Sealed Dry-Type Transformers Proved Safe by Test [includes discussion]

Tests were carried out to determine to what extent gross mistreatment of sealed dry-type transformers with class H insulation might be expected to involve fire or explosion hazards. Sealed transformers containing no organic material other than a small quantity of semiorganic silicone varnish were overloaded to destruction and subjected to internal power arcs. Analysis of pressure and temperature measurements indicate that this type of transformer may be operated with practically no danger from fire or explosion.