Drying Process _
For transformers up to 33 KV, drying is carried out in well ventilated, electrically heated oven for a period determined by electrical tests. The transformers are then immersed in freshly filtered hot oil and allowed to stand for a period until all trapped air is escaped.
For transformers with voltages of 66 KV and above, drying out treatment takes place in a vacuum drying oven. The core and windings assembly is placed in oven and initially heated at 90°C for some time. During this period, heated air is circulated rapidly and the moisture laden air is bleed off at frequent intervals. Vacuum is then applied, and heating of the core and windings assembly is continued simultaneously. The mixture of air and moisture that is extracted is passed through a condenser and collected in the form of water which is measured and recorded. The end point of drying process is decided by the measurement of insulation resistance, tan-delta, and the collection of water.
For bigger transformers, 25 MVA and above, Core coil assembly along with tank are in the oven and after completion of heating cycle, hot, degassed oil is then allowed into the transformer tank under vacuum. This oil is then circulated through the transformer and the oil degassing plant until all gas trapped in the core, windings, and the insulation is removed. This ensures a high degree of stability in the insulation structure and early attainment of its mature condition, which would not otherwise be achieved until the transformer had been in service for some time.
The core- coil assembly is placed in Vacuum Auto Enclave to eliminate moisture content which is targeted less then 0.5 % moisture. Drying process is to be carried out @ 90°C & respective vacuum cycle at rated interval to improve Insulation resistance and remove ingress of moisture in insulation material..
Contact : Atlanta Electricals Pvt. Ltd. Plot No. 1503/4, GIDC Estate, Vitthal Udyognagar - 388121. (VIA-Anand) Gujarat, India. | Phone : (02692) 235023 / 237185 | Fax : (02692) 237203