Dissertations / Theses on the topic 'Transmission Line Insulators'

A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure). The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties. This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date. It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.

A majority of utilities conduct maintenance of transmission line components based on the results of routine visual inspection. The inspection is normally done by inspectors who detect defects by visually checking transmission line components either from the air (in helicopters), from the ground (by using high-powered binoculars) or from the top of the structure (by climbing the structure). The main problems with visual inspection of transmission lines are that the determination of the defects varies depending on the inspectors' knowledge and experience and that the defects are often reported qualitatively using vague and linguistic terms such as "medium crack", "heavy rust", "small deflection". As a result of these drawbacks, there is a large variance and inconsistency in defect reporting (which, in time, makes it difficult for the utility to monitor the condition of the components) leading to ineffective or wrong maintenance decisions. The use of inspection guides has not been able to fully address these uncertainties. This thesis reports on the application of a visual inspection methodology that is aimed at addressing the above-mentioned problems. A knowledge-based Fuzzy Inference System (FIS) is designed using Matlab's Fuzzy Logic Toolbox as part of the methodology and its application is demonstrated on utility visual inspection practice of porcelain cap and pin insulators. The FIS consists of expert-specified input membership functions (representing various insulator defect levels), output membership functions (indicating the overall conditions of the insulator) and IF-THEN rules. Consistency in the inspection results is achieved because the condition of the insulator is inferred using the same knowledge-base in the FIS rather than by individual inspectors. The output of the FIS is also used in a mathematical model that is developed to suggest appropriate component replacement date. It is hoped that the methodology that is introduced in this research will help utilities achieve better maintenance management of transmission line assets.

Cette thèse s’inscrit dans le cadre de l’amélioration du comportement électrique des isolateurs de lignes haute tension ; l’objectif est d’assurer une meilleure fiabilité et qualité d’alimentation en énergie électrique. Ce travail a été motivé par la nécessité de répondre à trois questions liées au comportement des isolateurs verre en zone polluée. La première porte sur la recherche d’une méthode permettant de calculer la tension de contournement des chaînes polluées selon le type d’isolateur et ses caractéristiques. La deuxième question concerne la différence de comportement entre les isolateurs en verre et les isolateurs en porcelaine de type « outerrib » ; ce type d’isolateurs présente une forme spécifique adaptée aux environnements à forte pollution. Les tensions de contournement ainsi que les trajectoires de l’arc sur les isolateurs en verre sont très différentes de celles observées avec les isolateurs en porcelaine. Et la troisième question est relative à la défaillance des isolateurs recouverts de silicone lors des essais en chocs (des impulsions de tension) à front raide. En effet, les isolateurs recouverts d’une couche de 0.3 mm (ou plus) de silicone hydrophobe explosent lorsqu’ils sont soumis à des impulsions de tension à front raide d’amplitude très élevée pendant un temps très court. Différents mécanismes pouvant être à l’origine de l’explosion/éclatement des isolateurs recouverts d’une couche de silicone sont discutés. Il ressort des différents tests et analyses que le mécanisme le plus probable semble être la fragmentation par plasma. En effet, suite à l’application d’une tension à front raide, d’amplitude très élevée, des canaux (fissures) microscopiques prennent naissance là où le champ électrique est le plus intense. L’application répétitive des chocs de tension conduit au développement de décharges dans ces canaux (rupture diélectrique de l’air) c’est-à-dire des arcs (canaux de plasma) qui se développent/propagent dans le volume de l’isolateur. La puissance déchargée (c’est-à-dire l’énergie stockée dans les condensateurs du générateur en des temps très courts) dans ces canaux à chaque choc étant très élevée, elle conduit à l’explosion de l’isolateur après quelques chocs (parfois 5 ou 6 suffisent): c’est la fragmentation par plasma
This thesis deals with the improvement of the electrical behavior of insulators of high voltage lines; the objective is to ensure better reliability and quality of power supply. This work was motivated by the need to answer three questions related to the behavior of glass insulators in polluted areas. The first one concerns the search for method for calculating the flashover voltage of polluted chains according to the type of insulator and its characteristics. The second question concerns the difference in behavior between glass insulators and "outerrib" porcelain insulators; this type of insulator has a specific shape adapted to environments with high pollution. The flashover voltages as well as the trajectories of the arc on glass insulators are very different from those observed with porcelain insulators. And the third issue is the failure of silicon-coated insulators during shock tests (pulses) with a steep front. Indeed, insulators coated with a layer of 0.3 mm (or more) of hydrophobic silicone explode when subjected to very high amplitude steep-edge voltage pulses for a very short time. Different mechanisms that may be responsible for the explosion / puncturing of insulators covered with a layer of silicone are discussed. It appears from the various tests and analyzes that the most probable mechanism seems to be plasma fragmentation (cracking). Indeed, following the application of a steep front voltage, of very high amplitude, microscopic channels (fissures) originate where the electric field is most intense. The repetitive application of impulse voltages (shocks) leads to the development of discharges in these channels (breakdown of the air), i.e.; arcs (plasma channels) which develop / propagate in the volume of the insulator. The discharged power (i.e.; the energy stored in the capacitors of the generator in a very short times) in these channels (cracks) at each shock being very high, leads to the explosion of the insulator after some shocks (5 to 6 sometimes): it is the fragmentation by plasma or plasma cracking

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-04-24T16:40:39Z No. of bitstreams: 1 BRUNO ALBUQUERQUE DIAS – DISSERTAÇÃO (PPGEE) 2017.pdf: 3277136 bytes, checksum: 1277dbc3bda9c5d90497f95d8bf94878 (MD5)
Made available in DSpace on 2018-04-24T16:40:39Z (GMT). No. of bitstreams: 1 BRUNO ALBUQUERQUE DIAS – DISSERTAÇÃO (PPGEE) 2017.pdf: 3277136 bytes, checksum: 1277dbc3bda9c5d90497f95d8bf94878 (MD5) Previous issue date: 2017-03-17
CNPq
O acúmulo de poluentes na superfície dos isoladores, que compõem as linhas de transmissão, permite a formação de uma camada de substâncias que, sob incidência de névoa, chuva ou orvalho, produzem soluções condutoras. Na região norte do Brasil, muitos casos de poluição biológica são caracterizados como limo, associação de microalgas e fungos, a resistência dielétrica da superfície do isolador, nestes casos, é reduzida, causando falhas no sistema elétrico. Para investigar o efeito dessa poluição sobre os isoladores, o presente trabalho apresenta um modelo computacional que relaciona o aspecto visual do limo no isolador (intensidade, forma e local) com a sua corrente de fuga obtida por simulação e correlaciona eficiência da simulação com experimentos em laboratório. Os objetos de teste utilizados foram isoladores de disco de vidro, limpos e poluídos com limo. Os isoladores contaminados foram retirados da subestação de Guamá, Pará, Brasil e os experimentos realizados no Laboratório de Alta Tensão da Universidade Federal de Campina Grande, na Paraíba. As simulações computacionais utilizam o Método dos Elementos Finitos e, assim como as medições laboratoriais, foram realizadas para diferentes condições de umidade, uma vez que essa variável tem influência significativa na condutividade do limo. A simulação se mostrou eficiente e os resultados apresentados mostram que é possível estimar a corrente de fuga desse tipo de isolador sob diferentes condições de umidade e diferentes níveis de poluição.
The accumulation of pollutants on surface of insulators allows the formation of a layer of substances that, with mist, rain or dew, produces conductive solutions. The surface dielectric strength, in these cases, is reduced, causing failures in electrical system. In the northern region of Brazil, many cases of biological pollution are characterized as slimes, association of microalgae and fungi. To investigate the effect of this pollution on the insulators, the present work presents a computational model that relates the visual aspect of slime in the insulator (intensity, shape and location) with its leakage current obtained by simulation and correlates efficiency of the simulation with laboratory experiments. Test objects used were glass disk insulators, cleaned and polluted with slime. The contaminated insulators were removed from the Guamá Substation, Pará, Brazil and the tests performed at the High Voltage Laboratory of Federal University of Campina Grande in Paraíba, Brazil. Computational simulations using Finite Element Method and, as well as the laboratory measurements, were performed for different humidity conditions since this variable has a significant influence on slime conductivity. The simulation proved to be efficient and the presented results show that it is possible to estimate leakage current of this type of insulator under different humidity conditions and different levels of pollution.

Etude de l'aspect statique du contournement, on montre experimentalement que les criteres de wilkins et hampton ne s'appliquent qu'au modele d'obenaus. Mise en evidence de l'importance du champs electrique au voisinage de la decharge. Etude detaillee de la conduction electrolytique et de son evolution pendant le contournement

This thesis presents the design and fabrication of coplanar waveguide to microstrip transitions and planar spiral inductors, and the design of metal-insulator-metal capacitors, a planar band-pass, and a low-pass filter structures as an application for the inductors and capacitors using the RF MEMS technology. This thesis also includes a packaging method for RF MEMS devices with the use of benzocyclobutene as bonding material. The transition structures are formed by four different methods between coplanar waveguide end and microstrip end, and they are analyzed in 1-20 GHz. Very low loss transitions are obtained by maintaining constant characteristic impedance which is the same as the port impedance through the transition structures. The planar inductors are formed by square microstrip spirals on a glass substrate. Using the self-inductance propery of a conductive strip and the mutual inductance between two conductor strips in a proper arrangement, the inductance value of each structure is defined. Inductors from 0.7 nH up to 20 nH have been designed and fabricated. The metal-insulator-metal capacitors are formed by two coplanar waveguide structures. In the intersection, one end of a coplanar waveguide is placed on top of the end of the other coplanar waveguide with a dielectric layer in between. Using the theory of parallel plate capacitors, the capacitance of each structure is adjusted by the dimensions of the coplanar waveguides, which obviously adjust the area of intersection. Capacitors from 0.3 pF up to 9.8 pF have been designed. A low-pass filter and a band-pass filter are designed using the capacitors and inductors developed in this thesis. In addition to lumped elements, the interconnecting transmission lines, junctions and input-output lines are added to filter topologies. The RF MEMS packaging is realized on a coplanar waveguide structure which stands on a silicon wafer and encapsulated by a silicon wafer. The capping chip stands on the BCB outer ring which promotes adhesion and provides semi hermeticity. Keywords: Transition between transmission lines, planar spiral inductor, metal-insulator-metal capacitor, RF MEMS packaging, surface micromachining.

Comparaison des differentes modelisations electriques du systeme decharge-surface polluee utilisees dans l'etude du contournement des isolateurs. Utilisant un modele de laboratoire ou la pollution est representee par un canal rempli d'electrolyte, on a releve les valeurs de la tension de contournement en fonction de la resistance lineique du canal. Pour les resistances lineiques superieures a 7 kiloohms par centimetre, c'est le modele de rao et gopal qui est le mieux adapte; au-dessous, c'est le modele de wilkins dans lequel on poste les constantes de la decharge mesurees dans la vapeur d'eau. Nouvelle modelisation permettant de calculer, en fonction du temps, l'elongation de la decharge et le courant fourni par la source

碩士
國立高雄應用科技大學
電機工程系
99
Insulators are used to insulate between overhead transmission lines and their supporting tower for power delivery. Due to Taiwan is a north-south elongated island surrounded by the sea, important electrical equipment are located near coastal areas, insulators are frequently polluted by salt fog damage and dust fog etc, and causes fouling. The polluted insulators usually results in blackout of either local area or whole area along the power transmission line. Therefore, their performance has great influence on the safe operation of power equipment. This thesis first uses an analyze software of Alternative Transient Program-Electromagnetic Transient Program(ATP-EMTP) to simulate and establish voltage distribution model under both normal and degraded cases for 69kV and 161kV transmission line. Second, insulator leakage current measurement device which designs stainless steel ring closure mounted on insulator’s film surface nearest the tower side to measure leakage current is developed. In measurement unit, dsPIC microprocessor is selected as core processor to form peak value counting circuit to record the number of peak value of leakage current through the insulator. Finally, proposed designed device is tested by autotransformer located at high voltage laboratory of Taiwan Power Research Institute to justify the effectiveness and practicality by results.

Outdoor insulators are one of the most important parts of a power system. The reliability of a power system depends also on the reliability of the insulators. The main functions of an insulator used for outdoor applications are to give the necessary insulation, provide the necessary mechanical support to the transmission line conductor and also to resist the various environmental stresses like pollution, ultra violet rays etc. Traditionally porcelain and glass insulators have been used for outdoor insulator applications. They are good insulators under normal conditions and the cap and pin arrangement allows them to take up the mechanical load of the line. But owing to their large weight and brittle nature they are susceptible to vandalism and also they have increased cost of installation and commissioning. But the main problem of porcelain and glass insulators is its performance under polluted environmental condition. Under wet and polluted conditions, the porcelain insulators allow the formation of a conducting layer on the surface which results in setting up of leakage current, dry band arcing and power loss. This problem is further augmented under dc voltages where the stress is unidirectional and the contaminant deposition is higher as compared to ac. Polymeric insulators are a good alternative for porcelain and ceramic insulators for use especially under dc voltages because of their good pollution performance. The property of surface hydrophobicity resists the setting up of leakage currents and hence polymeric insulators help in reducing power loss. They are also light in weight and vandalism resistant and hence easier to install. But being polymeric, they form conductive tracks and erode when exposed to high temperatures which occur at the surface during dry band arcs and when exposed to corona discharges. The surface hydrophobicity is also temporarily lost when exposed to different electrical stresses. Silicone rubber is the most popular among the various choices of polymers for outdoor insulator applications. They have good surface hydrophobicity and tracking performance. But polymers in their pure form cannot be used as insulators because of their poor mechanical strength. Adding inorganic fillers into the polymer matrix not only improves its mechanical properties but also its erosion resistance. Micron sized Alumina Trihydrate (ATH) is used traditionally to improve the tracking and erosion resistance of polymeric insulators. A very high loading (up to 60%) is used. Adding such a high filler loading to the base polymer hampers its flexibility and the material processing. With the advent of nanotechnology, nano fillers have come into vogue. Studies conducted on nano filled polymers showed exciting results. A small amount of nano fillers in the polymer matrix showed significant improvement in the mechanical strength without hampering its flexibility. The electrical properties like tracking and erosion also improved with filler loading. Hence the use of nano filled silicone rubber is a good alternative for use as a high voltage insulator especially under dc voltages. Reports suggest that adding nano fillers into the silicone rubber matrix improves the tracking and erosion resistance and the corona degradation as compared to the unfilled samples under ac voltages. The literature on the dc performance of silicone rubber nano composites is scarce. So the present study aims to evaluate the performance of silicone rubber nano composites for tracking and erosion resistance and corona degradation under dc voltages. The tracking and erosion resistance under dc voltages was measured using the Inclined Plane Tracking and Erosion Resistance set up as per ASTM D2303 which was modified for dc voltage studies. The performance of nano Alumina and nano Silica fillers were evaluated under negative dc and the performance was compared with micron sized Alumina Trihydrate filled samples. The effect of filler loading was also studied. It was seen that the performance of the silicone rubber improved with filler loading. A small loading percentage of nano fillers were enough to give performance similar to silicone rubber filled with micron sized ATH filler. The silicone rubber performed better under negative dc as compared to ac and positive dc. The positive dc tests showed a migration of ions from the electrodes onto the sample surface. The increased surface conductivity resulted in very heavy erosion in the case of positive dc tested samples. The corona aging studies were also conducted on silicone rubber nano composites. Nano silica was used as filler in this case. Different filler loadings were employed to understand the effect of filler loading. The corona was generated using a needle plane electrode and samples were exposed to both positive and negative dc corona. The samples were exposed to corona for different time intervals – 25 and 50 hours to study the effect of exposure time. The hydrophobicity, crack width and surface roughness were measured after the tests. Adding nano fillers into the polymer matrix improved the corona performance. With filler loading, the performance improved. The samples exposed to positive dc corona performed better than those under negative dc corona. The loss of hydrophobicity, surface cracks and the surface roughness was less in the case of positive dc corona tested samples. With exposure time, the performance of silicone rubber became poorer for positive dc corona tested samples. For the negative dc corona tested samples, the performance seemed to improve with exposure time. The tracking and erosion resistance and the corona aging studies conducted showed that the performance of silicone rubber is improved by adding nano fillers into the polymer matrix. A small amount of nano filler loading was enough to perform similar to a heavily loaded micron filled sample. Hence nano fillers can be used as a good functional material to improve the performance of silicone rubber insulators especially under wet and polluted conditions.

Outdoor insulators are one of the most important parts of a power system. The reliability of a power system depends also on the reliability of the insulators. The main functions of an insulator used for outdoor applications are to give the necessary insulation, provide the necessary mechanical support to the transmission line conductor and also to resist the various environmental stresses like pollution, ultra violet rays etc. Traditionally porcelain and glass insulators have been used for outdoor insulator applications. They are good insulators under normal conditions and the cap and pin arrangement allows them to take up the mechanical load of the line. But owing to their large weight and brittle nature they are susceptible to vandalism and also they have increased cost of installation and commissioning. But the main problem of porcelain and glass insulators is its performance under polluted environmental condition. Under wet and polluted conditions, the porcelain insulators allow the formation of a conducting layer on the surface which results in setting up of leakage current, dry band arcing and power loss. This problem is further augmented under dc voltages where the stress is unidirectional and the contaminant deposition is higher as compared to ac. Polymeric insulators are a good alternative for porcelain and ceramic insulators for use especially under dc voltages because of their good pollution performance. The property of surface hydrophobicity resists the setting up of leakage currents and hence polymeric insulators help in reducing power loss. They are also light in weight and vandalism resistant and hence easier to install. But being polymeric, they form conductive tracks and erode when exposed to high temperatures which occur at the surface during dry band arcs and when exposed to corona discharges. The surface hydrophobicity is also temporarily lost when exposed to different electrical stresses. Silicone rubber is the most popular among the various choices of polymers for outdoor insulator applications. They have good surface hydrophobicity and tracking performance. But polymers in their pure form cannot be used as insulators because of their poor mechanical strength. Adding inorganic fillers into the polymer matrix not only improves its mechanical properties but also its erosion resistance. Micron sized Alumina Trihydrate (ATH) is used traditionally to improve the tracking and erosion resistance of polymeric insulators. A very high loading (up to 60%) is used. Adding such a high filler loading to the base polymer hampers its flexibility and the material processing. With the advent of nanotechnology, nano fillers have come into vogue. Studies conducted on nano filled polymers showed exciting results. A small amount of nano fillers in the polymer matrix showed significant improvement in the mechanical strength without hampering its flexibility. The electrical properties like tracking and erosion also improved with filler loading. Hence the use of nano filled silicone rubber is a good alternative for use as a high voltage insulator especially under dc voltages. Reports suggest that adding nano fillers into the silicone rubber matrix improves the tracking and erosion resistance and the corona degradation as compared to the unfilled samples under ac voltages. The literature on the dc performance of silicone rubber nano composites is scarce. So the present study aims to evaluate the performance of silicone rubber nano composites for tracking and erosion resistance and corona degradation under dc voltages. The tracking and erosion resistance under dc voltages was measured using the Inclined Plane Tracking and Erosion Resistance set up as per ASTM D2303 which was modified for dc voltage studies. The performance of nano Alumina and nano Silica fillers were evaluated under negative dc and the performance was compared with micron sized Alumina Trihydrate filled samples. The effect of filler loading was also studied. It was seen that the performance of the silicone rubber improved with filler loading. A small loading percentage of nano fillers were enough to give performance similar to silicone rubber filled with micron sized ATH filler. The silicone rubber performed better under negative dc as compared to ac and positive dc. The positive dc tests showed a migration of ions from the electrodes onto the sample surface. The increased surface conductivity resulted in very heavy erosion in the case of positive dc tested samples. The corona aging studies were also conducted on silicone rubber nano composites. Nano silica was used as filler in this case. Different filler loadings were employed to understand the effect of filler loading. The corona was generated using a needle plane electrode and samples were exposed to both positive and negative dc corona. The samples were exposed to corona for different time intervals – 25 and 50 hours to study the effect of exposure time. The hydrophobicity, crack width and surface roughness were measured after the tests. Adding nano fillers into the polymer matrix improved the corona performance. With filler loading, the performance improved. The samples exposed to positive dc corona performed better than those under negative dc corona. The loss of hydrophobicity, surface cracks and the surface roughness was less in the case of positive dc corona tested samples. With exposure time, the performance of silicone rubber became poorer for positive dc corona tested samples. For the negative dc corona tested samples, the performance seemed to improve with exposure time. The tracking and erosion resistance and the corona aging studies conducted showed that the performance of silicone rubber is improved by adding nano fillers into the polymer matrix. A small amount of nano filler loading was enough to perform similar to a heavily loaded micron filled sample. Hence nano fillers can be used as a good functional material to improve the performance of silicone rubber insulators especially under wet and polluted conditions.

Pollution is the single largest cause of transmission/distribution line outages, next to lightning, which result in expensive power outages. A major significance of the problem is that it can repeatedly occur even at normal working voltages. As a result, it has become the most detrimental factor affecting the safe operation of extra and ultra high voltage (EHV/UHV) transmission lines and substations. In reality, the phenomenon of pollution-induced flashover is a very complex, and vexatious problem that continues to challenge high voltage engineers even today. In spite of knowing this phenomenon for the past several decades, a solution has remained still elusive. Although there exist some remedial measures, there are associated limitations, which will become evident on long runs. The guaranteed solution seems to be the washing and cleaning of insulators for which utilities spend significant amount of money. Therefore, there is a need to develop a suitable mitigation technique which is cost effective and yield better performance in the field. Motivated by this, the present study is undertaken and it essentially aims to seek simple alternative solutions for the problem for strings with ceramic insulator discs. All the ten types (normal and anti fog) ceramic insulators, which are commonly employed in our country, are considered in the study. Amongst the several controllable and uncontrollable physical quantities leading to the pollution flashover phenomena, the maximum surface field identified as on of the major influencing factor. In fact, the field concentration near the pin can lead to early formation of dry band and scintillation/partial arcs. Considering this, it is intended to seek possible minimization of the maximum surface field occurring at the pin region. This is expected to yield enhanced pollution/contamination flashover strength and in addition, show an improvement in normal operation. The intended study requires a detailed knowledge on field distribution. However, the required data is found to be rather scarce. In view of this a detailed study on field distribution is taken up for all the ten types of disc insulators used in our country. For the problem under investigation, the governing equation has been identified for both clean and polluted conditions along with pertinent boundary conditions. Considering the open geometry nature of the problem along with presence of multiple dielectrics, Surface Charge Simulation (SCSM) methodology was found to be most suitable and hence adopted for the work. In particular, the Galerkin method with piecewise linear interpolation function is employed in the formulation. The method employed and the codes developed are verified with suitable examples. First, a detailed quantification of the field distribution under clean conditions is made for all the ten types of discs in single disc and string configuration. Subsequently, the task of reducing the maximum surface field gradient, which occurs at the pin, is attempted. Several consideration lead to an artificial extension of pin as one of best feasible choice. However, any attempt to extend the pin would lead to some reduction in total creepage length, possible enhancement of bulk stress in air and enhancement of stress in triple junction. After a careful study, involving several experimental trials, a novel field control element (FCE) is developed both for normal and anti-fog types of insulator discs. From the electric field simulation study, it is shown that the use of field control element for uniform pollution deposition prevailing under laboratory test conditions yields a significant reduction of maximum surface field for discs by about 47 to 54%. Similarly a reduction of about 37% to 55% in case of 3-disc string (for 33 kV class), 30% to 52% in case of 9-disc string (for 132 kV class), 27% to 52% in case of 14-disc string (220 kV class), 27% to 54% in case of 23/20 disc string (for 400 kV class) and 41% to 48% in case of 35/29 disc strings (for 765kV class) is achieved respectively for different strings. It is anticipated that this will lead to retardation in inception of scintillations/partial arcs, which in turn can reduce the risk of pollution induced flashover. Subsequently, it was aimed to experimentally evaluate the impact of field control element on the performance of disc/string under normal and that during polluted conditions. For this a national level unique artificial pollution test facility as per the international standards has been established for conducting pollution studies on disc insulator/strings up to 132kV system voltage (The rating of test source: 150kV/2A,100kV/3A,50kV/6A of 300kVA). Experimental investigations for the normal operation involving dry and wet power frequency flashover strengths, lightning impulse strength, radio interference level (RIV), visible discharge inception (Corona) level and voltage distribution along the string are carried out. The study showed that with the insertion of field control element, performance under normal condition is maintained and in fact noticeably improved in certain cases. Subsequently pollution flashover strength is evaluated using solid layer and cold fog methods. The pollution flashover strength exhibited an overall improvement 15 to 20% for all types of discs considered in the study. Similarly an improvement of 16 to 19% and 12-14% is observed for 3-disc string and 6-disc string respectively. The reasons for relatively lower gain in the pollution flashover strength as compared to reduction in maximum surface field are investigated. In particular, the reduction in improvement with number of discs in a string is dealt with. The non-uniform wet-ting against highly non-uniform drying of insulator surface and discs in a string, are identified as the cause for deviation. For an experimental verification of the same, the pollution layer resistance of individual discs in a 3-disc string is measured prior to and immediately after flashover. It is shown that the resistances of the different units become grossly different even though initial values were substantially the same. The values measured immediately after flashover show that the resistance of the top unit develops voltage enough to result in its flashover and subsequently, the flashover of the whole string. In summary, the main contribution of the present work is the development of novel field control element (FCE) for both normal and anti-fog type of ceramic disc insulators, which will enhance their pollution flashover strength. The actual cost of these elements is estimated to be about 1-2% of the cost of the disc, while the gain in strength is shown to be more than 12 - 20%.

Pollution is the single largest cause of transmission/distribution line outages, next to lightning, which result in expensive power outages. A major significance of the problem is that it can repeatedly occur even at normal working voltages. As a result, it has become the most detrimental factor affecting the safe operation of extra and ultra high voltage (EHV/UHV) transmission lines and substations. In reality, the phenomenon of pollution-induced flashover is a very complex, and vexatious problem that continues to challenge high voltage engineers even today. In spite of knowing this phenomenon for the past several decades, a solution has remained still elusive. Although there exist some remedial measures, there are associated limitations, which will become evident on long runs. The guaranteed solution seems to be the washing and cleaning of insulators for which utilities spend significant amount of money. Therefore, there is a need to develop a suitable mitigation technique which is cost effective and yield better performance in the field. Motivated by this, the present study is undertaken and it essentially aims to seek simple alternative solutions for the problem for strings with ceramic insulator discs. All the ten types (normal and anti fog) ceramic insulators, which are commonly employed in our country, are considered in the study. Amongst the several controllable and uncontrollable physical quantities leading to the pollution flashover phenomena, the maximum surface field identified as on of the major influencing factor. In fact, the field concentration near the pin can lead to early formation of dry band and scintillation/partial arcs. Considering this, it is intended to seek possible minimization of the maximum surface field occurring at the pin region. This is expected to yield enhanced pollution/contamination flashover strength and in addition, show an improvement in normal operation. The intended study requires a detailed knowledge on field distribution. However, the required data is found to be rather scarce. In view of this a detailed study on field distribution is taken up for all the ten types of disc insulators used in our country. For the problem under investigation, the governing equation has been identified for both clean and polluted conditions along with pertinent boundary conditions. Considering the open geometry nature of the problem along with presence of multiple dielectrics, Surface Charge Simulation (SCSM) methodology was found to be most suitable and hence adopted for the work. In particular, the Galerkin method with piecewise linear interpolation function is employed in the formulation. The method employed and the codes developed are verified with suitable examples. First, a detailed quantification of the field distribution under clean conditions is made for all the ten types of discs in single disc and string configuration. Subsequently, the task of reducing the maximum surface field gradient, which occurs at the pin, is attempted. Several consideration lead to an artificial extension of pin as one of best feasible choice. However, any attempt to extend the pin would lead to some reduction in total creepage length, possible enhancement of bulk stress in air and enhancement of stress in triple junction. After a careful study, involving several experimental trials, a novel field control element (FCE) is developed both for normal and anti-fog types of insulator discs. From the electric field simulation study, it is shown that the use of field control element for uniform pollution deposition prevailing under laboratory test conditions yields a significant reduction of maximum surface field for discs by about 47 to 54%. Similarly a reduction of about 37% to 55% in case of 3-disc string (for 33 kV class), 30% to 52% in case of 9-disc string (for 132 kV class), 27% to 52% in case of 14-disc string (220 kV class), 27% to 54% in case of 23/20 disc string (for 400 kV class) and 41% to 48% in case of 35/29 disc strings (for 765kV class) is achieved respectively for different strings. It is anticipated that this will lead to retardation in inception of scintillations/partial arcs, which in turn can reduce the risk of pollution induced flashover. Subsequently, it was aimed to experimentally evaluate the impact of field control element on the performance of disc/string under normal and that during polluted conditions. For this a national level unique artificial pollution test facility as per the international standards has been established for conducting pollution studies on disc insulator/strings up to 132kV system voltage (The rating of test source: 150kV/2A,100kV/3A,50kV/6A of 300kVA). Experimental investigations for the normal operation involving dry and wet power frequency flashover strengths, lightning impulse strength, radio interference level (RIV), visible discharge inception (Corona) level and voltage distribution along the string are carried out. The study showed that with the insertion of field control element, performance under normal condition is maintained and in fact noticeably improved in certain cases. Subsequently pollution flashover strength is evaluated using solid layer and cold fog methods. The pollution flashover strength exhibited an overall improvement 15 to 20% for all types of discs considered in the study. Similarly an improvement of 16 to 19% and 12-14% is observed for 3-disc string and 6-disc string respectively. The reasons for relatively lower gain in the pollution flashover strength as compared to reduction in maximum surface field are investigated. In particular, the reduction in improvement with number of discs in a string is dealt with. The non-uniform wet-ting against highly non-uniform drying of insulator surface and discs in a string, are identified as the cause for deviation. For an experimental verification of the same, the pollution layer resistance of individual discs in a 3-disc string is measured prior to and immediately after flashover. It is shown that the resistances of the different units become grossly different even though initial values were substantially the same. The values measured immediately after flashover show that the resistance of the top unit develops voltage enough to result in its flashover and subsequently, the flashover of the whole string. In summary, the main contribution of the present work is the development of novel field control element (FCE) for both normal and anti-fog type of ceramic disc insulators, which will enhance their pollution flashover strength. The actual cost of these elements is estimated to be about 1-2% of the cost of the disc, while the gain in strength is shown to be more than 12 - 20%.

碩士
國立高雄應用科技大學
電機工程系博碩士班
102
In the Past, the insulator design data had been collected by artificially to support the tower design of overhead transmission line in Taipower, because those data was not easy to collect so that some incorrect design data was caused, and that so the result of design is not correct. In this Study, the relation of insulator design data had been analyzed first and then the relation between those data and the design process had been studied also, and then the Relational database had been development to integrate those design data which include insulator material、 types and property , and then a web-based network application interface had been designed to complete the design process. In conclusion, the result of this research has been greatly promoted the efficiency of insulator design for the overhead transmission line in Taipower.

Σκοπόςτης παρούσας εργασίαςείναι αρχικά η δημιουργία ενός μοντέλου με τα χαρακτηριστικά ενός μονωτήρα υψηλής τάσης.Το μοντέλο αυτό θα ενσωματωθεί στο μοντέλο μιας γραμμής υψηλής τάσης διπλού κυκλώματος των 400kV, για να υπολογιστούν οι επαγόμενες υπερτάσεις σε παρακείμενο υπέργειο αγωγό μεταφοράς υδρογονανθράκων. Τα παραπάνω επιτυγχάνονταιμε τη μοντελοποίηση πραγματικών πυλώνων και γραμμών του Ελληνικού συστήματος μεταφοράς καθώς και υπέργειου αγωγού υδρογονανθράκων.Η εξομοίωση υλοποιείται μέσω του προγράμματος ATP-EMTP. Για τον σχεδιασμό του μοντέλου του μονωτήρα χρησιμοποιήθηκε το μοντέλοVolt-TimeCurve. Επίσης χρησιμοποιήθηκαν δύο τύποι κεραυνού για τις προσομοιώσεις, για γρήγορο και αργό σήμα, με τιμές ρεύματος 100kA. Για το γρήγορο, οι τιμές χρόνων μετώπου και ουράς 1.2/50μs και για το αργό σήμα 10/350μs. Σε αυτή τη διπλωματική εργασία υπάρχουν 8 κεφάλαια. Στα πρώτα 5 κεφάλαια έγινε μια παράθεση πληροφοριών και θεωρητική προσέγγιση όλων των επιμέρους τμημάτων που συνθέτουν τη συνολική διάταξη της μελέτης. Στο 5ο κεφάλαιο γίνεται λεπτομερής αναφοράστο πρόγραμμα ATP-EMTP στο οποίο πραγματοποιήθηκε η προσομοίωση.Στο 6o κεφάλαιο γίνεται η μοντελοποίηση όλων των στοιχείων της διάταξης και η ενσωμάτωσή τους στοATP-EMTP. Στο 7ο κεφάλαιο γίνεται παρουσίαση του μοντέλου του μονωτήρα που αναπτύχθηκε και στο 8ο κεφάλαιο γίνεται παρουσίαση των αποτελεσμάτων της προσομοίωσης και εξάγονται κάποια συμπεράσματα σχετικά με τη διάταξη.
The purpose of this paper is , at first, to create a model with the features of a high voltage insulator. This model will be incorporated into the model of a high-voltage line double circuit 400kV, to calculate the induced transients in adjacent aboveground pipeline hydrocarbons. These goals are achieved by modeling real pillars and lines of Greek transport system and overground pipeline hydrocarbons. The simulation is implemented through the ATP-EMTP. The model Volt-Time Curve is used for the modeling of the insulator. Also, two types of lightning are used for the simulations, for fast and slow signal, with current values 100kA. For fast signal, the prices of front and tail time are 1.2 / 50ms and for slow signal 10 / 350ms. In this thesis there are 8 chapters. In the first five chapters was a quote and information theoretical approach to all individual parts that make up the overall layout of the study. The 5 chapter is a detailed reference to the ATP-EMTP program which performed the simulation. The 6 chapter is the modeling of all elements of the layout and the incorporation into the ATP-EMTP. In chapter 7 we present the model of the insulator developed and in chapter 8 we present the simulation results and draw inferences about the layout.