Enhancing Service Life of Power Transformer through Inhibiting the Degradation of Insulating oil by New Approach

Abstract

Oil reclamation is a transformer insulation reconditioning technique which may be used as on-line or off-line. However, there is a need of evidence showing the effect of this process on conditions of the paper insulation, which indeed affects the life span of a transformer. This research work focuses on oil reclamation experiment on an old retired distribution transformer. Electrical testing and post-mortem analysis of the transformer were conducted, aimed at investigating the design aspects and collecting information on the insulation conditions prior to the oil reclamation. Temperature and moisture sensors were installed to monitor the conditions within the transformer during the oil reclamation [2]. The experimental process of transformer Oil reclamation was performed into two phases, with regular oil sampling to analyze the changes in key oil parameters, namely acidity number (AN), moisture and breakdown voltage (BV). This was accompanied by paper sampling at the end of each reclamation cycle to study the effects of oil reclamation on properties, particularly moisture, LMA and degree of polymerization. The transformer which was used for the entire experimental process was about 45 years old, 200kVA, 1100 / 415-240V distribution transformer. In order to study the long-term effect of oil reclamation, oil samples were collected from an on-site reclamation exercise performed in a laboratory-accelerated thermal ageing experiment. Oil samples collected before and after the reclamation were aged alongside new oils for comparison [4]. Through the regular monitoring and measurement of oil parameters (AN, moisture and BD strength) over 144 hours and paper parameters (LMA, moisture and DP) at specific stages of phase 1, it was observed that the transformer oil-paper insulation system was significantly improved. The entire research work was performed into two phases (phase 1 and phase 2). The “phase 1” was aimed to improve and restore the oil parameters comparable to the parameters of new oil as specified in “IEC-60296” and its effect on the paper insulation. “Phase 2” was aimed to compare the life span of reclaimed oil filled transformer with the transformer in which aged oil has been replaced by new oil[6]. Effective study of oil reclamation was analyzed through laboratory accelerated aging experiment and real time application on a 45 years old transformer. Through the regular monitoring and measurement of oil parameters (AN, moisture and BD strength) over 144 hours and paper parameters (LMA, moisture and DP) at specific stages of phase1, it was observed that the transformer oil-paper insulation system was significantly improved [15].