| Transformer is the core component of a power substation and the basis for the long-distance transmission of electricity.It plays an important role in network reliability and stability.Power transformers always use mineral oil as an insulating and cooling medium.Just like the blood in a human body,doctors are able to judge the health of the human body through blood examination.The insulating oil is an important indication of the health of the transformers.Maintenance staffs can have an initial diagnosis on the transformer by doing gas chromatographic analysis of insulating oil,without opening any cover of the transformer.Together with other important electrical test and measurement,maintenance staff can further determine maintenance strategy.This article study deeply into the relationship between the dissolved gas analysis(DGA)and transformer fault.Comparing different type of DGA interpretation,study the transformer fault diagnosis based on DGA and its application in Macau network.We discussed the transformer oil dissolved gas sources,including external intrusion,decomposition of insulating oil,decomposition of solid insulating materials as well as legacy from transformer manufacturing and special operations introducing and on load tap changer oil chamber leakage.Secondly,the comparative study of different DGA interpretation including the special gas interpretation,national standard GB three-ratio method,Duval’s triangle interpretation,IEEE Dornenburg ratio and Roger ratio method.Analysis the method among these interpretations,characteristics of each interpretation and the respective applicable scope and precautions.Study on the technical characteristics of Macao online DGA monitoring systems,and a detailed analysis on the Hydran201 Ti,Hydran M2,Calisto 2 and the latest generation Calisto 9 system and its associated technical principle.Finally,study the actual case of Macao network-Lotus Substation No.3 reactor overheating fault and Cotai Substation No.2 transformer bushing tank overheating fault.Considering the special combination of Hydran and Calisto Series online monitoring device,and also Transport X and Myrkos laboratory equipment in Macau network,this article developed an early warning,diagnosis,treatment guidance for Macau network transformers based on DGA monitoring and interpretation. |
