Study On Practical Analysis Method Of Transmission Tower-line System Reliability

The transmission tower-line system is an important lifeline project,and its safety and reliability assessment plays a vital role in the normal operation of the entire grid system.However,due to the structural components of the transmission tower are numerous and the composition of components of the transmission tower-line system is complex,the reliability analysis of both the transmission tower and the tower-line system is difficult.Using the traditional main failure mode identification method and combining with the narrow boundary method,the reliability of the transmission tower-line system is difficult to quantify.The principle of the equivalent extreme-value event and point estimation method(PEM)provides an effective way to analyze the system reliability of transmission tower-line system.However,the balance between the accuracy and the efficiency of point estimation method is difficult to achieve,which reduces the practicality of point estimation method.How to balance the accuracy and the efficiency of the point estimation method and how to apply it to the transmission tower-line system reliability analysis by combining with the single equivalent performance function are the two main purposes of this thesis.Therefore,the following work is carried out and completed:A new point estimation method based on FHDMR(Factorized High Dimensional Model Representation)is proposed.To solve the problem that the balance between the accuracy and the efficiency cannot be achieved when applying the exsiting summation approximation based point estimation method to the statistical moment estimation for product-based function,a new point estimation method is proposed by combining the adaptive multivariate FHDMR and direct numerical integration.As a result,the product approximation based Point Estimation Method is extended from the univariate form to the multivariate form.Several examples are investigated,and the proposed method is feasible,accurate and efficient compared with the existing summation approximation based Point Estimation Method.(2)A system reliability analysis method for the transmission tower is developed.To solve the problem that the existing transmission tower system reliability analysis method fails to reasonably establish the failure criterion of both component and system and accurately calculate the comprehensive failure probability,this thesis firstly establishes reasonable transmission tower component and system failure criteria.Secondly,the main failure mode of the system is identified by the stage critical strength branch-and-bound method.Then,the system reliability is calculated by combining the principle of equivalent extreme-value event and the proposed Point Estimation Method.It is verified that the reliability analysis method of transmission tower system developed in this thesis can analyze the reliability of transmission tower system simply,efficiently and practically.(3)The transmission tower-line system reliability analysis method is improved.The transmission tower-line system is composed of transmission towers,wires,fittings and insulators.The system reliability analysis of the transmission tower-line system should consider the influence of the all above components.However,most of the existing methods only consider the influence of the transmission tower and the wires,ignoring the effect of the fittings and insulators on the system.To solve this problem,this thesis comprehensively considers the influence of all components of the transmission tower-line system.The main idea is: Firstly,using ANSYS to establish the finite element models of the wires,fittings and insulators and calculating reliability index of the wires,fittings and insulators respectively.Then,the tower-line system is regarded as the series system consisting of transmission towers,wires,fittings and insulators;the principle of equivalent extreme-value event and the proposed Point Estimation Method are introduced to analysis the reliability of tower-line system.It has been verified that this method is feasible and effective.