ROLE OF FURAN AND DP ANALYSIS FOR REFURBISHMENT OF POWER TRANSFORMER : FEW CASE STUDIES

摘要

A significant population of the installed oil-filledpower transformers is exceeding the generallyaccepted life span of thirty years. The need tomake full use of installed assets and to plan well inadvance for any replacements has led to anincreased focus on the estimation of the residual lifeof transformer. Conventional condition monitoringtechniques including DGA (Dissolved Gas Analysis)are not enough for this study. Remanant life oftransformer in service should also be estimated byassessing extent of degradation of cellulosic paperthrough furan content in transformer oil or degree ofpolymerization (DP) of paper. However, it has beenexperienced that these relatively new analyticaltools can also help considerably by makingrefurbishment activity more appropriate andspecific. In event of a failure in power transformer,power utility and transformer manufacturer both arekeenly interested to accurately diagnose, quantifyand locate the fault as quickly as possible. Variousavailable diagnostic technique e.g. DGApolarization index, dielectric dissipation factor etc.May help in identifying the fault but they are notable to suggest about health of cellulosic material.The Furan and DP analysis can throw light onwhether complete or partial cellulose materialsneeds replacement or not. So far, this vitalinformation is not available and based onexperience only vague assessment is made.Ten case studies on power transformers of 66 kVvoltage class and above; were conducted. In all thecases transformers had failed during service. Mostof these transformers have been in service forabout 15-20 years. Paper and oil samples werecollected and analyzed for furan content and DPtest. Based on the results observed it is suggestedthat for those transformers where DP values arecloser to 150-200 or furan content of 10 ppm, it isadvisable to replace the winding duringrefurbishment.