Dry Band Arcing 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.

Research on the prediction method of porcelain insulator pollution degree based on electric field monitoring

The online monitoring of insulator surface pollution states is crucial for predicting/preventing pollution flashover accidents. This paper conducts artificial pollution tests on porcelain insulators at five pollution levels to obtain the electric field signal during the flashover process. Subsequently, the time-frequency performance of the electric field signal waveform at various discharge stages is discussed in detail. Finally, a method for predicting pollution degrees by combining back propagation (BP) neural networks and non-contact electric field signal monitoring is proposed and validated. Research results indicate that during the pollution flashover process of the porcelain insulator, the peak value of the electric field signal shows an upward trend in sections. As the equivalent salt deposit density (ESDD) increases, the curves of electric field values rise. The development of dry-band arcing clearly distorts the electric field signal waveform at its crest and trough parts, increasing the total harmonic distortion (THD) rate. The THD can reach 100–130 % when closing to flashover, with the third harmonic acting as the main component. By taking kmax (the rising rate of the E-field signal amplitude), g (the ratio of Emax to Erms), K3 (the third harmonic coefficient), and THD as inputs to the BP neural network model, an ESDD prediction with a relative error lower than 10.63 % is realized. This research can offer novel technical support for predicting pollution degrees.

Hydrophobicity classification of polymeric insulators using a masked autoencoder model in vision transformer

The loss of hydrophobicity on the polymeric insulator’s surface leads to a continuous water channel formation. This water channel formation can initiate dry band arcing and subsequent flashover. Therefore, accurately identifying the hydrophobicity class is crucial as it provides the surface ageing information of the polymeric insulators. This study proposed a novel approach utilizing a masked autoencoder-based vision transformer image classifier to classify the hydrophobic condition of polymeric insulators accurately. A comprehensive series of tests were conducted on deep learning image classifier models to assess robustness. The experimental findings demonstrated that the vision transformer model exhibited a significant recognition accuracy of 99.69%, surpassing the performance of the CNN, pre-trained CNN, and ViT models.

Risk assessment of contaminated composite insulators in pre-flashover conditions

In this paper, a novel approach for risk assessment of the outdoor polluted insulators is presented to predict dry band-arcing and flashover. Risk evaluation of the dry-band arcing and flashover are represented using leakage current (LC) behavior in order to understand pollution behavior of the pre-flashover conditions. Critical indexes of the dry-band arcing and flashover are extracted based on the presented risk assessment model using wavelet transform (WT). Then, the developed critical indexes are used for prediction of the operation risk of the composite insulators. In addition, the occurrence probabilities of the dry band arcing and flashover are calculated based on the analysis of critical indexes. Several sensitivity parameters including pollution level, wetting rate and geometry specification are considered in the presented model. Validation results show that risk of the insulator's service can be correlated to the represented critical indexes. The proposed approach can be adopted as an online monitoring tool in order to avoid pollution flashover of the outdoor insulators.

Tracking and Erosion of Polydimethlysiloxane With Different Molecular Weight for Outdoor Insulation

In this paper, the degradation mechanisms of unfilled polydimethylsiloxane with different molecular weights is investigated under dry-band arcing using the inclined plane tracking and erosion test and material characterization techniques. Tracks of carbonaceous residue formed as byproducts of radical-based crosslinking are prevalent over erosion as the molecular weight increases. Erosion becomes dominant with polydimethylsiloxane that undergoes mainly depolymerization during degradation at lower molecular weights. Accordingly, tracking due to a progressive carbonaceous residue formed on the surface is the degradation pattern observed under the dry-band arcing for the polydimethylsiloxane with higher molecular weights (45000 and 28000 g/mol) during the inclined plane test, whereas erosion due to depolymerization is more evident on the polydimethylsiloxane surfaces with lower molecular weights (17200 and 9400 g/mol). This study highlights the possibility to tune the tracking and erosion tendency of silicone rubber outdoor insulation by controlling the molecular weight of the organosiloxane base, without the sole reliance on fillers as commonly perceived.

A Study on the Development of New Silicone based Polymeric Outdoor Insulator Material for Enhanced Properties

Polymeric insulators have been increasingly popular in recent years as a result of their superior performance in contaminated environments due to their hydrophobic properties. However, research into the ageing condition of polymeric materials and their practicality for large-scale use is currently ongoing. Insulator deterioration is caused by environmental tracking and erosion factors. As insulators age, they develop immature failures and inconsistencies in their functioning. pollution performance of polymeric insulators is a vital factor in the quality and reliability of the power system. Over some time, dry band arcing can initiate the flashover and it causes degradation in the form of erosion and tracking. Polymeric insulators’ performance is heavily influenced by the constituent materials and their properties. There is a critical need to investigate innovative filler materials that can be combined with existing polymeric base materials to form composites. In this context the proposed research use silicone rubber as a base polymeric material, to which additives are added to produce three distinct composites by varying the filler concentration. Preliminary studies were made to evaluate the hydrophobicity, dielectric strength, hardness, specific gravity, tensile strength, ultimate elongation and tear strength properties of this HTV silicone rubbed-based composites by using ASTM standards and IEC 60587 requirements. Studies were also made by accelerated ageing on sample material by using the IPTE test. The results show substantial improvement in the electrical and ageing properties.

Energy Balance Model for Providing Mechanistic Insights Into HTV and LSR Performance in Inclined Plane Tests

Silicone rubber (SR) is widely used in external insulation. However, the utilization of either high-temperature vulcanized (HTV) SR or liquid SR (LSR) remains controversial in China because of their differences in tracking and erosion resistance and aging resistance due to various amounts of nonreinforcing fillers. Here, the tracking and erosion behaviors of HTV and LSR during the inclined plane test (IPT) are captured and compared for a detailed comprehension of the difference between the two materials. The results revealed that LSR was easily carbonized and formed electrical tracks initially. Then, the carbonization slowed because of developing a protective ceramic layer. The relatively stable ceramic layer resulted in less frequent rapid erosion but increased the average arc burning time. An energy balance model of dry-band arcing (DBA) was established to evaluate DBA’s energy dissipation and absorption. Then, the emission spectra of DBA were collected to analyze the arc temperature and resistance more accurately. The energy input from the system is dissipated primarily through heating and evaporation of the liquid film, with radiant energy only accounting for a minuscule fraction. In different erosion states, the power absorbed by the surface of samples is different. LSR shows an average absorption power of 19.9 W in the initial carbonization state, which is higher than that of HTV (16.5 W). The average absorption power in the fast erosion state is the same for both samples at about 30 W. The absorption power at 20–25 W is considered the threshold range of relatively stable erosion.

The Viability of the Filler Barrier Effect During the DC Dry-Band Arcing on Silicone Rubber

This article investigates the filler barrier effect on suppressing the erosion of silicone rubber composites during the dc dry-band arcing, by supplementing main microfillers in silicon rubber, i.e., ground silica and micro-sized alumina trihydrate, with fumed silica and nano-sized alumina trihydrate fillers. A study framework employing simultaneous thermogravimetric-differential thermal analyses (TGA-DTAs), the inclined plane tracking and erosion test, and the dry-arc test is employed. Fumed silica in silicone rubber increases the amount of the crosslinked residue and suppresses silicone rubber depolymerization, whereas nano-sized alumina trihydrate releasing water of hydration may adversely impact the residue coherence and promote combustion. The viability of the filler barrier effect is synergistically achieved by adding fumed silica to the main ground silica filler, thereby maintaining the residue integrity. The inclined plane-tracking erosion test confirms the importance of the filler barrier effect of fumed silica in supplementing the volume effect of ground silica in the suppression of the dc dry-band arcing. These filler effects appear to mainly govern the erosion resistance, with insignificant effect shown for thermal conductivity under dc. The dry-arc resistance test is shown as a useful method to simulate a stable dry-band arcing and obtain reproducible surface erosion patterns that correlate with the outcomes of the dc inclined plane tracking and erosion test.

A Dynamic Intelligent Approach Based on Gaussian Function for Prediction of the Flashover Voltage Conditions on Polluted Polymer Insulators

This research presents a dynamic modeling approach to predict flashover voltage (FOV) of polymer 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 study, experimental results of pollution flashover tests are used to develop a circuit model of pollution arcs based on Obenaus’ model. Estimation of circuit values is done by use of intelligent algorithm with no dependency on profile of insulators which is also more beneficial than typical analytical calculations. Then, separation and investigation of discharge and pollution voltage is done and proper classification is made. This classification is later used to predict pre-flashover conditions and pollution flashover. Gaussian model is used to make fitness of voltage of pollution layer and voltage of discharge on the surface of insulator. Gaussian representation of each stage in pollution flashover contains critical signals leading to complete discharge. Based on the obtained model, a flowchart is presented to predict dynamic stages of flashover. Comparison to various experimental data shows close correlations with the results of proposed model. An online monitoring system can be developed according to obtained results in order to prevent pollution flashover.

Investigation of the Tracking and Erosion Resistance of a Ceramifiable Filler System for Silicone Rubber Composites

Improving the tracking and erosion resistance of silicone rubber (SiR) is of great significance to outdoor SiR insulators. In this work, a feasible method to enhance the antitracking performance of SiR by a ceramifiable system is investigated. Through scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and other characterization methods, the mechanism that aluminum hydroxide (ATH) and low-melting glass (LMG) powder synergistically improve the tracking resistance of SiR is proposed. In this ceramifiable system, ATH plays a role in absorbing heat and serves as a precursor under the synergy with LMG, which promotes the formulation of dense mullite ceramic layer on the surface of SiR at the high temperature generated by dry band arc discharges, thereby the internal SiR is protected from degradation. Hydrophobicity and mechanical properties of ATH/LMG/SiR composites are also investigated, revealing that ATH/LMG improves the mechanical properties and hydrophobicity compared with one filler filled with the same amount. The ceramifiable system exhibits a good effect that the antitracking performance, mechanical properties, and hydrophobicity of SiR composites are improved at the same time. This system provides a new method for the research of antitracking SiR materials applied in outdoor SiR insulators.

Understanding Failure analysis using harmonic analysis and empirical mode decomposition techniques

The investigation pertains to the failure analysis of Fibre Reinforced Plastic rods used in overhead transmission line insulators using appropriate data acquisition and analysis. The leakage current data, over an experimental period is captured and time–frequency analysis is implemented for determining the in-service condition of the overhead transmission insulators. It is observed from the investigation that the signal displays various events like dry-band arcing, partial surface arcs and triple-point discharges at the electrodes. The study presents a simple time–frequency analysis used for presenting the phenomena, an algorithm is developed for the harmonic analysis, also Empirical Mode Decomposition is conducted to reinforce the analysis. The main focus of the study is to estimate the early failures with minimal time and with available data.

Experimental Study and Modeling of the Effect of ESDD/NSDD on AC Flashover of SiR Outdoor Insulators

Pollution flashover occurs when soluble and nonsoluble materials cover the surface of an insulator, and this may ultimately cause a reduction in its performance. In this paper, the common type of sodium chloride (NaCl) was used as a soluble pollutant (ESDD) and kaolin as a nonsoluble pollutant (NSDD). Samples of silicone rubber (SiR) insulators were selected for this study and fabricated at the Advanced High Voltage Engineering Research Centre (AHIVEC) at Cardiff University. The samples were preconditioned and polluted according to standard specifications. Additionally, the AC voltage ramp technique was used to achieve flashover (FOV) voltage with different pollution levels. The aim of this work was to investigate the effect of nonsoluble materials on flashover characteristics to understand their interaction with dry-band arcs by using FOV electrical equations and experimental data. The test results show that the FOV voltage of the silicone rubber insulator substantially decreased with the increase in both ESDD and NSDD values. It was also identified from these results that the dry-band arcs were considerably influenced by both ESDD and NSDD levels. This impact can be quantified by determining the variation of discharge parameters (N, n). Based on the FOV equations and experimental data, a mathematical model was suggested, taking into account the effect of both ESDD and NSDD.

Superhydrophobic nanocomposite coatings based on different polysiloxane matrices designed for electrical insulators

The present paper describes for the first time the influence of three different kinds of polysiloxane as hydrophobic agent on superhydrophobic coatings for electrical insulators: a trimethoxy (2,2,4-trimethyl pentyl)-based silane; a mixture of methyl methoxy siloxane with methylsilsesquioxane; a mixture of dimethyl siloxane, methylsilsesquioxanes and n-octyl silsesquioxanes. The polysiloxane properties were investigated by thermogravimetric (TGA) and hydrophobic (contact and sliding angles) analysis, indicating great differences on thermal properties and surface free energy. The polysiloxane binders were loaded with different sizes of microsized alumina trihydrate (ATH) and organophilic nanosilica functionalized with octyl-silane and polydimethylsiloxane (PDMS). The hydrophobicity of the coating was evaluated by water contact angle (WCA) and sliding angle (SA). The morphology and roughness of the coatings were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover the superhydrophobic durability of the coatings was evaluated by water immersion, hydrophobicity recovery, hydrophobicity transfer and adhesion. The effectiveness of these materials as coatings for glass electrical insulator was evaluated by tracking and erosion resistance using the inclined plane test (IPT). The results showed that the polysiloxane based on a mixture of methyl methoxy siloxane with methylsilsesquioxanee loaded with ATH and PDMS-treated silica exhibited the most promising characteristics as high contact angle, self-cleaning ability, good adhesion to the substrate and low number of leakage current peaks during the tracking and erosion resistance test. Such characteristics can bring benefits on electrical insulators like reducing the formation of conductive surface paths and the consequent degradation of the coating by dry band arcs, increasing its resistance when exposed to the electric field.

Method of quasi-distributed interface fiber Bragg gratings monitoring dry band arc on the moist pollution layer of composite insulators

Arc discharge on the insulator surface poses a threat to the safe operation of electrical power system. However, effective monitoring technology for arc discharge is lacking. In this paper, a 10 kV composite insulator with 3 × 4 quasi-distributed fiber Bragg gratings (FBGs) embedded at the insulator core-housing interface was developed to monitor dry band arc on the moist pollution layer. The temperature coefficient of interface FBGs was obtained by the temperature calibration test. The interface temperature variation exposed to the instantaneous arc with arc duration of 67 ms and the short-lived arc with arc duration of 2.1 s was observed. Results show that owing to the occurrence of short-lived arc, a new phenomenon was observed: interface temperature drops sharply first, then increases rapidly. Three criteria of ED (Euclidean Distance, i.e. the measuring standard for the otherness of interface temperature of different axial positions), the sharp drop of interface temperature and interface temperature rise are proposed to monitor dry band arc. Based on the three criteria, interface FBGs can effectively monitor the instantaneous arc and the short-lived arc. This paper provides a beneficial method for discharge monitoring and flashover warning of composite insulators.

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.

Recognition of Hydrophobicity Class of Polymeric Insulators Employing Residual Morphological Neural Network and Granulometry-Based Image Analysis

Hydrophobicity is an important property of polymeric insulators that allow formation of discrete water droplets on the insulator surface. However, with aging or under extreme humidification, the insulator surface loses its hydrophobic property, resulting in continuous water channel formation, which may lead to dry band arcing and subsequently flashover, thereby affecting the long-term performance of the insulator. Therefore, accurate recognition of hydrophobic class (HC) is important as it provides information regarding the surface condition of the insulator. Considering the above-said facts, this article investigates the feasibility of employing residual morphological neural network (Res-Morph-NN) to accurately recognize different HCs of polymeric insulators. In addition, for better understanding of the distribution of water droplets on the insulator surface, a novel approach based on multiscale mathematical morphology, i.e., granulometry, is used in this article. Our investigations revealed significant alterations in the granulometric patterns with the change in HC of polymeric insulators. The efficacy of the proposed framework employing Res-Morph-NN has been validated on HC images obtained from the experiment as well as on large set of images obtained from an online database, which returned satisfactory results. The proposed method can be efficiently used to discriminate different hydrophobicity classes, which can be implemented for monitoring insulator surface condition in real time.

Influence of dispersing aids on nano alumina/micro aluminum tri hydrate filled silicone rubber composites for outdoor high voltage insulators

AbstractNano alumina and micro aluminum tri hydrate filled high‐temperature vulcanizing silicone rubber composites were prepared with dispersing aids of surfactant Triton™‐X‐100 (TX‐100) and silane coupling agent 3‐methacryloxypropyltrimethoxysilane (KH‐570), through an in situ modification technique. Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD) analysis were carried out to understand the effects of dispersing aids on the structural and crystallographic properties of composites. Scanning electron microscopy images of TX‐100 dispersed composites revealed the presence of several localized regions of agglomeration, whereas KH‐570 dispersed composites showed moderate dispersion. Measurements of volume resistivity demonstrated an increment of four decades for KH‐570 dispersed nanocomposite over TX‐100. Better compatibility between fillers and base matrix through KH‐570 was evident from the low loss factor values. Inclined plane tracking and erosion results were discussed in detail with leakage current analysis. The binary composite prepared with KH‐570 was observed to resist the detrimental dry band arcing and subsequent erosion by 2 h and 20 min over TX‐100 dispersed composite. Dry arc resistance and the formation of thermal pathways connecting micro and nanofillers were discussed in detail. FTIR analysis of ash generated after inclined plane tracking and erosion test confirmed the surfacing of added fillers. KH‐570 dispersed composites showed superior properties as compared to composites prepared with TX‐100.

Viability of Fillers in HTV Silicone Rubber in the AC and DC Inclined Plane Tests

The viability of fillers for inhibiting the dry-band arcing damage on high temperature vulcanized silicone rubber under the critical AC and the equivalent DC voltages of inclined plane test is investigated. Alumina tri-hydrate and ground silica are employed in the study as common fillers employed in silicone rubber formulation for outdoor high voltage insulation, and thermal analysis is applied in order to understand the protective mechanisms of the fillers. Filler volume effect plays a role in improving the erosion performance, and the dilution effect of water of hydration is shown advantageous for preventing progressive (directed) erosion. Dilution effect promoted with internal oxidation is found only notable at 50 wt% alumina tri-hydrate in this study. On the other hand, alumina tri-hydrate at 10 or 30 wt% may yield a porous residue, which is conducive to thermo-oxidation (combustion) and consequently erosion. The erosion suppression effects reported for the fillers in the composites employed in this study are found less viable under the equivalent DC as compared to the critical AC voltages of the inclined plane test. This study clarifies common perceptions about the viability of fillers in silicone rubber for AC and DC outdoor insulation applications.

Understanding Variations in the Tracking and Erosion Performance of HTV-SR-Based Composites due to AC-Stressed Aging

Among the polymeric family, high-temperature-vulcanized silicone rubber (HTV-SR) is the most deployed material for high voltage insulation applications. However, in an outdoor environment, due to contamination and wetting-induced dry band arcing, consequently SR experiences surface tracking and erosion. From a practical standpoint, the tracking and erosion performance under multi-stress aging is required to be known. It is in that context that the present study was undertaken to measure and analyze the effect of multi-stress aging on tracking and erosion performance. Composite samples of SR having different filler concentrations of silica and alumina trihydroxide (ATH) were aged in a multi-stress chamber for a period of 5000 h, and after that their electrical tracking performance was studied. Simultaneously, unaged samples were also exposed to tracking test for comparison. To conduct this test, the inclined plane testing technique was used in accordance with IEC-60587. All samples exposed to tracking test were analyzed using different diagnostic and measuring techniques involving surface leakage current measurement, Fourier transform infrared spectroscopy (FTIR), thermal stability and hydrophobicity classification. Experimental results shown that the tracking lifetime increased through incorporation of silica and ATH fillers in the SR. Amongst all test samples, two samples designated as filled with 2% nano silica and 20% micro silica/ATH exhibited greater resistance to tracking. This was attributed to the optimum loading as well as better dispersion of the fillers in the polymer matrix. The presence of nano-silica enhanced time-to-tracking failure, owing to both improved thermal stability and enhanced shielding effect on the surface of nanocomposite insulators.

Tracking and Erosion of Silicone Rubber and EPDM Insulation in the DC Inclined Plane Test

This paper investigates the tracking and erosion of silicone rubber and EPDM insulation in the DC inclined plane tracking and erosion test. Silicone rubber filled with alumina tri-hydrate fails due to combustion in the gas phase or erosion paths, but with no evidence of tracking. EPDM fails due to tracking and surface capturing fire, from dry-band arcing leaving a black residue while impinging the surface. Carbonaceous residue on EPDM gives rise to leakage current magnitude, whereas fused silica-based residue on silicone rubber is shown to promote combustion. A high amount of alumina tri-hydrate replacing the polymeric fuel in the composite is shown as a primary factor preventing failure and changing the nature of the residue in the DC inclined plane tracking and erosion test. Depolymerization is the main degradation mechanism reported for silicone rubber and EPDM, with notable degrees of crosslinking reported only for silicone rubber. Crosslinking reduces the amount of silicone rubber undergoing depolymerization, thus, the amount of fuel prone to combustion is reported to promote a coherent residue shield against the eroding dry-band arcing.