Economic Life Evaluation Of Substation And Transmission Line And Its Application In Power Network Planning

With the further development of power grid, rapid transformation of power entity management and continuous innovation of power network planning concept, researches on several important problems about life cycle management are being carried out. The data from power entity have been used to solve economic problems and reliability problems derived from power network planning, construction and rebuilt and therefore realize scientific decision-making. Achievements on life-cycle cost analysis (economy) and failure rate prediction (reliability) are then applied to economic life prediction of substation and transmission line. Based on previous researches, economic optimization of power network planning is studied.In this paper, the following work has been done:(1) A method is presented to estimate economical operating life interval of substation. After operating environment and quality condition of substation are analyzed, the influence of factors above on the failure rate of the three types of failure which are ordinary failure, larger failure and catastrophic failure was established considering different enlistment ages of substation. Based on the change of the three types of failure rate, annual maintenance cost interval and failure cost interval are calculated. At last, the time interval with the minimum annual average cost is regarded as economical operating life interval of substation.(2) A method to estimate optimal economic life interval of transmission line is proposed. Firstly, evaluate the operating environment and quality condition of transmission line from the following four aspects which are climate and natural disaster, geography and external forces, component and civil work, and operation and maintenance. Secondly, in case of considering the different enlistment age of transmission lines, least squares support vector machine (LS-SVM) is adopted to analyze the influence of factors above on the failure rate of the three kinds of failures which are ordinary failure, larger failure and catastrophic failure. Combined with the theory of interval analysis and life cycle cost, annual maintenance cost interval and failure cost interval on the change of the three kinds of failure rates are calculated. Lastly, the time interval with the minimum annual average cost is regarded as retired time, which is optimal economical life interval of transmission line.(3) Interval analysis method, which is used to calculate the different cost and the result of failure rate prediction, is applied in the theory of life cycle cost in the economic life interval estimation of substation and transmission line. It eliminates the errors which are brought by certain value.(4) In economic optimization of power network planning, it is unreasonable to consider investment cost only while application of life cycle cost model is still facing some difficulties. Therefore, a comprehensive cost model considering boundary of fixed number of year as well as annual cost and present value in the end of planning year is established. Background of comprehensive cost model and differences between life cycle model and proposed model are introduced, proving that comprehensive cost model is more suitable for actual practice of planning and construction. Then, calculation models and processes for each part of cost are analyzed. The calculation mainly focuses on equipment with unequal costs, and old equipment among requires further economic life prediction to determine the necessity and time of renewal.The paper analyzes economic life of substation and transmission line, and then applies the results of researches in decision-making of power network planning. The method can also be used in decision-making of power network construction and rebuilt. Summary and expectation are concluded at last.