The case of an inadvertent transformer winding…
A new large turbogenerator in a UK power station was designed to have its 20kA three-phase output busbars split either side of one of its support pillars, because of a lack of space. The support pillars were steel, part of a steel framework, and created a single-shorted turn around one of the busbars. In operation, the pillar (made of 2 inch thick steel members) got hot enough to blister its paint, and increased in height by 5mm, putting a bearing out of alignment and causing a terrific noise which caused the station workers to run for their lives. (Editor’s note: a large turbogenerator up to speed and adrift from its bearings is a fearsome
object!) The cure was another shorted turn, this time around the pillar and made of ½ thick aluminium.
(Conversation at Mersey and District Club Européen, 28th January 1999.