Forensic analysis of a silicone oil filled mobile transformer

When a number of new silicone oil filled mobile transformers failed, an evaluation of one of the remaining transformers was commissioned. The forensic analysis involved the tear-down and evaluation of the working transformer and components. In this paper we will discuss the steps involved in developing this type of forensic analysis, a few of the findings, and recommendations. Problems identified a range from design issues through to insulation coordination issues that did not cause the initial failures, but were identified as high risk future issues.