A framework for reliability assessment in expansion planning of power distribution systems

This work proposes a framework that utilizes a method of analytical assessment of reliability to guide the expansion planning of power distribution systems (PDS) considering reliability criteria. The framework allows the estimation of reliability indices with and without the execution of expansion projects, thus supporting the decision-making process on investments in expansion projects. In the analytical assessment of reliability, failure rates of zones and restoration times are calculated from past data of interruptions in the primary distribution network. Additionally, the estimated reliability indices are adjusted to historical values through failure rates proportionate to the length of each zone. To test and validate the proposed framework, it was applied to a distribution network of the Roy Billinton Test System (RBTS). To validate the framework with real data of interruptions, two case studies were developed, one using a primary distribution feeder and another using a large-scale primary distribution network, both located in Southern Brazil. The results indicated that the proposed framework could help find the most attractive investments leading to improvements in reliability indices and reduction in unsupplied energy. This work formulates the impact of those alternatives of expansion that most affect reliability, namely: (i) the installation of normally closed sectionalizing switches, (ii) the installation of normally open switches with interconnection to adjacent feeders, (iii) the replacement of manual switches by remote controlled switches, and (iv) the replacement of existing bare overhead conductors by covered conductors. Nevertheless, the proposed framework allows the inclusion of other expansion alternatives. The computational performance of the adjustment processes of the estimated indices to the historical indices was evaluated for different reliability parameters, proving convergence and advantages for the chosen parameters. Finally, the proposed framework proved to be practical and useful for real-life applications by power distribution companies.Este trabalho propõe um framework que utiliza a avaliação analítica da confiabilidade para orientar o planejamento da expansão de sistemas de distribuição considerando critérios de confiabilidade. O framework proposto permite estimar indicadores de confiabilidade com e sem a execução de projetos de expansão, auxiliando assim a tomada de decisão sobre investimentos em projetos de expansão. Na avaliação analítica da confiabilidade, as taxas de falhas das zonas e os tempos de restabelecimento são calculados a partir de dados históricos de interrupções na rede de distribuição primária. Além disso, os indicadores de confiabilidade estimados são ajustados a valores históricos por meio de taxas de falhas proporcionais ao comprimento de cada zona. Para testar e validar o framework proposto, ele foi aplicado à uma rede de distribuição do Roy Billinton Test System (RBTS). Para validar o framework com dados reais de interrupções, foram desenvolvidos dois estudos de caso reais, um com um alimentador de distribuição primário e outro com um conjunto de oito alimentadores de distribuição primários de uma subestação, ambos localizados na região Sul do Brasil. Os resultados indicaram que o framework proposto pode ajudar a definir os investimentos mais atrativos levando a melhorias nos indicadores de confiabilidade e redução de energia não fornecida. Neste trabalho foi formulado o impacto das alternativas de expansão que mais afetam a confiabilidade: (i) a instalação de chaves de seccionamento normalmente fechadas (ii) a instalação de chaves normalmente abertas com interligação com alimentadores adjacentes, (iii) a substituição de chaves manuais por chaves telecomandadas, e (iv) a substituição de condutores aéreos nus de média tensão por condutores protegidos. No entanto, devido à flexibilidade do framework proposto, este permite a inclusão de outras alternativas de expansão que impactam na confiabilidade. O desempenho computacional dos processos de ajuste dos indicadores estimados aos indicadores históricos do framework foi avaliado para diferentes parâmetros de confiabilidade, provando a convergência e vantagens dos parâmetros escolhidos. Finalmente, o framework proposto provou ser prático e útil para aplicações reais por empresas de distribuição de energia

A framework for reliability assessment in expansion planning of power distribution systems

This article proposes a framework that uses analytical assessment of reliability to guide the expansion planning of power distribution systems (PDS) considering reliability criteria. The framework allows the estimation of reliability indices with and without the execution of expansion projects, thus supporting the decision-making process on investments in expansion projects. In the analytical assessment of reliability, failure rates of zones and restoration times are calculated from past data of interruptions in the primary distribution network. In addition, the estimated reliability indices are adjusted to historical values through failure rates proportionate to the length of each zone. To test and validate the proposed framework, it was applied to the distribution network at bus 5 of the Roy Billinton Test System (RBTS) and also to a real distribution feeder located in Brazil. The results indicated that the proposed framework can help define the most attractive investments leading to improvements in reliability indices and reduction in unsupplied energy. The estimation of reliability indices and energy not supplied, considered the following expansion alternatives: (i) the installation of normally-closed sectionalizing switches, (ii) the installation of normally-open switches with interconnection to adjacent feeders, (iii) the automation of switches, and (iv) the reconductoring of zones of the primary distribution network. Nevertheless, the proposed framework allows the inclusion of other expansion alternatives. Finally, the proposed framework proved to be handy and useful for real-life applications

Expansion planning of power distribution systems considering reliability : a comprehensive review

One of the big concerns when planning the expansion of power distribution systems (PDS) is reliability. This is defined as the ability to continuously meet the load demand of consumers in terms of quantity and quality. In a scenario in which consumers increasingly demand high supply quality, including few interruptions and continuity, it becomes essential to consider reliability indices in models used to plan PDS. The inclusion of reliability in optimization models is a challenge, given the need to estimate failure rates for the network and devices. Such failure rates depend on the specific characteristics of a feeder. In this context, this paper discusses the main reliability indices, followed by a comprehensive survey of the methods and models used to solve the optimal expansion planning of PDS considering reliability criteria. Emphasis is also placed on comparing the main features and contributions of each article, aiming to provide a handy resource for researchers. The comparison includes the decision variables and reliability indices considered in each reviewed article, which can be used as a guide to applying the most suitable method according to the requisites of the system. In addition, each paper is classified according to the optimization method, objective type (single or multiobjective), and the number of stages. Finally, we discuss future research trends concerning the inclusion of reliability in PDS expansion planning