Study On Rellability Evaluation Of Subway Traction Substation Considering Time-varying Failure Rate Of Equipment

The AC subway traction power supply system has become an advantage due to its convenient operation and maintenance,high power quality,fast operation speed,meeting large transportation needs,and the ability to safely and efficiently feed the electric energy of train regenerative braking to the grid without stray current problems.The new system has attracted much attention in the field of traction power supply.In the gradual application of AC subways,its reliability has also received more and more attention,but so far there has been little research on its reliability,especially on the reliability of each substation on the entire AC subway line.Therefore,it is of great practical significance to evaluate and study the reliability of AC subway traction substations.The existing reliability analysis idea of the traction power supply system was to evaluate the reliability of the entire substation based on the fault data of the traction power supply equipment and the power supply topology of the traction substation.However,the failure rate of the equipment in the general default system was a fixed value that followed an exponential distribution.It didn’t take into account time-related factors such as break-in,wear,and performance degradation during the entire life cycle of the equipment,resulting in only a constant stability availability,which didn’t reflect the time-varying reliability of the traction power supply system.For the traction power supply system,due to the long-term operation of the system,the wear and aging of the equipment leads to the failure rate of the equipment usually showing a time-varying characteristic,rather than a fixed value.To this end,the paper considered the time-varying failure rate of the equipment and conducted a reliability evaluation study of the AC traction substation.The main tasks are as follows:Introduced and analyzed the AC subway traction power supply system.First,from the perspective of the line,the basic structure of a new AC subway line in a city and the main-standby relationship between the substations on the line are analyzed.Secondly,from the perspective of the substation,the topological structure and operation mode of the four substations on the line are compared and analyzed.Finally,in order to facilitate the subsequent description and analysis,the four substations are divided into three categories according to their composition and structure.Established and analyzed the time-varying failure rate model of traction power supply equipment.First,the time-varying characteristics of the equipment failure rate were analyzed according to the service life of the equipment.By comparing the characteristics and applicable objects of exponential distribution,normal distribution,lognormal distribution and Weibull distribution,the Weibull distribution that best fit the failure rate characteristics of power supply equipment was selected as the fitting distribution.Secondly,the acquisition and preprocessing of equipment fault data,Weibull model parameter estimation and Weibull distribution fitting goodness test were completed.Finally,based on the historical statistical data of the equipment and the above-mentioned time-varying failure rate model,the time-varying failure rates of transformers,circuit breakers,disconnectors and cables were calculated.Established FTA reliability model of AC subway traction substation based on block processing.First,based on the analysis of the structure and operation mode of the three types of AC subway substations,each type of substation was partitioned according to the series-parallel relationship of the topology.Second,each block in the three types of substations was analyzed Power supply path.Finally,three types of substation FTA reliability models were established,and the power supply interval and main-standby relationship of the four substations on the line were analyzed to establish the line FTA reliability model.Solved and optimized the reliability of subway AC traction substation considering the time-varying failure rate of equipment.First,considering the time-varying failure rate of the key equipment in the institute,the FTA reliability models of three types of AC subway traction substations and lines were solved by sequential Monte Carlo simulation,and the reliability indexes of each type of substations and the lines were obtained.Secondly,through comparative analysis,the weak link of the system was found.Finally,the reliability level of AC subway traction substations and the line was improved by means of targeted reduction of the failure rate of weak links and verified.The research and analysis of the results show that: accurately understand the relationship between the failure rate of traction power supply equipment and service time,provide data support for the reliability evaluation of AC subway traction substations;consider in the reliability evaluation of AC subway traction substations The influence of the time-varying failure rate of the equipment can make the reliability index obtained closer to the actual operating conditions.The research in this paper can help subway operators better understand the operation status of AC subway traction substations and perceive their reliability level more intuitively.