Condition Assessment of High Voltage Power Transformer Using Dissolved Gas Analysis

Abstract

Condition monitoring is the process, which is used to monitor parameter of condition in machinery, such that if a significant change occurs it indicates that it may lead to failure of that machine. It is a major component of predictive routine maintenance. The use of conditional monitoring allows maintenance to be done in a scheduled manner or some other actions are to be taken to avoid the aftermaths of failure, before it leads to occurrence of any severe failure. Dissolved Gas Analysis (DGA) is a widely used technique to estimate the condition of oil-immersed transformers. The experimental results of the level and the change in concentration of different combustible gases in the insulating oil is a trustworthy diagnostic tool which can be used as indicator of undesirable events occurring inside the transformer, such as hot spots, electrical arcing or partial discharge. The objective of this paper is mainly to analyse available data from DGA, and investigate data that may be useful in quantitative modelling of the transformer’s reliability. Dissolved Gas Analysis (DGA) of transformer oil is the best indicator of a transformer’s overall condition. It will provide useful information about the condition of oil and help to identify the type of fault in the transformer. Depending upon the location of a transformer, its rating and the nature of its usage, some dissolved gas analysis is to be scheduled which will be appropriate for that transformer. The more critical the unit is the more frequently it should be sampled. Hence DGA is mainly performed in Power transformers.