A review of lifetime assessment of tranformers and the use of Dissolved Gas Analysis
Independent thesis Basic level (professional degree), 20 credits / 30 HE creditsStudent thesis
The Reliability-Centred Asset Maintenance (RCAM) is a structured approach to determine maintenance strategies for electric power system which is developed at KTH School of Electrical Engineering. RCAM focus on reliability aspects of the system and one of the main steps in RCAM in to modeling the relationship between reliability and the elect of maintenance for critical components within the system. The transformer has been identified as a critical component within a power system and in spring 2006 the Ph.D project “Life time modeling and management of transformers” was started within the RCAM group. The overall goal for the project is to develop a quantitative model for the lifetime distribution of a transformer with the final goal to implement the developed model into a maintenance planning.
Dissolved Gas Analysis (DGA) is a widely used technique to estimate the condition of oil-immersed transformers. Incipient faults within the transformer may be detected by analyzing the gases which are dissolved in the transformer-oil. The objective of this thesis is mainly to analyze available data from DGA, and investigate if this kind of data may be useful in quantitative modeling of the transformers reliability.
One conclusion from this work is that the difficulty in modeling the transformers reliability lies mainly in the limited availability of adequate data. Transformer is a reliable device and since the number of failures in critical in mathematical modeling of a component´s reliability it becomes very difficult to determine such models. Another aspect is the difficulty to draw conclusions about a transformer´s condition only from the DGA results. Although there are standards available for this purpose the DGA interpretation should also be based on other information about the particular transformed such as size, construction and operation circumstance. During this work no sources have been found from which the correlation between DGA data and probability for transformer failures could be estimated. For this reasons the proposed failure rate function in this work is based on several subjective assumptions and has not been possible to verify.
Place, publisher, year, edition, pages
Stockholm: Elektroteknisk teori & konstruktion , 2008. , 52 p.
IdentifiersURN: urn:nbn:se:kth:diva-4828OAI: oai:DiVA.org:kth-4828DiVA: diva2:14162