Some recent tests of oil circuit breakers

Whenever an electrical circuit carrying considerable energy is opened in oil, gases are generated. These expand and rise, and tend to force the oil out of the containing vessel. They also form with air explosive mixtures, and either explode, or burn for a considerable length of time when ignited. It is important, therefore, that oil circuit breakers be provided with strong oil containing vessels in order that they may withstand the high initial stresses which are often present under certain conditions and also that suitable provision be made for retaining the oil.