Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-04-10T14:04:24Z No. of bitstreams: 1 renatoribeiroaleixo.pdf: 11717772 bytes, checksum: 92418eff47ec8bfa0e099a19d849c068 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-04-10T14:22:50Z (GMT) No. of bitstreams: 1 renatoribeiroaleixo.pdf: 11717772 bytes, checksum: 92418eff47ec8bfa0e099a19d849c068 (MD5) / Made available in DSpace on 2018-04-10T14:22:50Z (GMT). No. of bitstreams: 1 renatoribeiroaleixo.pdf: 11717772 bytes, checksum: 92418eff47ec8bfa0e099a19d849c068 (MD5) Previous issue date: 2018-03-01 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Este trabalho tem como objetivo a proposta de uma Unidade de Medição Fasorial (do inglês, Phasor Measurement Unit)(PMU), de baixo custo, voltada para o monito-ramento da distribuição de energia elétrica. O medidor proposto pode ser conectado à rede de baixa tensão, possibilitando assim o monitoramento dos sistemas de dis-tribuição e transmissão de energia. O algoritmo de estimação fasorial que compõe o software embarcado do equipamento faz uso do filtro Savitzky-Golay como aproxima-ção da derivada, necessária no processo de estimação da frequência do componente fundamental do sinal. O hardware utilizado é composto pelo microprocessador ARM TM4C1294NCPDT da Texas Instruments, um módulo GPS NEO-6M da uBlox, um módulo Wi-Fi ESP8266, além de um circuito de condicionamento do sinal analógico. O sincronismo das medições realizadas é garantido graças ao sinal composto por um pulso por segundo fornecido pelo GPS. Para o envio dos dados gerados pelo medidor pro-posto, o protocolo definido na norma vigente para PMUs foi utilizado. As estimações podem ser armazenadas e vizualizadas em tempo real através de um software monitor de dados de sincrofasores. Os resultados contemplam os testes exigidos pela norma, avaliando-se o erro total da estimação do fasor, o erro de frequência e o erro de taxa de variação da frequência. Por último, a fim de se reafirmar o sincronismo existente entre as medições realizadas por mais de um equipamento, estimou-se os fasores e a frequência em pontos distintos do sistema 4 Barras do IEEE, simulado em tempo real no RTDS, onde pode-se observar a estimação correta da defasagem entre duas barras desse sistema. / The present work proposes of a low cost Phasor Measurement Unity (PMU), for monitoring the power distribution system. The proposed meter can be connected at the low voltage level, making possible the monitoring of the distribution system and the transmission system. The algorithm used to compute the phasor estimation that composes the embedded software in the equipment uses the Savitzky-Golay filter to approximate the differentiation process, necessary in the frequency estimation of the fundamental component of the signal. The hardware of the equipment is composed by a microprocessor AMR TM4C1294NCPDT of Texas Instruments, a uBlox GPS NEO-6M module, a Wi-Fi ESP8266 module and an analog conditioning circuit. The synchronism of the measurements is guaranteed due to a pulse per second signal from the GPS module. For the transmission of the data generated by the PMU, the protocol suggested by the standard is used. The estimated parameters can be visualized in real time through the Synchrophasor Data Monitor Software. The results contemplate the tests required by the IEEE standard C37.118.1 and the analyses of the total vector error, frequency error and rate of change of frequency error. Finally, to attest the synchronism between different PMUs, a test in a Real Time Digital Simulator (RTDS) was made, where the 4 bus IEEE system was simulated. The difference of the angles estimated for different buses was computed and the obtained values were according to the expected.

The rapid pace of urbanization heightens our interest to understand the role of urban areas in mediating climate changes at local, regional and global levels. The increasing amount of carbon (C) released by growing cities may influence the surrounding climates and lead to a rise in global ambient temperature. Fortunately, urban greenery may mitigate the risk of rising C by storing it in vegetation and soils. On the other hand, urban greenery may become a net CO₂ or other greenhouse gas emitter due to heavy maintenances. Thus, the exact impact of urban greenery on carbon balance in major metropolitan areas remains controversial. / We first investigated C footprints of urban turf operation and maintenance by conducting a research questionnaire on different Hong Kong turfs, and showed that turf maintenance contributed 0.17 to 0.63 kg Ce m⁻² y⁻¹ to C emissions. We then determined C sequestration capacity by urban turfgrasses and soils through both field study and laboratory-based investigation. Our data from field study showed that the C stored in turfgrass systems at 0.05 to 0.21 kg C m⁻² for aboveground grass biomass and 1.3 to 4.9 kg C m⁻² for soils (to 15 cm depth). We estimated that the C sink capacity of turfs could be offset by C emissions in 5-24 years under current management patterns, shifting from C sink to C source. / We further showed that dissolved organic C (DOC) export also contributed to C release from urban soils, under the influence of the maintenance practices of turfgrasses. Both irrigation and nitrogen (N) fertilizer inputs could enhance DOC export. We also observed that soil enzyme activity was sensitive to turfgrass maintenances practices, and played a key role in soil organic C (SOC) decomposition. In particular, cellulase was found to be a major player in regulating DOC and dissolved organic N (DON) export. On the other hand, urease activity was shown to be dependent on grass species, fertilizer inputs and substrates. / Finally, we then determined the CO₂ fluxes of turfgrass systems by chamber-based measurement. Our data demonstrated that grass species and photosynthetically active radiation (PAR) played a dominant role in CO₂ fluxes in greenhouse study. Maintenance practices also contributed to CO₂ fluxes of turfgrass systems. Both fertilizer and irrigation showed species-specific effect on CO₂ fluxes. We then showed in field studies that CO₂ fluxes and respiration rates of urban turfs varied with grass species, and were higher in wet season than dry season. / Together, our studies suggested that maintenance practices for urban greenery played a key role in SOC decomposition through regulating DOC export and C cycle associated enzymes, therefore may determine the C balance of urban greenery. Our studies further suggest that we can improve maintenance practices to reduce C footprint and enhance the environmental benefits of urban turfgrass systems. We propose that the environmental impact of turfgrass systems should be optimized by the rational design of maintenance schedules based on C sink and emission principles. / 城市化的快速發展提高了我們研究城市的興趣，具體在其對城區和地域性氣候及其對全球气候变化的調節。城區大量碳排放可能影響周圍氣候進而導致全球環境溫度的上升。城市綠化可以緩解這個危機因為植被和土壤能夠通過存儲碳。但是城市綠化系統的大量維護可能是導致二氧化碳或其他溫室氣體的排放。因此城市綠化對碳平衡的影響仍存在爭議。 / 我們以問卷方式調查了香港不同的草坪，計算了維護過程中的碳足跡。研究表明草坪每年的維護造成了相當於每平米0.17至0.63千克碳排放。我們還結合野外和實驗室分析測定了草坪地上生物量和15厘米深土壤的碳儲存量，每平米分別是0.05至0.21，1.3至4.9千克碳。據此我們估計，按照目前的管理模式，草坪的碳儲存量在5至24年可與維護的碳排放相抵，由碳匯轉變為碳源。 / 我們還發現溶解有機碳的流失也加劇了城市土壤碳釋放同時受草坪維護的影响。灌溉和施加氮肥會促進溶解有機碳的釋放。土壤酶對是草坪維護很敏感，而且對土壤有機有機碳分解起關鍵作用。特別是纖維素酶參與并有效調節了溶解有機碳和溶解有機氮的釋放。另外脲酶的活性受草種，施肥和土壤基質的影響。我們用二氧化碳分析儀测定了草坪的碳通量。溫室研究表明，草種和光合有效輻射對碳通量起主導作用。草坪的維護同樣影響草坪的碳通量，其中施肥和灌溉對不同草種的碳通量有不同程度的影響。野外實驗則發現城市草皮的碳通量和呼吸速率隨草種变化，且雨季高於旱季。 / 以上研究表明城市綠化系統的維護可以有效調節溶解有機碳和碳循環相關土壤酶，進而影響土壤有機碳的分解，最終決定城市綠化系統的碳收支。因此我們建議，由以經驗設計轉變為以碳匯和碳排放原則優化維護模式，以減少碳足跡從而提升城市綠化的環境效益。 / Kong, Ling. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references (leaves 191-212). / Abstracts and appendixes also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.