Vol.:(0123456789) 1 3 Electrical Engineering https://doi.org/10.1007/s00202-019-00756-2 ORIGINAL PAPER A methodology for reliability assessment of substations using fault tree and Monte Carlo simulation Jair D. Barbosa 1  · Ricardo C. Santos 1  · Jesus F. A. Romero 1  · Patricia T. L. Asano 1  · Antonio V. S. Neto 2  · João B. Camargo 2  · Jorge R. Almeida 2  · Paulo S. Cugnasca 2 Received: 3 January 2018 / Accepted: 14 February 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract This work presents a new methodology for reliability assessment of power substations. The proposed methodology is based on a combination of two diferent techniques for reliability studies, which are fault tree and Monte Carlo Simulation. Usually, these techniques are individually used for reliability evaluation purposes, but the solution here presented shows the advan- tages of combining both of them. Results reveal that by using a new procedure, based on these well-understood techniques, vulnerable points can be identifed in power substations, thus being a useful tool for deciding on new investments allocation. Firstly, the presented methodology is evaluated by using a system analytically solved, confrming its accuracy. Secondly, the proposed methodology is compared to a conventional method for reliability studies, showing its practical applicability, since both of them show the same expected results. Keywords Reliability assessment · Fault tree · Monte Carlo simulation · Power substation 1 Introduction To properly address the fnal customer expectation, reducing the number and duration of failures, minimum performance indices are defned by the energy regulatory agencies. If the utilities fail to achieve such performance, they are fned [1–10]. Moreover, fnancial losses resulting from failures are not restricted to the application of the fne, since com- mercial and industrial sectors are also afected. Additionally, it is important to point out that a failure can have signifcant negative efects on the society’s routine, bringing problems related to trafc, safety, among others. In turn, the devel- opment of new reliability/availability assessment methods became a priority for most utilities, as by means of an accu- rate estimation of these indices it would be possible that proper actions be taken to maintain or increase their levels. Considering the relevance of this subject, many works have been developed to address issues related to reliability/ availability assessment in power substations [3, 5, 7, 8], existing large electrical power systems [10] and distribu- tion systems with dispersed generation [1]. Procedures for evaluating the impact of a failure on the system’s indices [2], as well as to consider the components aging [4, 6, 9] are also discussed. In [1], a new hierarchical classifcation method to identify the operational state of distribution systems with distrib- uted generation is presented. This work considers the most important performance requirements related to distribu- tion systems. When a state is determined, it can be found intuitively if performance requirements are satisfed. Given the importance of a reliable fault diagnosis scheme (FDS) to recover and improve the distribution systems reliability indices, [2] compares two diferent FDS and their impact on the reliability indices, highlighting the advantages and disadvantages of each one. Regarding substation automation systems, [3] presents the application of fault-tree analysis to estimate the probability of failure of a substation monitoring system based on branch Phasor Measurement Units (PMUs). Models based on components aging are used in [4, 6] allow- ing evaluating this efect on the reliability indices, by using methodologies based on Markov Chains and stochastic mod- els, respectively. The reliability level of substations based on IEC 61850 is discussed in [5], where probabilistic relational * Ricardo C. Santos ricardo.santos@ufabc.edu.br 1 Center for Engineering, Modelling and Social Sciences, Federal University of ABC, Santo André, Brazil 2 Department of Computer and Digital Systems Engineering, University of São Paulo, São Paulo, Brazil