Non-uniform Pollution Research Articles

Simulation and Experimental Analysis of Electrical Characterization of Cap-Pin Glass Insulator under Uniform and Non-Uniform Pollution Layers

This paper deals with the analysis of the electrical performance of the glass cap-pin insulator under pollution conditions. The experiments are conducted in accordance with the IEC 60815 standard using artificial pollution (a distilled water mixture with NaCl). Several levels of applied voltage are used to evaluate the impact of both uniform and non-uniform pollution. For the same conditions, simulations are carried out using the COMSOL Multiphysics environment. Of interest, Leakage current waveforms are extracted from the current density and compared to those obtained from experiments. A proposed process, which aims to predict the effectiveness of the simulation in selecting appropriate parameters, geometry, boundaries etc., is investigated, where the findings are closely match the real model. Therefore, the electric field distribution on the insulator surface is presented, and 3D representations are considered for better visualizing the influence of the pollution on the insulating system. Accordingly, arcing discharges are characterized by high levels of electric field stress for uniform pollution, and dry-band arcing is simulated to correspond perfectly with laboratory findings for non-uniform pollution. Finally, this paper provides valuable insights into the electrical stress on the insulator under the effect of pollution conditions.

Quantifying Electric Charge on Cap-Pin Glass Insulator: Investigating the Impact of Pollution through Simulation and Experimental Approaches

The objective of this paper is to investigate the behavior of electric charges on cap-pin glass insulator under 50 Hz AC voltage. The study is conducted using COMSOL Multiphysics to understand the charge location, polarity, and parameters affecting their behavior. A 2D axisymmetric insulator design is used to visualize the overall charges on the insulating system (space charge) and along the insulating surface (surface charge density) under uniform and non-uniform pollution conditions. The research shows that the total charge accumulates over the surface area of the glass material. To quantify the amount of this charge, a simulation method based on using the surface integral of the electric displacement field over this area is introduced, which is supported by experimental tests. Comparing both simulation and experimental results provides insights into the simulation reliability and the parameters affinity used to those of the real model. Moreover, the simulation helps to identify the critical area where a high amount of charges is accumulated. The findings of this study are presented and examined.

Pollution Accumulation Simulation of Composite Insulators in Western Inner Mongolia

To study the effect of pollution accumulation on flashover voltage for composite insulators in western Inner Mongolia, COMSOL software was used to simulate the impact of non-uniform pollution deposition, different particle sizes, varying pollution severity levels, and different wind directions on the amount of accumulated pollution and the flashover voltage of composite insulators. The results indicate that after passing through the composite insulator, pollution particles accumulate to varying degrees on the surface, mainly concentrated at the edges of the insulator shed and the ridges of the skirt. The larger the particle size, the more pollutants accumulate on the composite insulator, which leads to a higher degree of distortion in the surface electric field. The accumulation of pollutants under oblique wind conditions is higher than that under horizontal wind conditions, and the lower skirt position of composite insulators is more prone to accumulation. The non-uniform distribution of pollution on composite insulators leads to an uneven distribution of the surface electric field upon energization, thus reducing the flashover voltage of the composite insulator and making it more susceptible to flashover incidents.

Segmented superimposed model of near-bore reservoir pollution skin factor for low porosity and permeability sandstone horizontal gas wells

Drilling and completion processes can often result in reservoir contamination around the wellbore, leading to decreased oil and gas productivity and significant economic losses for the oil field. This issue is particularly complex in sandstone reservoirs with low porosity and permeability horizontal wells, wherein traditional models have limited accuracy and applicability due to numerous unknown parameters. To address this challenge, this study focuses on non-uniform pollution around horizontal wells and proposes a new approach to divide the horizontal well pollution area into N micro-element sections. By establishing a seepage differential equation and employing the similar flow substitution method, we construct models for the pollution skin coefficient of each micro-element section as well as the total pollution skin coefficient. Furthermore, we combine empirical equation models and an oscillation-decreasing function model to develop a pollution radius distribution model that encompasses linear, parabolic, exponential, and logarithmic patterns. Through these advancements, we can realize a comprehensive reservoir damage assessment method. It is verified that the calculation error of this model is very small, and the influence of skin effect and reservoir anisotropy and the radius distribution of various heterogeneous pollution zones are fully considered. These findings indirectly suggest the rationality and practicality of the model presented in this paper. By incorporating actual gas well data into this model, it has been determined through discussion and analysis that the exponential distribution of the pollution radius has the greatest impact on the pollution skin factor along the horizontal well, from the heel to the toe. Increasing the pollution radius and decreasing the pollution permeability both result in an increase in the skin factor of the micro-segment and the total pollution skin factor of the horizontal well. However, compared to the pollution permeability, the radius of the pollution zone has a relatively minor effect on the total pollution skin factor. The proposed technique aims to serve as a valuable tool in optimizing and designing stimulation measures aimed at boosting production and minimizing formation damage. Through evaluation and analysis to reduce risks, protect reservoirs and extend well life, reduce costs, and enhance technical capabilities and economic benefits.

Electrical Performance Study of 11kV Coated Porcelain, Coated Glass, and Polymer Outdoor High Voltage Insulators

The study in this paper investigates how contaminations and different types of pollutants affect the electrical performance of outdoor coated porcelain, coated glass, and composite insulators when subjected to an 11 kV AC voltage. The ceramic insulators (porcelain and glass) coating layer is assumed to be RTV silicon rubber material with a 0.5 mm thickness. The effect of these three pollution cases on the electrical performance were investigated using a commercial software called COMSOL Multiphysics based on the finite element method (FEM). The three pollution cases were uniform, non-uniform pollution, and water droplets. In the uniform pollution condition, the pollution layer over the surface of the insulators was assumed to be 0.5 mm; however, in non-uniform pollution condition, water patches with a thickness varying from 0.5 to 1.5 mm was used. In water droplets condition, hemispherical shapes were used to model water droplets with a diameter of 1 mm. Voltage, electrical field distributions, and dissipated power were computed along the creepage distance of the three insulators models. The simulation results indicated that for the uniform case, the lowest electrical field appeared on the silicon rubber insulator. For the non-uniform case, the electrical field distribution became more non-uniform for the three models. In the water droplets case, more fluctuations appeared in the metal end fittings where the water droplets were located. The analysis indicated that the maximum dissipated power was found to be for the coated glass. The obtained results showed that the silicon rubber insulator offered better performance compared with coated porcelain and glass. Coated porcelain offered better performance compared with the coated glass insulator.

Switching Impulse Flashover Performance of Nonuniform Pollution Insulators in Natural Environment

Under natural conditions, insulators show a nonuniform pollution state, which has a great influence on the switching impulse flashover voltage of insulators. Meanwhile, the insulation level of transmission lines is selected according to the switching impulse flashover voltage of nonuniform pollution insulators. For this purpose, in this article, the wet pollution method is used to simulate nonuniform pollution conditions. Then, the switching impulse flashover tests and the switching impulse flashover tests with preloading ac voltage are conducted on two types of insulators, XP-70 and LXY-70, in natural environment. The flashover voltage of insulators is obtained, flashover performances are analyzed, and the flashover processes of insulators are photographed. Moreover, the equations of flashover voltage gradient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{{50}}$ </tex-math></inline-formula> under nonuniform pollution conditions are established. The results indicate that there is a conspicuous polarity effect and a polarity reversal phenomenon under different conditions. Besides, as the increase of the ratio of bottom surface pollution to top surface pollution, the flashover voltage changes in the opposite case of preloading and non-preloading ac voltage. Finally, the switching impulse flashover voltage of ordinary porcelain and glass suspension insulators under nonuniform pollution conditions can be calculated based on the established equations of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{{50}}$ </tex-math></inline-formula> . The results can provide theoretical support for the reasonable selection of the insulation level of transmission lines, which in turn can greatly reduce the cost of the transmission lines.

Simulation based electric stress estimation on silicone rubber polymeric insulators under multi-environmental conditions

Polymeric insulators lack intermediate metal elements, resulting in non-uniform electric fields along their surface, which are further exacerbated by environmental stresses such as pollution and moisture. Researchers focused on determining the critical stresses in the polymeric insulator, paying particular attention to uniform pollution and moisture. There are, however, few studies that investigate non-uniform pollution and combinations of environmental stresses, which could influence electric field distributions. In this work, complex multi-stress environmental conditions are modeled and simulated considering pollution of different thicknesses and conductivities, water droplets of different shapes and sizes, and dry bands of varying widths and locations. This paper analyzes an 11 kV polymeric insulator's potential and electric field distribution using finite element simulations, which can be applied to any high voltage insulator under the aforementioned contaminated conditions.

The Effect of Non-uniform Pollution on the Field Distributions of Insulator String

The Effect of Non-uniform Pollution on the Field Distributions of Insulator String

Flashover voltage of porcelain insulator under various pollution distributions: Experiment and modeling

The current work investigates the flashover voltage of an 11 kV porcelain insulator against changes in the location of the dry band, salt deposit density, humidity, non-uniform pollution degree, and polluted surface area. Generally, the flashover voltage of the polluted insulator dropped sharply compared to that of the clean insulator. Specifically, under salt deposit density (SDD) of 0.03 mg/cm2, the flashover voltages of scenarios A (full pollution), B (dry band 1), C (dry band 2), and D (dry band 3) decrease by 26%, 19%, 10%, and 2%, respectively, compared to 43.70 kV flashover voltage of the clean insulator. With an increase in SDD, the flashover voltage under all scenarios decreases steadily, with the median flashover voltage of scenario A being the lowest at 17.52 kV. The flashover voltage under all scenarios also varies with changes in the humidity level, non-uniform pollution degree and polluted surface area. Subsequently, an artificial neural network (ANN) and fuzzy logic (FL) hybrid model is proposed to predict the flashover voltage and condition of the insulator, where the model successfully yields the insulator condition index between 0 and 100% to indicate the pollution severity of the insulator.

FEM analysis of electric field distribution for polymeric insulator under different configuration of non-uniform pollution

Considering the extensive use of high voltage insulators, the reliable performance of insulators is challenged by various weather conditions such as pollution. According to recent researches under unidirectional wind, polymeric insulators are mostly exposed to non-uniform fan-shaped pollution. In many contamination patterns, the internal surface is covered with higher contamination than the external surface, and the non-uniform contamination shape on the insulator is similar to a ring-shape. In this paper, two conventional types of non-uniform pollution known as fan-shaped and ring-shaped are modeled for a 20 kV polymeric insulator, and a comparison is made in terms of the electric field between the two configurations using different thicknesses and electrical conductivity of the pollution layer. The electric field, during the arc length of the insulator, is studied under clean conditions, uniform contamination, and two types of non-uniform contamination. In addition, the effect of various thicknesses and conductivity of the pollution layer on the electric field distribution of this polymeric insulator is analyzed. The results show that the electric field distribution in non-uniform ring-shaped pollution is much more effective than the fan-shaped type by changing the thickness of the contamination layer. Moreover, ring-shaped pollution has a more uniform field distribution with fewer thicknesses of contamination layer.

Recognition of pollution layer location in 11 kV polymer insulators used in smart power grid using dual-input VGG Convolutional Neural Network

This paper portrays the application of a Partial Discharge (PD) signal combined with the dual-input VGG Convolution Neural Network (CNN) to predict the location of the pollution layer on 11 kV polymer insulators subjected to alternating current for smart grid applications. First, a non-uniform pollution layer artificially created for HV insulator with three straight shed ball end fitting in a laboratory setup and corresponding PD readings are measured. The wavelet transform is employed to represent the measured PD signal as scalogram patterns. In general CNN uses a single input pattern for feature extraction. If the pattern quality is low, it is easy to cause misclassification. Hence in this proposed work, the feature fusion of a dual-input Visual Geometry Group (VGG) based CNN is used for the classification of contamination layer. VGG 19 is a pretrained deep learning network used for extracting the rich features from the patterns. In continuation to that, hyperparameter (HP) play a vital role in deep learning algorithms because they directly manage the behaviours of training algorithms and have a significant effect on the performance of deep learning models. Hence, Bayesian Optimization (BO) is used for tuning the HP. At last, to check the practicality of the proposed algorithm, a new dataset is created for 11 kV polymer insulator with three alternate shed clevis end fitting and different pollution levels—acceptable results obtained by using dual-input CNN with the minimum quantity of data.

Experimental-based models for predicting the flashover voltage of polluted SiR insulators using leakage current characteristics

This study aims to predict the flashover voltage (FOV) of silicone rubber (SiR) insulators. Accordingly, it benefits from two methods, including an artificial neural network (ANN) model and a FOV gradient fitting model. The FOV and leakage current (LC) tests are carried out on one un-aged and three aged specimens under uniform and longitudinal non-uniform pollution circumstances. The proposed ANN model is designed based on equivalent salt deposit density (ESDD), pollution non-uniformity degree, aging time, LC first harmonic magnitude I 1 , and total harmonic distortion. Furthermore, a FOV gradient model is proposed based on ESDD, I 1 , and creepage distance. To validate the proposed models, the FOV and LC tests are conducted on two different types of SiR insulators. Then, the predicted FOV from the ANN model and calculated FOV from the voltage gradient model are obtained. The results indicate that the relative errors of the ANN model and FOV gradient fitting model are &lt;6.4 and 7.3%, respectively.

Assessing the distribution of air pollution health risks within cities: a neighborhood-scale analysis leveraging high resolution datasets in the Bay Area, California.

Background: Air pollution-attributable disease burdens are typically reported at country, state, or county levels, masking potential smaller scale geographic heterogeneity driven by non-uniform pollution levels and disease rates. Estimating the variation in air pollution health impacts within cities is now possible with high resolution pollutant concentrations derived from satellite remote sensing, modeling, and mobile monitoring. Objectives: We quantify neighborhood-level variation in air pollution health risks, using highly spatially resolved pollutant and disease rate datasets available for the Bay Area, California. Methods: We estimate mortality and morbidity attributable to nitrogen dioxide (NO2), black carbon (BC), and fine particulate matter (PM2.5) in the Bay Area using epidemiologically derived health impact functions. We compare geographic distributions of pollution-attributable risk estimates using pollutant concentrations from different sources: (1) mobile monitoring of NO2 and BC, covering roadways over a one-year period; and (2) models predicting annual NO2, BC and PM2.5 concentrations from land use variables and satellite observations, with full spatial coverage. We also compare the application of county versus census block group (CBG) level disease rates. Results: Across Bay Area counties, estimated pollution-attributable mortality rates (attributable deaths per 100,000 people) ranged by a factor 15, 13 and 8 for NO2, BC and PM2.5 (NO2 range=40-570, median=219; BC range=3-40, median=13; PM2.5 range=60-470, median=305). Applying concentrations from mobile monitoring and land use regression datasets resulted in similar spatial patterns of estimated NO2-attributable mortality rates, though the mobile monitoring concentrations yielded more spatial heterogeneity. Using CBG disease rates revealed spatial heterogeneity in estimated NO2 and PM2.5-attributable mortality rates that is masked when using county-level disease rates. Discussion: Estimated air pollutant attributable health burdens vary considerably between neighborhoods in the Bay Area, driven by spatial heterogeneity in both concentrations and disease rates. Future research should test the generalizability of these findings for other cities.

Experimental investigation on composite insulators AC flashover performance with fan-shaped non-uniform pollution under electro-thermal stress

Pollution deposition along with ultraviolet (UV) radiation and electro-thermal stress cause the composite insulators to face with critical conditions. The type of pollution which settles on insulators is not only uniform but also it can be non-uniform and uneven. In this study, the results of the uniform and fan-shaped non-uniform (FSNU) pollution tests on four various types of virgin and aged polymeric insulators under AC voltage are presented. To find the effects of accelerated aging on polymer chains of composite insulators, scanning electron microscopy (SEM) is carried out. Based on IEC 60507, the solid layer method is applied to settle pollution on the insulator surface. The results demonstrate that the flashover voltage of virgin and also aged samples decreased when pollution non-uniformity degree (J) increases from 1 to 13. The flashover voltage of studied insulators is reduced by increasing the occupation ratio (K). However, the impact of K was lesser than J on flashover voltage of the polymeric insulators. Investigated polymeric insulators have been aged up to six weeks (1000 h). Although the influence of two weeks (333 h) accelerated aging on flashover voltage and morphology of the composite insulators was not tangible, therefore flashover strength of the samples is decreased while the aging period time increases. Statistical analysis has been done to estimate the flashover voltage of accelerated aged composite insulators under uniform and FSNU pollution based on virgin insulators. The research aimed to select insulators in windy and sunny areas.

DC pollution flashover performance of HVDC composite insulator under different non-uniform pollution conditions

The non-uniform air flow field and electrical field distributing around insulators cause uneven deposition of pollution particles on different positions and parts of the insulator surfaces. Pollution-induced flashover is a serious threat to the safe operation of the power system, and non-uniform pollution distribution has great influence on flashover voltage of insulators. Towards this, in this study, the solid layer method was used to simulate different non-uniform pollution conditions. Then, DC pollution flashover tests of composite insulators were carried out and the flashover performances were analyzed. The results indicated that the increase of KL/W (from 1 to 15) decreased U50 by 27–32%. While the increase of KT/B (from 1 to 10) increased U50 by 35%, and the increase of KH/M (from 1 to 4) increased U50 by 25%. Where KL/W, KT/B and KH/M are the SDD (salt deposit density) ratio of windward to leeward side, top to bottom surface and high voltage to middle group respectively. Besides, higher proportion of leeward side area will reduce U50. U50 and SDD are still in agreement with the negative power function relationship, non-uniform pollution conditions have great effect on a (constant of power function), but less impact on n (characteristic index of power function). Finally, equations for calculating different non-uniform pollution flashover voltages were established and validated, also the relative errors are acceptable. The results are very important for guiding insulation design and anti-pollution works of operating transmission lines.

Transient Electric Field Analysis for Polluted Composite Insulators Under HVDC Stress

The present investigation highlights simulation study performed considering the temporal transformation of the electric field from capacitive to resistive. The effect of uniform pollution, single dry-band, multiple dry-bands and non-uniform pollution are studied in detail. The simulation results indicate the effect of surface current can literally decrease the voltage withstand capability of the insulator. The simulations are carried out under time domain so that the simplicity and the physical integrity of the problem is retained. Experimental investigations are conducted to verify the obtained theoretical results. Investigations show that there is substantial decrement of scintillation inception voltage with time, further experimental observations are explained based on the theoretical results that have been derived. Based on the theoretical and experimental observations, it is thought that proper insulation design and optimal creepage should be provided under DC, as field distribution can change over a period with increasing surface conductivity.

Analysis of leakage current characteristics during aging process of SiR insulator under uniform and longitudinal non-uniform pollution conditions

This paper presents the comprehensive analysis of Leakage Current (LC) of a silicone rubber insulator under uniform and longitudinal non-uniform pollution conditions based on a large amount of test data. The experimental tests are carried out under different humidity levels for un-aged and aged samples. The results obtained indicate that the LC harmonics magnitudes increase with increasing the salt deposit density, aging time, and humidity, while they decrease with increasing the pollution non-uniformity degree. The analysis of phase angle difference between LC and applied voltage (θI-V°) demonstrates that the θI-V° is in the range of 54.3°–60.4°, 20.1°–32.5°, and 7.5°–11.8° under clean condition, light pollution and moderate pollution conditions, respectively. In addition, the θI-V° is less than 2.3° under heavy pollution condition. The non-uniformity of pollution distribution and insulator aging time have very little effect on the θI-V°, while the increase of humidity leads to a slight decrease in the θI-V°.

Flash-over voltage prediction of silicone rubber insulators under longitudinal and fan-shaped non-uniform pollution conditions

This paper proposes an Artificial Neural Network (ANN) model for AC flash-over voltage prediction of Silicone Rubber (SiR) insulators based on the experimental tests. In flash-over tests, the flash-over voltages of four different types of SiR insulators are measured under the uniform, longitudinal non-uniform, fan-shaped non-uniform and combined longitudinal, and fan-shaped non-uniform pollution conditions. The proposed ANN model is designed with six inputs data (insulator geometry and pollution parameters) and one output data (flash-over voltage). In order to validate the model, three different types of SiR insulators are tested under different pollution conditions. Then, their flash-over voltages are predicted using the proposed ANN model. The validation of the model shows that the absolute values of relative errors between flash-over voltages of test and prediction are less than 6%. This indicates a high efficiency of ANN technique in the flash-over voltage prediction of SiR insulators.

DC Flashover Dynamic Model of Post Insulator under Non-Uniform Pollution between Windward and Leeward Sides

Experience shows that under unidirectional wind or certain terrain, the surface of post insulators is non-uniformly polluted between windward and leeward sides, which affects the flashover characteristics. In this paper, a formulation of residual pollution layer resistance was proposed under this non-uniformity and a typical post insulator was taken as an example to analyze and calculate its residual resistance. The theoretical resistance was verified by numerical simulations using COMSOL Multiphysics. The proposed resistance formulation was then implemented in a DC flashover dynamic model to determine the flashover voltage (Ucal), which was validated by artificial flashover tests. Then the factors affecting DC flashover voltage were analyzed. Research results indicate that: the residual resistance formulation agrees well with simulation results, especially when the arc length exceeds 70% of the leakage distance. The good concordance between theoretical and experimental flashover voltages with most relative error within ±10%, validates the flashover model and its residual resistance formulation. Ucal gets impaired under this non-uniformity. The degree of reduction is related to salt deposit density ratio (m) of windward to leeward side and leeward side area proportion (k).

Investigation and analysis of AC flashover voltage of SiR insulators under longitudinal and fan-shaped non-uniform pollutions

The pollution non-uniformity in the axial and circumferential directions of insulator surface has a great impact on the ac flashover voltage. So far, few studies have been conducted about the flashover voltage performance of Silicone Rubber (SiR) insulators under fan-shaped and longitudinal non-uniform pollutions. Therefore, this paper aimed to investigate the effects of longitudinal non-uniform, fan-shaped non-uniform, and combined longitudinal and fan-shaped non-uniform pollutions on the ac flashover voltage of four different types of SiR insulators. The analysis of experimental results indicated that longitudinal and fan-shaped non-uniform pollutions compared to uniform pollution contributed to an increase and a decrease in the ac flashover voltage, respectively. The ac flashover voltage increases with the increment of longitudinal non-uniformity degree and decreases with the increment of fan-shaped non-uniformity degree. Furthermore, a new correction factor of flashover voltage under combined longitudinal and fan-shaped non-uniform pollutions has been proposed. For all types of insulators, the correction factor under different non-uniform pollution conditions ranges from 0.85 to 1.13.