Outdoor Insulation and Gas Insulated Switchgears

This book focuses on theoretical and practical developments in the performance of high-voltage transmission line against atmospheric pollution and icing. Modifications using suitable fillers are also pinpointed to improve silicone rubber insulation materials. Very fast transient overvoltage (VFTO) mitigation techniques, along with some suggestions for reliable partial discharge measurements under DC voltage stresses inside gas-insulated switchgears, are addressed. The application of an inductor-based filter for the protective performance of surge arresters against indirect lightning strikes is also discussed

Prediction of polluted insulator based on leakage current resistance insertion performance of short and medium transmission line model

The main objective of the transmission lines is to deliver power from the generator to the customers, with less losses and without any interruptions. however, pollution sources are increasing around the world, which are affecting one of the most important components of a power line, namely, the high voltage outdoor insulators. the accumulation of pollution on the surface of the insulator can affect its physical properties and create leakage current resistance. under suitable conditions, this resistance will lead to leakage current on the surface of the insulator. in previous studies, leakage current measurement on the insulator surface was ignored because it is negligible. however, increasing pollution levels and the large number of transmission line insulators should take into account the effect of leakage current resistance in the transmission line model. in this thesis, an improved model is introduced to examine the effect of leakage current resistance on the parameters of the transmission line, the amount of additional active power losses, voltage drop and increased real power generation in power networks for both short and medium transmission lines. three levels of leakage resistance (high, medium, and low) that represent the three levels of pollution are incorporated into the transmission line model through a series of delta to star and star to delta conversion using a two-port network concept. then, by inserting the leakage current resistance, a simulation model was used to measure leakage current and voltage of the leakage current resistance. a simulation sensor is used to predict the level of pollution on the insulator and the location of highly polluted insulators using artificial neural network. this study was able to determine the changes in each parameter and the effects of these changes on the active power losses and voltage drop in three different systems. the application of the improved model have shown an increase in detection of power losses by 25.63% in high pollution conditions at the insulators in all short and medium transmission lines. thus, to compensate for these high losses, the system needs to increase real power generation by 0.61% when compared with during normal conditions. the prediction results by the simulation model for the 5- bus system clearly demonstrated that the overall correct classification rates for the predicted pollution levels were very high at 97.67% and 98.03%, for both short and medium models, respectively. meanwhile, the correct classification rate for the predicted locations of highly polluted insulators is 100% for both short and medium models. the results obtained in this study offer accurate information for polluted transmission line insulators, which could be used for maintenance and calculation of power loss for polluted insulators, in order to keep the power system in a reliable state

Effect of water on electrical properties of Refined, Bleached, and Deodorized Palm Oil (RBDPO) as electrical insulating material

This paper describes the properties of refined, bleached, deodorized palm oil (RBDPO) as having the potential to be used as insulating liquid. There are several important properties such as electrical breakdown, dielectric dissipation factor, specific gravity, flash point, viscosity and pour point of RBDPO that was measured and compared to commercial mineral oil which is largely in current use as insulating liquid in power transformers. Experimental results of the electrical properties revealed that the average breakdown voltage of the RBDPO sample, without the addition of water at room temperature, is 13.368 kV. The result also revealed that due to effect of water, the breakdown voltage is lower than that of commercial mineral oil (Hyrax). However, the flash point and the pour point of RBDPO is very high compared to mineral oil thus giving it advantageous possibility to be used safely as insulating liquid. The results showed that RBDPO is greatly influenced by water, causing the breakdown voltage to decrease and the dissipation factor to increase; this is attributable to the high amounts of dissolved water

A Corrosion Control Manual for Rail Rapid Transit

This manual addresses corrosion problems in the design, contruction, and maintenance of rapid transit systems. Design and maintenance solutions are provided for each problem covered. The scope encompasses all facilities of urban rapid transit systems: structures and tracks, platforms and stations, power and signals, and cars. The types of corrosion and their causes as well as rapid transit properties are described. Corrosion control committees, and NASA, DOD, and ASTM specifications and design criteria to which reference is made in the manual are listed. A bibliography of papers and excerpts of reports is provided and a glossary of frequently used terms is included

Fabrication and characterisation of Slippery Icephobic Coatings for application to High Voltage Insulators

Slippery liquid-infused porous surface (SLIPS) based on Nepenthes pitcher plant has attracted increasing interest in many applications, particularly for mitigating icing hazard. Aside from exhibiting a water repellency, such surfaces have low contact angle hysteresis of <2.5° and low tilt angle of <5°. Nonetheless, SLIPS still suffer from challenges related to the oil depletion that reduces their service life. Herein, two different approaches, namely, microtexturing and the use of oil absorbent, are presented to effectively produce the slippery surfaces for the enhanced durability of engineered lubricant-infused materials. In the first approach, the replication method was employed to produce liquid-infused textured surfaces (LITS) through the chemical etching technique. Analysis such as lubricant depletion/recovery, confirmed that the presence of microtextures and lubricant viscosity can have significant roles in controlling the oil migration rate. Furthermore, merging microtexturing and slipperiness in LITS can enhance the icephobic performance. Such surface demonstrated an ice adhesion strength of less than 20 kPa, which is four orders of magnitude lower than the pristine surface. Furthermore, LITS can offer more long-lasting icephobic properties compared with pristine surface lacking microtextures. For the second strategy, the lubricant-loaded carriers were used to prohibit the rapid oil consumption, thus prolonging the life service of the prepared coatings. Accordingly, the negative pressure was applied to promote the incorporation of the lubricant within carrier pores and increase the carrier loading capacity. For this purpose, the thermogravimetric analysis (TGA), and the BET (Brunauer, Emmett and Teller) method have been used to evaluate the lubricant infusion quantitively. High oil content (around 50 wt. %) has been commonly used to enhance icephobic performance, but the presence of excessive amount of lubricant within the matrix can result in decreased mechanical characteristics of the prepared surfaces. The combination of different anti-icing mechanisms, such as stress localization, slipperiness, and the formation of nonfrozen molecules can be helpful to obtain desirable icephobic properties at low oil contents. These mechanisms were achieved using blended matrix, infused lubricant, and hydroxyl-terminated lubricant. The slippery coating was developed by impregnating hydroxyl-terminated-lubricant-loaded carriers into a blend of polydimethylsiloxane (PDMS) and alkoxy-siloxane resin. The prepared coating showed desirable anti-icing and de-icing properties and long-lasting stability against UV exposure and humidity. The icephobic characteristics of the coating can be attributed from its slipperiness and formation of unfrozen molecules. The electrical properties of the coating were evaluated using a comprehensive set of methods, including dielectric spectroscopy, flashover, condensation, and inclined plane tests. In comparison with the reference sample, the coating containing lubricant-loaded carriers exhibited lower dielectric permittivity and loss factor. Moreover, the coating reduced the leakage current under high humidity. The lubricant-loaded-carrier-containing coating also heightened the flashover voltage in different conditions. The results confirmed that the coating containing lubricant-loaded carriers could be considered as a potential candidate for applying on high-voltage insulators. La surface poreuse glissante infusée de liquide (SPGIL), inspiré de la plante sarracénie, suscite un intérêt croissant dans de nombreuses applications, notamment pour les dangers associés à la formation de la glace. Outre la démonstration de leur potentiel hydrophobe, ces surfaces possèdent une faible hystérésis d'angle de contact inférieure à 2.5° et un faible angle d'inclinaison inférieur à 5°. Toutefois, les (SPGIL), sont confrontées à des défis liés au lessivage de l'huile qui réduit leur durée de vie. Ici, deux approches distinctes, notamment la micro-texturation et l'utilisation d'absorbants d'huile, sont présentées dans l’optique de produire efficacement des surfaces glissantes pour améliorer la durabilité de ces matériaux imprégnés de lubrifiant. Dans la première approche, la méthode de réplication a été employée pour produire des surfaces texturées imprégnées de liquide (STIL) par le biais de la technique de gravure chimique. Des analyses, comme la déplétion/récupération du lubrifiant, ont confirmé que la présence de micro-textures couplée à la viscosité du lubrifiant peuvent jouer un rôle significatif dans la régulation du taux de migration de l'huile. De plus, la combinaison de la micro-texturation et de la glissance dans les STIL peut améliorer de manière considérable les performances glaciophobes. En effet, une telle surface a démontré une contrainte d'adhérence de la glace inférieure à 20 kPa, ce qui représente quatre ordres de grandeur de moins que celle de la surface d'origine non traitée dépourvue de micro-textures. En plus, leur glaciophobicité a été montrée plus stable au fil du temps comparée à la surface d'origine dépourvue de micro-textures. Pour la deuxième stratégie, des porteurs chargés de lubrifiant ont été utilisés pour empêcher la consommation rapide d'huile, prolongeant ainsi la durée de vie des revêtements préparés. En conséquence, une pression négative a été appliquée pour favoriser l'incorporation du lubrifiant dans les pores des porteurs et augmenter ainsi sa capacité de charge. Afin, d’évaluer quantitativement l'infusion de lubrifiant, une analyse thermogravimétrique (TGA) et la méthode BET (Brunauer, Emmett et Teller) ont été utilisées. Habituellement, un taux élevé de lubrifiant (avoisinant 50 % m/m) est couramment utilisé pour améliorer les performances glaciophobes. Cependant, la présence d'une quantité excessive de lubrifiant dans la matrice peut entraîner une diminution des caractéristiques mécaniques des surfaces préparées. La combinaison de différents mécanismes anti-givres, comme la localisation de contrainte, la glissance et la formation de molécules non gelées, peut être bénéfique pour l’obtention des propriétés glaciophobes désirables à partir de faibles concentrations de lubrifiant. Ces mécanismes ont été obtenus en utilisant une matrice faite d’un mélange de résines, un lubrifiant infusé et un lubrifiant hydroxyl-terminé. Le revêtement glissant résultant a été développé en imprégnant des supports chargés de lubrifiant hydroxyle-terminé dans un mélange de résines polydiméthylsiloxane (PDMS) et d'alkoxy-siloxane. Le revêtement préparé a montré des capacités d’anti-givrage et de dégivrage intéressantes, ainsi qu'une bonne résistance à l'exposition aux UVs et à l'humidité. Les caractéristiques glaciophobes du revêtement peuvent être attribuées à sa glissance et à la formation de molécules non gelées. Les propriétés électriques du revêtement ont été évaluées à l'aide d'un ensemble complet de méthodes, notamment la spectroscopie diélectrique, les tests de contournement, de condensation et de plan incliné. En comparaison avec l'échantillon de référence, le revêtement contenant des porteurs chargés de lubrifiant a montré une permittivité diélectrique et un facteur de perte plus faibles. De plus, une réduction du courant de fuite, dans le cas d'humidité élevée, a été observée avec le revêtement développé. Ce dernier a également montré une augmentation de la tension d'éclatement dans différentes conditions. En somme, les résultats ont confirmé que la solution de revêtement développée contenant des supports chargés de lubrifiant pourrait être considérée comme un candidat potentiel pour une application glaciophobe sur des isolateurs à haute tension

Performance comparison of existing AC and DC transmission lines within southern Africa with predictions for lines above 765 KV

Transmission line faults caused by lightning, contamination, birds and fires largely determine the performance of AC and DC transmission line within Southern Africa. With the trend towards higher voltages, with specific reference to the Westcor HVDC link, been developed, a comparison of the performance between existing AC and DC lines will give insight not only into how the faults perform relative to each system but also what can be expected for lines exceeding 765 kV. This dissertation compares data for all the 400 kV transmission lines in South Africa and the ±533 kV Cahora-Bassa line, with reference made to the existing 765 kV AC lines in South Africa. Based on this comparison the findings include possible data acquisition inconsistencies, underperforming areas with respect to different fault types and performance predictions for lines exceeding 765 kV

Environmental pollution effects on insulators of high voltage overhead transmission line for locomotives.

Masters Degree. University of KwaZulu-Natal, Durban.The primary focus of this research is to report thoroughly on the addressed key questions of the proposal and to successfully compile a simulation based on environmental pollution effects on insulators of high voltage overhead transmission line for locomotives. The simulation design is done on FEMM, which provides useful models for solving electromagnetic problems, which will assist to compile a suitable insulation model design with results that can be interpreted in detail. This report includes the theoretical background of a high voltage insulator for different materials with different sizes and shapes affected by different environmental conditions. Ceramic insulators appear to be extremely susceptible. Polymeric insulators specially of silicone-rubber have achieved better performance under polluted states and have found increasing usage. The feasibility study conducted shows that the simulation design is feasible and transparent. The IEEE and ScienceDirect publications are the suitable sources that are used to conduct the literature review. The method used to collect data and information or research strategy which summarizes the way in which research will be undertaken is conduced. Furthermore, the preliminary research results and analysis evolve after investigating and analyzing the electric field distribution of a polymeric insulator, which is commonly used on high voltage overhead transmission line for locomotives when it is dry and when a water drop is applied with and without a corona ring. In the three cases investigated, the first case is when the insulator was dry, the second case is when water droplets reside as a discrete droplet on a polymeric insulator made of a silicon rubber material and the third case is when the corona ring is added, simulation was executed for both typical and optimized insulators. It was found that the presents of water droplets on the insulators either due to rain, fog, etc. leads to electric field enhancement causing partial discharge and dry arc which ultimately results in complete flashover. The current work has resulted in a simple model to estimate the flashover voltage of a polymeric insulator under contaminated states. To ensure reliability, simulation results are compared with existing work carried in the past

Vulnerability of Electric Power Systems to Volcanic Ashfall Hazards

Volcanic eruptions are powerful natural events which impact strongly on society. As human populations grow and expand into volcanically active areas, their exposure and vulnerability to volcanic hazards is also increasing. Of all volcanic hazards, ashfall is the most likely to impact lifelines because of the large areas affected. The widespread dispersal of ash can cause large-scale disruption of vital infrastructure services, aviation, and primary production. Electric power supply is arguably the most crucial of modern infrastructure systems, especially considering the dependence of other sectors on electricity to maintain functionality. During and immediately after ashfalls, electric power systems are vulnerable to a number of impacts, but disruption from volcanic ash-induced insulator flashover (unintended, disruptive electrical discharge) is most common. This thesis investigates the vulnerability of electric power systems to volcanic ashfall by examining impacts to the different sectors of the modern power system and exploring appropriate mitigation strategies. Analogue laboratory trials using a pseudo (synthetic) ash are undertaken to verify the environmental, volcanological and electrical parameters that most affect electrical conductivity and therefore the flashover mechanism in these experiments. While dry ash is highly resistant to the flow of electric current, increasing moisture content, soluble salt load, and compaction (bulk density) will reduce this resistance and, in turn, increase the potential for flashover. Volcanic ash is an acute form of airborne pollution for areas downwind of active volcanoes. Results from laboratory experiments in this thesis suggest that insulator pollution (volcanic ash) performance (dielectric strength) is primarily dictated by (1) the conductivity of the ash, and (2) insulator material, profile (shape) and dimensioning. Composite polymer insulators tested herein effectively minimise sinusoidal leakage current and partial discharge activity and also exhibit higher pollution performance when compared to ceramic equivalents. Irrespective of insulator material, however, the likelihood of flashover increases significantly once the bottom surface of suspension insulator watersheds become contaminated in wet ash. The thesis investigates the vulnerability (hazard intensity/damage ratio) of electric power systems to volcanic ashfall hazards. Identification, analysis, and reduction of the risk of ashfall impacts to power networks is explored as a part of holistic volcanic risk assessment. The findings of the thesis contribute to the readiness, response and recovery protocols for large electric power systems in volcanic disasters; which directly affects the functional operation and economics of industrial and commercial society