Research On Reliability Evaluation Method Of Transmission Network Considering Multiple Fault Influence Degree

It is the most basic responsibility of the power supply department to provide users with safe,reliable,and satisfying power requirements.However,with the continuous growth of power consumption and the complexity of the grid size and characteristics,the redundancy of power grid equipment varies greatly with geographical distribution,especially In the central area of the city,power grid equipment is heavily loaded,and there is a greater risk of power failure in the face of equipment failure.In recent years,there have been many power grid outage accidents abroad,which have caused major social and economic impacts.Therefore,it is very necessary to study practical and reliable transmission grid reliability evaluation methods,especially in power grid planning,reliability evaluation should be taken as an important evaluation criterion for scheme comparison and selection.However,the current actual power grid reliability evaluation mainly focuses on the improvement of power grid structure.From a qualitative point of view,the commonly used methods include multi-channel power supply structure integrity evaluation,equipment N-1 check,equipment N-1-1,equipment N-2 check,etc.These qualitative evaluation methods of reliability are more intuitive,and in general,the reliability is evaluated by the way of equipment redundancy.But this kind of method is often difficult to reflect the difference degree of system reliability,especially for the transmission network planning scheme,each node of a system can meet the equipment N-1 check,but each node has the difference of reliability,and the difference degree of reliability between nodes cannot be reflected.At present,the quantitative evaluation of transmission network reliability is rarely applied in engineering practice,and there are some difficulties,such as lack of professional commercial software,complex modeling,difficulty to get started,and increasing workload with the number of faults and the scale of power grid.In this paper,combined with the actual work needs of power companies,the reliability evaluation model of transmission network is studied.The probability method and state space method are used to analyze the influence degree of multiple faults respectively.By comparing the accuracy error of reliability index,the conditions of multiple faults are determined,so as to demonstrate the feasibility of ignoring more than two faults in engineering.On this basis,the power system department Bonneville power,which is widely used in China’s power industry and developed by China Electric Power Research Institute after being introduced,is adopted,Through the calculation and analysis of fault probability,fault influence range and load shedding amount,a reliability evaluation method suitable for practical engineering small-scale system reliability evaluation or power grid planning scheme comparison is proposed,and it is used to analyze the reliability of a transmission network in Zhejiang Province.