Failure Analysis of a Power Transformer Using Dissolved Gas Analysis – a Case Study

Reliable and continued performance of power Transformer is the key to profitable generation and transmission of electric power. Failure of a large power transformer not only results in the loss of very expensive equipment, but it can cause significant guarantied damage as well. Replacement of that transformer can take up to a year if the failure is not disastrous and can result in tremendous revenue losses and fines. A Power Transformer in operation is subjected to various stresses like thermal stress and electrical stress, resulting in liberation of gases from the hydrocarbon mineral oil which is used as insulant and coolant. Dissolved Gas Analysis is a technique used to assess incipient faults of the transformer by analyzing specific dissolved gas concentrations arising from the deterioration of the transformer. DGA is used not only as a diagnostic tool but also to track apparatus failure. In this case study the fault and defects that occurred in 400kV/220kV/132kV/66kV Sub Station can be found by DGA.