Study On State Evaluation Of Power Transmission Lines

There is a higher frequency of fault for overhead transmission lines because of the wide distribution, the difficulty of on-line monitoring, and the complexity of the terrain. The state of transmission lines will directly affect the reliability of the whole power system. Therefore, the evaluation of the operation state of the transmission lines has important theoretical and engineering application value to guide the maintenance and improve the reliability of power system.In view of the characteristics of the transmission lines, the paper combines the analytic hierarchy process and fuzzy comprehensive evaluation method to study the status of transmission lines, the main work and achievements are as follows:(1)The evaluation index system of transmission lines are selected and established. Using Delphi analysis method, 58 state evaluation indexes of transmission lines are selected. The expert questionnaire is designed and distributed. The scientific and reliability of survey data is measured by three indicators of positive coefficient, authority degree and coordination coefficient. The data are analyzed by using statistical analysis software SPSS, 58 indexes were removed, merged and adjusted according to the expert's opinion, and the state evaluation index system of transmission lines was established by 42 indexes.(2)The weights of the evaluation index of the transmission lines state evaluation are determined by using the nine scale analytic hierarchy process. According to the established evaluation index system of transmission lines, the index system is decomposed and a layer structure is constructed, which includes target layer, rule layer and index layer. According to the relative importance among the two indicators, the judgment matrix is set up, and the consistency of the judgment matrix is determined, and the weights of the first and second degree evaluation indexes are determined.(3)The state evaluation model of overhead transmission lines based on AHP and fuzzy comprehensive evaluation method are established. The membership function of transmission lines is determined by fuzzy statistical method. The fuzzy statistical questionnaire is designed and the M(?,?)operator is selected as the fuzzy operator to obtain the first and two stage fuzzy judgment matrix of the state evaluation of transmission lines. Finally, the state level of transmission lines is determined by the maximum membership degree principle.(4)The validity and feasibility of the method of state assessment of transmission lines based on analytic hierarchy process and fuzzy comprehensive evaluation method are verified by an example.Combining AHP and fuzzy comprehensive evaluation method, which not only overcomes the subjectivity of the index of AHP that is not easy quantification, but also avoids the neglect of index weight induced by fuzzy comprehensive evaluation method, can provide references to solve the complex multi-factor decision-making of state evaluation of power transmission lines.