Research On Condition Evaluation And Maintenance Decision-making Method Of Power Transformer

Power transformer is one of the most important transmission and transformation equipment in the power system,which is in the pivotal position in the power system.However,for a long time,the maintenance strategy of transformers and other power equipment in Chinese power system has been mainly carried out by means of periodic maintenance and breakdown maintenance.Such maintenance mode that ignores the actual operation state of the equipment,easily brings the problem of over-maintenance and not repairing on time.Compared with the periodic maintenance mode,the condition-based maintenance,which mainly relies on the data of operation status and repairs the equipment timely and accurately according to the actual situation,can save more financial resources and time cost of maintenance,improve the utilization rate of equipment and operation economic benefits,and enhance the safety and reliability of power grid operation.Thus implement condition-based maintenance for power equipment is promoted vigorously by the current electric power industry.Based on the condition-based maintenance of power equipment and from the point of view of equipment operation data and evaluation decision-making,a further study on the key issues such as the state evaluation method of power transformer and group decision-making analysis of maintenance scheme is made in this paper,which mainly includes the following contents.Firstly,combining with relevant rules and standards of equipment,a transformer condition evaluation index system covering qualitative and quantitative state parameters is constructed.On this basis,in view of the multiple uncertain factors involved in the evaluation indexes,the grey-fuzzy comprehensive evaluation model of transformer state under the intuitionistic fuzzy analytic hierarchy process(IFAHP)is proposed by combining intuitionistic fuzzy set,cloud model and grey-fuzzy theory.Secondly,considering the importance and the comprehensive characteristics of transformer bushing condition evaluation,a qualitative and quantitative hierarchical evaluation index system is constructed based on bushing test data and inspection items.Meanwhile,aiming at the fuzzy and uncertain factors of bushing parameter information,a fuzzy-evidence fusion evaluation model is proposed by combining fuzzy evaluation and evidence theory.In this model,the initial basic probability assignment(BPA)of state variables from each layer which is obtained by constructing membership function,is modified to the evidence fusion.Finally,considering the deficiencies of previous decision-making methods in processing qualitative evaluation information for transformer maintenance schemes,a group decision-making method based on intuitionistic linguistic evaluation is proposed by combination with intuitionistic fuzzy sets and linguistic evaluation.In this proposed method,the hesitation and negation of expert comments information are more complete expressed by introducing intuitionistic linguistic number,and the decision-making information of expert groups are integrated by using intuitive linguistic operators to realize the selected optimization and decision making of transformer maintenance schemes.