Single-core cable early fault positioning method, system, electronic device and storage medium

Abstract

The application belongs to the field of power distribution network fault positioning, and specifically discloses a single-core cable early fault positioning method, system, electronic equipment and storage medium. The method integrates the impedance parameters of the metal sheath, monitors the sheath ungrounded end voltage, sheath current and cable core end voltage in real time, combines the zero sequence equivalent circuit to solve the voltage on both sides of the fault point, obtains the quadratic equation to solve the fault position x, realizes the accurate calculation of the fault distance, effectively solves the dependence of the traditional method on the double-end current synchronous measurement and the high positioning error of the short cable. The application significantly improves the early fault positioning accuracy, avoids the influence of the invasive test on the cable operation, and enhances the reliability in the complex electromagnetic environment through the noise resistance of the zero sequence component. The method does not require complex double-end equipment, is suitable for real-time monitoring of single-core underground cables, significantly reduces the operation and maintenance cost, and improves the safety and practicability of the power distribution network.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault location, specifically to a method, system, electronic device, and storage medium for early fault location of single-core cables based on the impedance characteristics of metal sheaths, applicable to the detection and location of early faults in medium-voltage underground cables caused by insulation aging. Background Technology

[0002] Underground cables, as key transmission carriers in modern power systems, are widely used in urban power distribution networks and industrial power supply due to their high concealment and minimal susceptibility to environmental influences. Their reliable operation is crucial for ensuring power supply. However, the cable insulation layer is subjected to electrical, thermal, and mechanical stresses over a long period, which can easily lead to insulation aging and early faults (such as local transient discharges). Statistics show that approximately 70% of cable faults are phase-to-ground faults. If not detected and addressed in a timely manner, these faults may escalate into permanent faults, resulting in system outages and significant economic losses. Therefore, accurate detection and location of early cable faults are key to improving power grid reliability.

[0003] Traditional cable fault location methods mainly include impedance methods and traveling wave methods. Impedance-based methods calculate the fault distance by measuring the voltage and current at both ends of the cable and combining this with line parameters. However, these methods have significant limitations:

[0004] (1) Data needs to be collected from both ends simultaneously, which is complex to implement and has high requirements for communication synchronization;

[0005] (2) Short-length single-core cables have low impedance characteristics that lead to amplified errors, making it difficult to meet the positioning accuracy requirements; while the traveling wave method has higher accuracy, it is generally difficult to accurately identify the arrival time of the traveling wave front, and the equipment is expensive and easily affected by electromagnetic noise, making it difficult to be used stably in complex environments.

[0006] In summary, existing technologies have significant shortcomings in terms of high precision, low cost, and real-time performance. There is an urgent need for an early fault location method for single-core underground cables. This method should overcome the limitations of traditional technologies by simplifying the measurement architecture, integrating sheath parameters, and enhancing noise immunity, thereby providing a more reliable fault management solution for power systems. Summary of the Invention

[0007] This invention aims to solve the above-mentioned technical problems by providing a method, system, electronic device, and storage medium for early fault location of single-core cables based on the impedance characteristics of the metal sheath. The method has excellent noise resistance, high real-time fault location, and high location accuracy. The system is simple and easy to implement.

[0008] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0009] A method for locating early faults in a single-core cable includes the following steps:

[0010] (a) Real-time acquisition of cable voltage and current signals;

[0011] (b) Based on the acquired cable voltage and current signals, and according to the preset metal sheath threshold voltage and threshold current criteria, determine whether the cable has experienced an early fault.

[0012] (c) Based on the acquired voltage and current data, using the zero-sequence equivalent circuit model of the cable and the impedance characteristics of the metal sheath, the voltage equations on both sides of the fault point are established based on the total impedance of the metal sheath and the total capacitance of the cable. The equations are solved simultaneously to obtain the quadratic equation of the fault location x, and the fault location is obtained by solving the equation.

[0013] (d) Based on the calculation results of the fault location, trigger an alarm and generate a fault handling command to realize timely handling of early cable faults.

[0014] As a further aspect of the present invention: in step (a), acquiring the cable voltage and current signals includes:

[0015] The cable is a single-core underground cable, and the voltage and current signals obtained are the voltage at the ungrounded end of the metal sheath. Current in metal sheath and the source-end voltage of the cable conductor. and load terminal voltage ;

[0016] Voltage at the ungrounded end of the metal sheath for: ;

[0017] In the formula, This represents the geometric mean distance of the cable. The average diameter of the metal sheath layer. This is the load current;

[0018] Current in metal sheath for:

[0019] ;

[0020] In the formula, Metal-sheathed resistor, It is a metal-sheathed reactor.

[0021] As a further aspect of the present invention: in step (b), the criterion for determining whether the cable has failed is:

[0022] ;

[0023] In the formula, This refers to the threshold voltage of the cable's metallic sheath. This is the threshold current for the metal sheath of the cable.

[0024] According to claim 2, the method for early fault location of a single-core cable is characterized in that: the step (c) of solving the fault point voltage equation includes:

[0025] (i) The cable line is equivalent to a π-type equivalent circuit using the zero-sequence equivalent circuit model of the cable, which includes resistance per unit length. ,inductance and capacitor ;

[0026] (ii) Based on the total impedance of the metal sheath and the total capacitance C of the cable, establish the voltage equations on both sides of the fault point. Combine the voltage equations on both sides of the fault point to obtain a quadratic equation for the fault location x. Solve for the fault location, where the total impedance of the metal sheath is... for: ;

[0027] Metal-sheathed reactor It is the imaginary unit.

[0028] As a further aspect of the present invention: the zero-sequence component of the zero-sequence equivalent circuit model of the cable in step (c) is extracted as follows:

[0029] ;

[0030] In the formula, It is a three-phase voltage. It is a three-phase current.

[0031] As a further aspect of the present invention: the metal sheath is configured to be single-ended grounded, with a sheath voltage limiter installed only at the grounded end and no sheath voltage limiter installed at the non-grounded end.

[0032] As a further aspect of the present invention: in step (a), the transient current and voltage signals of the metal sheath are acquired by a high sampling rate data acquisition unit to detect short-term early faults with a duration ≤0.0042s.

[0033] In step (a), a high-sensitivity current probe with an accuracy of ±0.1% is used to measure the current of the metal sheath, and a precision voltage sensor with a bandwidth of ≥1MHz is used to measure the voltage of the ungrounded end of the metal sheath and the source and load ends of the cable conductor.

[0034] The present invention also provides an early fault location system for single-core cables, comprising:

[0035] A high-sensitivity current probe and a precision voltage sensor, wherein the high-sensitivity current probe has an accuracy of ±0.1% and the precision voltage sensor has a bandwidth of ≥1MHz, for monitoring the current and voltage of the metal sheath, and the source-end voltage and load-end voltage of the cable conductor;

[0036] The data acquisition device is connected to the high-sensitivity current probe and the precision voltage sensor to record the electrical parameters of the cable conductor and the metal sheath in real time.

[0037] The data processing unit is connected to the data acquisition device, executes the fault location algorithm, and generates handling instructions;

[0038] Build a historical database to store normal operating parameters and fault event data, and support machine learning models to optimize fault location accuracy.

[0039] An alarm unit, connected to the data processing unit, is used to receive the fault handling instructions and trigger an audible and visual alarm.

[0040] The present invention also provides an electronic device, comprising:

[0041] Memory, used to store computer programs;

[0042] A processor is used to implement the steps of the early fault location method for single-core cables when executing the computer program.

[0043] The present invention also provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the steps of the method for locating early faults in a single-core cable.

[0044] After adopting the above methods and steps, the present invention has the following advantages:

[0045] This invention proposes a method, system, electronic device, and storage medium for early fault location of single-core cables based on the impedance characteristics of the cable's metal sheath. This impedance-based location technology utilizes the impedance characteristics of the cable's metal sheath and analyzes the zero-sequence voltage and zero-sequence current components to construct a voltage balance equation on both sides of the fault point, thus solving for the fault location. Compared to traditional methods that require simultaneous acquisition of voltage and current data at both ends of the cable, this patented method only needs to monitor the voltage at the ungrounded end of the sheath. ), sheath current ( ) and voltage at both ends of the cable conductor ( This method significantly reduces hardware costs and engineering complexity by eliminating the need for synchronous acquisition of current at both ends of the cable. By integrating the impedance parameters and zero-sequence component analysis of the metal sheath, voltage equations are constructed on both sides of the fault point to determine its location with high accuracy, making it particularly suitable for short cables. This patent utilizes the sensitivity of the sheath current path, combined with the noise immunity of the zero-sequence component, to detect early faults with short durations (≤0.0042s) and suppress electromagnetic interference, improving detection reliability in complex environments. This patented method does not require interrupting cable operation or connecting additional equipment. Through real-time acquisition and analysis of sheath parameters, it achieves online monitoring of early faults, avoiding the impact of traditional invasive testing on power grid stability, reducing operation and maintenance costs, and is simple and easy to implement. Attached Figure Description

[0046] Figure 1 This is a flowchart of the present invention.

[0047] Figure 2 This is a schematic diagram of electrical quantity measurement according to the present invention.

[0048] Figure 3 This is the early fault equivalent circuit diagram of the present invention. Detailed Implementation

[0049] The present invention will now be described in further detail with reference to the full text.

[0050] Example 1:

[0051] A method for early fault location of single-core cables based on the impedance characteristics of the metal sheath is proposed. The method treats the cable line as an equivalent π-type circuit to obtain the line parameters; acquires the cable voltage and current signals in real time; determines whether a fault has occurred in the cable based on the acquired voltage and current signals; determines the fault location x by solving the fault point voltage equation based on the acquired voltage and current data, using the zero-sequence equivalent circuit model of the cable and the impedance characteristics of the metal sheath; and triggers an alarm to handle the fault based on the fault location calculation result.

[0052] In specific implementations of this invention, such as Figure 3 As shown, this is used to depict the voltage and current distribution relationship under the combined effect of cable distribution parameters before and after the fault point and the return channel. , These represent the voltages at both ends of the cable conductor; the potential of the cable's metallic sheath at the fault point is denoted as... , recorded at the end as In the diagram, the upper branch corresponds to the cable phase conductor channel, and the lower branch corresponds to the sheath channel; together they form a closed loop for fault current.

[0053] To describe the impact of fault location on line parameter distribution, a normalized distance coefficient x∈[0,1] is introduced, which physically represents the proportion of the distance between the fault point and the power supply side to the total line length. The total series impedance of the equivalent circuit is used... This indicates that the fault location is broken down into the segment preceding the fault point. and the section after the fault point The impedances from the power supply side to the fault point and from the fault point to the receiving end are respectively used to characterize the impedances. The distributed capacitance between the phase conductor and ground is characterized by the total capacitance C. The capacitance effect of the two lines is equivalent to the two branches to ground on both sides: the capacitance of the power supply side to ground is... The capacitance to ground at the end is The corresponding charging currents are denoted as follows: and This approach preserves the charging and discharging characteristics of distributed capacitance during fault transient / steady-state processes, while also facilitating the introduction of capacitor branch currents into the nodal equations, thereby improving the model's usability for fault mechanism analysis and parameter identification.

[0054] Referring to Figure 1, the specific steps of this method are as follows:

[0055] (a) Real-time acquisition of cable voltage and current signals;

[0056] In this step, a precision voltage sensor (bandwidth ≥ 1 MHz) is used to measure the voltage at both ends of the cable conductor and the voltage at the ungrounded end of the sheath. A high-sensitivity current probe (accuracy ± 0.1%) is used to measure the current flowing through the metal sheath. The data is transmitted to the control center in real time using fiber optic communication or wireless communication.

[0057] The cable is a single-core underground cable, and the voltage and current signals obtained are the voltage at the ungrounded end of the metal sheath. Current in metal sheath and the source-end voltage of the cable conductor. and load terminal voltage ;

[0058] Voltage at the ungrounded end of the metal sheath for: ;

[0059] In the formula, This represents the geometric mean distance of the cable. The average diameter of the metal sheath layer. This is the load current;

[0060] Current in metal sheath for:

[0061] ;

[0062] In the formula, Metal-sheathed resistor, It is a metal-sheathed reactor.

[0063] (b) Based on the acquired cable voltage and current signals, and according to the preset metal sheath threshold voltage and threshold current criteria, determine whether the cable has experienced an early fault.

[0064] The criteria for determining whether a cable has a fault are as follows:

[0065] ;

[0066] In the formula, This refers to the threshold voltage of the cable's metallic sheath. This is the threshold current for the metal sheath of the cable.

[0067] (c) Based on the acquired voltage and current data, using the zero-sequence equivalent circuit model of the cable and the impedance characteristics of the metal sheath, the voltage equations on both sides of the fault point are established based on the total impedance of the metal sheath and the total capacitance of the cable. The equations are solved simultaneously to obtain the quadratic equation of the fault location x, and the fault location is obtained by solving the equation.

[0068] Solving the voltage equation at the fault point includes:

[0069] (i) The cable line is equivalent to a π-type equivalent circuit using the zero-sequence equivalent circuit model of the cable, which includes resistance per unit length. ,inductance and capacitor ;

[0070] (ii) Based on the total impedance of the metal sheath and the total capacitance C of the cable, establish the voltage equations on both sides of the fault point. Combine the voltage equations on both sides of the fault point to obtain a quadratic equation for the fault location x. Solve for the fault location, where the total impedance of the metal sheath is... for: ;

[0071] Metal-sheathed reactor It is the imaginary unit.

[0072] The zero-sequence component extraction of the cable zero-sequence equivalent circuit model in step (c) is as follows:

[0073] ;

[0074] In the formula, It is a three-phase voltage. It is a three-phase current.

[0075] The metal sheath is configured to be single-ended grounded, with a sheath voltage limiter installed only at the grounded end and no sheath voltage limiter installed at the non-grounded end.

[0076] (d) Based on the calculation results of the fault location, trigger an alarm and generate a fault handling command to realize timely handling of early cable faults.

[0077] The transient current and voltage signals of the metal sheath are acquired by a high sampling rate data acquisition unit to detect short-term early faults.

[0078] Example 2:

[0079] To verify the effectiveness and reliability of the present invention, a single-phase grounding fault was set in the cable at 100m, 500m, 800m, and 1000m. The simulation results were compared with the traditional cable conductor double-end impedance positioning method and are shown in Table 1.

[0080] Table 1. Location results of traditional methods and the method of this patent for different fault locations.

[0081]

[0082] As shown in Table 1, the accuracy of the traditional distance measurement method using the double-end impedance of the cable conductor is lower than that of the distance measurement method based on the sheath impedance proposed in this patent, indicating that the accuracy of the method in this patent is higher than that of the traditional method.

[0083] Example 3:

[0084] An early fault location system for single-core cables based on the impedance characteristics of the metal sheath, comprising a high-sensitivity current probe (accuracy ±0.1%), a precision voltage sensor (bandwidth ≥1 MHz), a data acquisition device, a data processing unit, a historical database, and an alarm unit; the connection relationship and working principle of each unit are as follows:

[0085] A high-sensitivity current probe and a precision voltage sensor are installed at the ungrounded end of the metal sheath and both ends of the conductor of a single-core cable. They collect the current in the metal sheath, the voltage at the ungrounded end of the sheath, and the voltage at the source end and load end of the conductor, respectively, and transmit the analog signals to the data acquisition device.

[0086] The data acquisition device performs analog-to-digital conversion on analog signals, records the electrical parameters of the cable in real time, and transmits the digital signals to the data processing unit via optical fiber communication;

[0087] The data processing unit is an industrial computer, and its memory stores a computer program that implements the fault location method of the present invention. When the processor executes the program, it completes fault judgment, zero-sequence component extraction, fault location calculation, and generates fault handling instructions.

[0088] The historical database and data processing unit are connected via a network to store the normal operating parameters and fault event data of the cable in real time (including fault location, voltage and current signals at the time of the fault, etc.). This data is used to train a machine learning model to optimize the fault location algorithm and improve the location accuracy.

[0089] The alarm unit is an audible and visual alarm connected to the data processing unit. Upon receiving a fault handling command, it immediately triggers the audible and visual alarm to provide real-time fault alerts.

[0090] It also includes a computer device comprising a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the steps of the above-described method for early fault location of single-core cables based on the impedance characteristics of metal sheaths.

[0091] It also includes a storage medium on which a computer program is stored, which, when executed by a processor, implements the steps of the above-described method for early fault location of single-core cables based on the impedance characteristics of the metal sheath.

[0092] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown throughout are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for locating early faults in a single-core cable, characterized in that, Includes the following steps: (a) Real-time acquisition of cable voltage and current signals; (b) Based on the acquired cable voltage and current signals, and according to the preset metal sheath threshold voltage and threshold current criteria, determine whether the cable has experienced an early fault. (c) Based on the acquired voltage and current data, using the zero-sequence equivalent circuit model of the cable and the impedance characteristics of the metal sheath, the voltage equations on both sides of the fault point are established based on the total impedance of the metal sheath and the total capacitance of the cable. The equations are solved simultaneously to obtain the quadratic equation of the fault location x, and the fault location is obtained by solving the equation. (d) Based on the calculation results of the fault location, trigger an alarm and generate a fault handling command to realize timely handling of early cable faults.

2. The method for locating early faults in a single-core cable according to claim 1, characterized in that: In step (a), acquiring the cable voltage and current signals includes: The cable is a single-core underground cable, and the voltage and current signals obtained are the voltage at the ungrounded end of the metal sheath. Current in metal sheath and the source-end voltage of the cable conductor. and load terminal voltage ; Voltage at the ungrounded end of the metal sheath for: ; In the formula, This represents the geometric mean distance of the cable. The average diameter of the metal sheath layer. This is the load current; Current in metal sheath for: ； In the formula, Metal-sheathed resistor, It is a metal-sheathed reactor.

3. The method for locating early faults in a single-core cable according to claim 2, characterized in that: In step (b), the criterion for determining whether the cable has a fault is: ； In the formula, This refers to the threshold voltage of the cable's metallic sheath. This is the threshold current for the metal sheath of the cable.

4. The method for locating early faults in a single-core cable according to claim 2, characterized in that: The step (c) of solving the fault point voltage equation includes: (i) The cable line is equivalent to a π-type equivalent circuit using the zero-sequence equivalent circuit model of the cable, which includes resistance per unit length. ,inductance and capacitor ; (ii) Based on the total impedance of the metal sheath and the total capacitance C of the cable, establish the voltage equations on both sides of the fault point. Combine the voltage equations on both sides of the fault point to obtain a quadratic equation for the fault location x. Solve for the fault location, where the total impedance of the metal sheath is... for: ; Metal-sheathed reactor It is the imaginary unit.

5. The method for locating early faults in a single-core cable according to claim 1, characterized in that: The zero-sequence component extraction of the cable zero-sequence equivalent circuit model in step (c) is as follows: ； In the formula, It is a three-phase voltage. It is a three-phase current.

6. The method for locating early faults in a single-core cable according to claim 1, characterized in that: The metal sheath is configured to be single-ended grounded, with a sheath voltage limiter installed only at the grounded end and no sheath voltage limiter installed at the non-grounded end.

7. The method for locating early faults in a single-core cable according to claim 1, characterized in that: In step (a), the transient current and voltage signals of the metal sheath are acquired by a high sampling rate data acquisition unit to detect short-term early faults with a duration of ≤0.0042s. In step (a), a high-sensitivity current probe with an accuracy of ±0.1% is used to measure the current of the metal sheath, and a precision voltage sensor with a bandwidth of ≥1MHz is used to measure the voltage of the ungrounded end of the metal sheath and the source and load ends of the cable conductor.

8. A single-core cable early fault location system, characterized in that: include: A high-sensitivity current probe and a precision voltage sensor, wherein the high-sensitivity current probe has an accuracy of ±0.1% and the precision voltage sensor has a bandwidth of ≥1MHz, for monitoring the current and voltage of the metal sheath, and the source-end voltage and load-end voltage of the cable conductor; The data acquisition device is connected to the high-sensitivity current probe and the precision voltage sensor to record the electrical parameters of the cable conductor and the metal sheath in real time. The data processing unit is connected to the data acquisition device, executes the fault location algorithm, and generates handling instructions; Build a historical database to store normal operating parameters and fault event data, and support machine learning models to optimize fault location accuracy. An alarm unit, connected to the data processing unit, is used to receive the fault handling instructions and trigger an audible and visual alarm.

9. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, configured to implement the steps of the method for locating early faults in a single-core cable as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein when the computer program is executed by a processor, it implements the steps of the method for locating early faults in a single-core cable as described in any one of claims 1 to 7.

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