Condition-based Maintenance Study Including Power Grid Operation Risk

Equipment maintenance decision-making is one of the most crucial issues in the power grid. Appropriate maintenance can bring great benefits to the power grid, and increase equipment operation efficiency. On the contrary, it will cause sacrifices, and affect the reliability and economic of power grid operation. So, maintenance decision-making has been always the focus of attention of the academic and engineering.Now, the concept of condition-based maintenance (CBM) has been receiving increasing attention and trust with the development of power system technology. It is based on the equipment monitoring and diagnosis. The appropriate maintenance time for the single equipment can be found under the background of CBM, and this not only makes the decision of maintenance easy, but also improves the efficiency of the single equipment. However, from the perspective of the whole power transmission system, the appropriate maintenance time of the equipment depends on its own performance instantly, which arouses the discrepancy between the equipment and the power transmission system. Once this discrepancy can not be compromised, it will certainly arouse contradictions and conflicts between individual and whole, and loses the integral efficiency.Under this background, in order to solve those contradictions and conflicts, it needs a good compromised mechanism to deal with the differences of equipments maintenance time and the relationship between equipments maintenance and integral efficiency of transmission system operation. Based on this line, the maintenance theory has been researched in this thesis for transmission system equipments. The main works and innovative achievements of the thesis are as follows:1. Research on equipment failure rate expression and prognostic technology. Based on the summarizing the relative outcome, from the viewpoint of probability, the equipment failure rate model is given taking into account the device status, corrective maintenance and preventive maintenance using the total probability formula. The focus is reflected like:the relationship between health index and the equipment failure rate, the role of corrective maintenance and preventive maintenance, the probability of maintenance decision making, the relationship between the probability of equipment failure, failure rate and equipment status (reliable, unreliable). In short, with the existing research results, the comparatively systematic analysis and research to the failure rate has been carried on in this part, which gives a precondition for risk-based transmission system maintenance theory.2. Maintenance strategy evaluation method was proposed taking into account the power grid operation risk. On the basis of calculating expected energy not served in the power grid, the cost risk indicators, security risk indicators and environmental risk indicators were deduced from the comprehensive view of equipment individual and the whole power grid. According to the CBM needs, the concept of equipment importance (EI) was proposed. El index was to quantify considering the individual performance of equipment and overall operating performance of the grid. The order of maintenance was proposed according to El index. On the other hand, power grid maintenance strategy evaluation and sorting methods was given based on risk. The methods take into account the relationship between the equipment performance and the maintenance strategy. From the perspective of the whole power grid operation, the equipment important analysis and power gird maintenance strategy evaluation were given based on risk, which provide the quantitative basis for the CBM in power grid.3. On the analysis of dialectical relationship between equipment maintenance and system operation, the concept of condition-based maintenance for power grid (CBM-PG) is put forward. In CBM-PG, from the perspective of failure and maintenance, the failure risk and maintenance risk are defined. On the basis of the condition trend prediction for the transmission equipment, the mathematics model and corresponding solutions are presented to minimize the sum of failure risk and maintenance risk, and get a balance between the equipment maintenance, operation and the efficiency of power transmission system. The detail analysis of the RBTS-BUS6and IEEE-RTS79system demonstrates the validity and practicability of the proposed concept, which provides a necessary foundation for the further research on the cooperation decision-making between maintenance and operation of power systems.4. Under the study of condition-based maintenance for power grid (CBM-PG), the model and solution of condition-based maintenance for substation (CBM-S) was studied. The equipment involved in this paper were only associated with the substation from the view of the topology. The necessity of the research for CBM-S was discussed first, and the equipment condition in the research time was obtained by Markov process under the technique of state monitoring and forecasting. Furthermore, the quantitative expression of the failure risk and maintenance risk were provided, in which the maintenance time was the only parameter. Then, the decision-making model of CBM-S was established. The goal of the model was to minimize the sum of failure risk and maintenance risk, and the maintenance constraints were also considered in this model. The genetic algorithm was selected to solve the model. The analysis of simple example demonstrates the necessity and effectiveness of the study in this paper. This paper is the further study of the CBM-PG, and is an important part of the decomposition and coordination of the decision-making process for CBM-PG.5. Under the study of condition-based maintenance for power grid based on risk, a Decision Support System for CBM is built. The system has three basis functions:the risk assessment of power grid, the analysis of equipment important for maintenance and the analysis of equipment maintenance strategy based on risk. The system provides a friendly interactive interface, and is easy to use. It has been used in the Shandong power transmission system, and the results demonstrate the validity and practicability of the system.