Study On Operation Reliability Evaluation And Residual Life Prediction Of Power Transformer

With the increasing demand for electricity in society,power transformers are gradually developing towards UHV and large capacity.As an important voltage conversion equipment in power system,the operation reliability of power transformer directly affects the safe operation of power grid.Effective prediction of the operation reliability and residual life of transformer can discover latent failure in time and effectively reduce losses eaused by forced shutdown of transformer.In engineering practice,the condition-based maintenance of transformers is usually carried out on an annual basis.However,due to the influence of insulation aging,external environment and other factors on the reliability of transformers,there may be outage risk in the short-term.Therefore,this paper establishes dynamic failure rate models of transformers adapting to short-term and long-term prediction respectively.The residual life of transformer is modeled according to the calculated failure rate.The details are as follows:(1)By means of theoretical analysis and practical calculation,the influence of insulatfon aging degree,gas content in oil and production rate,moisture content of insulating paper,winding hot spot terrqjerature and failure time distribution parameters on transformer operation reliability is discussed respectively.The conclusion that considering the above factors can effectively improve the prediction accuracy of the model is verified.(2)Based on the Markov state transition process,considering the influence factors of gas content in oil,hot-spot temperature of winding and moisture content of insulating paper,a short-term failure rate prediction model of transformer is estab lished.This model studies the quantitative relationship between insulation aging degree and feilure rate.(3)Maricov chain Monte Carlo method is used to simulate the scene of transformer failure cycle.Considering the influence factors of gas content in oil,gas production rate and failure time distribution parameters,the medium and long term failure rate prediction model of transformer is established.The simulation method can effectively avoid the problem of direct solution by analytical method.(4)According to the predicted transformer feilure rate,the residual life prediction model of transformer fault-free time is established to provide intuitive transformer health data for conditfon-based maintenance of transformers.Through the analysis of examples in each chapter,it can be found that compared with the existing transformer feilure rate model which only considers the gas content data in oil,when considering the above factors,it can make full use of the monitoring data of transformers,effectively improve the prediction accuracy of the model.Thus,it can provide actual failure rate and residual life data for transformer condition-based maintenance,and guide the selection of appropriate maintenance strategies.