Research And Application Of Freezing-hazard Event And Risk Assessment System For Overhead Transmission Line

With the warming development of the global climate and the continuousexpansion development of the power grid, the catastrophic damage caused by the icestorm on overhead transmission lines is always occurred. The severe disconnectionfailure, interruption of power supply of transmission lines is caused by a wide rangeof transmission lines leaded by frozen disasters along with the snow and icing weather,which is difficult to estimate the economic losses caused to the power sector and otherindustries. The completion of the risk assessment system is designed based ontheoretical analysis and modeling, and also the transmission lines in a freezingdisaster the method of risk assessment is studied, according to the existingtransmission line ice thickness, disconnection probability and risk assessment studies,the introduction of Extreme Value Theory generalized Pareto distribution, the Copulajoin function and fuzzy comprehensive evaluation method.A probabilistic model of the transmission line ice thickness is built andGeneralized Pareto probability distribution between wind speed and frozenprecipitation distribution is proposed based on POT model with extreme value theory.On this basis, the probability distribution model of the transmission line ice and windload is proposed by combining thickness of the ice cover, and the transmission line iceload and wind load calculations. In addition, the interruption of power supply oftransmission lines mainly caused by ice together with wind load in the same weatherconditions. There is a certain relation between the ice load and wind load of thetransmission lines, which are not independent. So, by introducing the Copula joinfunction, the joint probability distribution between the ice and the wind load duringfrozen disasters at different times is proposed for accurately predicting asymmetriccorrelation transmission line breakage probability.Considering the transmission line disconnection probability of failure and poweroutages economic losses, a quantitative assessment of the impact of the ice storm onthe transmission lines is achieved, which is significance to the disaster preventionand mitigation of power system. Therefore, the transmission line risk assessmentindex system is built through the introduction of the concept of risk, fuzzycomprehensive evaluation method to calculate the level of risk of transmission lines.The Analytic Hierarchy Process (AHP) is introduced to improve the accuracy of risk assessment for the weight calculation of the fuzzy comprehensive evaluation method.Based on risk assessment and theoretical modeling,system is divided into threesubsystems: the thickness of the ice cover probability system of transmission lines，disconnection probability system and transmission line risk assessment system,whichis to design the database of the system.The calculation of the three subsystems isaccomplished through the design of MATLAB module. In addition, in order to achievethe overhead transmission lines frozen disaster risk, the software of risk assessmentsystem is designed according to the functional modules of the system design, userlogin, system functions, data entry, data calculations, contingency plans, and otherfunctional modules.In summary, a complete set of frozen disaster risk assessment system oftransmission lines is formed with combining the probability of line break in the frozendisaster, risk assessment and software system design,which can provide scientificsecurity risk for the relief decision-making and formulation of emergency disastermeasures through quantitative assessment of the operation of the transmission lines inthe freezing disaster.