Hitachi Energy has completed the development of the dry-type transformer intended for network applications, even submersible. The unit is inside of a completely sealed tank and both tank and active assembly have been designed and tested to the IEEE C57.12.40 standard for network transformers (amended for dry-type features). The absence of oil eliminates the threat to the surrounding environment during an internal failure.
Main features of dry-type submersible network transformer are: complete absence of oil, entirely welded tank assembly, N2 gas overpressure for tank deterioration monitoring, 2-position ground switch, 70 percent overloading capability, similar footprint to liquid-filled units with cooling fans and power rating up to 1,000 kVA and 15 kV primary voltages.
