10kV armored cable fault location method based on additional parallel inductors

Abstract

The invention discloses a 10kV armored cable fault distance measurement method based on an additional parallel inductor, and relates to the technical field of power equipment monitoring, and the method comprises the specific steps: S100, additional inductor configuration planning: analyzing the resistance, capacitance and inductance distribution of a power distribution network line and the parameters of an expected fault current. The method effectively solves the problems that the electrical quantity is difficult to detect and the distance measurement precision is influenced by asynchronous data in the fault distance measurement of the power distribution network, and after the power distribution network line breaks down, the line runs for a period of time with the fault by controlling the combination of a protection action and an algorithm and inputting an additional inductor, so that the steady-state electrical quantity is obtained for distance measurement calculation. The method not only increases the measurement time and the amplitude of the negative sequence component, but also provides steady-state positive sequence and negative sequence electrical quantities for distance measurement, so that fault information can be extracted more accurately after a fault occurs.

Description

Technical Field

[0001] The invention relates to the technical field of power equipment monitoring, and in particular to a 10kV armored cable fault distance measurement method based on additional parallel inductance. Background Art

[0002] As the topology of distribution networks becomes increasingly complex, it becomes increasingly important to improve the automation of distribution networks, ensure the reliability of power supply and meet the needs of power users. Timely and accurate fault distance measurement methods are of great significance for quickly repairing line faults and ensuring power supply reliability. Especially in the application of 10kV armored cables, the accuracy of fault distance measurement is directly related to the stable operation and maintenance efficiency of the power system.

[0003] At present, the fault distance measurement methods of distribution networks are mainly divided into traveling wave method and impedance method. The traveling wave method has the problems of difficulty in identifying reflected waves, high requirements for sampling equipment and positioning dead zone, which limits its effect in practical applications. The impedance law is affected by the small current grounding method of the neutral point of the distribution network. When a single-phase grounding fault occurs, although it can run with the fault for a period of time, the fault current is small, and the fault current caused by other types of faults decays rapidly and the effective time window is short, which makes it difficult to extract fault information. In addition, although the transient method in the impedance method uses the transient signal of the fault process for analysis, the fault component decays quickly and the effective time window is short. The steady-state law has the problems of small amplitude of fault electrical quantity, susceptibility to interference and the ranging accuracy being affected by asynchronous data.

[0004] Although the prior art has proposed some improvement schemes, such as simplifying the calculation by analyzing at a specific moment to achieve fast ranging, or introducing the asynchronous phase angle difference at both ends to eliminate the influence of asynchrony, these methods still have certain limitations. For example, the method of analyzing at a specific moment has high requirements on the sampling equipment and is not economical. The method of introducing the asynchronous phase angle difference at both ends can eliminate the influence of asynchrony to a certain extent, but when the time from the occurrence of a fault to the protection action is short, it is difficult to accurately measure the positive and negative sequence electrical quantities, thereby affecting the ranging accuracy. In addition, most of the existing ranging methods cannot be applied to all types of faults at the same time, which limits their scope of application.

[0005] Therefore, a 10kV armored cable fault location method based on additional shunt inductance was developed. The additional inductance was introduced to limit the short-circuit current, increase the measurement time and the amplitude of the negative-sequence component, thereby providing steady-state positive-sequence and negative-sequence electrical quantities for ranging, and eliminating the influence of asynchronous factors in principle, thereby improving the accuracy of fault ranging. Summary of the invention

[0006] The purpose of the present invention is to make up for the shortcomings of the prior art and provide a 10kV armored cable fault ranging method based on additional parallel inductance. The method is based on the technical principle of additional parallel inductance and effectively solves the problems in distribution network fault ranging. By putting additional inductance into use after the line trips, not only the short-circuit current is limited, but also the line can run with the fault for a period of time, thereby increasing the measurement time and the amplitude of the negative sequence component, providing stable positive sequence and negative sequence electrical quantities for ranging.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a 10kV armored cable fault distance measurement method based on additional parallel inductance, the specific steps of the distance measurement method are:

[0008] S100, additional inductor configuration planning: Analyze the resistance, capacitance, inductance distribution of the distribution network and the parameters of the expected fault current, use electrical calculation software to simulate the current response under different fault conditions based on the steady-state and transient characteristics of the power system, determine the rated inductance value, current carrying capacity, withstand voltage level and loss parameters, and connect the selected additional inductor to the bus-end circuit breaker through the installation structure and connection components;

[0009] S200, fault response control: build a fault monitoring system for the intelligent distribution network, integrate the real-time monitoring data of current transformers and voltage transformers and the fault diagnosis logic of intelligent protection devices. Once a line fault causes the current and voltage to exceed the preset threshold, the fault monitoring mechanism is immediately triggered to accurately identify the time, type and phase of the fault. At the moment of the fault, the QF1 circuit breaker quickly trips according to the set current setting value, and the timing module is started synchronously to record the fault time. The timing and mode of inductor access are determined according to the fault type. In the steady-state stage, the measuring equipment is used to continuously monitor the electrical quantity. After the acquisition is completed, the switch Q state is intelligently decided according to the instantaneous or permanent nature of the fault. When restarting the line for an instantaneous fault, the system electrical parameters and equipment health status are fully verified, and the QF1 circuit breaker is accurately closed to restore power supply. For a permanent fault, Q is opened to upload the fault information.

[0010] S300, fault information collection and optimization: Based on electromagnetic theory and field measured data mining technology, finite element analysis is used to determine the location of the head-end electrical quantity measurement point at the optimal measurement point of the negative sequence voltage. Wide-band voltage transformers and high-linearity current transformers are deployed here to build a multi-sensor collaborative acquisition network to capture the full-state changes of three-phase voltage and current signals, which are transmitted to the field data acquisition terminal via optical fiber. After pre-processing by the signal conditioning circuit with integrated filtering, amplification, isolation and anti-interference functions, the optimal value of the additional inductance is solved based on the precise model of the power grid and the fault equivalent circuit. After being put into operation, the line current and negative sequence voltage dynamic changes are monitored in real time, and the inductance parameters are adaptively fine-tuned;

[0011] S400, fault distance calculation:

[0012] The asymmetric fault distance measurement: When the line has an asymmetric fault, the symmetrical component method is used to analyze the positive and negative sequence networks, and the Kirchhoff's law is used to construct a complete relationship matrix equation covering the positive and negative sequence voltages, currents and impedances on both sides of the line. The electrical quantity measurement point at the head end is combined with the optimal measurement point of the negative sequence voltage and the high-precision voltage collection data at the end to substitute into the equation to solve the theoretical value of the positive and negative sequence voltage at the fault point. The S-end measurement device is used as a precise clock source to quantify the asynchronous phase angle δd generated by the timing error at the N-end. The asymmetric fault distance measurement function is constructed using the ratio of the positive and negative sequence voltages at the end. The formula is: in and They represent the positive and negative sequence fault point voltages inferred from the measured data at the S and N terminals respectively. The ratio of the fault distance to the entire line distance is obtained by solving the quadratic complex equation through complex domain operations. Among them, l SF is the distance from S to the fault point F, l SN For the total length of the line, select the effective K value according to the preset accuracy requirements and line parameter characteristics, and accurately locate the fault point based on the total length of the line;

[0013] Symmetrical fault distance measurement: In view of the characteristic of no negative sequence component, the voltage and current at the S terminal and the voltage at the N terminal of the A-phase and B-phase lines are selected as variables, and the symmetrical fault distance measurement function is constructed by referring to the asymmetric fault processing process and principle. The formula is: in are the S-terminal voltages of phase A and phase B respectively, are the N-terminal voltages of phases A and B respectively. The asynchronous angle error is eliminated by using the terminal voltage ratio, and the fault distance is obtained by solving the equation.

[0014] Furthermore, in S100, the distribution network line parameters considered in the additional inductance configuration planning also include the influence factors of wire core material, insulation characteristics, line length, conductor radius, line spacing and ambient temperature on line resistance, capacitance and inductance; the electrical calculation software adopts electromagnetic transient analysis software to set different fault types, fault locations and transition resistance values ​​when simulating fault conditions.

[0015] Furthermore, in the S100, the short-circuit current IL is calculated by a formula in the additional inductor configuration planning, and the formula is: Where E s represents the power supply electromotive force, ω0 is the system frequency, j represents the imaginary unit, the jth, L represents the additional inductance, Z s Indicates the impedance on the power supply side.

[0016] Furthermore, in the S100, the additional inductance configuration planning is performed by calculating the additional inductance L by a formula, and the formula is: Among them, I L Indicates the short-circuit current I L , Es represents the power supply electromotive force, ω0 is the system frequency, j represents the imaginary unit, the jth, L represents the additional inductance, Z s Indicates the impedance on the power supply side.

[0017] Furthermore, in the S200, the current and voltage exceeding thresholds in the fault response control are determined, and the thresholds are set according to the line rated current, rated voltage and system operation safety margin factors. e The current threshold is k1I e The value of k1 is determined according to the line load characteristics, the probability of fault occurrence and the system stability requirements, and is between 1.2 and 1.5. In terms of voltage, the rated voltage U e As a benchmark, considering the voltage fluctuation range and system insulation tolerance, the voltage threshold is set to U e (1±k2), k2 depends on the grid voltage level, line length and surrounding environmental factors, and its value is in the range of 0.05-0.1.

[0018] Furthermore, in S200, the preset current setting value of the QF1 circuit breaker in the fault response control is determined, and a probability statistical analysis of the line fault current is carried out. Based on the historical operation data, the frequency and amplitude distribution of the fault current are calculated for different fault scenarios, and the mean μ and standard deviation σ of each type of fault current are determined. The thermal stability limit of the equipment is comprehensively considered, and the thermal stability current I given in the equipment manual is calculated. th and the allowed duration t th , ensure that the setting value is less than I th At the same time, the protection selectivity requirements are followed. The upper protection action time t1 and the current protection action time t2 must satisfy t1>t2+Δt, where Δt is the time difference. Through calculation, analysis, verification and adjustment, the setting value is determined to be kI e , k value range is 1.5-3, and is fine-tuned according to the line characteristics.

[0019] Furthermore, in the S200, the timing and mode of inductor access in fault response control, a single-phase grounding fault and the current does not exceed the set value to allow operation with the fault, and other faults occur and the auxiliary switch Q is immediately closed to introduce the inductor; the current does not exceed the limit at the initial stage of a single-phase grounding fault but maintenance and distance measurement are required later, and the closing Q operation is controlled after QF1 trips. In the transient transition stage, the dynamic changes of electrical quantities are monitored in real time by a high-speed data acquisition system.

[0020] Furthermore, in the S300, the optimal measurement point of the negative sequence voltage at the head-end electrical quantity measurement point in the fault information collection and optimization is determined by comprehensively using finite element analysis and field measured data mining technology, taking into account the physical parameters of the line conductor material, length, radius, spacing and insulation medium characteristics, calculating the line resistance, inductance and capacitance distribution, and at the same time incorporating power supply characteristics such as electromotive force, internal impedance, and load distribution parameters such as power and power factor, to construct a model that is highly consistent with the actual power grid. For different types of faults, the parameters of the fault location and grounding resistance are set to simulate The changes in electrical quantities after the fault occurs, the distribution pattern of negative-sequence voltage along the line is analyzed, the theoretical value and change trend of negative-sequence voltage at different positions are predicted, and on-site measurements are carried out. Multiple temporary measuring points are set up at equal intervals along the line, and voltage transformers and data acquisition devices are installed. When an actual fault occurs, three-phase voltage data are collected synchronously, the negative-sequence voltage component is extracted, and the mean and standard deviation of the negative-sequence voltage at each measuring point are calculated. The theoretical results of finite element analysis are integrated with the on-site measured data. With the core goal of large and stable negative-sequence voltage amplitude, the data of each measuring point is classified and the optimal measuring point for negative-sequence voltage is screened out.

[0021] Furthermore, the S300, the process for solving the optimal value of additional inductance in fault information collection and optimization, solves the optimal value of additional inductance based on the precise model of the power grid system and the fault equivalent circuit analysis, firstly measures the line impedance, including resistance and reactance, and at the same time clarifies the power supply characteristics such as the magnitude of the electromotive force and the internal impedance, as well as the load distribution parameters, constructs corresponding fault equivalent circuits for different fault types, analyzes the changes in electrical quantities after the fault occurs, comprehensively considers the magnitude of the short-circuit current and its impact on the safe and stable operation of the line, and uses an optimization algorithm through continuous iterative calculations to find the optimal value of additional inductance.

[0022] Furthermore, in the fault distance calculation of S400, the positive sequence and negative sequence voltages of the fault point are calculated based on the voltage, current and line impedance parameters on both sides of the line. and They represent the positive and negative sequence fault point voltages inferred from the S and N terminal measurement data, respectively. The calculation formula is:

[0023]

[0024] in are the positive sequence and negative sequence voltage and current at the fault line S end, respectively. are the positive and negative sequence voltage and current at the N end of the line, Z1 and Z2 are the positive and negative sequence impedances of the line, C1 and C2 are the positive and negative sequence capacitances of the line, l SN is the distance from S to the fault point F, l SN The total length of the line.

[0025] Compared with the prior art, the 10kV armored cable fault location method based on additional parallel inductance has the following beneficial effects:

[0026] 1. The present invention effectively solves the problem that electrical quantities in distribution network fault ranging are difficult to detect and that asynchronous data affects ranging accuracy by introducing additional parallel inductance. After a distribution network line fails, additional inductance is added to allow the line to operate with the fault for a period of time by controlling the combination of protection actions and algorithms, thereby obtaining steady-state electrical quantities for ranging calculation. This not only increases the measurement time and the amplitude of the negative-sequence component, but also provides steady-state positive-sequence and negative-sequence electrical quantities for ranging, so that fault information can be extracted more accurately after a fault occurs. At the same time, the positive-sequence and negative-sequence electrical quantities are used to eliminate the asynchronous phase angle difference in the ranging equation, thereby avoiding the influence of asynchronous data on ranging accuracy in principle and improving the accuracy of fault ranging.

[0027] 2. The present invention constructs an intelligent distribution network fault monitoring system, integrates real-time monitoring data and intelligent protection device fault diagnosis logic, can accurately identify the time, type and phase of the fault, and determine the timing and mode of inductor access according to the fault type. In addition, in terms of fault information collection optimization, finite element analysis and field measured data mining technology are used to determine the position of the head-end electrical quantity measurement point at the optimal measurement point of the negative sequence voltage, and build a multi-sensor collaborative acquisition network to capture the full-state changes of the three-phase voltage and current signals. After being put into operation, it can also monitor the dynamic changes of the line current and negative sequence voltage in real time, and adaptively fine-tune the inductance parameters, thereby improving the reliability and accuracy of fault distance measurement.

[0028] Other advantages, objectives and features of the present invention will be set forth in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a flow chart of a 10kV armored cable fault location method based on additional parallel inductance;

[0031] Figure 2 Schematic diagram of the planning process for additional inductor configuration;

[0032] Figure 3It is the correlation matrix diagram of the influence of distribution network line parameters on electrical characteristics;

[0033] Figure 4 Provide intelligent decision-making mind map for fault response control process;

[0034] Figure 5 Screening of multi-source data fusion schematics for fault information collection points;

[0035] Figure 6 It is the convergence trajectory diagram of the dynamic optimization iteration for the optimal value of the additional inductance;

[0036] Figure 7 This is a deep analysis diagram of the calculation principle of symmetrical and asymmetrical fault distance measurement. DETAILED DESCRIPTION

[0037] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation mode, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0038] Embodiment 1

[0039] Application of 10kV armored cable fault distance measurement in urban distribution network

[0040] In the urban distribution network environment, a line with a length of l SN The 10kV armored cable line has a core made of copper with excellent insulation performance. The conductor radius is r, the wire spacing is d, and the operating environment temperature is usually maintained within a certain range.

[0041] Additional inductor configuration planning, using electromagnetic transient analysis software, fully considering the core material (copper), insulation characteristics, line length l SN , conductor radius r, line spacing d and ambient temperature on line resistance R, capacitance C, inductance L, simulate three-phase short circuit and single-phase grounding fault types. The fault position starts from the head end along the line and is set at a certain interval. The transition resistance value varies within a reasonable range, so as to accurately simulate the current response characteristics under different fault conditions.

[0042] According to the theory of steady-state and transient characteristics of power system, combined with the known power source electromotive force E s , system frequency ω0 and power supply side impedance Z s , the short-circuit current I is accurately calculated by the formula L , the formula is: The appropriate rated value of the additional inductance L is further determined according to the formula: At the same time, its current carrying capacity, voltage resistance level and loss parameters are strictly determined, and high-quality additional inductance components that meet the line operation requirements are selected. With the help of specially designed installation architecture and reliable connection components, the selected additional inductance is accurately connected to the bus-end circuit breaker to ensure a stable connection and reliable electrical performance, laying a solid foundation for subsequent fault ranging work.

[0043] Fault response control process, build intelligent distribution network fault monitoring system, deeply integrate the real-time monitoring data of current transformer (CT) and voltage transformer (PT) and the advanced fault diagnosis logic of intelligent protection device, according to the line rated current I e , Rated voltage U e As well as the key elements of system operation safety margin, the current threshold is scientifically set to k1I e and the voltage threshold is U e (1±k2).

[0044] When the line is in operation, once the current or voltage exceeds the preset threshold, the efficient and sensitive fault monitoring mechanism is immediately triggered to quickly and accurately identify the exact time, specific type and phase information of the fault. At the moment of the fault, the QF1 circuit breaker is set according to the current setting value kI e The circuit breaker trips quickly and decisively, and simultaneously starts the high-precision timing module to record the time when the fault occurs, providing an accurate time reference for subsequent fault distance measurement.

[0045] Intelligent decisions are made on the timing and mode of inductor access based on the type of fault. For example, in the event of a single-phase grounding fault and when the current does not exceed the set value to allow operation with the fault, the auxiliary switch Q is quickly closed to introduce the inductor to maintain the stable operation of the system. If other types of faults occur, Q is immediately closed to introduce the inductor to enhance the ability to capture the electrical characteristics of the fault. After the fault occurs, professional measuring equipment is used to continuously and closely monitor the changes in electrical quantities in the steady-state stage. After data collection is complete, intelligent decisions are made on the subsequent state of switch Q based on the instantaneous or permanent nature of the fault. For instantaneous faults, the system electrical parameters and equipment health status are fully verified when the line is restarted. After confirmation, the QF1 circuit breaker is accurately closed to restore power supply. If it is a permanent fault, Q is promptly opened to upload detailed fault information so that operation and maintenance personnel can quickly formulate maintenance strategies.

[0046] Fault information collection is optimized by using an innovative method that closely combines finite element analysis with field measured data mining technology to determine the optimal measurement point for the negative sequence voltage at the head end electrical quantity measurement point. In this process, the conductor material (copper), length l SN , radius r, spacing d and physical parameters of the insulating medium characteristics, accurately calculate the distribution of line resistance R, inductance L, and capacitance V, and also incorporate the power supply characteristics (electromotive force E s , internal impedance Z s) and load distribution parameters (power, power factor), and carefully build an accurate model that is highly consistent with the actual power grid operation status.

[0047] According to different types of fault scenarios, the parameters of fault location and grounding resistance are set in detail, the complex change process of electrical quantities after the fault occurs is realistically simulated, the distribution law of negative-sequence voltage along the line is deeply analyzed, and the theoretical value and change trend of negative-sequence voltage at different positions are scientifically predicted. At the same time, on-site measurement work is actively carried out, multiple temporary measuring points are set up at equal intervals along the line, and high-precision voltage transformers and advanced data acquisition devices are installed. When an actual fault occurs, three-phase voltage data is collected synchronously, and professional algorithms are used to extract negative-sequence voltage components. The mean and standard deviation of the negative-sequence voltage at each measuring point are accurately calculated, and the theoretical results obtained from finite element analysis are deeply integrated with the on-site measured data. With the large and stable amplitude of negative-sequence voltage as the core orientation, the data of each measuring point are systematically classified and strictly screened, and finally the optimal measuring point of negative-sequence voltage is accurately determined to ensure that the collected fault information is true, reliable, comprehensive and accurate, providing solid data support for fault distance measurement.

[0048] The optimal value of additional inductance is solved based on the precise model of the power grid and the fault equivalent circuit. First, the line impedance is measured using precision measuring instruments, and the power supply characteristics and load distribution parameters are clarified. A fault equivalent circuit that accurately matches different fault types is constructed. The dynamic change law of electrical quantities after the fault occurs is deeply analyzed. The short-circuit current and its impact on the safe and stable operation of the line are comprehensively considered. Advanced optimization algorithms are used to continuously iterate and calculate to continuously optimize the additional inductance value until the optimal solution is found. This ensures that in actual operation, the inductance parameters can be adaptively fine-tuned in real time according to the dynamic changes of line current and negative-sequence voltage, so that the system is always kept in the best operating state, effectively improving the fault distance measurement accuracy.

[0049] Fault distance calculation:

[0050] Asymmetric fault location: When an asymmetric fault occurs in the line, the symmetrical component method is used to thoroughly analyze the positive and negative sequence networks. According to Kirchhoff's law, a complete relationship matrix equation covering the positive and negative sequence voltage, current and impedance on both sides of the line is constructed. and They represent the positive and negative sequence fault point voltages inferred from the S and N terminal measurement data, respectively. The calculation formula is:

[0051]

[0052] Combine the electrical quantity measurement point at the head end with the optimal measurement point of negative sequence voltage and the high-precision voltage acquisition data at the end to solve the theoretical value of positive and negative sequence voltage at the fault point. Use the S-end measurement device as the precise clock source to accurately quantify the asynchronous phase angle δ generated by the timing error at the N-end. d, the asymmetric fault location function is constructed using the terminal positive sequence and negative sequence voltage ratio, the formula is: The ratio of the fault distance to the entire line distance is obtained by solving the quadratic complex equation through complex field operations. According to the preset accuracy requirements and line parameter characteristics, the effective K value is strictly selected, combined with the total line length l SN Accurately locate the fault point and provide precise navigation for maintenance personnel to quickly reach the fault site.

[0053] Symmetrical fault distance measurement: In view of the fact that symmetrical faults have no negative sequence component, the voltage and current at the S end and the voltage at the N end of the A-phase and B-phase lines are carefully selected as variables. Referring to the asymmetrical fault processing process and principle, a symmetrical fault distance measurement function is constructed. The formula is: By cleverly eliminating the asynchronous angle error through the terminal voltage ratio, using professional mathematical methods to solve the equation, the fault distance can be accurately obtained, the fault investigation time can be greatly shortened, the power supply restoration efficiency can be improved, the reliable operation of the urban distribution network can be guaranteed, and the impact of faults on residents' lives and urban operations can be reduced.

[0054] In summary, the 10kV armored cable fault distance measurement method based on additional parallel inductance proposed in the present invention shows high effectiveness and accuracy in the urban distribution network scenario. In the additional inductance configuration planning link, the electromagnetic transient analysis software is used to comprehensively consider many line parameters and fault conditions, accurately select the adaptive inductance components and properly connect them, and lay a solid foundation for subsequent fault handling. The fault response control process relies on the intelligent monitoring system and reasonable threshold and setting value settings to achieve rapid fault identification and accurate circuit breaker action. The inductance and switch state are flexibly adjusted according to the fault characteristics to effectively ensure power supply continuity and equipment safety. Fault information collection optimization determines high-quality measurement points and solves the optimal inductance value by integrating advanced technologies, providing reliable data and parameter support for distance measurement. The final fault distance measurement calculation is based on symmetrical and asymmetrical fault models, accurately calculates and locates the fault point, effectively shortens the fault investigation time, improves operation and maintenance efficiency, and effectively enhances the power supply reliability of the urban distribution network, reduces the adverse effects of faults on residents and urban functions, and has far-reaching significance for the urban power supply system.

[0055] Embodiment 2:

[0056] Practice of 10kV armored cable fault distance measurement in industrial plants

[0057] In the complex power supply scenario of an industrial plant, a specific 10kV armored cable line has a length of l SN The wire core is made of aluminum, the insulation state is stable, the wire radius is r, the wire spacing is d, and it is under specific industrial environment temperature conditions all year round.

[0058] Additional inductance configuration planning, with the help of the powerful functions of electromagnetic transient analysis software, all-round consideration of aluminum core, insulation condition, line length lSN , wire radius r, wire spacing d and industrial ambient temperature on line resistance R, capacitance C, inductance L. The simulation covers a variety of extreme and common fault conditions, including different fault locations and changing transition resistance values, and accurately simulates the fault current response characteristics, providing a reliable basis for the subsequent determination of inductance parameters.

[0059] According to the given power supply electromotive force E s , system frequency ω0 and power supply side impedance Z s , carefully calculate the short-circuit current I using the formula L , the formula is: The additional inductance L rating is further accurately determined by the formula: At the same time, its current carrying capacity, voltage resistance level and loss parameters are determined, and additional inductance components suitable for the complex working conditions of industrial plants are selected. After professional installation architecture and connection components, they are properly connected to the bus-end circuit breaker to ensure reliable electrical connection and stable signal transmission, laying a solid foundation for the stable operation of the fault monitoring and ranging system.

[0060] Fault response control process, carefully build intelligent distribution network fault monitoring system, realize the deep integration of current transformer (CT), voltage transformer (PT) real-time monitoring data and intelligent protection device fault diagnosis logic, according to the line rated current I e , Rated voltage U e And the safety margin requirements of industrial plant system operation, reasonably set the current threshold to k1I e and the voltage threshold is U e (1±k2)

[0061] During line operation, once the current or voltage exceeds the preset threshold, the fault monitoring mechanism is quickly activated to accurately determine the fault time, type (such as high-resistance grounding fault, complex type of short-circuit fault) and phase difference. At the moment of fault, the QF1 circuit breaker is set according to the preset current setting value kI e Rapidly trip and start the timing module to lock the time coordinate for fault distance measurement.

[0062] Intelligently select the inductor access strategy based on the fault type. For example, if the current does not exceed the limit in the initial stage of a single-phase grounding fault, continuous monitoring will be carried out and the inductor will be introduced in time to maintain operation. If the current exceeds the limit or other faults occur, Q will be immediately closed to introduce the inductor. In the steady-state stage after the fault, precision measuring equipment will be used to continuously monitor the electrical quantities, and the Q state will be determined based on the instantaneous or permanent characteristics of the fault. After the instantaneous fault is repaired, the system electrical parameters and equipment health status will be verified. After confirmation, QF1 will be accurately closed to restore power supply. For permanent faults, fault information will be uploaded in a timely manner to help the maintenance team respond quickly and reduce the loss of industrial production caused by the fault.

[0063] Fault information collection is optimized, and finite element analysis and field measurement data mining technology are used to accurately determine the optimal measurement point of the first-end electrical quantity measurement point at the negative sequence voltage, and comprehensively consider the line aluminum core and length l SN , radius r, spacing d and physical parameters of insulation characteristics, accurately calculate the distribution of line resistance R, inductance L, capacitance C, and incorporate power supply characteristics (electromotive force E s , internal impedance Z s ) and load distribution parameters (power, power factor) to build an accurate power grid model.

[0064] For typical fault scenarios in industrial plants, we carefully set the parameters of fault location and grounding resistance to simulate changes in electrical quantities, deeply analyze the negative-sequence voltage distribution law to predict theoretical values ​​and trends, conduct on-site measurements, set up temporary measuring points at equal intervals along the line to install high-precision transformers and data acquisition devices, and synchronously collect three-phase voltage data to extract negative-sequence voltage components in the event of an actual fault. We calculate the mean and standard deviation, integrate theoretical and measured data, and select the optimal measuring points based on the criterion of large and stable negative-sequence voltage amplitudes to ensure that the collected data truly reflects the fault characteristics, providing a highly reliable basis for fault distance measurement.

[0065] Based on the precise model of the power grid and the fault equivalent circuit, the optimal value of the additional inductance is solved, the line impedance is accurately measured, the power supply and load parameters are clarified, and the equivalent circuit is constructed for different faults to analyze the changes in electrical quantities. Combined with the impact of short-circuit current on the line, the optimization algorithm is used to iteratively calculate and determine the optimal value, and dynamically fine-tune it according to the line operating current and negative-sequence voltage to ensure that the system can accurately and reliably measure fault distance in complex industrial environments, thereby improving the power supply reliability and production continuity of the factory.

[0066] Fault distance calculation:

[0067] Asymmetric fault location: When the line fails, the symmetrical component method is used to analyze the positive and negative sequence networks. The complete relationship matrix equation is constructed according to Kirchhoff's law. and They represent the positive and negative sequence fault point voltages inferred from the S and N terminal measurement data, respectively. The calculation formula is:

[0068]

[0069] Integrate the positive and negative sequence voltage, current and impedance parameters on both sides of the line, combine the optimal measurement point of the negative sequence voltage at the head end and the high-precision voltage data at the end to solve the theoretical value of the positive and negative sequence voltage at the fault point, and use the S end as the clock source to quantify the phase angle δ of the timing error at the N end. d , the asymmetric fault location function is constructed using the terminal positive sequence and negative sequence voltage ratio, the formula is: Solve the quadratic complex equation by complex number domain operation to get the ratio of fault distance to full line distance The effective K value is selected according to the accuracy and line characteristics, and the total length is combined to accurately locate the fault point, accelerate the fault repair process, and reduce the interruption time of industrial production.

[0070] Symmetrical fault distance measurement: In view of the non-negative sequence characteristics of symmetrical faults, the voltage and current at the S terminal of phase A and B and the voltage at the N terminal are carefully selected as variables, and the distance measurement function formula is constructed according to the principle of asymmetric fault processing: The terminal voltage ratio is used to eliminate timing errors and solve equations to accurately determine the fault distance, which effectively ensures stable power supply to key production equipment in industrial plants and improves overall production efficiency and economic benefits.

[0071] In summary, in the complex power environment of industrial plants, the fault distance measurement method of the present invention has its advantages. In the configuration planning stage, the characteristics of industrial lines are fully considered to determine the inductance parameters to ensure the adaptability of the system. The fault response process is based on rigorous threshold and set value settings and intelligent inductance control strategies to quickly respond to and accurately handle various complex faults, minimize production stagnation losses caused by faults, and maintain production order. The collection optimization and utilization technology is coordinated to accurately locate the measurement points and determine the optimal inductance value, so as to collect high-quality data for distance measurement. The distance measurement calculation relies on rigorous theoretical models and precise algorithms to accurately lock the fault location in both asymmetric and symmetric fault situations, greatly improving the power supply stability of industrial plants, helping the stable operation of production processes, and providing key technical support for reliable energy supply for industrial production activities. It plays a key role in ensuring industrial output value and improving enterprise operating efficiency.

[0072] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A 10kV armored cable fault location method based on additional parallel inductance, characterized in that: The specific steps of the ranging method are: S100, additional inductor configuration planning: Analyze the resistance, capacitance, inductance distribution of the distribution network and the parameters of the expected fault current, use electrical calculation software to simulate the current response under different fault conditions based on the steady-state and transient characteristics of the power system, determine the rated inductance value, current carrying capacity, withstand voltage level and loss parameters, and connect the selected additional inductor to the bus-end circuit breaker through the installation structure and connection components; S200, fault response control: build a fault monitoring system for the intelligent distribution network, integrate the real-time monitoring data of current transformers and voltage transformers and the fault diagnosis logic of intelligent protection devices. Once a line fault causes the current and voltage to exceed the preset threshold, the fault monitoring mechanism is immediately triggered to accurately identify the time, type and phase of the fault. At the moment of the fault, the QF1 circuit breaker quickly trips according to the set current setting value, and the timing module is started synchronously to record the fault time. The timing and mode of inductor access are determined according to the fault type. In the steady-state stage, the measuring equipment is used to continuously monitor the electrical quantity. After the acquisition is completed, the switch Q state is intelligently decided according to the instantaneous or permanent nature of the fault. When restarting the line for an instantaneous fault, the system electrical parameters and equipment health status are fully verified, and the QF1 circuit breaker is accurately closed to restore power supply. For a permanent fault, Q is opened to upload the fault information. S300, fault information collection and optimization: Based on electromagnetic theory and field measured data mining technology, finite element analysis is used to determine the location of the head-end electrical quantity measurement point at the optimal measurement point of the negative sequence voltage. Wide-band voltage transformers and high-linearity current transformers are deployed here to build a multi-sensor collaborative acquisition network to capture the full-state changes of three-phase voltage and current signals, which are transmitted to the field data acquisition terminal via optical fiber. After pre-processing by the signal conditioning circuit with integrated filtering, amplification, isolation and anti-interference functions, the optimal value of the additional inductance is solved based on the precise model of the power grid and the fault equivalent circuit. After being put into operation, the line current and negative sequence voltage dynamic changes are monitored in real time, and the inductance parameters are adaptively fine-tuned; S400, fault distance calculation: The asymmetric fault distance measurement: When the line has an asymmetric fault, the symmetrical component method is used to analyze the positive and negative sequence networks, and the Kirchhoff's law is used to construct a complete relationship matrix equation covering the positive and negative sequence voltages, currents and impedances on both sides of the line. The electrical quantity measurement point at the head end is combined with the optimal measurement point of the negative sequence voltage and the high-precision voltage collection data at the end to substitute into the equation to solve the theoretical value of the positive and negative sequence voltage at the fault point. The S-end measurement device is used as a precise clock source to quantify the asynchronous phase angle δd generated by the timing error at the N-end. The asymmetric fault distance measurement function is constructed using the ratio of the positive and negative sequence voltages at the end. The formula is: in and They represent the positive and negative sequence fault point voltages inferred from the measured data at the S and N terminals respectively. The ratio of the fault distance to the entire line distance is obtained by solving the quadratic complex equation through complex domain operations. Among them, l SF is the distance from S to the fault point F, l SN For the total length of the line, select the effective K value according to the preset accuracy requirements and line parameter characteristics, and accurately locate the fault point based on the total length of the line; Symmetrical fault distance measurement: In view of the characteristic of no negative sequence component, the voltage and current at the S terminal and the voltage at the N terminal of the A-phase and B-phase lines are selected as variables, and the symmetrical fault distance measurement function is constructed by referring to the asymmetric fault processing process and principle. The formula is: in are the S-terminal voltages of phase A and phase B respectively, are the N-terminal voltages of phases A and B respectively. The asynchronous angle error is eliminated by using the terminal voltage ratio, and the fault distance is obtained by solving the equation.

2. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In the S100, the distribution network line parameters considered in the additional inductance configuration planning also include the influence factors of wire core material, insulation characteristics, line length, conductor radius, line spacing and ambient temperature on line resistance, capacitance and inductance; the electrical calculation software adopts electromagnetic transient analysis software to set different fault types, fault locations and transition resistance values ​​when simulating fault conditions.

3. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In the above S100, the short-circuit current IL is calculated by the formula in the additional inductor configuration planning, and the formula is: Where E s represents the power supply electromotive force, ω0 is the system frequency, j represents the imaginary unit, the jth, L represents the additional inductance, Z s Indicates the impedance on the power supply side.

4. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In the above S100, the additional inductance L is calculated by a formula in the additional inductance configuration planning, and the formula is: Among them, I L Indicates the short-circuit current I L , E s represents the power supply electromotive force, ω0 is the system frequency, j represents the imaginary unit, the jth, L represents the additional inductance, Z s Indicates the impedance on the power supply side.

5. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: S200, determination of current and voltage exceeding thresholds in fault response control, the thresholds are set according to line rated current, rated voltage and system operation safety margin factors, for a rated current of I e The current threshold is k1I e The value of k1 is determined according to the line load characteristics, the probability of fault occurrence and the system stability requirements, and is between 1.2 and 1.

5. In terms of voltage, the rated voltage U e As a benchmark, considering the voltage fluctuation range and system insulation tolerance, the voltage threshold is set to U e (1±k2), k2 depends on the grid voltage level, line length and surrounding environmental factors, and its value is in the range of 0.05-0.

1.

6. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In S200, the preset current setting value of the QF1 circuit breaker in the fault response control is determined, and a probability statistical analysis of the line fault current is carried out. Based on the historical operation data, the frequency and amplitude distribution of the fault current are calculated for different fault scenarios, and the mean μ and standard deviation σ of each type of fault current are determined. The thermal stability limit of the equipment is comprehensively considered, and the thermal stability current I given in the equipment manual is calculated. th and the allowed duration t th , ensure that the setting value is less than I th At the same time, the protection selectivity requirements are followed. The upper protection action time t1 and the current protection action time t2 must satisfy t1>t2+Δt, where Δt is the time difference. Through calculation, analysis, verification and adjustment, the setting value is determined to be kI e , k value range is 1.5-3, and is fine-tuned according to the line characteristics.

7. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: S200, in the fault response control, the timing and mode of inductor connection, during the period of single-phase grounding fault and the current not exceeding the setting value, the fault-carrying operation is allowed, and when other faults occur, the auxiliary switch Q is immediately closed to introduce the inductor; The current does not exceed the limit in the initial stage of a single-phase grounding fault, but maintenance and distance measurement are required in the later stage. After QF1 trips, the closed Q operation is controlled. In the transient transition stage, the dynamic changes of electrical quantities are monitored in real time by using a high-speed data acquisition system.

8. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In the S300, the optimal measurement point of the negative sequence voltage at the head-end electrical quantity measurement point in the fault information collection and optimization is determined by comprehensively using finite element analysis and field measured data mining technology, taking into account the physical parameters of the line conductor material, length, radius, spacing and insulation medium characteristics, calculating the line resistance, inductance, and capacitance distribution, and at the same time incorporating power supply characteristics such as electromotive force, internal impedance, and load distribution parameters such as power and power factor, to construct a model that is highly consistent with the actual power grid. For different types of faults, the fault location and grounding resistance parameters are set to simulate the fault occurrence. The changes in electrical quantities after the fault occurs are analyzed, the distribution law of negative-sequence voltage along the line is analyzed, the theoretical value and change trend of negative-sequence voltage at different positions are predicted, and on-site actual measurement work is carried out. Multiple temporary measuring points are set up at equal intervals along the line, and voltage transformers and data acquisition devices are installed. When an actual fault occurs, the three-phase voltage data are collected synchronously, the negative-sequence voltage component is extracted, the mean and standard deviation of the negative-sequence voltage at each measuring point are calculated, the theoretical results of finite element analysis are integrated with the on-site measured data, and the data of each measuring point are classified and the optimal measuring point for negative-sequence voltage is screened out with the core goal of large and stable negative-sequence voltage amplitude.

9. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: The S300, the process of solving the optimal value of additional inductance in fault information collection and optimization, solves the optimal value of additional inductance based on the precise model of the power grid system and the fault equivalent circuit analysis, firstly measures the line impedance, including resistance and reactance, and at the same time clarifies the power supply characteristics such as the magnitude of the electromotive force and the internal impedance, as well as the load distribution parameters, constructs corresponding fault equivalent circuits for different fault types, analyzes the changes in electrical quantities after the fault occurs, comprehensively considers the magnitude of the short-circuit current and its impact on the safe and stable operation of the line, and uses an optimization algorithm through continuous iterative calculation to find the optimal value of additional inductance.

10. A 10kV armored cable fault location method based on additional parallel inductance according to claim 1, characterized in that: In the above S400, the positive and negative sequence voltages at the fault point are calculated based on the voltage, current and line impedance parameters on both sides of the line in the fault distance calculation. and They represent the positive and negative sequence fault point voltages inferred from the S and N terminal measurement data, respectively. The calculation formula is: in are the positive sequence and negative sequence voltage and current at the fault line S end, respectively. are the positive and negative sequence voltage and current at the N end of the line, Z1 and Z2 are the positive and negative sequence impedances of the line, C1 and C2 are the positive and negative sequence capacitances of the line, l SF is the distance from S to the fault point F, l SN The total length of the line.

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