| At present,the urban rail traction power supply system generally adopts the DC1500 V power supply system.More than 95% of DC feeder cables use XLPE cables without armor.During the operation of DC cables,due to various reasons such as design,manufacturing,construction,operation and maintenance,etc.,cable failure events occur from time to time.Operating experience shows that the DC feeder cable insulation failure is the most frequently occurring equipment failure in the urban rail power supply system.And because most of the DC feeder cables do not have armor and shielding layers,and the online cable monitoring technology developed based on the characteristics of AC high-voltage cables is to identify the characteristics of the cable shielding layer or armor layer discharge or leakage current.Parameters to reflect whether the main insulation is defective.For the implementation of the DC feeder cable online monitoring function of the urban rail power supply system,there is currently no complete technical solution.Based on the pain points of the industry,this thesis realizes the real-time monitoring of DC cable leakage and operation status tracking and establishes the cable status assessment system by studying the key technologies of DC cable online monitoring of urban rail power supply system.The thesis is mainly divided into five chapters:The introduction part of the first chapter first introduces the current status of AC high-voltage cable online monitoring technology,and discusses the feasibility of its technical principles applied to urban rail DC feeder cables.Secondly,it discusses the status quo of the online monitoring technology of urban rail DC feeder cables,points out the existing problems of the existing online monitoring system,and proposes the research direction of this paper.The second chapter first designs the technical architecture and hardware scheme of the DC feeder cable online monitoring system,focusing on the working principle and technical requirements of the core component of the DC sensor,and the method verified by experiments to test the output accuracy of the sensor under a small current input of 0～100m A less than 1%.At the same time,a small current signal sampling circuit is designed,and through calculations,it is verified that the error of the design scheme is less than meeting the requirements of use.Chapter 3 Design of the DC feeder cable online monitoring system software program,through the load balancing server distribution technology,realize a large range of data acquisition and signal processing functions,for the processing and access of a large number of data within the network range in the future,data between different systems Interactively formulate software technical solutions.Chapter 4 establishes a comprehensive evaluation system for urban rail DC feeder cables based on the fuzzy comprehensive evaluation method.Establish the characteristic vector and weight coefficient of the DC feeder cable,establish the membership relationship for qualitative and quantitative indicators,and use the existing cable operating data to verify the rationality of the algorithm.In the verification,it is found that the fuzzy comprehensive evaluation method has the problem of low resolution.The algorithm is further optimized,and the feature vector is evaluated hierarchically by the hierarchical fuzzy evaluation method,and finally a three-level hierarchical fuzzy evaluation system is established.The evaluation results are verified by samples and meet the requirements for use.Chapter 5 statistically summarizes the installation situation and monitoring data of the cable condition assessment system.The online monitoring and testing results have a good correlation with the offline insulation test results.Therefore,verify the rationality of the online system design and production.The conclusion part summarizes the results and innovations of this paper and plans the next work plan. |
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