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

Welding mask

Welding and welding safety are nothing new for all of us because this welding have been known around since 1800’s.A welding mask is one of the most important pieces of the personal protection that an equipment for the welder on having it. This welding can be used for the mask or helmet. Choose a good mask or helmet can protect the eyes and skin for not only from the severe sparks but also protect from potentially vision on damaging an ultraviolet and infrared rays that can be emitted by the arc

Novel technique for estimating pollution-associated leakage current in high voltage insulators based on adaptive filtering in long-term recording

[EN] Moist polluting substances on high-voltage insulator surfaces can cause power-line failures by triggering electric arcs. There are at present no effective methods of measuring insulator pollution levels during normal operations. In this work, we attempt to estimate insulator pollution leakage current (PLC) as an indirect method of measuring deposits in a 30 month period of simultaneously recording leakage current and related environmental variables in substation insulators. We analyzed the relationship between raw leakage current and environmental variables. We canceled out the influence of relative humidity on leakage current by adaptive filtering and then obtained the PLC by filtering out the anomalous peaks in the recording. The proposed method considerably reduces the correlation between leakage current and relative humidity (0.826 vs 0.019). The resulting signal was only slightly correlated with other environmental variables (<0.03), suggesting that the relationships between leakage current and temperature, wind direction and speed are mainly attributable to their influence on relative humidity. The PLC presents a quasi-annual smooth fluctuation over time with a magnitude similar to those obtained in laboratory tests. This novel technique could be used to monitor insulator PLC in real time and thus improve power supply continuity and reduce maintenance costs.Bueno-Barrachina, J.; Cañas Peñuelas, CS.; Ye Lin, Y.; Fuster Roig, VL. (2021). Novel technique for estimating pollution-associated leakage current in high voltage insulators based on adaptive filtering in long-term recording. Measurement Science and Technology. 32(5):1-10. https://doi.org/10.1088/1361-6501/abea3dS11032

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

Condition Monitoring of Outdoor High Voltage Insulators, Online and Offline Techniques: A review

Outdoor insulator plays a vital role in high voltage transmission and distribution system. The performance and properties of outdoor insulator may severely affect due to various types of pollutants. The failure of insulation in high voltage system results in loss of supply and a huge loss of electrical energy to distribution utilities. In order to reduce power losses and provide a reliable power transmission, selection and design of insulators is very important. To monitor the condition and performance of outdoor insulator in contaminated conditions an appropriate diagnostic technique is required. In this paper various online and offline techniques for conditioning monitoring of outdoor insulators are reviewed under different contaminated conditions. To maintain the healthy environment, the condition monitoring of power line insulators is an important requirement. There are number of techniques that have been introduced to fulfil this requirement. Each technique used at different contaminated condition have their own pros and cons. The findings indicate that the most important effect on the surface of the insulators based on the contamination on the surface leakage current and the flashover voltage. This paper will help in the selection and design of condition monitoring techniques for high voltage outdoor insulator

Investigations of ZnO microvaristor for stress control on polymeric outdoor insulators

This thesis is concerned with the investigation of the efficacy of Zinc Oxide microvaristor compound for stress control on polymeric outdoor insulators. The preliminary work has involved a comprehensive literature survey, followed by extensive computational modelling and simulation studies as well as laboratory works covering experimental investigations and fabrication of insulator prototypes. The literature survey reviewed stress-induced degradations as the cause of ageing and insulation failures, the determination of electric field distributions, considerations for outdoor insulator modelling, and field-optimisation techniques for achieving stress relief. An 11 kV polymeric insulator has been modelled and simulated under dry-clean and wet-polluted surface conditions in order to obtain electric field distribution along the insulator creepage path. The critical high field regions on polymeric surfaces were identified. In addition, clean fog solid layer tests were carried out to experimentally examine dry band formation and electric discharges. Experimental investigations confirmed the results previously achieved from theoretical simulations. A non-linear pollution model has been developed for simulating polluted outdoor insulators. The field-dependent conductivity was derived from layer conductance measurements in a non-standard low voltage test. The proposed model was used to simulate insulators under fog and light rain conditions which respectively represent a uniform and non-uniform wetting action in practice. It was demonstrated that the nonlinear pollution model yields a more detailed and realistic field distribution compared with results obtained with models using constant/linear conductivity. Short-length microvaristor coating, having a cone-shaped structure, was introduced at both insulator ends for controlling high field, particularly near the high voltage and ground terminals. The performance of field grading was evaluated through a number of simulation scenarios. The introduction of microvaristor material with an appropriate switching characteristic has led to a substantial improvement in the electric field and heat distributions along the insulator profile. The prototype of an 11kV insulator with microvaristor grading material was fabricated in-house for preliminary tests. Lightning impulse (1.2/50 μs) flashover tests were carried out using the ‘up and down’ method, and the flashover voltage was estimated by the 50% probability breakdown, U50. The results of the lightning impulse test have indicated a considerable increase in the flashover voltage up to 21% when using microvaristor-graded insulator. Favourable field distributions obtained in the simulation study have indicated a strong correlation with the experimental results.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Two-arc dynamic modeling of AC and DC flashovers of EHV post station insulators covered with ice based on laboratory experiments

L'accumulation de glace et de neige sur les isolateurs a été reconnue comme l'un facteur de risque les plus importants dans la fiabilité des lignes de transmission aériennes et des postes électriques. La glace accumulée sur les isolateurs peut amorcer des décharges électriques le long des zones exempts de glace, souvent appelés espaces d'air. En présence d'un film d'eau très conducteur à la surface de la glace, sous une tension appliquée suffisamment élevée, des décharges partielles peuvent être initiées et se développer en arcs partiels. Sous certaines conditions, ces arcs partiels peuvent entraîner le contournement total de la chaîne d'isolateurs et provoquer des pannes d'électricité. L'objectif général de cette recherche est d'étudier le phénomène du contournement électrique des isolateurs de poste extra-haute tension (THT) recouverts de glace. Ainsi, des modèles dynamiques à deux arc, basées sur des modèles mathématiques existants a été proposé pour prédire les paramètres du contournement en courant continu (CC) et alternatif (CA). Le modèle considère l'arc comme une impédance dépendant du temps, constituée d'une résistance en série avec une inductance. La couche de glace résiduelle est définie en termes de résistance équivalente, où la conductivité surfacique équivalente est calculée en tenant compte du film d'eau coulant à la surface de la glace. La présente contribution propose une nouvelle approche permettant de déterminer la conductivité surfacique équivalente. Cette approche est basée sur des concepts de mécanique des fluides incluant les équations de Navier-Stokes, ainsi que sur une série d'expériences menées pour quantifier le débit du film d'eau et la conductivité surfacique équivalente. De plus, les mécanismes à l'origine de l'amorçage des décharges et du développement de l'arc sur la surface de la glace accumulée sur les isolateurs ont été étudiés. Une attention particulière a été accordée à l'évaluation de l'effet de la conductivité volumique de la surface de la glace sur la vitesse de propagation de l'arc pour différentes conductivités de l'eau de congélation, en utilisant des techniques d'enregistrement par caméras vidéo à haute vitesse. Les modèles proposés ont été validés avec succès en laboratoire sur des isolateurs de poste - généralement utilisés dans Hydro-Québec 735 kV - sous tensions CA et CC. La tension de tenue maximale en CC et CA ont été déterminées expérimentalement basés sur la norme IEEE Std 1783. En outre, l'influence du nombre et la position des intervalles d'air sur le contournement des isolateurs recouverts de glace a été étudiée expérimentalement. Les résultats expérimentaux ont montré que la configuration des espaces d'air affecte significativement la tension de tenue maximale. Les principales caractéristiques de contournement, comprenant la tension minimale de contournement et le courant de fuite, prédits par le modèle dynamique à deux arc proposé, concordent à la variation des principaux paramètres, à savoir, la longueur de 'isolateur et la conductivité de l'eau de congélation. Enfin, pour interpréter la performance des isolateurs sous différentes positions des espaces d'air, les distributions de champ électrique et tension le long de l'isolateur recouvert de glace ont été simulés numériquement au cours de la période de fonte, en utilisant la méthode des éléments finis (MEF). Les résultats de simulations confirment que l'augmentation du nombre d'espace d'air améliore la tension de tenue maximale ainsi que l'uniformité de la distribution de tension le long des isolateurs de poste THT. Selon les résultats obtenus, l'utilisation des jupes d'appoint (booster sheds) et anneaux de garde pour améliorer les performances d'isolation des isolateurs de poste dans des conditions de givrage est recommandé. Cette recherche peut être considérée comme une base importante pour le développement de modèles multi-arc et un outil puissant pour la conception et le choix des isolateurs THT soumis à l'accumulation de glace. - Ice and snow accretion on insulators has been recognized as a significant risk factor in the reliability of overhead transmission lines and substations. Accumulated ice on insulators can initiate corona discharge along ice-free zones, often called air gaps. In the presence of a highly conductive water film on the surface of the ice, while applied voltage is sufficiently high, corona discharge activity may be initiated and developed into partial arcs. Under certain conditions, these partial arcs may result in complete flashover. The general objective of this research is to study the flashover phenomenon on icecovered extra-high-voltage (EHV) post insulators. Hence, a two-arc dynamic model based on the existing mathematical models was proposed to predict the parameters of AC and DC flashovers. The model considers the arc as time-dependent impedance constituted of a resistance in series with an inductance. The residual ice layer is defined in terms of an equivalent resistance, where the equivalent surface conductivity is calculated by taking into account the water film flowing along the ice surface. The present contribution proposes a novel approach to determine the equivalent surface conductivity, based on fluid mechanics and the Navier-Stokes equations, as well as on a series of experiments carried out to measure the water film flow rate and conductivity. Moreover, the mechanisms of discharge initiation and arc development on the surface of the ice accumulated on the insulators were studied. Special attention was paid to evaluate the effect of the volume conductivity of the ice surface on the arc propagation velocity for different freezing water conductivities, using high-speed video camera techniques. The proposed models were successfully validated in laboratory using station post insulators - typically used in Hydro-Quebec 735 kV substations - under AC and DC voltages. The maximum AC and DC withstand voltages were experimentally determined based on IEEE Std 1783. Furthermore, the influence of the number and position of air gaps on the flashover performance of ice-covered insulators was investigated experimentally. Experimental results revealed that the air gap configuration affects the maximum withstand voltage significantly. The main characteristics of flashover, including minimum flashover voltage and leakage current, derived from the proposed two-arc dynamic model, respond properly to the variation of major parameters, namely, insulator length and freezing water conductivity. Finally, in order to interpret the performance of insulators under different air gap positions, the voltage and electric field distributions along the ice-covered insulator were simulated numerically during the melting period, using the Finite Element Method (FEM). Simulations results confirm that increasing the number of air gaps improves the maximum withstand voltage and uniformity of voltage distribution of EHV post insulators. Based on the results, the use of booster sheds and grading rings to improve the insulating performance of post insulators under icing conditions is recommended. This research may be regarded as an important basis for the development of multi-arc models and a powerful tool for the design and selection of EHV insulators subjected to ice accretion

Pollution flashover characteristics of coated insulators under different profiles of coating damage

Based on experiments and numerical analysis techniques, this paper aims to investigate the influence of the four different coating damage profiles on the performance of coated 33 kV porcelain insulator strings under polluted and clean surface conditions. The performance of the insulators coated with room temperature vulcanizing (RTV) under partial coating damage and undamaged coating was evaluated. The influence of humidity on pollution flashover was taken into consideration. The ring-shaped, fan-shaped, and random-shaped coating was applied following coating damage. The results showed that the flashover characteristic of the RTV-coated insulators had a significant difference as compared to the normal insulators. Electrical characteristics such as the flashover voltage, critical current, and surface resistance were significantly affected by coating damage distribution and humidity level on the insulators’ surface. The electric field and potential difference were analyzed as well using the finite element method (FEM). The initiation of the arc was observed to appear at the area of insulators where the electric field was the highest. It was also observed that different coating distributions of pollution and humidity levels resulted in a change in the surface pollution layer resistance and an uneven distribution of the electric field. This indicates that the coated insulators’ parameters are directly related to the coating damage distribution on the insulator surface, particularly in the presence of humidity