Electrical insulation limits the volume of electrical equipment in a water environment

The life of electrical insulation in water is limited by steam (24 psig) which shows three orders of magnitude reduction in life as determined by AIEE #57. Power equipment in water must be temperature controlled to avoid the steam condition. This means larger volume of equipment, lower power densities and lower temperature rise above the ambient. If this is not done by the designer then the operator is forced to downrate the equipment to preserve useful life. To overcome this limitation in size one must develop steam resistant electrical insulation in order to be able to operate at higher temperatures. Techniques to seal the system to exclude water are not satisfactory because small amounts of water passing through barriers or internally generated in the system, may be the equivalent of operating the electrical equipment in 100% steam if temperature is not controlled.