Research On Dynamic Maintenance Planning Of Hydroelectric Components

The purpose of formulating maintenance plan is to determine scientific and reasonable maintenance activities to ensure the best reliability of the system with the minimum maintenance cost.In most of the small and medium-sized hydropower stations that have been put into operation,the maintenance plan is based on experience,which combines timed based maintenance with breakdown maintenance.Time based maintenance plans are mostly formulated according to experience and ignore the actual running state of the equipment,leading to poor operating economy.Breakdown maintenance can only repair the equipment when there is a problem,which cannot guarantee the safety of the equipment in time.Both of them have drawbacks.As the operating conditions of hydroelectric generating units become more and more complex,higher requirements for safety are put forward,the existing maintenance strategies have gradually failed to meet the actual needs and may lead to the waste of resources With the slowing down of investment and construction of existing hydropower stations in China and the number of hydropower units put into production gradually increases,how to scientifically and rationally formulate maintenance strategies has become one of the focus of current research.In order to explore more safe and economical maintenance strategies,more and more researchers focus on dynamic maintenance planning such as condition based maintenance.Dynamic maintenance planning is based on monitoring and analyzing the operating data of components to predict the variation trend of the operating state,and then comprehensively consider the components to develop maintenance programs.The implementation of dynamic maintenance planning can scientifically develop targeted maintenance schemes according to the state of components and can save more costs and have the characteristics of better economy.Therefore,on the basis of considering the whole life cycle of the hydroelectric unit,this paper studies the degradation law of the hydroelectric unit from the perspective of safety and economy and puts forward targeted dynamic maintenance strategies.At the same time,a multicomponent imperfect opportunity maintenance strategy of the hydroelectric unit is developed based on the comprehensive cost-effectiveness.The main contents and results of this paper are as follows:(1)For the purpose of exploring the equipment degradation process,the HMM is used to evaluate the possible residence time of each deterioration state by combining with the historical crack data of the runner,the maintenance cycle is dynamically updated according to the remaining time of different states and the safety of components to meet the economic and safety requirements under the current operating conditions.A series of inspections should be arranged in different states at alternate time points within a maintenance cycle,and the state evaluation and dynamic update of maintenance cycle can be realized by updating the crack sequence correction transition probability according to the inspection results.The research results provide a certain basis and theoretical basis for revealing the law of equipment degradation of hydroelectric generating sets and studying the dynamic renewal maintenance cycle.(2)For the problem of developing a targeted maintenance plan to ensure the safe operation of the hydroelectric generating sets,based on the results of the life cycle assessment,the probability of contribution of cracks in different states to the risk under the current time is quantified by the backward traceability reasoning method,and the crack with the highest probability of contribution to risk is used to form the optimal maintenance plan.The universal maintenance plan is put forward,and the different service ages and operating conditions of different runner are taken into account,so as to make customized maintenance plans for different runner.Finally,the repair activities are arranged in combination with resources and maintenance time to avoid blind repairs leading to waste or insufficient repairs.(3)In order to make use of the correlation between components to reduce the resources spent in a single maintenance,a reliability-centered multi-component opportunistic maintenance plan for hydroelectric generating sets is proposed.The key components of hydro generators are selected and the historical operation data are used for parameter estimation to establish the Weibull model which conforms to the degradation characteristics.According to the degree of component degradation predicted by the model,three types of maintenance care were carried out,and the maintenance time cycle was dynamically updated to avoid unreasonable maintenance care activities.In order to improve the accuracy of the model,the degradation growth rate,maintenance time and power generation loss during maintenance were considered.The economic advantages of the proposed opportunistic maintenance plan are evaluated by using the average daily maintenance cost as the evaluation index.Several key parameters affecting the maintenance plan cycle and cost were selected,local sensitivity analysis was conducted and high contribution factors were selected to provide guidance for making maintenance plan in engineering practice.