Real-time thermal state and component loading estimation in active distribution networks

Highly stochastic loading and distributed generation in the emerging active distribution networks means that electric utilities need to deploy intelligent network management tools in order to use their assets to the fullest. Real-Time Thermal Rating (RTTR) provides the possibility for short term and even real-time active distribution network management, enabling the network to run closer to an overload state without damage. In this dissertation, pertinent developments and proposals are presented in three stages on the path towards the development of a real-time monitoring and operation system for active distribution networks. The first stage is the development of distribution network component thermal models for real time implementation. In this dissertation, a numerical model of the air-gap convective heat transfer for underground cable installations inside unfilled conduit is developed. In addition, a dynamic thermal model is developed for prefabricated secondary substation cabins. The most dominant but difficult to solve heat transfer mechanism, natural convection, is modelled by introducing the stack effect principle into the problem. Measurements from a scaled model of prefabricated substations, measurements from actual cabins and 3D Finite Element Method (FEM) simulations are used to validate the numerical model. In the second stage, this dissertation explores the usability of customer level automatic meter reading (AMR) measurements for distribution network state estimation and for load forecasting applications. A method to forecast substation level loads with their respective confidence intervals using hourly AMR metered customer level consumptions is presented. The forecasting and monitoring of a distribution network in real-time can be met with the modeling of classified type load classes. However, it requires careful incorporation of the necessary factors, such as within-group and between-group correlations of customer classes. Binding the aforementioned findings, in the third stage, a framework for day-ahead hour-by-hour thermal state forecasting and thermal ratings of distribution network components is proposed and studied. This work has demonstrated that up to three hours ahead thermal state forecasting of an active distribution network can be achieved with an acceptable level of accuracy. In this dissertation, the benefits and practical implications of the real-time thermal rating are investigated. The introduction of real-time thermal rating in an active distribution network management system enhances the loading capacity significantly compared to static rating. This has been revealed through an increased utilization of installed DGs and through better integration potential of additional DGs

Techno-economic analysis of the thermal energy saving options for high-voltage direct current interconnectors

High-voltage direct current interconnection stations are increasingly used for long-distance electricity transport worldwide, due to efficiency and economic reasons. The identification and evaluation of cost-effective waste heat sources appropriate for recovery and reutilisation represent an opportunity that can improve the efficiency of high-voltage direct current stations, resulting in significant savings in energy consumption and reduction of the carbon footprint. The paper is the first to investigate the technological and economic feasibility of heat recovery at a major interconnector power station. Once identified the potential recoverable heat sources and evaluated the latest advancements in thermal energy recovery technology, a technological and economic analysis of two potential heat recovery strategies has been performed. While the heat-to-electricity technology was proved to be technologically but not economically feasible, the realisation of a combined liquid desiccant and evaporative cooling heat recovery strategy was proved to present the best economic performance with a payback period of about 5 years and a levelised cost of saved energy of 0.155 €/kWh, depending on the heat recovery and size of the system. Additional economic savings can be obtained for high-voltage direct current stations located in hot and humid climates, where the moisture removal ability of liquid desiccant technology could be particularly advantageous

Design optimization of ann-based pattern recognizer for multivariate quality control

In manufacturing industries, process variation is known to be major source of poor quality. As such, process monitoring and diagnosis is critical towards continuous quality improvement. This becomes more challenging when involving two or more correlated variables or known as multivariate. Process monitoring refers to the identification of process status either it is running within a statistically in-control or out-of-control condition, while process diagnosis refers to the identification of the source variables of out-of-control process. The traditional statistical process control (SPC) charting scheme are known to be effective in monitoring aspects, but they are lack of diagnosis. In recent years, the artificial neural network (ANN) based pattern recognition schemes has been developed for solving this issue. The existing ANN model recognizers are mainly utilize raw data as input representation, which resulted in limited performance. In order to improve the monitoring-diagnosis capability, in this research, the feature based input representation shall be investigated using empirical method in designing the ANN model recognizer

Energy Efficient Window Development

The paper investigates the development of energy efficient windows in the past 30 years. The focus is on the development and interlinkages among technology, actors´ interaction and market diffusion in a broader policy context. The paper shows that in singular development cycles, different factors and the interfaces among these factors influenced the improvement and penetration of energy efficient window technologies. Such factors includes a) surrounding factors, such as climate characteristics, oil crisis and international concerns and strategies, b) policy instruments, like building codes and technology procurement programs, as well as c) industry initiatives, including niche market strategies

Smart operation of transformers for sustainable electric vehicles integration and model predictive control for energy monitoring and management

The energy transmission and distribution systems existing today are stillsignificantly dependent on transformers,despite beingmore efficient and sustainable than those of decadesago. However, a large numberof power transformers alongwith other infrastructures have been in service for decades and are considered to be in their final ageing stage. Anymalfunction in the transformerscouldaffect the reliability of the entire electric network and alsohave greateconomic impact on the system.Concernsregardingurban air pollution, climate change, and the dependence on unstable and expensive supplies of fossil fuels have lead policy makers and researchers to explore alternatives to conventional fossil-fuelled internal combustion engine vehicles. One such alternative is the introduction of electric vehicles. A broad implementation of such mean of transportation could signify a drastic reduction in greenhouse gases emissions and could consequently form a compelling argument for the global efforts of meeting the emission reduction targets. In this thesis the topic of a high penetration of electric vehicles and their possible integration in insular networksis discussed. Subsequently, smart grid solutions with enabling technologies such as energy management systems and smart meters promote the vision of smart households, which also allows for active demand side in the residential sector.However, shifting loads simultaneously to lower price periods is likely to put extra stress on distribution system assets such as distribution transformers. Especially, additional new types of loads/appliances such as electric vehicles can introduce even more uncertaintyon the operation of these assets, which is an issue that needs special attention. Additionally, in order to improve the energy consumption efficiencyin a household, home energy management systems are alsoaddressed. A considerable number ofmethodologies developed are tested in severalcasestudies in order to answer the risen questions.Os sistemas de transmissão e distribuição de energia existentes hoje em dia sãosignificativamente dependentes dos transformadores, pese embora sejammais eficientes e sustentáveis do que os das décadas passadas. No entanto, uma grande parte dos transformadores ao nível dadistribuição, juntamente com outras infraestruturassubjacentes, estão em serviço há décadas e encontram-se nafasefinal do ciclo devida. Qualquer defeito no funcionamento dos transformadorespode afetara fiabilidadede toda a redeelétrica, para além de terum grande impactoeconómico no sistema.Os efeitos nefastos associadosàpoluição do arem centro urbanos, asmudançasclimáticasea dependência de fontes de energiafósseis têm levado os decisores políticos e os investigadores aexplorar alternativas para os veículos convencionais de combustão interna. Uma alternativa é a introdução de veículos elétricos. Umaampla implementação de tal meio de transporte poderia significar uma redução drástica dos gases de efeito de estufa e poderiareforçar os esforços globais para ocumprimento das metas de redução de emissõesde poluentes na atmosfera.Nesta tese é abordado o tema da elevada penetração dos veículos elétricose a sua eventual integração numarede elétricainsular. Posteriormente, são abordadas soluções de redeselétricasinteligentes com tecnologias específicas, tais como sistemas de gestão de energia e contadores inteligentes que promovamo paradigmadas casas inteligentes, que também permitem a gestão da procura ativano sector residencial.No entanto, deslastrando significativamente as cargaspara beneficiar de preçosmais reduzidosé suscetíveldecolocarconstrangimentosadicionaissobre os sistemas de distribuição, especialmentesobre ostransformadores.Osnovos tipos de cargas tais como os veículos elétricospodem introduzir ainda mais incertezassobre a operação desses ativos, sendo uma questão que suscitaespecial importância. Além disso, com ointuitode melhorar a eficiência do consumo de energia numa habitação, a gestão inteligente daenergia é um assunto que também éabordadonesta tese. Uma pletora de metodologias é desenvolvida e testadaemvários casos de estudos, a fim de responder às questões anteriormente levantadas