Incremental admittance-based low-voltage alternating current system insulation defect early warning method and system

Abstract

The application discloses a kind of low-voltage alternating current system insulation defect early warning method and system based on incremental admittance, the residual voltage and current of each line in substation station low-voltage alternating current system are collected, residual voltage and current mutation variable, Fourier value are structured, and starting threshold trigger detection is set;When meeting the starting condition of insulation state early warning detection, controllable voltage disturbance is applied to substation station low-voltage alternating current system by neutral point voltage regulating device;Synchronous acquisition line residual voltage and each feeder residual current before and after disturbance, extract equivalent ground conductance component and equivalent ground admittance component;According to equivalent ground conductance component and equivalent ground admittance component, the leakage current constant of each feeder is calculated, and insulation state quantitative characteristic quantity is constructed;The insulation state quantitative characteristic quantity is compared with preset criterion, and the insulation state type of each feeder is identified according to the comparison result, and is respectively determined as normal state, recoverable insulation defect or unrecoverable insulation defect.

Description

Technical Field

[0001] This invention belongs to the field of insulation condition monitoring and defect early warning technology for low-voltage AC systems used in substations, specifically relating to a method and system for early warning of insulation defects in low-voltage AC systems based on incremental admittance. Background Technology

[0002] The substation low-voltage AC system is responsible for supplying power to important loads such as protection and control devices, communication equipment, DC system auxiliary power, lighting, ventilation, heating and dehumidification, and maintenance power. It is a crucial foundational system for ensuring the safe and stable operation of the substation. This system operates continuously for extended periods, with numerous feeders, complex load types, and varying laying environments. Cable insulation, terminal connections, and internal insulation components of switchgear are susceptible to the effects of temperature, humidity, condensation, dust, mechanical vibration, and long-term electrical stress, gradually leading to defects such as insulation aging, moisture absorption, surface contamination, localized carbonization, and increased leakage to ground.

[0003] The aforementioned insulation defects typically do not immediately manifest as obvious protective actions or power outages in their early stages. Instead, they exhibit insidious characteristics such as a slow increase in leakage current, a gradual decrease in insulation margin, and changes in ground admittance. If these defects are not detected and warned of in their early stages, they may further evolve into single-phase grounding, intermittent arcing, equipment malfunctions, or even station power system failures, thereby affecting the reliable power supply to secondary equipment and auxiliary systems. Therefore, conducting online monitoring, early identification, and tiered warning systems for insulation aging defects in station low-voltage AC systems is of significant engineering importance.

[0004] Existing methods for monitoring the insulation status of low-voltage AC substation systems include insulation resistance testing, residual current monitoring, grounding alarms, or manual inspections. Insulation resistance testing typically requires power outages or partial equipment shutdowns, making continuous online monitoring difficult. Manual inspections rely on maintenance experience, limiting their real-time performance and quantification. While residual current monitoring can reflect line-to-ground leakage, most methods rely on residual current amplitude thresholds for judgment. In the early stages of insulation aging defects, the leakage current change is small and often insufficient to trigger an alarm, easily leading to missed early defects.

[0005] Meanwhile, the low-voltage AC system used in the station contains a large number of single-phase loads, switching power supplies, UPS, heating and dehumidification devices, etc. The switching process and changes in operating status of these devices can cause fluctuations in residual current, changes in harmonic components, and the superposition of inherent leakage current. This makes the monitoring method that relies solely on the amplitude of residual current easily affected by load fluctuations, harmonic interference, electromagnetic interference, and inherent leakage of equipment, resulting in misjudgments and omissions. It is difficult to accurately distinguish insulation aging defects, capacitor switching, load disturbances, and other normal operating fluctuations.

[0006] Existing methods for detecting insulation defects in low-voltage systems include identification methods based on zero-sequence voltage, grounding current, harmonic characteristics, transient characteristics, or time-frequency analysis, as well as condition assessment methods based on data-driven or intelligent algorithms. Threshold-based monitoring methods are simple in structure but not sensitive enough to early insulation aging and high-resistance leakage defects; methods based on transient or time-frequency characteristics can extract some non-stationary anomaly information, but are more suitable for identification after anomalies occur and cannot stably reflect the gradual degradation process of insulation condition; methods based on intelligent algorithms can integrate multi-source features, but usually rely on a large number of defect samples and labeled data. In situations where defect samples in station low-voltage systems are scarce, operating conditions are complex, and equipment varies greatly, there are still problems with insufficient generalization and weak interpretability. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for early warning of insulation defects in low-voltage AC systems based on incremental admittance, overcoming the problems existing in current monitoring of insulation status in substation low-voltage AC systems, such as difficulty in identifying early defects, susceptibility of residual current amplitude thresholds to load fluctuations, and insufficient generalization of intelligent identification methods due to scarce defect samples. This invention applies a controllable neutral point voltage disturbance after the start-up conditions are met, obtains the line residual voltage and residual current response of each feeder before and after the disturbance, calculates the zero-sequence incremental admittance of each feeder, and further extracts the equivalent ground conductance component, equivalent ground susceptance component, and leakage current constant. This achieves a quantitative characterization of the insulation leakage state and its development trend of each feeder, thereby improving the sensitivity, reliability, and interpretability of early warning of insulation aging defects in substation low-voltage AC systems.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance includes the following steps: Step 1: Collect the residual voltage and current of each line in the substation's low-voltage AC system, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. Step 2: When the insulation condition early warning detection start conditions are met, a controllable voltage disturbance is applied to the substation service low-voltage AC system through the neutral point voltage regulation device to cause a preset change in the line residual voltage; the line residual voltage and the residual current of each feeder before and after the disturbance are collected simultaneously, the residual voltage change and the residual current change are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and the equivalent ground susceptance component are extracted. Step 3: Calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. Step 4: Compare the quantified insulation state features with the preset criteria, identify the insulation state type of each feeder based on the comparison results, and determine it as normal state, recoverable insulation defect or non-recoverable insulation defect, and output the corresponding defect warning result.

[0009] Further, in step 1, the remaining voltage at the beginning of the line and the remaining current of each feeder are collected. The Fourier algorithm is used to calculate the Fourier values ​​of the remaining voltage and the remaining current of each feeder, respectively. Based on the changes in the Fourier values ​​within adjacent sampling windows, the sudden changes in the remaining voltage and the remaining current are constructed. The Fourier values ​​of the remaining voltage, the Fourier values ​​of the remaining current of each feeder, and their sudden changes are compared with the corresponding thresholds to construct an insulation aging defect early warning activation criterion to determine whether to trigger detection. The criterion is as follows:

[0010] in, U 0 is the Fourier transform value of the residual voltage. U th It is the threshold value of the residual voltage Fourier transform. It is the first n The Fourier transform value of the residual current of the line. It is the threshold for the sudden change in the Fourier transform value of the residual current. It is the first n The sampled value of the residual current of the line. t f The defect warning activation time is determined based on the comparison results of the Fourier values ​​of the residual voltage, the Fourier values ​​of the residual current, their abrupt changes, and the corresponding thresholds. t d The delay time for enabling insulation aging defect detection after the early warning activation criteria are met.

[0011] Furthermore, in step 2, based on the insulation aging defect early warning activation criterion obtained in step 1, it is determined whether the substation service low-voltage AC system meets the insulation aging defect early warning detection activation conditions; when it is determined that the insulation aging defect early warning detection is met, a controllable voltage disturbance is applied to the substation service low-voltage AC system through the neutral point voltage regulating device, so that the residual voltage of the low-voltage line produces a preset change, and the residual voltage of the line and the residual current of each feeder before and after the disturbance are collected simultaneously to construct the residual voltage change and the residual current change.

[0012] Furthermore, the construction of the residual voltage change and residual current change, the calculation of the zero-sequence incremental admittance of each feeder, and the extraction of the equivalent ground conductance component and the equivalent ground susceptance component specifically include: Before applying the voltage disturbance, the remaining line voltage under the pre-disturbance condition is simultaneously acquired. and the i residual current of feeder After the voltage disturbance is applied, the remaining line voltage under the disturbance state is simultaneously collected. and the i residual current of feeder Based on the measurement results before and after the disturbance, the changes in the line residual voltage and the feeder residual current are constructed:

[0013]

[0014] Calculate the zero-sequence incremental admittance of the i-th feed:

[0015] The zero-sequence incremental admittance is decomposed into an equivalent ground conductance component and an equivalent ground susceptance component:

[0016] in, For the first i The equivalent ground conductance component of a feeder is used to characterize the resistive leakage of the feeder. For the first i The equivalent ground susceptance component of a feeder is used to characterize the ground capacitance characteristics of the feeder.

[0017] Furthermore, in step 3, the equivalent ground conductance component obtained in step 2 is... and equivalent ground susceptance component Calculate the first i The leakage current constant of the feeder is used to construct a quantitative characteristic of the insulation state by combining it with a pre-established historical health benchmark. No. i The leakage current constant of the feeder is expressed as:

[0018] in, ω The system angular frequency, K i For the first i The leakage current constant of a feeder increases when the feeder insulation deteriorates, as its equivalent ground conductivity component increases, thus affecting the leakage current constant. K i The corresponding increase.

[0019] Furthermore, when the leakage current constant is detected to be greater than a preset threshold... K th1 At that time, calculate the insulation condition recovery rate:

[0020] in, Ki,peak This represents the peak value of the leakage current constant during the abnormal process. K i,stable This represents the leakage current constant during the stable phase after the anomaly. R K,i It is the insulation state recovery rate.

[0021] Furthermore, in step 4, the leakage current constant and insulation state recovery rate of each feeder obtained in step 3 are compared with the preset insulation state type criterion to determine the insulation state type of each feeder. Specifically, the following criteria are used to provide early warning of line defects:

[0022] in, S i This is the comprehensive determination quantity for the insulation status of the i-th feeder. K th1 The preset threshold for the leakage current constant. R th1 This is a preset threshold for the insulation state recovery rate.

[0023] A low-voltage AC system insulation defect early warning system based on incremental admittance includes: The first module is used to collect the residual voltage and current of each line in the low-voltage AC system of the substation, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. The second module is used to apply a controllable voltage disturbance to the substation's low-voltage AC system through the neutral point voltage regulation device when the insulation condition early warning detection activation conditions are met, so that the line residual voltage will produce a preset change; the line residual voltage and the residual current of each feeder before and after the disturbance are collected simultaneously, the residual voltage change and the residual current change are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and the equivalent ground susceptance component are extracted. The third module is used to calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and to construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. The fourth module is used to compare the quantified insulation state features with preset criteria, identify the insulation state type of each feeder based on the comparison results, determine it as normal state, recoverable insulation defect or unrecoverable insulation defect, and output the corresponding defect warning result.

[0024] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for early warning of insulation defects in low-voltage AC systems based on incremental admittance.

[0025] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the low-voltage AC system insulation defect early warning method based on incremental admittance.

[0026] A computer program product includes a computer program that, when executed by a processor, implements the steps of the incremental admittance-based low-voltage AC system insulation defect early warning method.

[0027] Compared with the prior art, the present invention has the following beneficial technical effects: This invention applies a controllable neutral point voltage disturbance to obtain the residual voltage of the line and the residual current response of each feeder before and after the disturbance, and calculates the zero-sequence incremental admittance of each feeder, thus avoiding misjudgments and omissions caused by simply relying on the residual current amplitude threshold. By extracting the equivalent ground conductance component, the equivalent ground susceptance component, and the leakage current constant, it can more directly characterize the degree of feeder insulation leakage to ground, which has clear physical meaning and good interpretability. Combining historical health benchmarks to construct the leakage current constant offset rate and change trend can realize early identification, trend tracking, and graded early warning of insulation aging defects. At the same time, this method can perform insulation status assessment for each feeder separately, which is convenient for locating abnormal feeders. The criterion is simple and easy to set, making it suitable for deployment in online monitoring and intelligent operation and maintenance scenarios of station low-voltage AC systems. Attached Figure Description

[0028] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] Figure 1 Flowchart of the method of this invention; Figure 2 Flowchart of the defect warning algorithm activation criteria; Figure 3 Flowchart for zero-sequence incremental admittance calculation; Figure 4 Line defect early warning flowchart; Figure 5 Defect simulation model diagram. Detailed Implementation

[0030] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] Example 1 A method for early warning of insulation aging defects in substation low-voltage AC systems based on zero-sequence incremental admittance includes the following steps: Step 1: Collect the residual voltage and current of each line in the substation's low-voltage AC system, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. Step 2: When the insulation condition early warning detection start conditions are met, a controllable voltage disturbance is applied to the substation service low-voltage AC system through the neutral point voltage regulation device to cause a preset change in the line residual voltage; the line residual voltage and the residual current of each feeder before and after the disturbance are collected simultaneously, the residual voltage change and the residual current change are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and the equivalent ground susceptance component are extracted. Step 3: Calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. Step 4: Compare the quantified insulation state features with the preset criteria, identify the insulation state type of each feeder based on the comparison results, and determine it as normal state, recoverable insulation defect or non-recoverable insulation defect, and output the corresponding defect warning result.

[0033] This invention enables the proactive acquisition of the ground insulation response characteristics of each feeder under uninterrupted power conditions using measurable information such as residual line voltage and feeder residual current. By applying a controllable neutral point voltage disturbance, the changes in residual voltage and feeder residual current before and after the disturbance are constructed. The zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component, equivalent ground susceptance component, and leakage current constant are further extracted. This allows for a more direct characterization of the feeder insulation leakage degree and its changing trend, thereby enabling early identification, trend tracking, and graded early warning of insulation aging defects in substation low-voltage AC systems.

[0034] Example 2 like Figure 1 As shown, this invention is a method for early warning of insulation aging defects in substation low-voltage AC systems based on zero-sequence incremental admittance, specifically including the following steps: I. Setting Early Warning Activation Criteria. The residual voltage at the beginning of the substation's low-voltage AC system lines and the residual current of each feeder are collected. The Fourier algorithm is used to calculate the Fourier values ​​of the residual voltage and the residual current of each feeder, respectively. Based on the changes in the Fourier values ​​within adjacent sampling windows, the abrupt changes in residual voltage and residual current are constructed. The Fourier values ​​of the residual voltage, the Fourier values ​​of the residual current of each feeder, and their abrupt changes are compared with corresponding thresholds to construct an insulation aging defect early warning activation criterion. This determines whether the insulation aging defect early warning detection is triggered. The criteria are as follows:

[0035] in, U 0 is the Fourier transform value of the residual voltage. U th It is the threshold value of the residual voltage Fourier transform. It is the first n The Fourier transform value of the residual current of the line. It is the threshold for the sudden change in the Fourier transform value of the residual current. It is the first n The sampled value of the residual current of the line. t f The defect warning activation time is determined by the Fourier value criterion of residual voltage. t d It is the delay time for opening insulation aging defect detection after the early warning activation criteria are met.

[0036] According to such Figure 2 The defect early warning detection flowchart shown indicates that when the Fourier transform value of the residual voltage of the station low-voltage AC system line is detected to be greater than a certain value... U th At that time, the residual voltage Fourier transform value mutation criterion is activated, and the mutation time is recorded. t f The residual voltage sample value abrupt change criterion is activated. td If the residual current sample value suddenly becomes less than within a certain time period i th If the condition is met, the early warning method for insulation aging defects in the substation's low-voltage AC system will be activated; otherwise, the early warning method for insulation aging defects in the substation's low-voltage AC system will not be activated.

[0037] II. Calculate the zero-sequence incremental admittance, such as Figure 3 The flowchart shown illustrates the calculation of zero-sequence incremental admittance. A controllable voltage disturbance is applied to the low-voltage AC system of the substation through a neutral point voltage regulation device, causing a preset change in the residual voltage of the low-voltage line. The residual voltage of the line and the residual current of each feeder are collected simultaneously before and after the disturbance to construct the changes in residual voltage and residual current.

[0038] Specifically, before applying the voltage disturbance, the remaining line voltage in the state before the disturbance is synchronously acquired. and the i residual current of feeder After the voltage disturbance is applied, the remaining line voltage under the disturbance state is simultaneously collected. and the i residual current of feeder Based on the measurement results before and after the disturbance, the changes in residual voltage of the line and the changes in residual current of the feeder are constructed:

[0039]

[0040] Calculate the first i Zero-sequence incremental admittance of the feeder:

[0041] The zero-sequence incremental admittance is decomposed into an equivalent ground conductance component and an equivalent ground susceptance component:

[0042] in, For the first i The equivalent ground conductance component of a feeder is used to characterize the resistive leakage of the feeder. For the first i The equivalent ground susceptance component of a feeder is used to characterize the ground capacitance characteristics of the feeder.

[0043] III. Construction of Defect Early Warning Criteria, such as Figure 4As shown, by constructing quantitative characteristics of insulation status, the degree of insulation leakage to ground of each feeder and its changing trend relative to historical health status are characterized, thereby achieving hierarchical identification of different insulation statuses. Specifically, after calculating the zero-sequence incremental admittance of each feeder, the leakage current constant is calculated based on the equivalent ground conductance component and the equivalent ground susceptance component. Combined with the pre-established historical health benchmark, the leakage current constant offset rate and the changing trend of the leakage current constant are further calculated to construct a comprehensive quantitative characteristic of insulation status: Specifically, no. i The leakage current constant of the feeder is expressed as:

[0044] in, ω The system angular frequency, K i For the first i The leakage current constant of a feeder. When the insulation condition of the feeder deteriorates, its equivalent conductance to ground increases, thus increasing the leakage current constant. K i The corresponding increase.

[0045] When the leakage current constant is detected to be greater than a preset threshold K th1 Then, calculate the insulation condition recovery rate:

[0046] in, K i,peak This represents the peak value of the leakage current constant during the abnormal process. K i,stable This represents the leakage current constant during the stable phase after the anomaly. R K,i It is the insulation state recovery rate.

[0047] IV. Defect Early Warning: Based on the leakage current constant and insulation recovery rate of each feeder obtained in step 3, compare them with the preset insulation condition criteria to determine the insulation condition type and defect risk level of each feeder.

[0048] Specifically, the following criteria are used to provide early warning of line defects:

[0049] in, S i This is the comprehensive determination quantity for the insulation status of the i-th feeder. K th1 The preset threshold for the leakage current constant. R th1 This is a preset threshold for the insulation state recovery rate.

[0050] Example 3 The early warning scheme in this invention is illustrated in the PSCAD simulation environment. A low-voltage power distribution system is established in PSCAD, and the simulation schematic diagram is shown below. Figure 5 As shown. G1 is a 10kV equivalent power source, and T1 is a 10kV / 380V transformer. Z line,i Let be the line impedance in region i. Z load,i For the equivalent load of feeder i, CS is used to simulate capacitor switching, and LS is used to simulate load switching. The main parameters of the model are as follows: line positive sequence resistance: 0.022Ω / km; line positive sequence reactance: 0.001889Ω / km; line positive sequence capacitive reactance: 0.25477MΩ / m; line residual resistance: 0.341Ω / km; line residual reactance: 0.002434102Ω / km; line residual capacitive reactance: 1.098177MΩ / m; the distance between loads is 100 meters, the first load is 100 meters away from the transformer, the power factor of the load is 0.9, the three-phase load is unbalanced, phase A is heavily loaded, and phase C is lightly loaded.

[0051] Table 1 Statistical Table of Defect Early Warning Experiment Results

[0052] Analysis of the experimental results shows that the proposed method can effectively identify the insulation status changes of each feeder in the low-voltage AC system of substation, accurately distinguish between normal state, recoverable insulation defects and unrecoverable defects, and is less affected by load switching and operating condition fluctuations. It has good early warning capability for insulation aging defects and engineering applicability.

[0053] Example 4 This invention provides an insulation defect early warning system for low-voltage AC systems based on incremental admittance, comprising: The first module is used to collect the residual voltage and current of each line in the low-voltage AC system of the substation, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. The second module is used to apply a controllable voltage disturbance to the substation's low-voltage AC system through the neutral point voltage regulation device when the insulation condition early warning detection activation conditions are met, so that the line residual voltage will produce a preset change; the line residual voltage and the residual current of each feeder before and after the disturbance are collected simultaneously, the residual voltage change and the residual current change are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and the equivalent ground susceptance component are extracted. The third module is used to calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and to construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. The fourth module is used to compare the quantified insulation state features with preset criteria, identify the insulation state type of each feeder based on the comparison results, determine it as normal state, recoverable insulation defect or unrecoverable insulation defect, and output the corresponding defect warning result.

[0054] Example 5 The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the low-voltage AC system insulation defect early warning method based on incremental admittance.

[0055] Example 6 The present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for early warning of insulation defects in low-voltage AC systems based on incremental admittance.

[0056] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0057] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0058] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1The function specified in one or more boxes.

[0059] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A method for early warning of insulation defects in low-voltage AC systems based on incremental admittance, characterized in that, Includes the following steps: Step 1: Collect the residual voltage and current of each line in the substation's low-voltage AC system, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. Step 2: When the insulation condition early warning detection start conditions are met, a controllable voltage disturbance is applied to the substation station service low-voltage AC system through the neutral point voltage regulation device to cause a preset change in the line residual voltage. The residual voltage of the line and the residual current of each feeder are collected synchronously before and after the disturbance. The changes in residual voltage and residual current are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and equivalent ground susceptance component are extracted. Step 3: Calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. Step 4: Compare the quantified insulation state features with the preset criteria, identify the insulation state type of each feeder based on the comparison results, and determine it as normal state, recoverable insulation defect or non-recoverable insulation defect, and output the corresponding defect warning result.

2. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 1, characterized in that, In step 1, the remaining voltage at the beginning of the line and the remaining current of each feeder are collected. The Fourier algorithm is used to calculate the Fourier values ​​of the remaining voltage and the remaining current of each feeder, respectively. Based on the changes in the Fourier values ​​within adjacent sampling windows, the abrupt changes in the remaining voltage and the remaining current are constructed. The remaining voltage Fourier values, the remaining current Fourier values ​​of each feeder, and their abrupt changes are compared with corresponding thresholds to construct an insulation aging defect early warning activation criterion, determining whether to trigger detection. The criterion is as follows: in, U 0 is the Fourier transform value of the residual voltage. U th It is the threshold value of the residual voltage Fourier transform. It is the first n The Fourier transform value of the residual current of the line. It is the threshold for the sudden change in the Fourier transform value of the residual current. It is the first n The sampled value of the residual current of the line. t f The defect warning activation time is determined based on the comparison results of the Fourier values ​​of the residual voltage, the Fourier values ​​of the residual current, their abrupt changes, and the corresponding thresholds. t d The delay time for enabling insulation aging defect detection after the early warning activation criteria are met.

3. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 2, characterized in that, In step 2, based on the insulation aging defect early warning activation criteria obtained in step 1, it is determined whether the substation station service low-voltage AC system meets the insulation aging defect early warning detection activation conditions. Once the insulation aging defect early warning detection is met, a controllable voltage disturbance is applied to the substation's low-voltage AC system through the neutral point voltage regulation device, causing a preset change in the residual voltage of the low-voltage line. Simultaneously, the residual voltage of the line and the residual current of each feeder before and after the disturbance are collected to construct the changes in residual voltage and residual current.

4. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 3, characterized in that, The process involves constructing the residual voltage and residual current changes, calculating the zero-sequence incremental admittance of each feeder, and extracting the equivalent ground conductance and equivalent ground susceptance components. Specifically, this includes: Before applying the voltage disturbance, the remaining line voltage under the pre-disturbance condition is simultaneously acquired. and the i residual current of feeder After the voltage disturbance is applied, the remaining line voltage under the disturbance state is simultaneously collected. and the i residual current of feeder Based on the measurement results before and after the disturbance, the changes in the line residual voltage and the feeder residual current are constructed: Calculate the zero-sequence incremental admittance of the i-th feed: The zero-sequence incremental admittance is decomposed into an equivalent ground conductance component and an equivalent ground susceptance component: in, For the first i The equivalent ground conductance component of a feeder is used to characterize the resistive leakage of the feeder. For the first i The equivalent ground susceptance component of a feeder is used to characterize the ground capacitance characteristics of the feeder.

5. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 1, characterized in that, In step 3, the equivalent ground conductance component obtained in step 2 is used. and equivalent ground susceptance component Calculate the first i The leakage current constant of the feeder is used to construct a quantitative characteristic of the insulation state by combining it with a pre-established historical health benchmark. No. i The leakage current constant of the feeder is expressed as: in, ω The system angular frequency, K i For the first i The leakage current constant of a feeder increases when the feeder insulation deteriorates, as its equivalent ground conductivity component increases, thus affecting the leakage current constant. K i The corresponding increase.

6. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 5, characterized in that, When the leakage current constant is detected to be greater than a preset threshold K th1 At that time, calculate the insulation condition recovery rate: in, K i,peak This represents the peak value of the leakage current constant during the abnormal process. K i,stable This represents the leakage current constant during the stabilization phase after the anomaly. R K,i It is the insulation state recovery rate.

7. The method for early warning of insulation defects in low-voltage AC systems based on incremental admittance according to claim 6, characterized in that, In step 4, the leakage current constant and insulation state recovery rate of each feeder obtained in step 3 are compared with the preset insulation state type criteria to determine the insulation state type of each feeder. Specifically, the following criteria are used to provide early warning of line defects: in, S i This is the comprehensive determination quantity for the insulation status of the i-th feeder. K th1 The preset threshold for the leakage current constant. R th1 This is a preset threshold for the insulation state recovery rate.

8. A low-voltage AC system insulation defect early warning system based on incremental admittance, characterized in that, include: The first module is used to collect the residual voltage and current of each line in the low-voltage AC system of the substation, construct the residual voltage and current abrupt changes and Fourier values, and set the start threshold to trigger detection. The second module is used to apply a controllable voltage disturbance to the substation's low-voltage AC system through the neutral point voltage regulator when the insulation condition early warning detection activation conditions are met, so that the residual voltage of the line will produce a preset change. The residual voltage of the line and the residual current of each feeder are collected synchronously before and after the disturbance. The changes in residual voltage and residual current are constructed, the zero-sequence incremental admittance of each feeder is calculated, and the equivalent ground conductance component and equivalent ground susceptance component are extracted. The third module is used to calculate the leakage current constant of each feeder based on the equivalent ground conductance component and the equivalent ground susceptance component, and to construct the insulation state quantitative characteristic quantity, which includes the leakage current constant and the insulation state recovery rate. The fourth module is used to compare the quantified insulation state features with preset criteria, identify the insulation state type of each feeder based on the comparison results, determine it as normal state, recoverable insulation defect or unrecoverable insulation defect, and output the corresponding defect warning result.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the low-voltage AC system insulation defect early warning method based on incremental admittance as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the low-voltage AC system insulation defect early warning method based on incremental admittance as described in any one of claims 1 to 7.

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