining a key electrical quantity, comparing the key electrical quantity with a preset threshold, and determining a comparison result; determining fault feature information based on the comparison result; determining a fault point based on the fault feature information and a fault positioning equation.

[0007] In a possible implementation, the cable electrical model is established based on the electrical parameters, including: a distribution parameter model is constructed based on the metal sheath impedance, the total length of the line, a sheath voltage threshold, a current threshold and a line capacitance; an equivalent circuit model of the medium-voltage single-core cable is established based on the distribution parameter model, wherein the equivalent circuit model comprises a main conductor, an insulation layer and a metal sheath; and the metal sheath is only grounded at the power supply side and remains open at the load side.

[0008] In a possible implementation, the key electrical quantities are acquired, including: the relative ground voltage at the power supply end, the relative ground voltage at the load end and the relative ground voltage of the sheath are collected using a differential voltage probe; the sheath current is collected using a current probe.

[0009] In a possible implementation, the fault feature information is determined based on the comparison result, including: in a case where the relative ground voltage at the power supply end, the relative ground voltage at the load end, the relative ground voltage of the sheath and the sheath current are greater than preset thresholds, a fault feature waveform is recorded.

[0010] In a possible implementation, the fault positioning equation is a quadratic equation about the normalized fault distance x : A x 2 +B x +C=0; wherein the coefficients A , B , C are calculated based on the relative ground voltage at the power supply end, the relative ground voltage at the load end, the relative ground voltage of the sheath, the sheath current and the distribution parameters of the cable.

[0011] In a possible implementation, the coefficients A , B , C are calculated in the following manner:

[0012] wherein is the relative ground voltage at the power supply end, is the relative ground voltage at the load end, is the relative ground voltage of the sheath and is the sheath current, is the resistance per unit length of the metal sheath, and is the inductance per unit length of the metal sheath.

[0013] In a possible implementation, the acquisition speed of the key electrical quantities is not less than 2 GSa / s.

[0014] According to a second aspect of the embodiments of the present specification, a cable early fault location device based on metal sheath parameters is provided, comprising: A model establishing module is configured to establish a cable electrical model based on electrical parameters; A threshold comparison module is configured to obtain a key electrical quantity, compare the key electrical quantity with a preset threshold, and determine a comparison result; A feature obtaining module is configured to determine fault feature information based on the comparison result; A point determining module is configured to determine a fault point based on the fault feature information and a fault location equation.

[0015] According to a third aspect of the embodiments of the present specification, a computing device is provided, comprising: A memory and a processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions, which realize the steps of the above-mentioned cable early fault location method based on metal sheath parameters.

[0016] According to a fourth aspect of the embodiments of the present specification, a computer readable storage medium is provided, which stores computer executable instructions, which realize the steps of the above-mentioned cable early fault location method based on metal sheath parameters when executed by a processor.

[0017] According to a fifth aspect of the embodiments of the present specification, a computer program is provided, wherein when the computer program is executed in a computer, the computer executes the steps of the above-mentioned cable early fault location method based on metal sheath parameters.

[0018] The embodiments of the present specification provide a cable early fault location method and device based on metal sheath parameters, wherein the cable early fault location method based on metal sheath parameters comprises: establishing a cable electrical model based on electrical parameters; obtaining a key electrical quantity, comparing the key electrical quantity with a preset threshold, and determining a comparison result; determining fault feature information based on the comparison result; and determining a fault point based on the fault feature information and a fault location equation. This scheme introduces the metal sheath parameters into the fault location algorithm by utilizing the impedance characteristics of the cable metal sheath. This method effectively reduces the positioning error and significantly improves the accuracy of the early fault location process, and provides a more efficient and more accurate solution to solve the detection and positioning problem of the power system in the early fault stage. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flowchart of a cable early fault location method based on metal sheath parameters provided by an embodiment of the present specification; Figure 2 is a structural schematic diagram of a cable early fault location device based on metal sheath parameters provided by one embodiment of the present specification; Figure 3 is a structural block diagram of a computing device provided by one embodiment of the present specification. DETAILED DESCRIPTION

[0020] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present specification. However, the present specification can be practiced without the specific details, other than those described herein, and it is understood that the present specification can be practiced with yet other embodiments that are apparent in light of, and tailored to, the overall context of the present specification and that the scope of the present specification is defined by the appended claims.

[0021] The terminology used in one or more embodiments of the present specification is for the purpose of describing particular embodiments only and is not intended to be limiting of one or more embodiments of the present specification. As used in one or more embodiments of the present specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in one or more embodiments of the present specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] It will be understood that, although the terms first, second, etc. can be employed in describing various information, such information should not be limited by these terms. These terms are only used to differentiate one piece of information from another. For example, a first can be termed a second, and, similarly, a second can be termed a first, without departing from the scope of one or more embodiments of the present specification. Depending on the context, the word "if" as used herein can be interpreted to mean "when" or "in response to determining".

[0023] The existing cable fault location technology is difficult to meet the reliability requirements of the power grid, especially in the application of single-point grounding underground cables, mainly manifested in: 1. Insufficient positioning accuracy: the positioning error is large for early faults (insulation layer micro transient discharge); 2. Dependence on complex measurement system: existing methods generally need to measure the voltage and current at both ends of the cable (double-end measurement), which is difficult to deploy and high in cost; 3. Difficulty in extracting fault features: early fault signals are weak, short-lived and easily covered by load current and noise, making it difficult for traditional protection systems to effectively detect.

[0024] The reasons for the above problems are mainly three aspects: 1. The particularity of single-point grounding cable: this type of cable is usually short in length and low in impedance, making the traditional impedance method insensitive to parameter changes. At the same time, its metal sheath is only grounded at one point, resulting in a significant difference between the fault current path and the traditional (such as double-ended grounding) model.

[0025] 2. Measurement limitations: the double-ended measurement scheme not only requires high-precision synchronization equipment, but also its measurement results are easily disturbed by load current fluctuations, affecting the accuracy of fault signal extraction.

[0026] 3. Interference of fault resistance: the early fault resistance value has uncertainty and non-linear characteristics, while the traditional method often needs to rely on arc models or parameter estimation, thereby introducing additional errors.

[0027] The difficulty of solving the above technical problems lies in: 1. Simplify the measurement architecture: a single-ended measurement scheme needs to be developed, i.e., only using the sheath current and ungrounded sheath voltage to replace the complex double-ended current measurement. The key difficulty lies in how to effectively decouple the influence of load current on the measurement results.

[0028] 2. Improve noise immunity: since the early fault signal is extremely weak, it is easily overwhelmed by environmental electromagnetic noise (such as adjacent cable interference), the difficulty lies in how to reliably extract and identify effective fault features in a strong noise background.

[0029] 3. Eliminate fault resistance dependence: the difficulty lies in designing an algorithm that makes the positioning result independent of the unknown and nonlinear fault resistance value, thereby avoiding the error introduced by estimating this parameter in the traditional method.

[0030] Thus, in the present specification, a cable early fault positioning method based on metal sheath parameters is provided, the present specification also relates to a cable early fault positioning device based on metal sheath parameters, a computing device, and a computer-readable storage medium, which are described in detail one by one in the following embodiments.

[0031] Referring to Figure 1 , Figure 1 A flowchart of a cable early fault positioning method based on metal sheath parameters according to one embodiment of the present specification is shown, which specifically includes the following steps.

[0032] Step 101: Establish a cable electrical model based on electrical parameters.

[0033] In a possible implementation, the cable electrical model is established based on the electrical parameters, including: constructing a distributed parameter model based on the metal sheath impedance, the total length of the line, the sheath voltage threshold and the current threshold, and the line capacitance; establishing an equivalent circuit model of the medium-voltage single-core cable based on the distributed parameter model, wherein the equivalent circuit model includes the main conductor, the insulation layer and the metal sheath; and the metal sheath is only grounded at the power supply side and kept open at the load side.

[0034] In actual application, the electrical parameters of the underground cable model are input, such as the metal sheath impedance Z b , the total length of the line L , the sheath voltage threshold V b,th , and the current threshold I b,th , and the line capacitance C , to establish a physical basic model for the algorithm.

[0035] Specifically, in the cable model construction, an equivalent circuit model of the medium-voltage single-core cable is established, which explicitly includes the main conductor, the insulation layer and the metal sheath. In this model, the ground fault current flows to the metal sheath through the deteriorated insulation, and the fault resistance exists between the main conductor and the sheath, and the metal sheath serves as the only return path for the fault current to flow back to the power supply.

[0036] Further, a single-ended grounding configuration is adopted: the metal sheath is only directly grounded at the power supply side and kept open at the load side. This configuration effectively eliminates the circulating current of the sheath in the double-ended grounding cable, thereby reducing the loss.

[0037] Further, a distributed parameter model is constructed based on the input parameters to support subsequent fault simulation and positioning calculation. Specifically, the cable is discretized into multiple sections of π-type equivalent circuit, the metal sheath is integrated as an independent branch (including R b , L b ), and the insulation layer capacitance C distributed parameters are set.

[0038] Step 102: Obtain the key electrical quantity, compare the key electrical quantity with the preset threshold, and determine the comparison result.

[0039] In a possible implementation, the key electrical quantity is obtained, including: using a differential voltage probe to collect the power supply end voltage relative to ground, the load end voltage relative to ground and the sheath voltage relative to ground; and using a current probe to collect the sheath current.

[0040] In actual application, a laboratory test device is designed to simulate the actual working condition of the insulated cable. The core of the measurement system includes: High-speed data acquisition unit: equipped with a sampling rate of ≥2 GSa / s, ensuring accurate capture of short-duration transient signals generated by initial fault.

[0041] Precise sensing equipment: (1) Voltage measurement: precise acquisition using differential voltage probes V S , V L , V b ; (2) Current measurement: high-sensitivity current probes for monitoring I b .

[0042] (3) Intelligent threshold triggering mechanism: the system compares the monitored I b and V b with the normal operating condition reference values calculated based on standards in real time. Once the I b or V b exceeds the preset threshold, the system immediately starts high-speed recording and records the key electrical quantity waveforms at the time of fault occurrence, providing effective input for subsequent fault location algorithms.

[0043] Step 103: Determine fault characteristic information based on comparison results.

[0044] In one possible implementation, determining fault characteristic information based on comparison results includes: in the case where the power end relative ground voltage, load end relative ground voltage, sheath relative ground voltage, and sheath current are greater than the preset threshold, recording the fault characteristic waveform.

[0045] In actual application, the system continuously compares the measured values of V b and I b with the V b,th , I b,th threshold; once any parameter exceeds the limit, the high-speed recording mechanism is triggered, and the fault characteristic waveform is recorded completely.

[0046] Step 104: Determine the fault point based on fault characteristic information and fault location equation.

[0047] In actual application, when any parameter exceeds the limit, the algorithm calls the core positioning equation, which represents the fault point voltage V xthe power side expression and the load side expression, solving the real roots of the quadratic equation after eliminating, and finally outputting the normalized fault distance x ∈ [0, 1], and converted into the actual position x • L (m).

[0048] In one possible implementation, the fault location equation is a quadratic equation about the normalized fault distance x : A x 2 +B x +C=0; where the coefficients A , B , C are calculated by the source end relative ground voltage, the load end relative ground voltage, the sheath relative ground voltage, the sheath current and the distributed parameters of the cable.

[0049] In one possible implementation, the coefficients A , B , C are calculated as follows:

[0050] where is the source end relative ground voltage, is the load end relative ground voltage, is the sheath relative ground voltage, and is the sheath current, is the resistance per unit length of the metal sheath, is the inductance per unit length of the metal sheath.

[0051] Specifically, the above fault location equation is derived as follows: Section " x " (derived from the power side): Assuming that the fault point is located at a distance x (normalized length) from the power source, the goal is to locate the fault by determining the impedance to the fault point.

[0052] The total impedance of the metal sheath is denoted as Z b , and the expression of the fault point voltage V x is:

[0053] expanded into the time domain form:

[0054] where, L b ,R b The distributed inductance and resistance of the metal sheath, carrying the capacitive leakage current I 1 is defined as:

[0055] Where, C is the distributed parameter of the insulation capacitance. From this, the complete expression for V x

[0056] Section "1- x " (derived from the load side): Similarly, the derivation from the opposite side of the cable V x

[0057] Expanded into time domain form:

[0058] Load side capacitive current I C2

[0059] From this, the complete expression for V x

[0060] Further, the simultaneous equations are solved for the fault location x : Let the power source side derivation of V x be equal to the load side derivation of V x , which after rearrangement becomes a quadratic equation in the standard form (A x x 2 +B x +C=0), the expressions for the coefficients A, B, and C are:

[0061] From this, it can be seen that the solution of the coefficients A, B, and C is completely dependent on the known cable body parameters and real-time measurement signals.

[0062] Finally, these parameters are taken as signal inputs to determine the coefficients of the quadratic equation. After solving the equation, the real roots are screened and the solution that satisfies x ∈[0,1] is taken as the normalized fault distance, and finally through x •​​​​​L (m)( L (Total cable length) is converted to the actual fault location.

[0063] Furthermore, it also includes the generation of event logs. The calculation results and the original waveform data are synchronously stored in the event log, forming a complete fault record that includes timestamps, positioning errors, and parameter deviations. This provides data support for subsequent cable condition assessment and preventive maintenance, thereby achieving millisecond-level accurate positioning of initial faults in single-end grounded cables.

[0064] This application has significant practical advantages in cable condition monitoring and fault location, mainly in four aspects: simplified deployment, reduced interference, compatibility with existing systems, and improved maintenance efficiency.

[0065] 1. Simplified deployment and real-time continuous monitoring: Only one monitoring device needs to be installed at one end of the cable (no load-side wiring required) to achieve full-time monitoring with high-speed sampling of ≥2 GSa / s, which significantly reduces the deployment difficulty in densely populated urban areas or industrial pipe corridors, while ensuring that no transient fault signals are missed.

[0066] 2. Reduced intrusion and interference: By utilizing sheath parameter measurement technology, the need for invasive testing procedures is minimized, resulting in less interference and less damage to the operating cable system.

[0067] 3. High equipment compatibility: Relies on standard measuring equipment (such as precision voltage sensors and high-sensitivity current probes) to ensure compatibility with existing monitoring systems and facilitate integrated applications.

[0068] 4. Improve maintenance efficiency and reliability: The ability to detect faults early provides operators with sufficient lead time to schedule planned maintenance, reducing unplanned downtime and related economic losses.

[0069] In summary, this application significantly improves the convenience, economy, and reliability of cable management through innovative non-intrusive continuous monitoring, the application of standard equipment, and effective early warning of faults.

[0070] Corresponding to the above method embodiments, this specification also provides embodiments of a cable early fault location device based on metal sheath parameters. Figure 2 A schematic diagram of a cable early fault location device based on metal sheath parameters, according to one embodiment of this specification, is shown. Figure 2 As shown, the device includes: Model building module 201 is configured to build a cable electrical model based on electrical parameters; The threshold comparison module 202 is configured to acquire key electrical quantities, compare the key electrical quantities with preset thresholds, and determine the comparison result. Feature acquisition module 203 is configured to determine fault feature information based on comparison results; The fault location determination module 204 is configured to determine the fault location based on fault characteristic information and fault location equation.

[0071] In one possible implementation, an electrical model of the cable is established based on electrical parameters, including: A distributed parameter model is constructed based on the metal sheath impedance, total line length, sheath voltage threshold, current threshold, and line capacitance. An equivalent circuit model of a medium-voltage single-core cable is established based on a distributed parameter model. The equivalent circuit model includes the main conductor, insulation layer, and metal sheath. The metal sheath is grounded only on the power supply side and remains open on the load side.

[0072] In one possible implementation, obtaining key electrical quantities includes: Use a differential voltage probe to collect the voltage between the power supply terminal and ground, the voltage between the load terminal and ground, and the voltage between the sheath and ground; The sheath current is collected using a current probe.

[0073] In one possible implementation, fault characteristic information is determined based on the comparison results, including: When the voltage to ground at the power supply end, the voltage to ground at the load end, the voltage to ground at the sheath, and the sheath current are all greater than preset thresholds, record the fault characteristic waveforms.

[0074] In one possible implementation, the fault location equation is given by the normalized fault distance. x The quadratic equation: A x 2 +B x +C=0; Where the coefficient A , B , C It is calculated from the voltage to ground at the power supply end, the voltage to ground at the load end, the voltage to ground at the sheath, the sheath current, and the distributed parameters of the cable.

[0075] In one possible implementation, the coefficient A , B , C Calculated in the following way:

[0076] in, The voltage between the power supply terminal and ground, For the load terminal relative to ground voltage, For the sheath relative to ground voltage and For sheath current, Resistance per unit length of metal sheath The inductance per unit length of the metal sheath.

[0077] In one possible implementation, the sampling rate for acquiring key electrical quantities is no less than 2 GSa / s.

[0078] The above is a schematic scheme of a cable early fault location device based on metal sheath parameters according to this embodiment. It should be noted that the technical solution of this cable early fault location device based on metal sheath parameters belongs to the same concept as the technical solution of the cable early fault location method based on metal sheath parameters described above. Details not described in detail in the technical solution of the cable early fault location device based on metal sheath parameters can be found in the description of the technical solution of the cable early fault location method based on metal sheath parameters described above.

[0079] Figure 3 A structural block diagram of a computing device 300 according to one embodiment of this specification is shown. The components of the computing device 300 include, but are not limited to, a memory 310 and a processor 320. The processor 320 is connected to the memory 310 via a bus 330, and a database 350 is used to store data.

[0080] The computing device 300 also includes an access device 340, which enables the computing device 300 to communicate via one or more networks 360. Examples of these networks include Public Switched Telephone Network (PSTN), Local Area Network (LAN), Wide Area Network (WAN), Personal Area Network (PAN), or combinations of communication networks such as the Internet. The access device 340 may include one or more of any type of wired or wireless network interface (e.g., a network interface card (NIC)), such as an IEEE 802.11 Wireless Local Area Network (WLAN) wireless interface, a Wi-MAX (Worldwide Interoperability for Microwave Access) interface, an Ethernet interface, a Universal Serial Bus (USB) interface, a cellular network interface, a Bluetooth interface, or a Near Field Communication (NFC) interface.

[0081] In one embodiment of this specification, the aforementioned components of the computing device 300 and Figure 3 Other components, not shown, can also be connected to each other, for example, via a bus. It should be understood that... Figure 3 The block diagram of the computing device shown is for illustrative purposes only and is not intended to limit the scope of this specification. Those skilled in the art can add or replace other components as needed.

[0082] The computing device 300 can be any type of stationary or mobile computing device, including mobile computers or mobile computing devices (e.g., tablet computers, personal digital assistants, laptop computers, notebook computers, netbooks, etc.), mobile phones (e.g., smartphones), wearable computing devices (e.g., smartwatches, smart glasses, etc.) or other types of mobile devices, or stationary computing devices such as desktop computers or personal computers (PCs). The computing device 300 can also be a mobile or stationary server.

[0083] The processor 320 executes computer-executable instructions, which, when executed by the processor, implement the steps of the aforementioned cable early fault location method based on metal sheath parameters. The above is an illustrative scheme of a computing device according to this embodiment. It should be noted that the technical solution of this computing device and the technical solution of the aforementioned cable early fault location method based on metal sheath parameters belong to the same concept. Details not described in detail in the technical solution of the computing device can be found in the description of the technical solution of the aforementioned cable early fault location method based on metal sheath parameters.

[0084] An embodiment of this specification also provides a computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the above-described cable early fault location method based on metal sheath parameters.

[0085] The above is an illustrative scheme of a computer-readable storage medium according to this embodiment. It should be noted that the technical solution of this storage medium belongs to the same concept as the technical solution of the cable early fault location method based on metal sheath parameters described above. For details not described in detail in the technical solution of the storage medium, please refer to the description of the technical solution of the cable early fault location method based on metal sheath parameters described above.

[0086] An embodiment of this specification also provides a computer program, wherein when the computer program is executed in a computer, it causes the computer to perform the steps of the above-described cable early fault location method based on metal sheath parameters.

[0087] The above is an illustrative example of a computer program in this embodiment. It should be noted that the technical solution of this computer program belongs to the same concept as the aforementioned method for locating early cable faults based on metal sheath parameters. Details not described in detail in the computer program's technical solution can be found in the description of the aforementioned method for locating early cable faults based on metal sheath parameters.

[0088] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0089] The computer instructions include computer program code, which may be in the form of source code, object code, executable file, or certain intermediate forms. The computer-readable medium may include any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. It should be noted that the content included in the computer-readable medium may be appropriately added to or subtracted according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable media may not include electrical carrier signals and telecommunication signals.

[0090] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments in this specification are not limited to the described order of actions, because according to the embodiments in this specification, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in this specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the embodiments in this specification.

[0091] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0092] The preferred embodiments disclosed above are merely illustrative of this specification. The optional embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the embodiments described herein. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the embodiments, thereby enabling those skilled in the art to better understand and utilize this specification. This specification is limited only by the claims and their full scope and equivalents.

Claims

1. A method for locating early cable faults based on metallic sheath parameters, characterized in that, include: Establish an electrical model of the cable based on electrical parameters; Acquire key electrical quantities, compare them with preset thresholds, and determine the comparison result; Based on the comparison results, fault characteristic information is determined; The fault location is determined based on the fault characteristic information and the fault location equation.

2. The method according to claim 1, characterized in that, The establishment of the cable electrical model based on electrical parameters includes: A distributed parameter model is constructed based on the metal sheath impedance, total line length, sheath voltage threshold, current threshold, and line capacitance. An equivalent circuit model of a medium-voltage single-core cable is established based on the distributed parameter model. The equivalent circuit model includes a main conductor, an insulation layer, and a metal sheath. The metal sheath is grounded only on the power supply side and remains open on the load side.

3. The method according to claim 1, characterized in that, The acquisition of key electrical quantities includes: Use a differential voltage probe to collect the voltage between the power supply terminal and ground, the voltage between the load terminal and ground, and the voltage between the sheath and ground; The sheath current is collected using a current probe.

4. The method according to claim 3, characterized in that, The step of determining fault characteristic information based on the comparison results includes: When the voltage relative to ground at the power supply terminal, the voltage relative to ground at the load terminal, the voltage relative to ground at the sheath, and the sheath current are all greater than the preset threshold, the fault characteristic waveform is recorded.

5. The method according to claim 4, characterized in that, The fault location equation is about the normalized fault distance. x The quadratic equation: A x 2 +B x +C=0; Where the coefficient A , B , C It is calculated from the voltage to ground at the power supply end, the voltage to ground at the load end, the voltage to ground at the sheath, the sheath current, and the cable's distributed parameters.

6. The method according to claim 5, characterized in that, The coefficient A , B , C Calculated in the following way: Among them, the The voltage between the power supply terminal and ground, For the load terminal relative to ground voltage, For the sheath relative to ground voltage and For sheath current, Resistance per unit length of metal sheath The inductance per unit length of the metal sheath.

7. The method according to claim 1, characterized in that, The sampling rate for acquiring key electrical quantities shall not be less than 2 GSa / s.

8. A cable early fault location device based on metal sheath parameters, characterized in that, include: The model building module is configured to build a cable electrical model based on electrical parameters; The threshold comparison module is configured to acquire key electrical quantities, compare the key electrical quantities with preset thresholds, and determine the comparison result. The feature acquisition module is configured to determine fault feature information based on the comparison result; The fault location determination module is configured to determine the fault location based on the fault characteristic information and the fault location equation.

9. A computing device, characterized in that, include: Memory and processor; The memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions, which, when executed by the processor, implement the steps of the cable early fault location method based on metal sheath parameters as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing computer-executable instructions that, when executed by a processor, implement the steps of the cable early fault location method based on metal sheath parameters as described in any one of claims 1 to 7.

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