Optimization of a dynamic uncertain causality graph for fault diagnosis in nuclear power plant |
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Authors: | Yue Zhao Francesco Di Maio Enrico Zio Qin Zhang Chun-Ling Dong Jin-Ying Zhang |
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Affiliation: | 1. Institute of Nuclear and New Energy Technology of Tsinghua University, Beijing 100084, China;2. Energy Department, Politecnico di Milano, 20156 Milan,Italy;3. Energy Department, Politecnico di Milano, 20156 Milan,Italy;Chair System Science and the Energy Challenge, Fondation Electricité de France(EDF), CentraleSupélec, Université Paris Saclay, 92290 Chatenay-Malabry, France;4. Institute of Nuclear and New Energy Technology of Tsinghua University, Beijing 100084, China;Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China;5. Department of Computer Science and Technology, Tsinghua University, Beijing 100084, China;6. Department of Economic and Management, North China Electric Power University, Beijing 102206, China |
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Abstract: | Fault diagnostics is important for safe operation of nuclear power plants (NPPs).In recent years,data-driven approaches have been proposed and implemented to tackle the problem,e.g.,neural networks,fuzzy and neurofuzzy approaches,support vector machine,K-nearest neighbor classifiers and inference methodologies.Among these methods,dynamic uncertain causality graph (DUCG)has been proved effective in many practical cases.However,the causal graph construction behind the DUCG is complicate and,in many cases,results redundant on the symptoms needed to correctly classify the fault.In this paper,we propose a method to simplify causal graph construction in an automatic way.The method consists in transforming the expert knowledge-based DCUG into a fuzzy decision tree (FDT) by extracting from the DUCG a fuzzy rule base that resumes the used symptoms at the basis of the FDT.Genetic algorithm (GA) is,then,used for the optimization of the FDT,by performing a wrapper search around the FDT:the set of symptoms selected during the iterative search are taken as the best set of symptoms for the diagnosis of the faults that can occur in the system.The effectiveness of the approach is shown with respect to a DUCG model initially built to diagnose 23 faults originally using 262 symptoms of Unit-1 in the Ningde NPP of the China Guangdong Nuclear Power Corporation.The results show that the FDT,with GA-optimized symptoms and diagnosis strategy,can drive the construction of DUCG and lower the computational burden without loss of accuracy in diagnosis. |
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Keywords: | Dynamic uncertain causality graph Fault diagnosis Classification Fuzzy decision tree Genetic algorithm Nuclear power plant |
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