Newly Developed and Cost-Effective Submersible Dry-Type Network Transformers

This paper describes the development of submersible dry-type network transformers. These transformers are safer for the public and are less potentially damaging to the environment. The dry-type transformers are installed in a sealed corrosive-resistant tank and are capable of operating in open air, partially submerged or completely submerged. The ratings are in the range of 100 kVA to about 1500 kVA and 25-kV voltage. A HV grounding switch is installed in the tank with electromechanical interlock to prevent closing when energized and with externally operated handle. Dimensions and losses are comparable to those of liquid-immersed transformers. Tank pressure and tank air temperature can be remotely monitored. These network transformers have been tested and verified to be compliant to IEEE C37.20.07, C57.12.01, C57.12.52 and C57.12.91.