Research On Risk Assessment And Strategy Of Condition-based Maintenance For Distribution Transformer

As the terminal part of the power system,the operation safety and stability of the distribution network directly affect the power supply reliability of the power system.As one of the key equipment of the distribution network,the condition based maintenance work of the distribution transformer is more and more concerned.In order to ensure the stable operation of distribution transformer,it is of great significance to evaluate its health status,then to carry out risk assessment,and to formulate condition based maintenance strategy.First of all,in view of the problem fuzziness and randomness of distribution transformer health evaluation index,the multi-level index factors are selected to build the health status evaluation index system of distribution transformer,and the weight of each index is determined by combining the analytic hierarchy process(AHP)and entropy weight method;The membership degree value of each index to each status level of distribution transformer is calculated by membership degree formula and cloud model parameters;The fuzzy comprehensive evaluation method is introduced to build the fuzzy evaluation matrix,the evaluation result is calculated using the evaluation formula,and the maximum membership degree principle is used to determine the distribution transformer health status level,and the distribution transformer health status evaluation results are obtained.Secondly,in order to quantitatively analyze the failure probability of distribution transformer,the relationship between the health status assessment and the health index of distribution transformer is analyzed and calculated;In order to quantify the total value of distribution transformer assets,the value,status and user level of distribution transformer are analyzed and calculated;In order to quantify the degree of asset loss caused by distribution transformer failure,from repair cost,environmental impact,human Personal safety and power grid performance are analyzed and calculated.Based on the results of fault probability,asset evaluation and asset loss degree evaluation of distribution transformer,combined with the quantitative calculation method of risk value of distribution transformer,the risk of distribution transformer is evaluated.Finally,according to the results of health assessment and risk assessment of distribution transformer,a decision-making model of condition based maintenance based on D-S evidence theory is proposed.Established a condition based maintenance decision frame and a maintenance decision index system,taking the maintenance decision index as the source of evidence and the maintenance scheme as the identification frame.Then the standardized index value,index weight and expert weight under each scheme are integrated into the basic probability distribution of D-S evidence theory.The comprehensive group decision of maintenance mode and maintenance period is realized,which provides scientific basis forreasonable maintenance arrangement of distribution transformer,and the effectiveness of the model is verified by an example.Through the study of health status assessment,risk assessment and condition based maintenance strategy of distribution transformer,it is shown that the combination of cloud model theory and fuzzy comprehensive evaluation method can effectively eliminate the fuzziness and randomness of health status assessment indicators of distribution transformer.By using D-S evidence theory to study the condition based maintenance strategy,a reasonable condition based maintenance strategy can be obtained,which is in line with the actual situation and has certain application value.