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- Creators: Ayyanar, Raja
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Description
Dynamic loading is the term used for one way of optimally loading a transformer. Dynamic loading means the utility takes into account the thermal time constant of the transformer along with the cooling mode transitions, loading profile and ambient temperature when determining the time-varying loading capability of a transformer. Knowing the maximum dynamic loading rating can increase utilization of the transformer while not reducing life-expectancy, delaying the replacement of the transformer. This document presents the progress on the transformer dynamic loading project sponsored by Salt River Project (SRP). A software application which performs dynamic loading for substation distribution transformers with appropriate transformer thermal models is developed in this project. Two kinds of thermal hottest-spot temperature (HST) and top-oil temperature (TOT) models that will be used in the application--the ASU HST/TOT models and the ANSI models--are presented. Brief validations of the ASU models are presented, showing that the ASU models are accurate in simulating the thermal processes of the transformers. For this production grade application, both the ANSI and the ASU models are built and tested to select the most appropriate models to be used in the dynamic loading calculations. An existing application to build and select the TOT model was used as a starting point for the enhancements developed in this work. These enhancements include: Adding the ability to develop HST models to the existing application, Adding metrics to evaluate the models accuracy and selecting which model will be used in dynamic loading calculation Adding the capability to perform dynamic loading calculations, Production of a maximum dynamic load profile that the transformer can tolerate without acceleration of the insulation aging, Provide suitable output (plots and text) for the results of the dynamic loading calculation. Other challenges discussed include: modification to the input data format, data-quality control, cooling mode estimation. Efforts to overcome these challenges are discussed in this work.
ContributorsLiu, Yi (Author) / Tylavksy, Daniel J (Thesis advisor) / Karady, George G. (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2011
Description
The Kasturba Gandhi Balika Vidyalaya (KGBV) policy scheme launched in 2004 by the Ministry of Human Resource Development, the Government of India, aims to provide secondary level education (grade 6-8) for girls residing predominantly in minority communities, the Scheduled Caste (SC), the Scheduled Tribe (ST), and the Other Backward Caste (OBC). Since its launch, the Government of India established 2,578 KGBV schools in 27 states and union territories (UTs). The present study examines the new policy and its implementation at three KGBV schools located in rural villages of Uttar Pradesh (UP), India. The purpose was to analyze the Government of India's approach to increasing education opportunity and participation for educationally disadvantaged girls using the empowerment framework developed by Deepa Narayan. Observations at three schools, interviews with teachers and staff members of the implementation agency (i.e., Mahila Samakhya (MS)), and surveys administered to 139 teachers were conducted over a four month period in 2009. Adopting creative teaching approaches and learning activities, MS creates safe learning community which is appropriate for the rural girls. MS gives special attention to nurturing the girls' potential and empowering them inside and outside the school environment through social discussion, parental involvement, rigid discipline and structure, health and hygiene education, and physical and mental training. Interviews with the state program director and coordinators identified some conflicts within government policy schemes such as the Teacher-pupil ratios guidelines as a part of the programs for the universalization of elementary education. Major challenges include a high turnover rate of teachers, a lack of female teachers, a lack of provision after Class 8, and inadequate budget for medical treatment. Recommendations include promoting active involvement of male members in the process of girls' empowerment, making MS approaches of girls' education in rural settings standardized for wider dissemination, and developing flexible and strong partnership among local agencies and government organizations for effective service delivery.
ContributorsWatanabe, Miku (Author) / Fischman, Gustavo (Thesis advisor) / Wiley, Terrence (Committee member) / Mccarty, Teresa (Committee member) / Arizona State University (Publisher)
Created2011
Description
The development of a Solid State Transformer (SST) that incorporates a DC-DC multiport converter to integrate both photovoltaic (PV) power generation and battery energy storage is presented in this dissertation. The DC-DC stage is based on a quad-active-bridge (QAB) converter which not only provides isolation for the load, but also for the PV and storage. The AC-DC stage is implemented with a pulse-width-modulated (PWM) single phase rectifier. A unified gyrator-based average model is developed for a general multi-active-bridge (MAB) converter controlled through phase-shift modulation (PSM). Expressions to determine the power rating of the MAB ports are also derived. The developed gyrator-based average model is applied to the QAB converter for faster simulations of the proposed SST during the control design process as well for deriving the state-space representation of the plant. Both linear quadratic regulator (LQR) and single-input-single-output (SISO) types of controllers are designed for the DC-DC stage. A novel technique that complements the SISO controller by taking into account the cross-coupling characteristics of the QAB converter is also presented herein. Cascaded SISO controllers are designed for the AC-DC stage. The QAB demanded power is calculated at the QAB controls and then fed into the rectifier controls in order to minimize the effect of the interaction between the two SST stages. The dynamic performance of the designed control loops based on the proposed control strategies are verified through extensive simulation of the SST average and switching models. The experimental results presented herein show that the transient responses for each control strategy match those from the simulations results thus validating them.
ContributorsFalcones, Sixifo Daniel (Author) / Ayyanar, Raja (Thesis advisor) / Karady, George G. (Committee member) / Tylavsky, Daniel (Committee member) / Tsakalis, Konstantinos (Committee member) / Arizona State University (Publisher)
Created2011
Description
The following dissertation provides perspectives on the social, political, economic, and academic influences on language use, and particularly heritage language use, within the Filipino American community. What is the nature of language in this community? In what ways does language exist or co-exist? The hypothesis that autochthonous Filipino languages in the United States cease to be spoken in favor of English by Filipino Americans was tested through mixed methods of research. Literature and databases were reviewed which provided information concerning statistics, issues, and policies relating to language in Filipino America. Field research and interviews were conducted in which language use was of key interest. Results varied individually and contextually. Language seems to exist within the Filipino American community on a dynamic continuum. Immigrant Filipino Americans appear to be bilingual and multilingual. Second generation Filipino Americans tend to be English dominant with a range of bilingualism. The California Department of Education (CDOE) appears to foster bilingualism / multilingualism through its World Languages Departments (secondary education level), by offering language courses, such as Tagalog-based Filipino. Efforts to maintain non-English, Filipino languages in Arizona are less conspicuous, but they do exist primarily in familial and entrepreneurial ways.
ContributorsAxel, Joseph (Author) / Mccarty, Teresa (Thesis advisor) / Wiley, Terrence (Committee member) / Faltis, Christian (Committee member) / Arizona State University (Publisher)
Created2011
Description
ABSTRACT External accountability is embedded in every school system across the United States. This dissertation study focuses on how ten principals negotiate the accountability system placed upon their school by the state of Arizona. The federal accountability policy, No Child Left Behind (NCLB), requires that states use a standardized assessment to document student achievement. Arizona's policy to meet the federal requirements of NCLB is Arizona Learns (AZLearns). AZLearns outlines the formulas for determining which schools are achieving and which schools need to improve. Each school is tagged with a label annually. The labels are Excelling, Highly Performing, Performing Plus, Performing, Underperforming and Failing. The foundation of this study lies in the interpretation, application and negotiation of a school's label by its principal. To investigate the relationship between external accountability and the daily life of a principal, I interviewed ten Arizona elementary school principals. The research questions of this study are: (R1) What effects do external accountability measures have on the development of the organizational capacity of a school? (R2) How do Arizona principals negotiate their school's assigned label in their everyday professional practice? (R3) What are Arizona principals' views of the state accountability process? A qualitative, phenomenological research methodology was used to interview the participants and analyze their stories for common themes. The commonalities that surfaced across the experiences of the principals in response to the labels placed on their school are Accountability, Achievement and Attitude. This study found that Accountability was based on multiple interpretations of policies enforced by the federal government, state or district guidelines and parent or school expectations. Achievement was a result of multiple factors including data collected from test scores, the quality of teachers or instruction and the personal goals of the principals. Attitude was a process embedded in the high stakes testing era, boundaries or conflicts within the location of the school and the personal experiences of the principals. This research is an attempt to share the multiple voices of principals that may lead to alternative meanings or even provoke questions about the labeling system in Arizona schools.
ContributorsMcNeil, David Michael (Author) / Davey, Lynn (Thesis advisor) / Mccarty, Teresa (Committee member) / Donofrio, Robert (Committee member) / Arizona State University (Publisher)
Created2011
Description
Recent changes in the energy markets structure combined with the conti-nuous load growth have caused power systems to be operated under more stressed conditions. In addition, the nature of power systems has also grown more complex and dynamic because of the increasing use of long inter-area tie-lines and the high motor loads especially those comprised mainly of residential single phase A/C motors. Therefore, delayed voltage recovery, fast voltage collapse and short term voltage stability issues in general have obtained significant importance in relia-bility studies. Shunt VAr injection has been used as a countermeasure for voltage instability. However, the dynamic and fast nature of short term voltage instability requires fast and sufficient VAr injection, and therefore dynamic VAr devices such as Static VAr Compensators (SVCs) and STATic COMpensators (STAT-COMs) are used. The location and size of such devices are optimized in order to improve their efficiency and reduce initial costs. In this work time domain dy-namic analysis was used to evaluate trajectory voltage sensitivities for each time step. Linear programming was then performed to determine the optimal amount of required VAr injection at each bus, using voltage sensitivities as weighting factors. Optimal VAr injection values from different operating conditions were weighted and averaged in order to obtain a final setting of the VAr requirement. Some buses under consideration were either assigned very small VAr injection values, or not assigned any value at all. Therefore, the approach used in this work was found to be useful in not only determining the optimal size of SVCs, but also their location.
ContributorsSalloum, Ahmed (Author) / Vittal, Vijay (Thesis advisor) / Heydt, Gerald (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2011
Description
In this study, I investigate the digital literacy practices of adult immigrants, and their relationship with transnational processes and practices. Specifically, I focus on their conditions of access to information and communication technologies (ICTs) in their life trajectories, their conditions of learning in a community center, and their appropriation of digital literacy practices for transnational purposes. By studying the culturally situated nature of digital literacies of adult learners with transnational affiliations, I build on recent empirical work in the fields of New Literacy Studies, sociocultural approaches to learning, and transnational studies. In this qualitative study, I utilized ethnographic techniques for data collection, including participant observation, interviewing, and collection of material and electronic artifacts. I drew from case study approaches to analyze and present the experiences of five adult first-generation immigrant participants. I also negotiated multiple positionalities during the two phases of the study: as a participant observer and instructor's aide during the Basic Computer Skills course participants attended, and as a researcher-practitioner in the Web Design course that followed. From these multiple vantage points, my analysis demonstrates that participants' access to ICTs is shaped by structural factors, family dynamics, and individuals' constructions of the value of digital literacies. These factors influence participants' conditions of access to material resources, such as computer equipment, and access to mentoring opportunities with members of their social networks. In addition, my analysis of the instructional practices in the classroom shows that instructors used multiple modalities, multiple languages and specialized discourses to scaffold participants' understandings of digital spaces and interfaces. Lastly, in my analysis of participants' repertoires of digital literacy practices, I found that their engagement in technology use for purposes of communication, learning, political participation and online publishing supported their maintenance of transnational affiliations. Conversely, participants' transnational ties and resources supported their appropriation of digital literacies in everyday practice. This study concludes with a discussion on the relationship among learning, digital literacies and transnationalism, and the contributions of critical and ethnographic perspectives to the study of programs that can bridge digital inequality for minority groups.
ContributorsNoguerón, Silvia Cecilia (Author) / Warriner, Doris S (Thesis advisor) / Faltis, Christian J (Committee member) / Mccarty, Teresa (Committee member) / Wiley, Terrence (Committee member) / Arizona State University (Publisher)
Created2011
Description
There is a nationwide gap in which African American, Hispanic and low-income students perform significantly lower than their peers. Research suggests that teachers hold lower expectations for these students resulting in lower achievement. There are four main factors that influence teacher expectations: stereotypes, teacher self-efficacy, school culture, language and formal policies and programs aimed at increasing teacher expectations. The purpose of this study was to inquire into the following questions: (1) What are the factors that influence teachers' academic expectations for low-income and minority students? (2) What are teacher's perceptions on the effectiveness of formal policies and programs that are aimed at increasing teacher expectations? More specifically, do teachers feel that top-down formal policies, such as teacher evaluations, uniform curriculum, and performance-based pay are effective in impacting their expectations, or do teachers believe that bottom-up policies, such as book studies and professional learning communities, make more of an impact on increasing their expectations? Ten teachers were interviewed in a school district that is consistent with the state and national achievement gap. The findings revealed that teacher expectations are influenced by the four factors I found in the research as well as two other factors: a cultural disconnect among teachers and students and teachers' level of motivation. A combination of top-down and bottom-up formal policies and programs are needed as teachers are individuals and all respond to various forms of formal policies and programs differently.
ContributorsCraig, Tina (Author) / Mccarty, Teresa (Thesis advisor) / Davey, Lynn (Committee member) / Miller, Lynn (Committee member) / Arizona State University (Publisher)
Created2011
Description
Due to restructuring and open access to the transmission system, modern electric power systems are being operated closer to their operational limits. Additionally, the secure operational limits of modern power systems have become increasingly difficult to evaluate as the scale of the network and the number of transactions between utilities increase. To account for these challenges associated with the rapid expansion of electric power systems, dynamic equivalents have been widely applied for the purpose of reducing the computational effort of simulation-based transient security assessment. Dynamic equivalents are commonly developed using a coherency-based approach in which a retained area and an external area are first demarcated. Then the coherent generators in the external area are aggregated and replaced by equivalenced models, followed by network reduction and load aggregation. In this process, an improperly defined retained area can result in detrimental impacts on the effectiveness of the equivalents in preserving the dynamic characteristics of the original unreduced system. In this dissertation, a comprehensive approach has been proposed to determine an appropriate retained area boundary by including the critical generators in the external area that are tightly coupled with the initial retained area. Further-more, a systematic approach has also been investigated to efficiently predict the variation in generator slow coherency behavior when the system operating condition is subject to change. Based on this determination, the critical generators in the external area that are tightly coherent with the generators in the initial retained area are retained, resulting in a new retained area boundary. Finally, a novel hybrid dynamic equivalent, consisting of both a coherency-based equivalent and an artificial neural network (ANN)-based equivalent, has been proposed and analyzed. The ANN-based equivalent complements the coherency-based equivalent at all the retained area boundary buses, and it is designed to compensate for the discrepancy between the full system and the conventional coherency-based equivalent. The approaches developed have been validated on a large portion of the Western Electricity Coordinating Council (WECC) system and on a test case including a significant portion of the eastern interconnection.
ContributorsMa, Feng (Author) / Vittal, Vijay (Thesis advisor) / Tylavsky, Daniel (Committee member) / Heydt, Gerald (Committee member) / Si, Jennie (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2011
Description
All-dielectric self-supporting (ADSS) fiber optic cables are used for data transfer by the utilities. They are installed along high voltage transmission lines. Dry band arcing, a phenomenon which is observed in outdoor insulators, is also observed in ADSS cables. The heat developed during dry band arcing damages the ADSS cables' outer sheath. A method is presented here to rate the cable sheath using the power developed during dry band arcing. Because of the small diameter of ADSS cables, mechanical vibration is induced in ADSS cable. In order to avoid damage, vibration dampers known as spiral vibration dampers (SVD) are used over these ADSS cables. These dampers are installed near the armor rods, where the presence of leakage current and dry band activity is more. The effect of dampers on dry band activity is investigated by conducting experiments on ADSS cable and dampers. Observations made from the experiments suggest that the hydrophobicity of the cable and damper play a key role in stabilizing dry band arcs. Hydrophobic-ity of the samples have been compared. The importance of hydrophobicity of the samples is further illustrated with the help of simulation results. The results indi-cate that the electric field increases at the edges of water strip. The dry band arc-ing phenomenon could thus be correlated to the hydrophobicity of the outer sur-face of cable and damper.
ContributorsPrabakar, Kumaraguru (Author) / Karady, George G. (Thesis advisor) / Vittal, Vijay (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2011