Study On Multi-level Maintenance Strategy Of Power Transformers Based On Quantitative Risk Assessment

As a key equipment of power system, the operating status of power transformerimpacts is the security and stability of the grid. Fault diagnosis and prediction oftransformer in the complex operating environment to assess the operating status oftransformer, and then analysis the risk of equipment to make appropriate maintenancestrategy, which has important guiding significance for the transformers’ operation andmaintenance in the current context of grid equipment rapid increasing.Power transformer is a complex system, its uncertainty and ambiguitycharacteristic data is difficult to effectively analyze, a new fault diagnosis andprediction method based on cloud theory and implicit semi-Markov model is proposedto improve the lack of existing fault diagnosis and prediction method. To improve thelack of ssociation between existing risk assessment and maintenance strategy, a powertransformer dynamic integrated risk assessment methods is proposed based on thetransformer’s operating status and environment to achieve the quantification of thetransformer economy risk. The whole life cycle fixed maintenance plan and amulti-dimensional multi-level maintenance strategy based on dynamic risk assessmentis proposed through the analysis of maintenance decision indicators and maintenanceperformance. The main results of the paper obtained are as follows:①The DGA data is trained by Cloud-based theory to construct observation spaceof transformer state, which is available to analysze the membership of ambiguity anduncertainty boundary transformer DGA data. Through the introduction of aging factorand long history state information with weighted multi-step method Markov chain, aweighted hidden semi-Markov model is proposed to predict the operating state oftransformer, based on the relationship of transformer degradation and the change ofDGA.②Through the analysis of the transformer risk under different operatingconditions, a transformer risk correction factor is introduced based on the wingding hottemperature that reflects its comprehensive operating conditions. Based on the analysisof contingency, the economic loss of transformer under different risk patterns and itsrelated systemic risk caused by transformer outage is quantitative analysed.③The status changes of transformer, and its age reduction as well as thecorresponding revenue under different maintenance levels is analysed. Accoding to the regular pattern of transformer’ operation in the life cycle, a fixed maintenance plans oflife cycle can be optimized with the objective function of annual cost-effectiveness. Atlast, a multi-dimensional multi-level transformer maintenance optimization strategy isproposed, which is optimized in reliability, economy and maintenance resources fromthe substation level, device level and component level.