Importance of bushing- DGA in condition assessment of power transformers

Power transformers and shunt reactors are an integral part in ascertaining the reliability of any power utility. Utilities are facing considerable pressure to ensure their critical asset´s reliability due to deregulation, increased demand, economic pressures, and profit constrains. Most of the power transformers and shunt reactors develop faults and get critical over a period of time. A transformer´s and reactor´s condition is normally assessed based on DGA supported by electrical tests. In this paper three Case studies on 315 MVA transformers 63 MVAr are investigated. These jobs have seen high hydrogen and methane, showing faults in these jobs. However it was not supported by electrical tests such as isolation test and low voltage tests in any of the case. These jobs were physically inspected and investigated for further details. DGA was monitored throughout their period. The fault analysis is covered in this paper.