Failure Probability Assessment And Risk Warning Of Transmission Lines Considering The Development Process Of Freezing

Meteorological disasters frequently occur in China,and long-distance transmission corridors often go through harsh climate regions.The iced conductor excited by strong wind may cause structural failure under the conditions of freezing weather,with the addition of strength loss due to wind and sand abrasion,which pose a severe risk to the safe operation of the power grid.Therefore,the transmission line in a strong wind and sand region in Xinjiang Power Grid was taken as the object in this paper.An ice-covered prediction model of the transmission line was constructed by taking into account the time accumulation effect of meteorological factors.The evaluation method of failure probability of the ice and wind load considering the wind-sand abrasion was studied.A dynamic early warning method for transmission line risk under freezing weather was proposed.The research results will help the grid operation and maintenance personnel to check the operation status of the transmission line in time to prevent the failure caused by ice and wind in the transmission line.The main research work of this paper is as follows:The existing mechanism-based ice thickness prediction models take too many factors into considerations,so their disadvantages are structure complex,large prediction error,and did not consider the time accumulation effect.Thus,based on the micro-meteorological monitoring data and numerical weather prediction of transmission lines,an ice-covered prediction model for transmission lines that take into account the cumulative effect of meteorological elements is established in this paper.By analyzing the relation between the thickness of ice growth and time accumulation,the indexes of the ice thickness growth which taking into account the cumulative duration of meteorological elements is constructed.The historical meteorological data is used to calculate the indexes and the training data set is composed of the ice thickness monitoring data.The SVM regression method is used to train and obtain the prediction model.The validity and accuracy of the proposed method are verified by the case study and comparison of various methods.Aiming at the problem of an insufficient study of structural failure caused by wind and sand abrasion on transmission lines,an evaluation method for the failure probability of ice and wind load on transmission lines considering wind and sand wear is proposed in this paper.Based on the ice growth prediction model,the ice load of the transmission line is estimated,and the wind load is calculated by wind speed monitoring and wind numerical prediction.The combined calculation of the wind and wind combined load of the transmission line is carried out.Aim at the deicing jump that may occur in the later stage of the ice process;the dynamic deicing load is calculated based on the momentum conservation.On the basis of the monitoring and test data of conductor and fitting abrasion in Xinjiang power grid,the empirical formula of residual strength after sand abrasion is fitted,and the influence of sand abrasion online strength is quantitatively evaluated.Finally,using the intensity interference theory of the reliability of the transmission line structure,combined with the analysis of the case studies,the failure probability of the ice and wind load on the transmission line considering the sand abrasion is evaluated.A dynamic early warning method for transmission line risk under freezing weather is proposed.On the basis of the ice growth index of the transmission line,the degree index which satisfies the meteorological conditions of the deicing is constructed,it can estimate the dynamic ice process of the transmission line.Then,by using the proposed failure probability assessment method of the transmission line,the failure risk of the transmission line at each time stage is dynamically evaluated for the frozen weather development process,and the risk warning is issued according to the risk evaluation results,and corresponding risk reduction measures are given.Finally,the application case of this method in Xinjiang Power Grid is introduced,and the effectiveness of the proposed method is verified.