1,720,998 research outputs found
Degradation Studies on Polymeric Insulators used for EHV and UHV Transmission
No full textHigh voltage insulators used in overhead power transmission systems are of key im-
portance for safe, reliable, and effcient operation of transmission line in transferring huge
amount of electrical power. Conventionally, ceramic/ glass insulators were used in electri-
cal power transmission, recently composite/ polymeric insulators are being used in over-
head transmission lines. The polymeric insulators offer numerous promising advantages
over conventional insulators such as light weight, higher impact strength, better pollution
performance, resistance to vandalism due to its slim design etc. Moreover, the inherent
property of polymeric insulators of being hydrophobic make it more advantageous over
conventional insulators. However, the polymeric material being organic in nature, un-
dergo degradation due to different stresses such as environmental stresses (thermal, UV,
moisture, fog etc,), and electrical stresses. Further, the presence of electrical discharges
such as corona, surface scintillations, occurrence of dry band arcing, operation in adverse
conditions, etc., are recognized as the major accelerating factors for material degrada-
tion. Presence of heavy ionic deposition over the surface leads to surface discharges and
localized temperature rise leads to material erosion which results in electrical tracking
formation and eventually leads to
ash-over/ line outage of power transmission.
In the present work, silicone rubber based polymeric insulators are experimentally in-
vestigated for their material properties and long-term service performance. The available
literature show that polymeric insulators are quite sensitive to their local environmental
conditions and their long-term performance depends on field service environment. The
material properties get affected in adverse environment and foul weather condition. The
unavoidable service conditions such as moisture, fog, acidic rain, snow, pollution etc.,
alter their service life by accelerating their aging which directly affect their long-term
performance. The evaluation of material properties such as surface electrical resistance
and long-term performance of these composite insulators are still under consideration.
The present thesis work focuses on the study of majorly two aspects of polymeric
insulators which governs its performance in service life. One of them is the material prop-
erty, which provides the surface electrical resistance; important role in avoiding the surface
electrical tracking in the polymeric insulators under polluted/ contaminated conditions.
The second aspect is the long-term performance analysis. In the first part of the thesis
work, the experimental investigation are conducted using indigenously developed experi-
mental arrangements. The investigation pertaining to surface resistance of silicone rubber
insulating material investigations, Inclined plane tracking and erosion (IPT) method is
utilized. The evaluation of the material property is conducted under different environ-
mental condition simulating as per standard (normal condition) and acid rain condition
under AC and DC voltage application. The acidity value and salt contents of artifi cial
acid rain is simulated based on the physically observed acid rain information.
In summary, the main contribution of present work is to understand the effect of
different environmental condition on the degradation of silicone rubber insulators and
its effect on material properties and long-term performance. Recurrence plot analysis
performed on measured leakage current present the visual pattern that provide clear
discrimination between fresh and degraded sample. It is proposed that this method could
be used as an important tool to detect and diagnosis the loss of material property of
polymeric insulators. The investigation presents more realistic contribution towards the
surface degradation studies on Polymeric Insulators used for EHV and UHV Transmission
Experimental and Theoretical Investigations on High Voltage Polymeric Insulators
No full textHigh Voltage Ceramic and glass Insulators have been widely used by various transmission and
distribution utilities for several decades across the globe. Recently composite or silicone rubber
insulators have evolved and are now replacing ceramic/glass insulators due to their improved
advantages; however, these Insulators suffer from degradation over a period of service. The
first few chapters of the thesis deal with the study of silicon rubber/polymer insulators under
various climatic conditions. Exhaustive experimental studies were conducted to understand
the degradation of insulators under different climatic conditions which prevail in the Country.
Studies on polymer insulators under sub-zero and under extremely high-temperature conditions
were attempted experimentally to evaluate their performance. During experimentation,
the leakage current was continuously monitored. Later, material analysis, which is a very
important aspect and essential to correlate with the morphological changes of the insulator
surface, was examined. The experimental investigations demonstrate that there is a need to
conduct multi-stress experimentation under specific climatic conditions before the Insulators
are installed in the field. The next portion of the thesis work deals with the failure mechanism
of a Fibre Reinforced Plastic (FRP) Rod. Some portion of the work deals with mathematical
analysis being extended to condition monitoring of dielectric surfaces and understanding the
performance of FRP rods under high AC voltages. Further, experimental investigations are
performed on FRP Rods to analyze the behaviour witnessed, as the field failures reported on
Silicon rubber Insulators, interesting results are reported. Condition monitoring of dielectric
surfaces is very important; hence it was felt necessary to analyze the field performance of transmission/
distribution composite Insulators. To understand further, a mathematical analysis
based on Chaos has been evaluated for leakage current data and quantization of comparative
degradation for a dielectric surface is presented. Later, Empirical Mode Decomposition is also
used for understanding leakage current and implied degradation under minimal data conditions,
and the results are analyzed and presented. Subsequently, the Surface electric field of insulators
exposed to HVDC is studied considering the temporal boundary conditions which may arise
due to the capacitive-resistive transients. The last portion of the thesis deals with a theoretical
study of the bulk conductivity of polymer material. The Electric Field dependence of conductivity
on the application of voltage and subsequent space charge distribution is attempted, and
the results are analyzed and presented. In short, this thesis is a work where both experimental,
simulation and theoretical studies pertaining to silicone rubber insulators are presented
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Design and Development of Non-Intrusive Load Monitoring Techniques and Solar Photovoltaic-Thermoelectric Hybrid Energy Conversion Systems
No full textStandalone Solar Photovoltaic (PV) Systems are deployed where access to the conventional Electric Grid is not present. It is necessary to extract most of the available power from the Solar PV modules as the supply is limited. In such cases, the breakdown of energy demand must be monitored in real-time. Energy Disaggregation is employed to understand the components of the loads connected to the system. One of the techniques used for Energy Disaggregation is Non-Intrusive Load Monitoring (NILM). In this approach, only a single, smart energy meter upstream of the demand side is used to estimate the individual constituents of the load, removing the need for multiple sensors to monitor each load. NILM works by training a Machine Learning model through historical data or power signatures of different appliances and deducing individual components in real-time. In the thesis work, the Factorial Hidden Markov Model is applied for NILM wherein the Hidden States of the model, which are the same as the Appliance States, are estimated based on the power signal from the Smart Energy Meter. Training of the Factorial Hidden Markov model requires historical sub-metered data of each appliance which may be challenging to acquire. Significant contributions of this work are to synthetically develop training datasets based on known parameters of appliances using an Energy Demand Model. The appliance datasets are compared with the Indian Dataset for Ambient Water and Energy (iAWE). With the advent of the Internet of Things (IoT) technology, it is now possible to remotely control individual circuits. Another contribution of this work is providing a single platform to monitor and control Appliances using IoT devices. The data regarding the states of these IoT devices is fed back to the NILM algorithm to improve the accuracy and reduce computation times. The other part of the thesis work mainly consists of Solar PV systems with maximum power point tracking. The Optimum value of Voltage and Current needs to be tracked independently of the load and weather conditions. Amongst the Control Strategies, Voltage Control is most prevalent, and there was a need to investigate Current Control as literature is limited. A framework for Current Control Strategies for Boost Converters was developed and experimentally verified. The Hill-Climbing or the Perturb and Observe method was used for implementation, in which momentum based on past perturbations, was introduced which showed improved performance. Further, a domain-independent Bond Graph approach to model hybrid thermoelectric systems was established. A modular Thermoelectric System is designed, which shows potential for Improvement in the Cooling Capacity and Coefficient of Performance of the system. An Active Heating and Cooling controlled chamber with a Standalone Solar PV System including Energy Disaggregation to Monitor the demand is fabricated and installed
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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