Research On Non-uniform Ice-shedding Dynamic Response Of Transmission Lines And Risk Assessment

The severe uneven distribution of hydropower resources in China means that there is a huge demand for national power transmission projects.Transmission lines inevitably pass through ice-covered areas.The problem of wire under icing and ice-shedding had caused a series of electrical accidents,and line trip accidents caused by ice-shedding were extremely common.In order to ensure the normal operation of the power grid,this paper used the finite element simulation method to study the dynamic response of ice-shedding on the transmission line,analyzed the factors affecting the wire jump-height after ice-shedding.Then this paper established a risk assessment system of ice-shedding on the wire,and mad reasonable and effective predictions for line trips.The main contents of this paper are as follows:Firstly,this paper described the finite element simulation method for ice-shedding on transmission lines.Based on the finite element software ANSYS,the transmission line simulation model was established,and elaborate modeling was performed for transmission towers,conductor lines,ground wires,insulator strings,fittings and spacers,respectively.The equivalent circular method was used to simulate the icing of the wire and the density change method was used to simulate the ice-shedding of the wire.Horizontal wind loads were applied to the lines and the insulator,and the model was verified to be correct.Secondly,this paper studied on parametric analysis of the jump-height of transmission lines after ice-shedding.This paper set the standard ice-shedding conditions of the transmission line,and studied its influence on the wire jump-height after ice-shedding from three aspects of finite element modeling parameters,line design parameters and applied load parameters.Then this paper analyzed the trajectories of the interaction between the mean wind and the ice-shedding load on the wire,and between the pulsating wind and the iceshedding load on the wire,and also analyzed the effects on the jump-height after ice-shedding.Thirdly,this paper investigated the effect of non-synchronous ice-shedding and nonuniform ice-shedding on the jump-height of transmission lines.Based on the study of simultaneous ice-shedding of transmission lines,this paper modeled and analyzed the nonsynchronous ice-shedding,such as single-span “Unzipping” ice-shedding and multi-span “Unzipping” ice-shedding.And the effects of ice-shedding form and ice-shedding speed on the jump-height of the wire were studied.Finally this paper studied the dynamic response of wires after the random non-uniform ice-shedding,and discussed the position of the maximum jump-height after ice-shedding which was caused by the non-uniform iceshedding.Based on the key influencing factor of the ice-shedding amount,the jump-height of the non-uniform ice-shedding was significantly larger than the uniform ice-shedding.Finally,based on the MATLAB prediction algorithm,the risk of ice-shedding on the transmission line was evaluated.The probability distribution model of meteorological parameters(wind speed,ice-shedding length,and ice thickness)related to the ice-shedding on the transmission line was established.Then the jump-height after ice-shedding and corresponding horizontal displacement of wires were obtained by finite element calculation,and this paper established a data file about ice-shedding.Based on the software MATLAB,this paper established KNN algorithm model and BP neural network model,trained the data file,and optimized algorithm prediction model.According to the line trip conditions by iceshedding,through a large number of sampling,prediction and statistics,the line trip probability by ice-shedding was obtained and the risk level was determined.Taking a project of the ice-shedding trip as an example,the warning of the ice-shedding risk assessment model was consistent with the actual situation.