Transformer Bushings: Current technology trends, Developments & it's relevance in Monitoring of Bushings in service Rao Pramod1, Patel Nirav1, Shah Keyur1, Nikam Gautam1, Vlesik Laurent2, Nisslé Boris2 1Yash Highvoltage Limited, India 2MGC Moser Glaser, Switzerland Online published on 18 April, 2020. Abstract Transformer Bushings are expected to be highly reliable components of Transformers. In the event of Failure of Transformer Bushings, usually the result is downtime of several weeks of a power transformer accompanied by financial losses & urgency to restore the system at the earliest. Majority of the Bushings in service (for past many years) are Bushings with OIP (Oil Impregnated Paper) Insulation System. In India, major usage of RIP (Resin Impregnated Paper) Insulated Bushings commenced in 2011–12 & recently in 2018 RIS (Resin Impregnated Synthetics) Insulated Bushings have been also introduced in Indian Grid. OIP Bushings are well established up to 800 kV & RIP Bushings are now in use up to 420 kV and RIS Bushings are reported to be available up to 245 kV. This paper reviews the Current Technology Trends. In view of Various Insulation Technologies in use, it is essential to understand technical aspects of Insulation Degradation Mechanism and their effects on Service Behaviour of Bushings. This paper describes these aspects in detail. Tan Delta has been considered as a vital health monitoring parameter for OIP Bushings & different utilities have adopted stringent limits for Tan Delta (when compared with IEC Limits of 0.007). Data based evaluation & trend analysis of increase in Tan Delta gives a preliminary clue about Bushing Health, however this needs to be supplemented by DGA Analysis of Oil Sample. This paper describes it in detail. For dry RIP & RIS Bushings, however Capacitance and Partial Discharges Monitoring reveals the information about health of these Bushings. Tan Delta reveals status of pre-commissioning health. This paper describes in detail, associated technical aspects to help identify more relevant/reliable and safe practices for condition monitoring and interpretation of tests in case of dry RIP/RIS bushing fleet. Described in detail are the difference in Tan Delta behaviour between OIP Bushings & RIP Bushings. The experimentation results of Temperature Dependence of Tan Delta of OIP & RIP are shared in this paper. Various site conditions which influence the Tan Delta measurements & the precautions to be taken to prevent wrong conclusions are described. Top Keywords Transformer, Transformer Bushings, Condenser bushings, OIP, RIP, RIS, Tan Delta, Bushing condition monitoring. Top |