Bulk Power System Reliability Evaluation Considering Dynamic Thermal Rating And Network Topology Optimization

Modern national economic development and industry production closely depend on the reliability performance of power systems step by step.Unfortunately,transmission network has the difficulty of meeting the customers' required reliability demand due to its limited transmission capacity.Considering the huge cost needed for new construction of power delivery facilities,utilities are more willing to explore the potential adequacy of transmission capacity,which is useful and helpful to improve the system reliability performance.Recent researchers have pointed out that two measures,i.e.dynamic thermal rating(DTR)of overhead transmission lines and network topology optimization(NTO)of transmission networks,are promising to improve the potential transmission performance of a bulk power system,and is,therefore,helpful to improve the reliability of a power system.Since transmission system is one of the most important constituent part of a power system,this thesis has focused on bulk power system reliability evaluation incorporating DTR and NTO.The main contributions of this thesis include the followings:To fully explore the environmental impact on the dynamic capacity of transmission lines,a capacity model for transmission lines considering operation conditions in local areas is proposed based on IEEE Std.738,and therefore,a dynamic capacity estimation model for the whole overhead transmission lines is proposed.First,the ambient temperature,ambient wind speed,latitude and operating hour are adopted as input parameters.Based on IEEE Std.738,the convection heat loss rate,the radiated heat loss rate and the solar heat gain of transmission lines can be calculated,and the dynamic thermal line ampacity can be determined through the heat balance equation.Then a dynamic thermal line rating increment is defined to measure the environmental impact on line ratings in local areas.Finally,using the minimum increment within all areas crossed by the line,the dynamic thermal rating of a whole transmission line can be estimated and incorporated in the bulk power system reliability evaluation thereby.Case studies have been conducted on modified IEEE RTS-79 and RTS-96 systems.The results have shown that,with the incorporation of DTR,the system LOLE index can be reduced within 0 ~ 45.8%,and the EENS index can be reduced within 0 ~ 44.4%,as well.To fully explore the impact of network topology optimization mechanism on bulk power system reliability,a DC power flow based comprehensive bulk power network topology optimization model considering transmission line switching and substation reconfiguration is proposed.With the goal of minimizing total load curtailment,the optimal transmission switching(OTS)model and the optimal substation reconfiguration(OSR)model,which consider line switching mechanism and bus-bar splitting mechanism respectively,are firstly developed.In addition,with both the transmission line switching and substation reconfiguration being taken into consideration,the comprehensive network topology optimization(NTO)model is then proposed and incorporated in the bulk power system reliability evaluation.Case studies have been conducted on modified IEEE RTS-79 and RTS-96 systems.The results have shown that,with the incorporation of NTO,the system LOLE index can be reduced within 0 ~ 55.09%,the EENS index can be reduced within 0 ~ 27.04%.Such reliability enhancement would be maximized if both the transmission switching and substation reconfiguration are taken into consideration.To fully explore the impact of both dynamic thermal rating and network topology optimization on power system reliability,a comprehensive model considering both DTR and NTO is proposed and incorporated into the power system reliability evaluation then.Based on the NTO model which considers both transmission switching and substation reconfiguration,with the introducing of DTR to model constraints,the comprehensive model considering DTR and NTO is firstly developed.Then such model is incorporated into the power system reliability evaluation.Case studies have been conducted on modified IEEE RTS-79 and RTS-96 systems.The results have shown that with such incorporation,the system LOLE index can be reduced within 0 ~ 70.80%,and the EENS index can be reduced within 0 ~ 47.19% as well.In order to analyze the impact of operating environment as well as the network topology control mechanism on power system reliability,based on the previously developed comprehensive model considering both DTR and NTO,the influence of ambient temperature,ambient wind speed,number of switchable lines and substation busbars are investigated.Case studies have been conducted on modified IEEE RTS-79 system with in total 8 levels of ambient temperatures,ambient wind speed and 6 levels of switchable lines and busbars.The results have shown that the impact of ambient wind speed is stronger than the impact of ambient temperature,while the impact of number of allowable switchable lines and busbars are similar to each other.