Basics of Dissolved Gas analysis and Case studies for Power Transformers

Electrical insulating oils of petroleum origin are extensively used in transformers. The physical, electrical and chemical properties of such oils are subject to change due to environment and electrical stresses. For use in any electrical apparatus the oil has to comply with certain requirements and determination of these properties before fi lling the apparatus is of utmost importance. It is also equally important to monitor the condition of oil in service. Condition Monitoring of Insulating oil of power transformer is performed by oil contamination and dissolved gas analysis. In Oil contamination test comprise of breakdown voltage, water content, neutralization value, sediment & sludge, resistivity, dielectric dissipation factor, interfacial tension and fl ash point. DGA analysis is obtained by IEC ratio method, Rogers ratio method, Key gas method and Dual triangle method to distinguish the possible fault types by analyzing the amount of gases dissolved in the insulating oil. Total 108 no’s transformer tested for oil contamination test and dissolved gas analysis. Out of them 3 no’s case study chosen for analyzing Insulating oil condition. Also other 2 no’s case study is chosen from Different industries for analysis purpose.