Non-soluble Deposit Density Research Articles

Simulation and experimental research on laser cleaning of glass insulators

The pollution flashover of glass insulators can be effectively mitigated through regular or irregular cleaning. However, the existing cleaning methods are difficult to popularize on a large scale due to labour intensive, high cost or low safety. The effectiveness and safety of laser cleaning on glass insulators has been analyzed in this paper. A number of artificial contaminated and clean glass insulators are tested. By measuring the equivalent salt deposit density (ESDD) and the non-soluble deposit density (NSDD) before and after cleaning, laser cleaning can reduce both of them to different degrees. The main factors affecting the maximum temperature of the contamination layer include the class of pollution, laser power and scanning velocity during laser cleaning. When addressing pollution levels above class b, by employing a laser scanning velocity of 8 m/s and adjusting the laser power within the range of 80–200 W, the pollution class after laser cleaning reduces effectively to class b or lower. To verify the safety of laser cleaning, simulations and experimental analyses are carried out. The result demonstrates that sufficient safety can be satisfied when laser cleaning is applied to clean glass insulators.

Analysis of Natural Pollution Accumulation Characteristics of Insulators for Railroads in High-Altitude Environment

Railway system insulators are affected by pollution, altitude, and other environmental situations during operation, which causes reduced electrical performance or even flashover accidents. These factors threaten the safety of railway operations in high-altitude areas. However, the natural contamination characteristics of a railroad in a plateau area is still unclear. In this study, a natural pollution accumulation test for railway insulators in a high-altitude area was carried out, and the distribution rules of nonsoluble deposit density (NSDD), equivalent salt deposit density (ESDD), NSDD/ESDD ratio, and nonuniformity (T/B) of the pollution distribution of the tested insulators were calculated. Meanwhile, the chemical compositions of the pollution from different test sites were analyzed. The differences of pollution accumulation between railway insulators and suspended insulators of a power system and the influencing factors were compared and analyzed by combining with a numerical simulation. The results show that the pollution level of railroad insulators is mainly distributed in level b and above. A pollution sample is mainly composed of sodium chloride, while the NSDD/ESDD ratio of pollution is mostly distributed from 0 to 5, with T/B value ranges from 1/0.62 to 1/1.76. The amount of insulator contamination is influenced by the location inside and outside the tunnel. Additionally, the pollution amount is influenced by the structure and type of insulators. Finally, this paper studies the creepage distance and structural height required by railway insulators in a plateau area according to the natural pollution accumulation characteristics of railway insulators, which can provide a reference for a railway electrical external insulation configuration in a high-altitude area.

Experimental Analysis of Ceramic Insulators with Different Profiles Under Very High Pollution Zone by Solid Layer Method

The outdoor insulators in service are exposed to marine, agricultural waste and industrial pollution. These pollutants get deposited on the insulator surface and lead to flashovers under fog conditions. There has been an abnormal increase in pollution levels due to rapid industrialization in the past two decades. This exponential increase in pollution levels causes frequent flashovers of insulators, leading to the tripping of transmission lines consecutively may result in blackouts, which severely affects the reliability of the power systems. The ESDD and NSDD measurement on the insulator surface are critical parameters for determining the pollution severity levels. This paper discusses ESDD and NSDD measurement procedures. In this paper, field pollution severity has been simulated in the Artificial Pollution Lab. In addition, the Non-Soluble Deposit Density (NSDD) component of pollutants for designing the creepage distance of ceramic insulators under heavy pollution conditions has been emphasized.

The Characteristic Analysis of ESDD and NSDD Detection of Composite Insulators Based on Hyperspectral Technology

Pollution flashover of insulators has been viewed as a common issue existing in the area of power systems for a long term. However, traditional detection methods such as equivalent salt density and leakage current (LC) can hardly satisfy the requirements of the progressing smart grid. Herein, a novel highly-efficient method is proposed for classifying the pollution degree detection of insulators based on hyperspectral technology. The insulating sheets and actual insulators were set as the research object and their hyperspectral images are obtained. Moreover, the data for describing the characteristic wavelengths and the G color components of the samples were extracted from the images as the characterization of the equivalent salt deposit density (ESDD) and nonsoluble deposit density (NSDD) respectively. The ESDD and NSDD detection model is established based on the multiple linear regression (MLR) algorithm and the random forest (RF) algorithm. Ultimately, the proposed model reaches a detection accuracy of above 84% on the insulating sheets and 75% on the actual insulators, which can be viewed as acceptable. The hyperspectral imaging technique has considerable potential for the non-contact detection of ESDD and NSDD.

Leakage current characteristics in estimating insulator reliability: experimental investigation and analysis

The monitoring of leakage current (LC) and voltage characteristics in transmission line insulators is regarded as a good technique for anticipating the physical state of in-service insulators. In the current work, the temporal and frequency characteristics of LC and voltage under various situations were derived for assessing the health condition of porcelain, glass, and silicone rubber insulators. The contamination severity indicated by soluble deposit density, wetting level (Wt), non-soluble deposit density, and uneven pollution distribution (Pu/PL) were chosen as the environmental factors that impact the insulators. Six criteria were utilized to evaluate the physical state of the insulators, with four of those derived from the LC signal in the time domain, namely, the LC signal peak (C1), the phase shift between applied voltage and LC (C2), the LC signal slope between two consecutive peaks (C3), and the crest factor (C4). The remaining two indices, namely, the total harmonics distribution (C5) and the harmonics ratio indicator (C6), were obtained from the frequency domain of the LC signal. In addition, the flashover voltage index (C7) was also employed. The LC indicators were then classified based on the laboratory test results to reflect the physical state of the insulators. The findings revealed that the proposed indicators had an important impact in determining the physical state of the insulators. Furthermore, a confusion matrix was created for the test and prediction data using the suggested indicators to determine the effectiveness of each indicator.

Polymeric Insulator Conditions Estimation by Using Leakage Current Characteristics Based on Simulation and Experimental Investigation.

The current work contributes an estimate of the time-frequency characteristics of a leakage current in assessing the health condition of a polluted polymeric insulator. A 33 kV polymer insulator string was subjected to a series of laboratory tests under a range of environmental conditions, including pollution, wetting rate (WR), non-soluble deposit density (NSDD), and non-uniform distribution pollution (FT/B). The temporal and frequency features of the leakage current were then extracted and used as assessment indicators for insulator conditions based on laboratory test findings. Two indices were generated from the leakage current waveform in the time domain: the curve slope index (F1), which is determined by measuring the inclination of the curve between two successive time peaks of the leakage current, and the crest factor indicator (F2). The frequency domain of the leakage current signal was used to calculate the other two indices. These are the odd harmonic indicators derived from the odd frequency harmonics of the leakage current up to the 9th component (F3) and the 5th to 3rd harmonics ratio (F4). The findings showed that the suggested indicators were capable of evaluating insulator conditions. Finally, the confusion matrix for the experimental and prediction results obtained with the proposed indices was used to assess which indicator performed the best. Therefore, the analysis suggests an alternative and effective method for estimating the health condition of a polluted insulator through leakage current characteristics obtained in the time and frequency domains.

An Improved Dynamic Multi-Arcs Modeling Approach for Pollution Flashover of Silicone Rubber Insulator

This article presents a dynamic modeling approach to analyze pollution flashover of silicone rubber insulators. Pre-flashover conditions can be used to represent analytical formulations for different stages of dry band arcing activities on the surface of polluted insulator. In this article, effects of dust deposit as nonsoluble deposit density (NSDD) are investigated on the dynamic behavior of partial arcs on the surface of insulators by means of a proposed multi-arcs modeling approach. It is shown that analytical formulations of dynamic resistance of surface pollution can be used to analyze different modes of arcing as unstable and stable. Real data of leakage current (LC) and flashover voltage (FOV) of polluted insulator are used to make correlation with analytical multi-arcs formulations. The proposed analytical multi-arcs model is based on an artificial neural network (ANN) which is able to predict the LC and FOV of the insulator in real-time monitoring. In addition, effects of pollution resistance as variable surface conduction and thickness of pollution layer are investigated on LC and FOV of the insulators. It is shown that the proposed multi-arcs representation has a closer correlation with real testing data in comparison to previous single-arc and multi-arcs models.

Research on Flashover Voltage Prediction of Catenary Insulator Based on CaSO4 Pollution with Different Mass Fraction

Pollution flashover accidents occur frequently in railway OCS in saline-alkali areas. To accurately predict the pollution flashover voltage of insulators, a pollution flashover warning should be made in advance. According to the operating environment of insulators along the Qinghai-Tibet railway, the pollution flashover experiments were designed for the cantilever composite insulator FQBG-25/12. Through the experiments, the flashover voltage under the influence of soluble contaminant density (SCD) of different pollution components, non-soluble deposit density (NSDD), temperature (T), and atmospheric pressure (P) was obtained. On this basis, the GA-BP neural network prediction model was established. P, SCD, NSDD, CaSO4 mass fraction (w(CaSO4)), and T were taken as input parameters, 50% flashover voltage (U50%) of the insulator was taken as output parameters. The results showed that the prediction deviation was less than 10%, which meets the basic engineering requirements. The results could not only provide early warning for the anti-pollution flashover work of the railway power supply department, but also be used as an auxiliary contrast to verify the accuracy of the results of the experiments, and provide a theoretical basis for the classification of pollution levels in different regions.

A Study of the Cleansing Effect of Precipitation and Wind on Polluted Outdoor High Voltage Glass Cap and Pin Insulator

In this work, the extent of natural cleansing effect of rainfall, wind and fog or a combination of these on an insulator string were investigated. Results showed that pollution losses progress with time, with a considerable fraction of losses occurring within 15 minutes of testing. While wind alone played little or no role in surface cleansing, it increases the extent of cleansing by rainfall. The topsides of insulators were found to be more affected by natural cleansing compared to the underside. Equivalent Salt Deposit Density (ESDD) and Non-Soluble Deposit Density (NSDD) measurements were carried out. ESDD was found to be higher in the lower disc irrespective of the weather condition the insulator string has been subjected to. NSDD measurements established no pattern on how natural cleansing was impacted by disc position on a string, demonstrating the random nature of pollution-cleansing cycle of outdoor insulators. Insulator performance was assessed by high voltage AC tests and monitoring of partial discharge events using Radio Frequency antennas and a High Frequency Current Transformer (HFCT). Measured output by the HFCT showed that leakage current decreases uniformly with time, and the speed at which this occurs is an indication of the intensity of natural cleansing activity.

Wind tunnel experiments on the pollution characteristics of suspension insulators in an ion flow field

Contamination particles in the air are charged by the ion flow field around a DC corona discharge wire. The electric force acting on the charged particle is associated with the ion flow field and affects the particle deposition on insulators. In this study, the pollution characteristics of the porcelain insulators in an ion flow field were investigated by pollution experiments in a wind tunnel. The conductor wire was applied a higher DC voltage than the corona onset voltage and connected to a test insulator string. As the test parameters, the DC voltage was variable, the contamination particle diameter was set at 20 μm, and the wind speed was 2 m/s. The nonsoluble deposit density (NSDD) and its distribution on test insulators were measured, compared, and analyzed. The relationship was discussed between insulator pollution characteristics, the electric force on dust particles, and the ion flow field. The pollution characteristics revealed that the pollution on the upper part of the string increased with the test voltage and corona current. The non-uniformity of pollution along the string and on the upper/lower insulator surfaces also increased. However, the non-uniformity of pollution on the windward/leeward of the insulators decreased. The discussions indicated that the spatial ion flow field around the conductor affected dust motion when the dust was away from the insulator. The direction and magnitude of the electric force on the charged particles impacted the pollution distribution. The pollution level of the strings in the unenergized test was considerably lower than that in energized tests. The pollution level could be reduced by increasing the conductor corona under a specific corona current range.

Numerical Analysis and Experimental Study of the Laser Cleaning of Ceramic Insulator Contamination

Contamination flashover of insulators is one of the main threats to the safety of power systems, and regular cleaning of insulator surface pollution is an effective solution to this problem. In this paper, the laser cleaning of ceramic insulators is studied via simulations and experiments. The adhesion between a contamination layer and an insulator surface is estimated. A laser cleaning model for contaminated insulators is established, and a numerical analysis of the thermal stress field distribution characteristics of laser cleaning is carried out. Various factors that affect the thermal stress field distribution, including the laser power, laser scanning speed and thickness of the contamination layer, are also analysed. The optimal cleaning parameters for the best performance of laser cleaning are obtained through simulation and experiments. The result shows if the equivalent salt deposit density (ESDD) is 0.05 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and the nonsoluble deposit density (NSDD) is 0.25 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the best cleaning effect could be achieved when the laser power is 100 W and the scanning speed reached 6000 mm/s.

Effect of Seawater and Fly Ash Contaminants on Insulator Surfaces Made of Polymer Based on Finite Element Method

Polymer is an insulating substance that has become increasingly popular in recent years due to its benefits. Light density, superior dielectric and thermal properties, and water-resistant or hydrophobic properties are only a few of the benefits. The presence of impurities or pollutants on the insulator’s surface lowers its dielectric capacity, which can lead to current leakage. The influence of seawater and fly ash pollutants on the distribution of the electric field and the current density of the insulator was simulated in this study. The finite element method was used to execute the simulation (FEM). Polymer insulators are subjected to testing in order to gather current leakage statistics. The tested insulator is exposed to seawater pollution, which varies depending on the equivalent salt density deposit value (ESDD). The pollutant insulator for fly ash varies depending on the value of non-soluble deposit density (NSDD). The existence of a layer of pollutants increased the value of the electric field and the value of the surface current density, according to the findings. Both in simulation and testing, the ESDD value of seawater pollutants and the NSDD value of fly ash contaminants influenced the value of the leakage current that flowed. The greater the ESDD and NSDD values are, the bigger the leakage current will be.

Lessons to Learn from Post-Installation Pollution Levels Assessment of Some Distribution Insulators

Among the main causes of outdoor insulation failures is their poor specifications in terms of leakage distances. This happens when the selected criteria are unable to cope with all the stresses imposed by the changes in environmental pollutions. Therefore, it is important for utilities to fully understand the actual pollution characteristics of the service environment in which the insulators are operating. In this paper, the pollution severity and performance of some 13.2 kV ceramic insulators, sampled in different areas of a Canadian aluminum factory, are assessed. The investigations were performed taking into account the influence of air humidity. Various characteristics were investigated to assess the pollution levels of the insulators, such as equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD), surface resistance, and leakage current characteristics (density, 3rd harmonic amplitude, and phase). It was witnessed that the insulators, collected around the factory, were much more polluted in comparison to the initial expectation. The pollution level should not be considered static due to the environmental parameters’ dynamics. Lessons to learn: the reliability of an electrical grid is dependent on components whose own reliability is strongly affected by external factors, of which there is often a poor awareness. If care is not taken to re-evaluate the post-installation pollution levels of the insulators, the light may simply turn out!

Dynamic Pollution Prediction Model of Insulators Based on Atmospheric Environmental Parameters

Pollution-induced flashover is one of the most serious power accidents, and the pollution degree of insulators depends on atmospheric environmental parameters. The pollution models used in the power system research are usually static, but the environmental parameters are dynamic. Therefore, the study on the dynamic pollution prediction model is of great importance. In this paper, the dynamic pollution prediction model of insulators based on atmospheric environmental parameters was built, and insulators’ structure coefficients were proposed based on the model. Firstly, the insulator dynamic pollution model based on meteorological data (PM2.5, PM10, TSP (total suspended particulate), and wind speed) was proposed, and natural pollution tests were also conducted as verification tests. Furthermore, insulator structure coefficients c1, c2 (c1: pollution ratio of U210BP/170 to XP-160; c2: calculated pollution ratio of U210BP/170T to XP-160) were then obtained, and their influence factors were discussed. At last, insulator structure coefficients were calculated, and it can be seen that the calculated error of insulator structure coefficients was acceptable, with the average re (relative errors) at 9.0% (c1) and 13.5% (c2), which verifies the feasibility of the model. Based on the results in this paper, the NSDD (non-soluble deposit density) of insulators with different structures can be obtained using the insulators’ structure coefficient and the reference XP-160 insulator’s NSDD.

Correction of flashover voltage of catenary insulators based on analysis of soluble salt compositions in saline‐alkali region

AbstractCalcium sulfate and other slightly soluble salts in the natural pollution of catenary insulators could result in differences in flashover voltages between artificially and naturally polluted insulators at the same salt deposition density. Based on the insulator pollution characteristics in saline‐alkali areas and the saturated water absorption of polluted insulators, the equivalent salt deposit density and nonsoluble deposit density of insulators are corrected according to the influence of other coexisting soluble salts on the solubility of calcium sulfate. The correction formula of the insulator flashover voltage is proposed, which considers the equivalent salt deposit density, nonsoluble deposit density and pollution components. The results from the correction formula are compared with the experimental data from the artificial pollution test of the ceramic cap and pin insulator. The results show that salt‐alkali areas are more easy to flashover than other areas. The remaining pollutants can change the conductivity of the pollutant layer by inhibiting or promoting the dissolution of calcium sulfate. Moreover, its effect on the flashover voltage cannot be ignored. The error between the calculated value based on the correction formula and the experimental data is below 6%. A pollution flashover warning mechanism based on relevant meteorological data is proposed. The results can be used as an important reference for the operation and maintenance of catenary insulators in saline‐alkali areas. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Pixel-Level Classification of Pollution Severity on Insulators Using Photothermal Radiometry and Multiclass Semisupervised Support Vector Machine

Pollution flashover is a serious accident with a wide range of impacts in power grid. Accurate and timely classification of pollution severity is both a key to preventing pollution flashovers and a crucial challenge. This article proposes an innovative method based on photothermal radiometry (PTR) and multiclass semisupervised support vector machine for the classification of insulator pollution severity. The introduction of time-dimension information makes it possible to achieve pixel-level image identification instead of image- or region-level image identification. The PTR physical model for pollution severity measurement is established to determine the effect of pollution severity parameters such as the equivalent salt deposit density and the nonsoluble deposit density on the transient and frequency-domain thermal radiation characteristics of contamination layer. The relevant features are extracted by using principal component analysis. A semisupervised classifier is proposed to solve the problem of poor generalization due to insufficient labeled samples in industrial applications. Experimental results verify the satisfactory efficiency and accuracy of the proposed method and an estimation framework for fast, accurate, and nondestructive industrial application without the tedious work of labeling large amounts of data is concluded.

Contamination Characteristics of Typical Transmission Line Insulators by Wind Tunnel Simulation

In this paper, contamination distribution results on 4 insulators surface as well as NSDD (non-soluble deposit density) in different test conditions were obtained. Further, contamination performances of 4 insulators were compared. Finally, contamination process was simulated by the Eulerian multiphase model based on computational fluid dynamics. Research results showed that: contamination performances of insulators were obviously affected by insulator structures, wind speed and RH (relative humidity). Contamination distribution is non-uniform on 4 insulators. Contamination degree of 4 insulators on leeward surface is greater than that of windward surface. NSDDB (NSDD of bottom surface) of disc shaped insulators is higher than NSDDT (NSDD of top surface), the opposite is true for shed shaped insulators. Besides, the saturated contamination characteristics of 4 insulators are different in saturated NSDD and saturated time. Wind speed and RH both have great influence on the insulators contamination. The increase of wind speed and RH will lead to higher NSDD. However, it is noteworthy that RH has little impact on NSDD of composite insulators. In addition, the numerical simulation based on computational fluid dynamics and experimental results in wind tunnel are in good agreement. So it is suggested that numerical simulation can be used to test the anti-pollution performance of insulators with different structures in different environments.

Analysis of Pollution in High Voltage Insulators via Laser-Induced Breakdown Spectroscopy.

Surface pollution deposition in a high voltage surface can reduce the surface flashover voltage, which is considered to be a serious accident in the transmission of electric power for the high conductivity of pollution in wet weather, such as rain or fog. Accordingly, a rapid and accurate online pollution detection method is of great importance for monitoring the safe status of transmission lines. Usually, to detect the equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD), the pollution should be collected when power cut off and bring back to lab, time-consuming, low accuracy and unable to meet the online detection. Laser-induced breakdown spectroscopy (LIBS) shows the highest potential for achieving online pollution detection, but its application in high voltage electrical engineering has only just begun to be examined. In this study, a LIBS method for quantitatively detecting the compositions of pollutions on the insulators was investigated, and the spectral characteristics of a natural pollution sample were examined. The energy spectra and LIBS analysis results were compared. LIBS was shown to detect pollution elements that were not detected by conventional energy spectroscopy and had an improved capacity to determine pollution composition. Furthermore, the effects of parameters, such as laser energy intensity and delay time, were investigated for artificial pollutions. Increasing the laser energy intensity and selecting a suitable delay time could enhance the precision and relative spectral intensities of the elements. Additionally, reducing the particle size and increasing the density achieved the same results.

Evaluation of thermoplastic polyolefin materials for the hard shed of composite insulators

AbstractThis article explores the possibility of using polyolefin materials for composite insulator sheds. The transfer component (silicone oil or erucamide) is added into a polyolefin material to improve its hydrophobic properties. Results show that the silicone oil‐modified polyolefin material (polyolefin‐S) exhibited an obvious hydrophobicity transfer property. When the equivalent salt deposit density and nonsoluble deposit density are 0.1 and 0.5 mg/cm2, respectively, the static contact angle increases from 75° to 87° as the silicone oil transfer time increases from 24 to 96 hr. Meanwhile, polyolefin‐S exhibits high mechanical strength, hardness, volume resistivity, and surface resistivity values of 21.4 MPa, 62.6 HD, 1.7 × 1015 Ω m and 1.2 × 1016 Ω, respectively. Moreover, polyolefin‐S shows excellent tracking and erosion resistance of 4.5 kV level in the inclined plane test. The results verify that the polyolefin material is a promising candidate material for the hard shed of composite insulators.

Performance Evaluation of 230 kV Polymer Insulators in the Coastal Area of Saudi Arabia

This article investigates the technical performance of 230 kV field-aged composite insulators in the coastal region of Saudi Arabia. Two insulator samples removed from the 230 kV line after 20 years of service are assessed at KFUPM High Voltage Lab (KHVL). Different assessment techniques, such as visual inspection, contact angle, surface pollution severity, electrical withstand, and material characterization are utilized to evaluate the insulator performance. Equivalent salt deposit density (ESDD) and non-soluble deposit density (NSDD) techniques are used for the surface pollution severity measurements. Clear views of surface changes and surface hydrophobicity conditions are displayed. Scanning electron microscope (SEM), energy dispersive x-ray spectrometry (EDX), and Fourier-transform infrared spectroscopy (FTIR-IR) techniques are utilized for the material characterization. The visual inspection reveals small and big cracks in the insulator sheds. Hard breakable portion areas, many shed cuts, changed color areas, and whitish parts are visually noticed in the insulator surface. Such changes confirm the aging condition effect of the insulator units. Furthermore, the samples are subjected to laboratory clean fog tests to check the electrical performance of the samples. Informative results are given for the current condition and performance for the 20-years, field-aged insulators. Additionally, the experimental results are presented for the rest of the insulator life period. Utilization of the existing line insulators has been evaluated. Finally, discussions and recommendations for the future handling of the insulators at the 230 kV line are highlighted.