A method for identifying zero-value insulators based on pollution level correction

Abstract

This invention discloses a method for identifying zero-value insulators based on pollution level correction, belonging to the field of transmission line insulation condition detection and intelligent inspection technology. This method comprehensively considers the pollution level of the target area, insulator string type, voltage level, and local electric field distribution characteristics. It combines dual-probe local electric field detection with a pollution level correction mechanism to achieve accurate identification of zero-value insulators in complex environments. The method includes the following steps: S1: Acquire local electric field data; S2: Calculate the deviation rate η; S3: Detect the pollution level to obtain P; S4: Calculate the correction coefficient Kpoll; S5: Update the deviation rate criterion; S6: Determine whether it is a zero-value insulator. This invention maintains a high accuracy rate in identifying zero-value insulators under different pollution environments, including light, medium, heavy, and extremely heavy pollution, significantly reducing the probability of false positives and false negatives, and exhibiting better environmental adaptability and robustness. The algorithm structure is clear and computationally intensive.

Description

Technical Field

[0001] This invention belongs to the field of transmission line insulation condition detection and intelligent inspection technology, and in particular, a method for identifying zero-value insulators based on pollution level correction. Background Technology

[0002] As transmission lines extend into complex environments such as coastal salt spray areas, industrial pollution zones, and high-humidity mountainous areas, insulator surfaces are highly susceptible to the accumulation of salt, dust, industrial particles, and other pollutants during long-term operation. Under conditions of humidity, condensation, fog, or light rain, the contaminants adhering to the insulator surface absorb moisture and form a conductive wet layer, leading to a significant increase in surface leakage current and noticeable distortion of the surface electric field distribution. When the insulator further breaks down, cracks, or experiences a significant decrease in insulation resistance, a zero-value insulator is formed. The presence of a zero-value insulator not only alters the voltage distribution of the entire insulator string but also significantly increases the risk of flashover, string drop, and line faults, seriously threatening the safe and stable operation of transmission lines.

[0003] Currently, on-site detection methods for zero-value insulators mainly include the spark gap method, distributed voltage method, infrared detection method, ultrasonic detection method, resistance measurement method, and non-contact detection methods based on local electric field sensing. Among these, the dual-probe local electric field detection method is gradually becoming an important development direction in intelligent inspection of transmission lines due to its advantages such as fast detection speed, no need for whole-string scanning, and ease of integration with robots or drones. Existing dual-probe identification methods are usually based on the mechanism of abnormal local electric field distribution near zero-value insulators. They simultaneously collect local field strength using two probes and construct a deviation rate index to determine whether the target insulator is in a zero-value state.

[0004] However, most existing methods are based on the assumption that the surface condition of insulators is uniform or that environmental influences are negligible, failing to fully consider the coupled effects of different pollution levels on local electric field distribution characteristics. In actual operation, differences in pollution levels not only cause a shift in the overall electric field strength of the insulator but also alter the local electric field gradient distribution characteristics. This can lead to insulators that are in good condition exhibiting near-abnormal electric field responses under heavily polluted conditions, while insulators with zero values ​​under lightly polluted conditions may be difficult to identify accurately due to insignificant changes in electric field strength. If a fixed single threshold is still used for judgment, it is easy to misjudge heavily polluted insulators or miss lightly polluted zero-value insulators, thus limiting the engineering applicability and identification reliability of the dual-probe identification method in complex environments.

[0005] Current methods for identifying zero-value insulators have the following shortcomings: First, most methods establish criteria under ideal clean operating conditions, without considering the coupling effects of different pollution levels, surface wettability, and leakage current changes on the local electric field, resulting in a lack of environmental adaptability in the identification threshold. Second, some methods require scanning the entire string piece by piece or power outage testing, which has low on-site efficiency and is difficult to meet the needs of large-scale online inspections. Third, traditional fixed threshold methods cannot distinguish the differences in electric field characterization between "heavily polluted intact insulators" and "lightly polluted zero-value insulators," which can easily lead to misjudgments or omissions. Fourth, there is a lack of quantitative correction mechanisms for different pollution levels, making it difficult to form replicable and deployable engineering application solutions. Summary of the Invention

[0006] The purpose of this invention is to provide a zero-value insulator identification method based on pollution level correction. By introducing a pollution level correction coefficient to dynamically adjust the basic identification threshold, the accuracy and reliability of insulator status identification under different pollution environments are improved.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for identifying zero-value insulators based on pollution level correction, comprising the following steps:

[0008] Acquiring Local Electric Field Intensity Values: Two local electric field intensity values, E1 and E2, are simultaneously measured in the target insulator skirt area using dual electric field probes arranged along the insulator axis with a spacing of 70mm to 125mm. Specifically, an 80mm spacing is used for 110kV lines; a 100mm spacing is used for 220kV lines; and a 120mm spacing is used for 500kV lines. This scheme uses dual electric field probes arranged along the insulator axis with a spacing of 70mm to 125mm (adjusted according to voltage level) to simultaneously measure two local electric field intensity values, E1 and E2, in the target insulator skirt area. This design allows for accurate local electric field data even in complex field environments. Compared with traditional single-point measurements, the dual-probe design can more effectively capture changes in electric field distribution caused by internal defects or external contamination of the insulator, thus significantly improving the accuracy of insulator condition assessment. Especially for high-voltage lines, a reasonable probe spacing setting can further optimize signal acquisition quality, reduce noise interference, and ensure the validity and reliability of the data.

[0009] Calculate the local electric field deviation rate Calculate the local electric field deviation rate based on the measured E1 and E2. The calculation formula is as follows: ,in, The local electric field deviation rate of the dual probe is used to characterize the degree of anomaly in the local electric field gradient of the target insulator; The local electric field intensity is measured by the first electric field probe; is the local electric field strength measured by the second electric field probe.

[0010] Determine the pollution level index P: Obtain the pollution level index P of the area where the target insulator is located. P is a dimensionless parameter after normalization, and its value range is 0-1. The value of P can be obtained through various methods. For example, measure the equivalent salt deposit density ESDD or the ash density NSDD on the insulator surface and perform normalization processing; extract the characteristic quantity of the leakage current on the insulator surface and map it to P; or determine the value of P based on the analysis results of the insulator surface image. The pollution level index P corresponds to the pollution area level, and the pollution area level is divided according to the equivalent salt deposit density ESDD as follows:

[0011] When ESDD ≤ 0.03 mg / cm², it is a Class I pollution area, corresponding to = 1.00;

[0012] When 0.03 mg / cm² < ESDD ≤ 0.06 mg / cm², it is a Class II pollution area, corresponding to = 0.85;

[0013] When 0.06 mg / cm² < ESDD ≤ 0.10 mg / cm², it is a Class III pollution area, corresponding to = 0.70;

[0014] When ESDD > 0.10 mg / cm², it is a Class IV pollution area, corresponding to = 0.55.

[0015] This solution allows multiple ways to determine the pollution level index P, including but not limited to measuring the equivalent salt deposit density ESDD or the ash density NSDD on the insulator surface and performing normalization processing; extracting the characteristic quantity of the leakage current on the insulator surface and mapping it to P; or determining the value of P based on the analysis results of the insulator surface image. This diversified data source method not only enriches the information collection means but also improves the adaptability to various complex working conditions. Compared with the traditional method that only relies on a single parameter, this solution provides a more comprehensive and flexible solution, which can better meet the diverse needs in practical engineering.

[0016] Calculate the pollution level correction coefficient : Based on the known pollution level index P, calculate the pollution level correction coefficient according to the following formula :

[0017]

[0018] where β is an empirically calibrated coefficient, and its usual value range is 0.3-0.5. For example, in a Class III pollution area, when the pollution level index P = 0.60 and the empirical coefficient β = 0.50, =0.70.

[0019] This scheme not only considers the differences in local electric field intensity, but also incorporates the pollution level index P of the area where the target insulator is located, and calculates the corresponding pollution level correction coefficient based on this. . The threshold decreases as the P-value increases, meaning the recognition threshold decreases at higher levels of contamination. This method fundamentally solves the problem of misjudgment that easily occurs under high pollution conditions with the traditional fixed threshold method. For example, preferably, in a Class III pollution zone, when P=0.60, the empirical coefficient β is set to 0.50. =0.70, at this point the corrected threshold Only the original base threshold 70%. This indicates that in highly polluted environments, by appropriately lowering the threshold standard, true zero-value insulators can be more accurately distinguished, greatly reducing the risk of misjudgment caused by environmental factors and improving the overall reliability of the detection.

[0020] Calculate the corrected zero-value recognition threshold : Using preset basic recognition thresholds and the previously calculated pollution level correction factor To calculate the corrected zero-value recognition threshold :

[0021]

[0022] Determine the insulator condition: If the calculated local electric field deviation rate Less than the corrected threshold If the value is zero, the insulator can be determined to be a zero-value insulator; otherwise, it can be determined to be a good insulator.

[0023] Equipment Installation and Calibration: The dual electric field probe can be installed on inspection robots, drones, or live-line testing devices, maintaining a consistent relative distance to the insulator surface during testing. Before identification, a corresponding electric field response database can be established based on the voltage level, insulator string type, and pollution level of the target transmission line, through on-site measurements, artificial pollution tests, or numerical simulations, for calibration. Or verify The effectiveness.

[0024] This plan emphasizes that before conducting identification, a corresponding electric field response database should be established based on the specific conditions of the target transmission line (such as voltage level, insulator string type, and pollution level) through methods such as field measurements, artificial pollution tests, or numerical simulations. This approach helps to accurately calibrate the basic identification threshold under different operating conditions. and verify The effectiveness of this assessment, particularly regarding the baseline identification threshold obtained through simulation or field calibration under clean or baseline soiled conditions. The insulator should be zero-value under these conditions. If the percentage falls within the 1.5% to 12% range, the insulator is intact. This results in a result within the 17% to 50% range. This fine-tuning process ensures the stability and consistency of the entire testing system during long-term operation, overcoming the problem of result fluctuations caused by the lack of targeted calibration in traditional methods.

[0025] Compared with the prior art, the technical effects and advantages of the present invention are as follows:

[0026] The zero-value insulator identification method based on pollution level correction (1) achieves accurate measurement of local electric field intensity differences through dual electric field probe design, thereby improving the accuracy of insulator status identification;

[0027] (2) By introducing a pollution level correction factor The calculation enables dynamic adjustment of the basic identification threshold under different polluted environments, effectively avoiding the occurrence of misjudgment.

[0028] (3) By comprehensively considering multiple ways to obtain the pollution level index P, the applicability and flexibility of the method are enhanced, and it can meet the needs of different application scenarios.

[0029] (4) By establishing an electric field response database, the basic identification threshold under specific working conditions was realized. Precise calibration and verification ensure long-term stability and consistency.

[0030] In summary, this technical solution can maintain a high accuracy rate in identifying zero-value insulators under different environments, including light pollution, medium pollution, heavy pollution, and extremely heavy pollution, significantly reducing the probability of false positives and false negatives. Compared with fixed threshold identification methods, it has better environmental adaptability and robustness. The algorithm has a clear structure and low computational cost, making it suitable for real-time execution in edge devices. It can provide reliable technical support for condition-based maintenance, defect early warning, and intelligent inspection of transmission lines. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0032] Figure 1 This is the mesh division result of the present invention;

[0033] Figure 2 This is a schematic diagram of the overall potential distribution (unit: kV) of the 220kV parallel insulator string of the present invention;

[0034] Figure 3 This is a schematic diagram of the local electric field distribution (unit: kV / m) of the 220kV parallel insulator string of the present invention;

[0035] Figure 4 This is a flowchart of a zero-value insulator identification method based on pollution level correction according to the present invention. Detailed Implementation

[0036] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0037] This embodiment provides, for example Figures 1 to 4 The method shown is a zero-value insulator identification method based on pollution level correction. This method comprehensively considers the pollution level of the target area, the insulator string type, the voltage level and the local electric field distribution characteristics. By combining dual-probe local electric field detection with pollution level correction mechanism, it can accurately identify zero-value insulators in complex environments.

[0038] In this embodiment, the pollution level of the target area for zero-value detection is determined: based on the natural and operating environment of the area where the target transmission line is located, the pollution level of the line to be tested is determined. The pollution level can be determined based on current power industry standards, line design data, operation and maintenance records, or on-site pollution detection results. The target area can be different types of areas such as coastal salt spray areas, industrial pollution areas, high-humidity mountainous areas, and ordinary inland areas. The pollution level reflects the degree of pollution that the insulator surface may receive in the operating environment of the target line and is an important basis for establishing subsequent pollution correction criteria. For areas with different pollution levels, the typical salt density, ash density level, moisture sensitivity, and flashover risk differences formed on the insulator surface during long-term operation should be considered.

[0039] In this embodiment, the insulator string type and voltage level are determined by collecting the structural and operational parameters of the insulator strings for the target transmission line, including: voltage level; insulator type; insulator string type; size of a single insulator piece; number of insulator pieces; string length; skirt spacing; installation direction and arrangement. The insulator string type can include different structural forms such as suspension insulator strings, tension insulator strings, double strings, and V-strings. The voltage level can include 110kV, 220kV, 500kV, 750kV, and ultra-high voltage levels. Different insulator string types and voltage levels result in differences in the surrounding electric field distribution, the field strength gradient under normal conditions, and the local abrupt change characteristics under zero-value conditions. Therefore, it is necessary to establish corresponding detection windows and basic criteria for specific insulator string types and voltage levels.

[0040] In this embodiment, electric field tests are conducted in the corresponding polluted areas: based on the determined pollution level, insulator string type and voltage level, local electric field tests or simulation calibrations are carried out under the corresponding operating conditions to obtain the electric field distribution law of this type of insulator under the corresponding pollution conditions.

[0041] The electric field test can be carried out in one or more of the following ways:

[0042] ① On-site measurement: On actual transmission lines or test lines, local electric field measurements are carried out on typical insulator strings to obtain electric field data under the intact state and the zero-value state;

[0043] ② Artificial pollution test: Simulate different pollution levels such as light pollution, medium pollution, heavy pollution and extremely heavy pollution on the test platform to conduct electric field tests on the insulator strings;

[0044] ③ Numerical simulation: Using electric field simulation software, insulator models with different pollution levels, different insulator string types, and different voltage levels are constructed to analyze the local electric field distribution characteristics at the dual probe locations.

[0045] The above tests were conducted to obtain the difference in local electric field response between intact insulators and zero-value insulators under the corresponding pollution level, providing a basis for subsequent correction of the zero-value judgment threshold.

[0046] In this embodiment, a dual-probe electric field measurement structure is constructed: two electric field probes are arranged axially on the outer side of the target insulator skirt surface, with a distance of 70mm to 125mm between the two probes, preferably 100mm. The dual probes can be installed on an inspection robot, a live-line testing device, or a drone platform, and their relative measurement distance to the insulator surface remains consistent to reduce geometric errors.

[0047] The local electric field intensities output by the dual probes are denoted as E1 and E2, respectively. Since the local electric field distribution in the region of the zero-value insulator typically undergoes significant abrupt changes, the dual-probe structure can effectively capture the abrupt changes and gradient anomalies in the local electric field curve. The detection window is preferably positioned near the skirt of a single insulator to achieve rapid local detection without requiring scanning each insulator section of the entire string.

[0048] Simulation of local electric field under normal operating conditions and selection of basic threshold: In order to determine the basic criteria for identifying zero-value insulators, a finite element calculation model of the target insulator string is first established under normal operating conditions, and the local electric field distribution characteristics of the dual-probe measuring points are extracted based on the simulation results, and then the basic identification threshold is selected.

[0049] In this embodiment, the design of "dual electric field probe spacing set according to voltage level" (110kV / 80mm, 220kV / 100mm, 500kV / 120mm) ensures that the probe spacing matches the scale of the electric field gradient distribution of the insulator string (principle: at high voltage levels, the insulator is longer and the shed spacing is larger, resulting in a smoother local electric field change, requiring a larger probe spacing to capture effective differences). This not only optimizes the sensitivity of the local electric field deviation rate η but also ensures the stability of the denominator in the deviation rate formula. If the probe spacing is too small, under high voltage... and The difference is slight, and η is easily affected by noise; if it is too large, it may span multiple insulators, introducing inter-string coupling errors. Therefore, this spacing setting not only improves the signal-to-noise ratio but also ensures that the calculated η falls within the defined effective discrimination range of 1.5% to 50%, realizing a closed-loop design of "hardware configuration - signal quality - threshold effectiveness," thus avoiding the unexpected effect of the entire recognition logic failing due to improper probe placement.

[0050] Specifically, a finite element method (FEM) model was established for 220kV transmission line insulator strings. The model focuses on analyzing the impact of zero-value insulators at different positions within the insulator string and variations in the number of zero-value insulators on the overall electric field distribution characteristics. In this embodiment, the influence of zero-value insulators on the local electric field distribution is mainly considered. Therefore, in the model, the iron caps and steel legs connected to the top and bottom of the zero-value insulators are coupled with potential degrees of freedom to simulate the conduction state after a significant decrease in insulation performance. The main dielectric parameters used in the model are shown in Table 1.

[0051] Table 1: Medium Parameters

[0052]

[0053] In this embodiment, a two-dimensional axisymmetric model is preferably used to approximate the actual three-dimensional electric field distribution during the modeling process, in order to reduce computational resource consumption while ensuring computational accuracy. The simulation region is preferably set to 5 times the outer dimension of the insulator string to reduce the impact of boundary effects on the simulation results. Zero-potential boundaries are used as boundary conditions to simulate the far-field environment; operating voltage is applied to the high-voltage end, and the low-voltage end is grounded. To improve the simulation accuracy of key parts, the mesh is locally refined in the contact area between the insulator and the fittings, preferably with the minimum element size controlled within 1 mm, while a gradually thickening mesh is used in areas far from the insulator. The mesh generation results are as follows: Figure 1 As shown.

[0054] Based on the above model, the overall potential distribution and local electric field distribution of the insulator string under normal operating conditions are simulated and analyzed. Figure 2 This is a diagram showing the overall potential distribution of a 220kV parallel insulator string. Figure 3 This is a local electric field distribution diagram of a 220kV parallel insulator string.

[0055] In this embodiment, by Figure 2 It can be seen that under normal operating conditions where there are no zero-value insulators in the insulator string, the overall potential of the insulator string gradually decreases along the string direction from the high-voltage end to the grounding end, and the overall potential distribution is stable. Figure 3 It can be seen that although the overall potential gradually decreases along the string direction, the local electric field distribution does not change uniformly. The electric field strength at both ends of the insulator string, that is, near the high voltage side and the grounding side, increases significantly. Especially at the connection between the steel foot and the steel cap, due to the changes in structural geometry and material dielectric properties, the local electric field is further concentrated, forming a region with a higher field strength.

[0056] In this embodiment, based on the simulation under normal operating conditions, local electric field data of the dual-probe measuring points are further extracted under the conditions of intact insulators and zero-value insulators, respectively. The corresponding deviation rates are calculated, and statistical analysis is performed on the simulation results and measured samples. The analysis results show that there is a significant difference in the local electric field deviation rate between intact and zero-value insulators: the deviation rate is generally higher under the intact condition, while the deviation rate is generally lower under the zero-value condition. Based on the deviation rate distribution range of the two types of samples, and taking the principle of minimizing the combined false positive rate and false negative rate, a basic identification threshold is selected.

[0057] Table 2: Referring to the following simulation and test data, we can see that:

[0058]

[0059] Under normal circumstances, η is typically in the range of 1.5% to 12% in the zero-value state;

[0060] Under normal circumstances, the percentage of intact units (η) is between 17% and 50%.

[0061] Therefore, basic criteria can be set under normal circumstances: .

[0062] In this embodiment, the deviation rate η is calculated.

[0063] The instantaneous electric field intensities measured by the dual probes are E1 and E2, respectively, and the expression for the deviation rate η is:

[0064]

[0065] in, The local electric field deviation rate of the dual probe is used to characterize the degree of anomaly in the local electric field gradient of the target insulator; The local electric field intensity is measured by the first electric field probe; The local electric field intensity is measured by the second electric field probe.

[0066] The deviation rate η is mainly used to reflect the degree of anomaly in the local electric field gradient. Under normal circumstances, the local electric field distribution near a zero-value insulator is significantly different from that of an intact insulator. Therefore, the deviation rate η can be used to construct a basic identification criterion.

[0067] Based on simulation and testing patterns, under baseline conditions: in the zero-value state, η is usually in the lower range; in the intact state, η is usually in the higher range.

[0068] Therefore, basic criteria can be preset under baseline soiling or clean conditions. This serves as the baseline threshold for subsequent corrective identification.

[0069] In this embodiment, the impact of insulator surface contamination level is analyzed: When salt, dust, industrial particles, and other contaminants adhere to the insulator surface, the contamination layer alters the electrical conductivity characteristics of the shed surface and the distribution of the electric field along the surface. Especially under conditions of humidity, condensation, fog, or light rain, the contaminants absorb moisture and form a wet contamination layer with a certain degree of conductivity, increasing the surface leakage current and further distorting the local electric field distribution.

[0070] Its main manifestations are: the overall horizontal shift of E1 and E2 measured by the probe; changes in the local electric field gradient distribution; and overall drift of the deviation rate η under different pollution levels.

[0071] In actual operation, different pollution levels can cause even intact insulators to exhibit electric field characteristics approaching an abnormal state. If a fixed criterion is still used for judgment in this case, the following problems may occur: heavily polluted intact insulators may be misjudged as zero-value insulators; lightly polluted zero-value insulators may be missed. Therefore, this embodiment introduces a pollution level correction mechanism to dynamically compensate for the deviation rate criterion.

[0072] In this embodiment, the design of "the pollution level index P can be obtained through image analysis, leakage current, and ESDD / NSDD multi-source fusion" enables the system to estimate the P value based on UAV visible light / infrared images even in remote lines lacking traditional pollution monitoring equipment (such as salt density meters) (principle: the pollution layer changes the surface optical properties and thermal distribution). This not only solves the problem of P availability but also unexpectedly triggers a deep collaborative design with the "inspection robot / UAV platform". When the UAV equipped with a vision sensor performs routine inspections, it can simultaneously complete P estimation and E1 and E2 measurements, achieving "one flight, dual diagnosis"—identifying both mechanical defects and assessing electrical condition. This multimodal data fusion capability upgrades this solution from a single electric field detection method to an intelligent comprehensive diagnostic process, achieving the additional effects of reducing operation and maintenance costs and improving inspection efficiency, far exceeding the traditional isolated judgment mode that relies solely on electric fields or pollution parameters.

[0073] In this embodiment, a pollution level correction coefficient is established and a zero-value judgment threshold is corrected:

[0074] 1. Definition of Correction Factor: Let P be the pollution level index of the insulator surface, then the pollution level correction factor Kpoll can be defined as:

[0075]

[0076] in, This is used to correct the basic identification threshold based on the degree of contamination on the insulator surface; P is the insulator surface contamination level index, preferably a normalized dimensionless parameter, with a value range of 0 to 1; β is an empirical coefficient, typically ranging from 0.3 to 0.5, used to characterize the degree of influence of the contamination level on the identification threshold; 1 is the baseline coefficient, the higher the contamination level, the higher the threshold value. The smaller.

[0077] 2. Revised Criterion

[0078] Original basic criteria Revised to:

[0079]

[0080] in, The zero-value identification threshold is the value after correction for the level of contamination. The basic identification threshold is a pre-set deviation rate criterion under baseline dirty or clean conditions. This is a correction factor for the level of pollution.

[0081] That is, the deviation rate η and the corrected recognition threshold By comparing different levels of contamination, adaptive judgment can be achieved.

[0082] In this embodiment, the national standard GB / T 26218.3—2011 "Selection and Size Determination of High Voltage Insulators for Use under Polluted Conditions Part 3: Porcelain and Glass Insulators for AC Systems" is followed. More importantly, the State Grid Corporation of China's enterprise standard Q / GDW 1168—2013 "Test Procedures for Condition-Based Maintenance of Transmission and Transformation Equipment" and subsequent updated versions (such as Q / GDW1168—2023) clearly adopt the "Class I to IV Pollution Zone" classification system and provide the corresponding equivalent salt density (ESDD) range. This system is still widely used in the power industry. The pollution zone classification is based on the general standards used in the power industry, using equivalent salt density (ESDD) as the criterion: Class I pollution zone (ESDD ≤ 0.03 mg / cm²), Class II pollution zone (0.03 < ESDD ≤ 0.06 mg / cm²), Class III pollution zone (0.06 < ESDD ≤ 0.10 mg / cm²), and Class IV pollution zone (ESDD > 0.10 mg / cm²). This classification method is consistent with the current operation and maintenance procedures of State Grid Q / GDW 1168, and is convenient for field application.

[0083] This correction mechanism can effectively solve the misjudgment problem caused by the overall drift of the deviation rate under different pollution levels.

[0084] In this embodiment, the following parameters are established to characterize the level of pollution:

[0085] 1. Characterization of equivalent salt density

[0086] The pollution level index P is obtained by detecting the equivalent salt density (ESDD) on the surface of the insulator.

[0087] 2. Gray density characterization

[0088] The degree of contamination is quantitatively characterized by detecting the NSDD (neutral dust density) on the surface of the insulator.

[0089] 3. Characterization of Leakage Current Characteristics

[0090] By measuring the leakage current signal on the surface of the insulator, characteristic quantities such as amplitude, root mean square value, pulse number, and harmonic components are extracted, and P is determined accordingly.

[0091] In this embodiment, the zero-value identification process and its flow are as follows: Figure 4 As shown:

[0092] Step S1: Acquire local electric field data

[0093] The detection device is moved to the target insulator skirt area, and the two probes simultaneously collect the electric field strengths E1 and E2.

[0094] Step S2: Calculate the deviation rate η

[0095]

[0096] Step S3: Detect the pollution level and obtain P. Determine the pollution level index P based on the equivalent salt density, ash density, leakage current characteristic quantity or surface image characteristics.

[0097] Step S4: Calculate the correction factor Kpoll

[0098]

[0099] Step S5: Update the deviation rate criterion

[0100]

[0101] Step S6: Determine if it is a zero-value insulator: η < If the value is zero, it is considered to be intact; otherwise, it is considered intact.

[0102] Example 1

[0103] This embodiment takes a suspension insulator string of a 220kV transmission line in a Class III pollution area in my country as an example to verify the feasibility and accuracy of the method for identifying zero-value insulators under different pollution levels proposed in this embodiment.

[0104] In this embodiment, the pollution level and insulator string parameters of the target area are determined: insulator strings of a 220kV transmission line in a Class III pollution area in my country are selected as the test objects. This area is affected by industrial dust, salt deposition and humid climate for a long time, and a relatively obvious pollution layer is easily formed on the surface of the insulators, exhibiting typical Class III pollution operation characteristics.

[0105] The structural and operational parameters of the target insulator string are obtained, including voltage level, insulator type, single-piece size, number of insulator pieces, string length, skirt spacing, and installation method. The selected object is a single-span suspension insulator string with a voltage level of 220kV. The detection window is set in the area near the skirt of a single insulator piece to accommodate dual electric field probes and collect local electric field data.

[0106] In this embodiment, a dual-probe local electric field detection model is constructed: two electric field probes are arranged axially on the outer side of the target insulator skirt surface, with a probe spacing of 100mm. The two probes simultaneously measure the local electric field intensity, denoted as E1 and E2 respectively. The dual probes are mounted on the end effector of a live-line inspection robot, maintaining a consistent relative measurement distance to the insulator surface to reduce geometric position errors.

[0107] In this embodiment, electric field testing under Class III pollution conditions is conducted: Based on the confirmed Class III pollution area, local electric field tests are performed on the target insulator strings under the corresponding pollution conditions. The test objects include insulators in good condition and insulators with zero pollution values. Local electric field characteristic data at the dual-probe measurement points are extracted using a combination of field testing and simulation calibration.

[0108] To obtain the identification threshold correction parameters under Level III pollution conditions, this embodiment further selects insulator samples of the same type, voltage level, and structural size, and conducts group tests under both the baseline clean condition and the Level III pollution condition. For each condition, dual-probe local electric field data of intact insulator samples and zero-value insulator samples are collected, and the corresponding deviation rate distribution is calculated to determine the optimal identification threshold that can balance the false positive rate and the false negative rate under that condition.

[0109] Test results show that under Class III pollution conditions, there are significant differences in the electric field distribution between intact insulators and zero-value insulators within the dual-probe detection window. The local electric field change is slower in the area corresponding to zero-value insulators, and the difference in electric field measured by the dual probes is smaller; the local electric field gradient is larger in the area corresponding to intact insulators, and the difference in probe output is relatively more obvious. Furthermore, compared to the baseline clean condition, the deviation rate of both types of samples shifts towards a lower value range under Class III pollution conditions.

[0110] In this embodiment, the deviation rate is calculated under Level III pollution conditions as follows: Based on the local electric field strengths E1 and E2 measured by the dual probes, the deviation rate η is constructed as a zero-value identification index, and its expression is as follows:

[0111]

[0112] In this embodiment, the local electric field test results of a selected insulator sheet are as follows:

[0113] (1) Under normal conditions, the first probe measures an electric field strength of E1 = 11.8 kV / m, and the second probe measures an electric field strength of E2 = 10.3 kV / m. The deviation rate is:

[0114]

[0115] (2) Under zero-value conditions, the first probe measures a field strength of E1 = 12.1 kV / m, and the second probe measures a field strength of E2 = 11.0 kV / m. The deviation rate is:

[0116]

[0117] Therefore, it can be seen that under Level III pollution conditions, the deviation rate under the zero-value state is still significantly lower than that under the good state, but compared with clean or lightly polluted conditions, its overall distribution has shifted to a certain extent.

[0118] In this embodiment, the pollution level correction coefficient and threshold correction for Level III pollution are as follows: For Level III pollution conditions, the pollution level index P of the target insulator surface is obtained. This index can be determined comprehensively based on the equivalent salt density ESDD, ash density NSDD, leakage current characteristics, or surface image characteristics. After normalization, in this embodiment, P = 0.60 and β = 0.50.

[0119] To avoid directly assigning correction coefficients empirically, this embodiment calibrates and obtains the basic threshold and the Level III pollution correction threshold. Specifically, under the baseline cleaning condition, insulator samples of the same type are tested, and the basic identification threshold under the baseline cleaning condition is determined by combining the distribution boundaries of the two types of samples:

[0120]

[0121] Under the conditions of P=0.60 and β=0.50, we can obtain:

[0122]

[0123] The optimal identification threshold for Level III pollution conditions is determined as follows:

[0124]

[0125] In this embodiment, simulation results are compared and zero-value identification is performed.

[0126] Due to (1) the deviation rate under intact condition:

[0127]

[0128] (2) Deviation rate under zero-value state:

[0129]

[0130] (3) Correction threshold under Level III pollution conditions:

[0131]

[0132] Therefore:

[0133] , , ,

[0134] This indicates that when a fixed threshold is used When making the judgment, both intact insulators and zero-value insulators meet the following conditions. In this case, intact insulators will be mistakenly identified as zero-value insulators.

[0135] When using the Level III fouling correction threshold proposed in this embodiment When making a judgment, the deviation rate of intact insulators is higher than the correction threshold and will not be misjudged; while the deviation rate of zero-value insulators is lower than the correction threshold and can still be correctly identified.

[0136] This demonstrates that, under Level III pollution conditions, the pollution level correction method proposed in this embodiment can effectively overcome the problem of fixed threshold criteria failing in complex environments. It avoids misjudging intact insulators and ensures the correct detection of zero-value insulators, thereby significantly improving identification reliability.

[0137] It should be noted that, in this document, relational terms such as "one" and "two" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0138] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for identifying zero-value insulators based on pollution level correction, characterized in that, It includes the following steps: S1: Obtain two local electric field intensity values ​​in the target insulator skirt region. and The and Arranged along the axial direction of the insulator with a spacing of The electric field was measured synchronously by the dual electric field probes; S2: According to the above and Calculate the local electric field deviation rate ; S3: Obtain the pollution level index P of the area where the target insulator is located, where P is a normalized dimensionless parameter with a value range of [value missing]. ; S4: Calculate the pollution level correction coefficient based on the pollution level index P. ,in It decreases as P increases; S5: Based on the preset basic recognition threshold and stated Calculate the corrected zero-value recognition threshold ; S6: If the deviation rate Less than the corrected threshold If the value is zero, the insulator is determined to be a zero-value insulator; otherwise, it is determined to be a good insulator.

2. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The local electric field deviation rate The calculation method is as follows: 。 3. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The pollution level correction factor Determined in the following manner: ， in, These are empirical calibration coefficients, with a range of values ​​of [value range missing]. .

4. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The pollution level index P is obtained by any of the following methods: Measure the equivalent salt deposit density ESDD on the insulator surface and normalize it; Measure the non-soluble deposit density NSDD on the insulator surface and normalize it; Extract the characteristic quantity of the leakage current on the insulator surface and map it to P; Determine P based on the analysis result of the pollution degree of the insulator surface image.

5. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The basic identification threshold The values ​​are obtained through simulation or actual measurement calibration under clean or baseline contamination conditions, and are chosen such that the insulator has a zero value under those conditions. fall into Section, intact insulator fall into Interval.

6. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The dual electric field probe is installed on an inspection robot, an unmanned aerial vehicle or a live detection device, and keeps the relative distance from the insulator surface consistent during detection.

7. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: The pollution level index P corresponds to the pollution area level, and the pollution area level is divided according to the equivalent salt deposit density ESDD as follows: When ESDD ≤ 0.03 mg / cm², it is a Class I pollution area, corresponding to Kpoll = 1.00; When 0.03 mg / cm² < ESDD ≤ 0.06 mg / cm², it is a Class II pollution area, corresponding to Kpoll = 0.85; When 0.06 mg / cm² < ESDD ≤ 0.10 mg / cm², it is a Class III pollution area, corresponding to Kpoll = 0.70; When ESDD > 0.10 mg / cm², it is a Class IV pollution area, corresponding to Kpoll = 0.

55.

8. A method for identifying zero-value insulators based on pollution level correction according to any one of claims 1-7, characterized in that: Before conducting identification, an electric field response database under corresponding operating conditions is established based on the voltage level, insulator string type, and pollution level of the target transmission line, through on-site measurements, artificial pollution tests, or numerical simulations, for calibration. Or verify The effectiveness.

9. The method for identifying zero-value insulators based on pollution level correction according to claim 8, characterized in that: The spacing of the dual electric field probe is set according to the voltage level of the transmission line: For 110 kV lines, the spacing is 70 mm to 90 mm; For 220 kV lines, the spacing is 95 mm to 110 mm; For 500 kV lines, the spacing is 115 mm to 125 mm.

10. The method for identifying zero-value insulators based on pollution level correction according to claim 1, characterized in that: In a Class III polluted area, when the pollutant level index Empirical coefficient hour, Corrected threshold Original base threshold of This helps avoid misclassifying intact insulators as zero-value insulators.

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