The best course available is the Doble "Life of a Transformer" program held in the US each February. Last year 400 people attended this week long course, which has 30 guest speakers (best of the best in the industry) deliver one hour presentations on their area of expertise. The course also had a trip to the GE Bradenton transformer manufacturing plant, where you could actually witness the things that you learned in the lectures. The course is setup to discuss transformers from cradle to grave, which means that they talk about specifications, design, manufacturing, factory testing, transportation, site design, installation, field testing, commission testing, operations, loading, maintenance, repairs, and failure. The course also gets into specific components, such as load tap changers, surge arresters, control cabinets, bushings, etc. I highly recommend it to anyone at all levels from beginner to expert.