Presented by Peter Brosz, Brosz Technical Services

This presentation will focus on advanced transformer diagnostic testing for condition and failure analysis, with emphasis on Dissolved Gas Analysis (DGA) of the insulating liquid medium. State of the art methodology for DGA review, in conjunction with all available data related to the transformer in question will be covered. Other diagnostic testing and inspection techniques, including newer methods such as SFRA (Sweep Frequency Response Analysis) AND DFR (Dielectric Frequency Response) and others will be presented. These techniques are all part of the more comprehensive inspection and testing toolkit. An overview of all the inspection and testing techniques for liquid filled transformers will be discussed. A description and review of the related guides, codes, and standards will be covered. Takeaways for those performing electrical testing and owners/operators of transformers will be provided. This includes how to quickly identify potential DGA problems, techniques to assess the severity, and the complete package of information that is useful for transformer diagnostics and condition assessments in order to avoid failures or assess condition. Four (4) case studies will be presented: - A 10 MVA shell type electric arc furnace type transformer failure due to localized overheating. - Another 10 MVA shell type electric arc furnace type transformer pulled from service due to concerning DGA levels. - A 140 MVA stacked core electric arc furnace transformer that was severely gassing until its final demise after a major tapchanger swap out mistake. - An 8.752 MVA cyclotransformer used for a sag mill power supply at a mine in Chile. A review of historical DGA and maintenance data prior to the DETC (De-Energized TapChanger) failure. Present day supply chain challenges related to electrical equipment costs and lead times, including transformers, will also be briefly discussed.