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Abstract(s)
A monitorização da segurança de abastecimento da produção de eletricidade a nível nacional é uma peça fundamental para avaliar as necessidades do sistema eletroprodutor para fazer face à procura de eletricidade no curto, médio e longo prazo. Neste contexto, a metodologia usada pela REN (Redes Energéticas Nacionais), o operador da rede de transporte (TSO), para estudar a segurança de abastecimento de eletricidade a médio e longo prazo em sistemas eletroprodutores complexos com um número elevado de produção térmica, hidráulica e produção intermitente (eólica e solar), consiste na integração de dois modelos, cada um com as suas vantagens: VALORAGUA e RESERVAS.
Os indicadores de fiabilidade associados às paragens fortuitas e programadas a serem considerados atualmente nas centrais produtoras (nomeadamente nas grandes centrais térmicas e hídricas), têm por base a informação dos CAE (contratos de aquisição de energia) que foram efetuados pelo grupo EDP, na altura que esta era verticalmente integrada, e têm por base também estudos encomendados pela REN à empresa KEMA. Todas estas informações tomaram como base um sistema eletroprodutor com características diferentes das verificadas nos dias de hoje.
O aumento produção de eletricidade obtida a partir de fontes de energia renovável tem colocado enormes desafios aos operadores da rede de forma a obter soluções para conseguir lidar com o aumento progressivo da complexidade do sistema, que é constituído atualmente por uma percentagem significativa de fontes de produção intermitente.
Face à consciência da necessidade de perceber se os indicadores de fiabilidade associados às paragens fortuitas e programadas atualmente em uso nos grupos das centrais, estão adequados ao atual panorama do sistema eletroprodutor, e perceber também a eventual necessidade de atualizar os parâmetros usados nos programas VALORAGUA E RESERVAS, foram desenvolvidas duas ferramentas em Microsoft Office Excel – Visual Basic for Application capazes de calcular os seguintes parâmetros: FOR (Forced Outage Rate), MOR (Maintenance Outage Rate), Avarias/ano, MTTF (Mean Time To Fail), MTTR (Mean Time To Repair), MTIM (Mean Time In Maintenance), tempo de funcionamento e tempo em paragem com base num ficheiro .xlsm relativo ao registo das paragens anuais entre os anos compreendidos entre 2006 e 2017. Com estas ferramentas de cálculo foi possível automatizar todo o processo de cálculo destes indicadores, sendo que são ferramentas que têm como objetivo, ser usadas no futuro para eventuais estudos de planeamento do sistema eletroprodutor.
Tendo por base os dados recolhidos relativos às paragens das centrais produtoras em estudo, procedeu-se a uma comparação das médias dos indicadores associados às falhas fortuitas entre os anos de 2006 e 2017 com as médias entre os anos de 2000 e 2005 (período do anterior estudo realizado pela REN), de forma a tentar perceber como evoluíram estes indicadores. Foi realizada uma análise estatística que incide sobre a altura do ano em que as centrais têm tendência para realizar as suas manutenções, e um estudo que incidiu sobre as disponibilidades médias consideradas atualmente pela REN nos grupos das centrais.
Os resultados obtidos, permitiram concluir que a taxa de indisponibilidade anual associada a paragens fortuitas diminui em grande parte das centrais hídricas nos últimos 12 anos comparativamente ao período entre 2000 e 2005.
Foi possível visualizar em gráfico, em que altura do ano os quatro tipos de produção estudados neste relatório (centrais térmicas a carvão e ciclo combinado, centrais hídricas em albufeira e a fio de água) realizam as suas manutenções, e conclui-se que nas centrais hídricas, o pico das paragens em manutenção planeada acontece nos meses mais secos (junho a setembro) e que as centrais térmicas encaixam os seus planos de manutenção de forma a poder estar disponíveis quando não existem condições favoráveis à produção de energia hídrica e quando os picos de procura são mais reduzidos (meses de primavera e outubro).
No estudo que incide sobre as disponibilidades médias anuais consideradas atualmente nas grandes centrais produtoras térmicas e hídricas foi possível chegar a alguns resultados conclusivos. Devido a taxas de utilização anuais bastante reduzidas a partir de 2012, os tempos de paragem para manutenção nas centrais a ciclo combinado apresentam uma tendência decrescente. Nas centrais carvão, o tempo médio atualmente a ser usado como referência nas paragens fortuitas, apresenta um valor bastante conservador ao analisar os registos dos tempos de paragens por avaria nos últimos 12 anos.
Monitoring the security of supply of electricity production at the national level is a key element in assessing the needs of the electric power system in order to anticipate possible short, medium and long term needs. In this context, the methodology used by REN (National Energy Networks), the transmission system operator (TSO), to study the security of médium and long-term electricity supply in complex systems with a high level of thermal, hydraulic and intermittent production (wind and solar), consists of the integration of two models, each with its advantages: VALORAGUA and RESERVAS. The reliability indicators associated with the random and scheduled stoppages currently being considered in the production plants (namely in the large thermal and hydroelectric plants), are based on information from the PPAs (power purchase agreements) that were carried out by the EDP group at the time that it was vertically integrated, and also based on studies commissioned by REN from KEMA. All this information was based on na electroproduction system with characteristics different from those verified today. Increased production of electricity from renewable energy sources has put enormous pressure on network operators to find solutions to deal with the progressive increase in system complexity, which currently consists of a significant proportion of intermitente production. Given the awareness of the need to understand if the reliability indicators currently in use are adequate to the current panorama of the electroproduction system, and also to realize the possible need to update the parameters used in the VALORAGUA AND RESERVAS programs, two tools were developed in Microsoft Office Excel - Visual Basic for Application, which can calculate the following parameters: FOR (Forced Outage Rate), MOR (Maintenance Outage Rate), Failures / year, Mean Time To Fail (MTTR), Mean Time To Repair (MTTR) Maintenance), running time and downtime based on an .xlsm file relating to the registration of annual stops between the years 2006 and 2017. With these calculation tools it was possible to automate the whole process of calculating these indicators, being tools which are intended to be used in the future for possible studies. Based on the data collected on the stops of the producing power stations under study, a statistical analysis was carried out which focuses on the height of the year in which the plants tend to carry out their maintenance, and a study that focused on the average availability considered currently by REN in these plants. The obtained results, allowed to conclude that the annual unavailability rate associated to random stops decreased in large part of the hydroelectric plants in the last 12 years compared to the period between 2000 and 2005. It was possible to visualize in charts, at what time of year the four types of production studied in this report (Coal, combined cycle, reservoirs and water line) carry out their maintenance, and it is concluded that in the hydroelectric power stations, the peak of the stops in Planned maintenance takes place in the drier months (June to September) and that thermal power plants fit their maintenance plans so that they can be available when there are no favorable conditions for the production of hydropower and when peak demand is lower (months of spring and october). In the study that focuses on the annual availability averages currently considered in the large thermal and hydroelectric power plants, it was possible to reach some conclusive results. Due to very low annual utilization rates from 2012 onwards, downtimes for maintenance in combined cycle plants show a decreasing trend. In coal-fired power plants, the average time currently used as a reference in forced outage rates is very conservative when analyzing the records of breakdown times for the last 12 years.
Monitoring the security of supply of electricity production at the national level is a key element in assessing the needs of the electric power system in order to anticipate possible short, medium and long term needs. In this context, the methodology used by REN (National Energy Networks), the transmission system operator (TSO), to study the security of médium and long-term electricity supply in complex systems with a high level of thermal, hydraulic and intermittent production (wind and solar), consists of the integration of two models, each with its advantages: VALORAGUA and RESERVAS. The reliability indicators associated with the random and scheduled stoppages currently being considered in the production plants (namely in the large thermal and hydroelectric plants), are based on information from the PPAs (power purchase agreements) that were carried out by the EDP group at the time that it was vertically integrated, and also based on studies commissioned by REN from KEMA. All this information was based on na electroproduction system with characteristics different from those verified today. Increased production of electricity from renewable energy sources has put enormous pressure on network operators to find solutions to deal with the progressive increase in system complexity, which currently consists of a significant proportion of intermitente production. Given the awareness of the need to understand if the reliability indicators currently in use are adequate to the current panorama of the electroproduction system, and also to realize the possible need to update the parameters used in the VALORAGUA AND RESERVAS programs, two tools were developed in Microsoft Office Excel - Visual Basic for Application, which can calculate the following parameters: FOR (Forced Outage Rate), MOR (Maintenance Outage Rate), Failures / year, Mean Time To Fail (MTTR), Mean Time To Repair (MTTR) Maintenance), running time and downtime based on an .xlsm file relating to the registration of annual stops between the years 2006 and 2017. With these calculation tools it was possible to automate the whole process of calculating these indicators, being tools which are intended to be used in the future for possible studies. Based on the data collected on the stops of the producing power stations under study, a statistical analysis was carried out which focuses on the height of the year in which the plants tend to carry out their maintenance, and a study that focused on the average availability considered currently by REN in these plants. The obtained results, allowed to conclude that the annual unavailability rate associated to random stops decreased in large part of the hydroelectric plants in the last 12 years compared to the period between 2000 and 2005. It was possible to visualize in charts, at what time of year the four types of production studied in this report (Coal, combined cycle, reservoirs and water line) carry out their maintenance, and it is concluded that in the hydroelectric power stations, the peak of the stops in Planned maintenance takes place in the drier months (June to September) and that thermal power plants fit their maintenance plans so that they can be available when there are no favorable conditions for the production of hydropower and when peak demand is lower (months of spring and october). In the study that focuses on the annual availability averages currently considered in the large thermal and hydroelectric power plants, it was possible to reach some conclusive results. Due to very low annual utilization rates from 2012 onwards, downtimes for maintenance in combined cycle plants show a decreasing trend. In coal-fired power plants, the average time currently used as a reference in forced outage rates is very conservative when analyzing the records of breakdown times for the last 12 years.
Description
Keywords
Fiabilidade (MOR e FOR das centrais) Plano de manutenção Produção hídrica Produção térmica Modelos de simulação do sistema electroprodutor Reliability (MOR and FOR of plants) Maintenance plan Water production Thermal production Simulation models of the electroproduction system