Abstract: Power transformers are ‘ the heart of substation’. They are the vital links between generation and transmission. A failure can cause hug revenue loss to utilities. It can cause non availability of transformers for long hours. Several diagnostic tests are carried out and remedial actions are initiated through the operational lifetime of transformers for ensuring trouble free, non interrupted power supply to consumers. Oil filled transformers in service for more than 15 years, it is highly recommended to assess the remnant life. RLA can be done by assessing the deterioration of cellulose from furan concentration and degree of polymerization. This analysis helps utilities to take timely decisions regarding refurbishment or replacement of the transformer. This paper presents the real life case study of assessing the health of cellulosic paper insulation and transformer oil of six different transformers in the state of Punjab. All the transformers have been in service for more than 40 years.