Analysis of the Transformer Failure using a Measurement-Simulation Approach : A Case Study

The diagnosis of transformer failures is based on various inputs, including the behaviour prior to failures (vibration, noise etc.), relay indications, and post-failure inspection/measurements. Condition monitoring tools like Frequency Response Analysis (FRA) may also provide early evidence of an evolving problem. Transformers are often subject to close-in faults, which may precipitate their failure. Current and voltage measurements corresponding to these events, obtained from relay fault recorders or disturbance records, can also be used in conjunction with analytical tools like simulation and electromagnetic field computation software to provide additional insights and corroborative evidence for the diagnosis. This is demonstrated using a real-life example of the failure of a 315 MVA, 400/220/33 kV auto-transformer at a 400 kV substation on the 14th of February 2018, following a close-in external fault.