The Study On Hierarchy And Sub-unit Condition Assessment Of Power Transformer

With the development of the domestic EHV and UHV transmission technology, thepower grid capacity is increasing, the whole power system security and stability facehuge challenges, especially as the hub of system equipment, the healthy operation oflarge power transformer and insulation status directly related to the power grid securityand stability, it is very important for ensure grid safe and improve the health level ofequipment that have advanced repair method; and the management and maintenance ofpower equipment from periodic preventive maintenance to condition maintenance isimperative, and the basis of condition maintenance is condition assessment. Study onpower transformer condition assessment and grasp the operation of the powertransformer state accurate and timely not only ensure the safe operation and reduce theincidence of failure but also has important practical significance for guiding the stateoverhaul.This article through in-depth analysis that the existing methods have not strongpertinence, considering indicators are imperfect. According to independence of thepower transformer parts and the difference of the indicators nature, the transformer isdivided into body、bushing、cooling system and on-load tap-changer. They are evaluatedrespectively. According to different characteristic of components, this thesis adoptsdifferent assessment methods and different weight determination method and evaluationmodel. Finally comprehensive assessment of various components evaluation results todetermine the overall state of the transformer. The paper gets the following mainachievements:①Through the existing research results, combined with the related regulations,analyzes the evaluation index of different parts and proposes a hierarchical assessmentmethod, a hierarchical evaluation index system is established which have componentsassessment system and overall evaluation framework.②For quantitative index of transformer body, this paper propose Fuzzy set-valuedstatistic to determine the proportion between subjective indicators, and by using entropyvalue method to modify the subjective weights, the problem of the weight is hard todetermine is solved, for the transformer body has complex structure and many faults,many characters. At last use kernel vector space model to effective pull open thedistance between each state and normal state and realize the transformer body insulation assessment.③In view of the power transformer bushing has few characters, the existingevaluation lacks can intuitively reflect the insulation itself performance indicators, thendigs the new index parameter. Proposes cloud model to determine the weight ofcharacteristic and by using the unascertained theory to correct the weight. At the sametime identify the new index parameter weight. Finally use kernel vector space modelto realize the bushing insulation condition assessment.④For the cooling system and on-load tap-changer, non-electricity systemincluding the qualitative index of body and bushing. These parameters can be obtainedthrough tour. Therefore through the principle of penalty realize the evaluation oftransformer components. For the components which have quantitative index, at thesame time make quantitative evaluation, combined with evaluation results ofcomponents, the transformer overall state is determined by using Fuzzy comprehensivejudgment.⑤The instants analysis indicate that the based on the vector space model and thedivision evaluation method of deduction and the transformer overall state determined byusing Fuzzy comprehensive judgment method. Not only can intuitively reflect thehealth of the transformer parts but also reflect the overall state, compared with othercomprehensive methods this method has stronger pertinence and operability; it can alsoprovide a reference for condition maintenance and has strong practical value.