Research On Reliability And Risk Assessment Of High-speed Railway Traction Power Supply System Based On Operation Characteristics

With the development of high-speed railway(HSR)in domestic and international transportation systems in recent years,the status is becoming more and more important,and its safety and reliability are also attracting attention.As the sole source of power to the HSR,the traction power supply system(TPSS)plays a key role in electric power conversion and energy supply.The occurrence of a failure in the TPSS may cause high-speed trains to run behind the schedule or even suffer from downtime,which would directly affect the entire scheduling and cause inestimable loss.At the same time,data such as historical fault records indicate that the operating characteristics of HSR traction power supply equipment(TPSE)and systems will have an impact on their safety and reliability,resulting in the possibility and risk of failure of TPSE and TPSS.Therefore,in order to ensure the reliability and economic level of high-speed rail transportation,and provide effective information and support for operational maintenance management decisions,the reliability and risk assessment of TPSS based on operational characteristic are very necessary and urgent.This paper analyzes the operating characteristics of TPSE and TPSS,and summarizes the short-time high-speed traction load characteristics,the long-term TPSE performance degradation characteristics,the impact of relay protection on system operation,the external service environment characteristics,as well as the system maintenance impact characteristics.It is pointed out that the existing data information in TPSS can be fully utilized,and the reliability and risk status can be evaluated from the perspective of equipment level and system level.In terms of reliability,reliability evaluation methods based on operational characteristics are proposed for TPSE.Firstly,based on the influence of short-time high-speed traction load characteristics on transformer reliability,transformer derating rate is calculated based on the standard IEEE C57.110 procedures,and thermal circuit model and its differential equations are applied to obtain transformer hot-spot temperature and quantify the traction load characteristics.Then Arrhenius-Weibull model is utilized for transformer reliability assessment.At the same time,a reliability evaluation method based on long-term degradation characteristics is proposed for large-scale similar TPSE.Based on continuous Markov process and IEEE standard,the equipment state is classified into four levels.The state duration and transition rate are obtained through equipment failure record.Then the uniform acceleration technique is applied to calculate reliability parameters,and the number of equipment in each state can be evaluated.A reliability evaluation method considering the operating characteristics of relay protection is proposed for TPSS.Based on the analysis of the influence of relay protection on the reliability of TPSS,the failure mode and effects analysis(FMEA)tables are established based on the main wiring diagram of the TPSS and its equipment composition to qualitatively analyze the failure modes of primary and secondary equipment and their influence.According to the FMEA tables,the fault tree model(FTM)of the traction substation and catenary system considering relay protection is established respectively,and the system reliability indexes are calculated through Monte Carlo simulation.The actual example analysis shows that the proposed reliability model and evaluation method can obtain rich and intuitive system reliability indicators through simulation calculation,and can reflect the influence degree of relay protection on system reliability.It provides effective means for the overall reliability evaluation of TPSS.The reliability evaluation of TPSE and TPSS quantifies the possibility of faults.To further consider the severity of the fault consequences,risk assessment methods for TPSE based on operational characteristics is proposed.Considering the influence of multiple factors such as the external environment,a multi-factor fusion method for estimating the risk of equipment failure is proposed.By improving an interval probability estimation methodology integrating the credal network model and IDM,we obtain the mathematical expression of probability interval pertaining to the failure of TPSE.And we present a thorough understanding of the main wiring structure and TPSE so as to establish the RB-FMEA for qualitatively analyzing the failure modes,influence and risk states pertaining to the various key pieces of equipment associated with the traction power supply system.From the perspectives of economic loss and time loss,we also quantify the risk metrics associated with the equipment with various failure levels.At the same time,considering the maintenance of TPSE,a risk assessment method based on fault prediction is proposed.Firstly,a fault prediction model based on Bayesian network classifier model is established.By comparing the prediction results with the actual equipment operation state,statistical parameters are obtained to calculate the reliability and economic indices for the maintenance strategies.The comprehensive maintenance risk is then quantified by integrating the dynamic inspection and fault risk costs for the TPSE,so as to achieve the purpose of quantifying and optimizing the state maintenance effect.The risk assessment methods considering the protection operation characteristics are proposed for TPSS.Firstly,based on the characteristics of protection action trip statistics and system failure risk,an assessment method reflecting the risk of TPSS is proposed from the aspects of time and space difference characteristics,and its index system is constructed.The case analysis shows that the proposed risk assessment method and indicators can deeply reveal the risk difference characteristics of the trip failure of the high-speed rail TPSS,and fully reflect the external environmental impact law,the disaster prevention and resistance of TPSS.Meanwhile,considering the reliability of relay protection,a risk assessment method for TPSS is proposed.Based on Markovian state-space method,the reliability of the protection system is evaluated;the misoperations of the protection system and their possible consequences are analyzed by FMEA method.Three types of economic loss indices are defined to establish the quantitative risk consequence model;the risk of TPSS is thereby quantified by integrating risk probability and risk consequence.By quantifying the impact of relay protection,it helps to improve the safe operation level of TPSS.Through the theoretical method research and case analysis,this paper starts from the operating characteristics of,fully considers the influence of internal and external factors,and realizes the quantitative evaluation of reliability and risk of equipment level and system level.Relevant decisions such as operation and maintenance of TPSS provide effective data support and decision-making confidence,in order to improve the operational reliability of TPSE and TPSS,and reduce or even avoid the risk of failure.