Research On Operation Risk Evaluation Method Of Urban Power Grid

Urban power grid is facing the power users,which connects the large power network with the customers.In recent years,the large urban power grid load is growing and the scale of the power grid has been expanding.With the 220 kV and even 500 kV substations go into the city center,the characteristics of large urban power grid has undergone great changes.During the peak load period,some of the equipment in the power grid are overloaded,which reduces the safety margin of the power grid and increases the risk of power outages.The continuous and reliable power supply and safe and stable operation of the urban power grid are greatly affected.Therefore,it is of great significance to carry out risk evaluation according to the structure and operation characteristics of the urban power grid.Risk assessment of power grid operation is an important part of power system security assessment,and the calculation and evaluation of risk index is an important basis for analyzing the risk of power grid.Whether the evaluation result is correct or not depends not only on the construction of the index system,but also on the choice of scientific evaluation method.Based on the analysis of the domestic and foreign research result about the operation risk evaluation of urban power grid,the deficiency of existing index system and comprehensive evaluation method is compared.And the operation risk evaluation method of urban power grid is further researched in this paper,the main research contents are as follows:1)The construction of risk index system for urban power grid is researched.Following the principles and ideas of constructing operation risk index system and considering the actual demand of power grid dispatching,the characteristics and calculation methods of grid safety margin risk,grid structural integrity damage risk,grid equipment loss risk and grid load loss risk are researched.Then a practical set of urban power grid operation risk index system is presented.2)A method for calculating the risk value of urban power grid based on fuzzy reasoning is researched.For the basic risk index of urban power grid operation risk index system,classification method of risk consequences level and risk occurrence probability level is researched,based on which,the fuzzy reasoning method is used to calculate the risk consequence value and the risk occurrence value so as to obtain the risk value of basic risk index,which provide the basis for the comprehensive evaluation of urban power grid operation risk.3)Comprehensive evaluation method of urban power grid operation risk is researched.Through the analysis of characteristics of subjective and objective weighting method,the combination weighting method considering the subjective and objective weight is studied to obtain the weight of urban power grid operation risk index.And then based on the risk value of urban power grid basic risk index,weighted comprehensive model is used to calculate the comprehensive operation risk value of the power grid,so as to evaluate the operation risk of urban power grid in a scientific and rational way.