Outdoor oil cooled instrument transformers are hermetically sealed type in construction. The whole CTPT unit is dried in an air heating oven under very high vacuum & strictly controlled conditions. Measurement of amount of moisture taken out from the CTsPTs is done at regular intervals during the vacuum drying process. After the process is over the CTPTs are filled with filtered, de-aerated EHV grade transformer oil under vacuum. The oil filtration plant, the processed oil storage tank & the vacuum drying chambers are all interfaced together to ensure that the CTsPTs are filled with oil untouched by human hand. To seal the CTPTs the space left for expansion on the top is filled with dry & pure -nitrogen gas through a non -returnable valve at pre determined pressure.

Outdoor oil cooled instrument transformers are hermetically sealed type in construction. The whole CTPT unit is dried in an air heating oven under very high vacuum & strictly controlled conditions. Measurement of amount of moisture taken out from the CTsPTs is done at regular intervals during the vacuum drying process. After the process is over the CTPTs are filled with filtered, de-aerated EHV grade transformer oil under vacuum. The oil filtration plant, the processed oil storage tank & the vacuum drying chambers are all interfaced together to ensure that the CTsPTs are filled with oil untouched by human hand. To seal the CTPTs the space left for expansion on the top is filled with dry & pure -nitrogen gas through a non -returnable valve at pre determined pressure.