No abstract

No abstract

No abstract

A conventional mineral oil/cellulose insulated transformer's functional life is limited by the life of the cellulose paper. Since cellulose paper aging is accelerated by temperature, moisture and oxygen, poly-aramid-based synthetic insulation paper, with better thermal stability, has emerged for use in transformers. Two ASTM tests methods: DP V "degree of polymerization" as a direct diagnostic tool according to ASTM D4243 and DGA "Dissolved Gas Analysis" as an indirect diagnostic tool to quantify carbon oxides (CO and CO 2 ) according to ASTM D3612 were used to monitor the thermal aging of the cellulose paper within solid hybrid insulation aged with mineral oil. It was then submitted to local overheating, with a comparison to cellulose paper aged with mineral oil to provide a benchmark for evaluation. The results indicate that the cellulose paper within solid hybrid insulation is slightly less degraded compared to the cellulose paper of conventional insulation.

The aging process of the insulating oils of an electrical transformer is initiated as soon as the transformer is put into service. The quality of these oils must therefore be rigorously evaluated to have reliable and exploitable data for decision‐making. In general, the decision is to continue monitoring, reclaiming/regenerating, or replacing the oil in extreme cases. Thus, early diagnosis of power transformer oils helps prevent potential breakdowns that could considerably impact the electrical energy transmission and distribution network. This research used an imaging technique called SLIPI (Structured Laser Illumination Planar Imaging) to accurately determine the extinction coefficient in different samples of optically dense biodegradable oils (natural and synthetic esters). The variation in the extinction coefficient as a function of the aging of these biodegradable oils under test has been investigated. The results indicate that the SLIPI is reliable as a diagnostic tool for biodegradable oils in power transformers. This technique could therefore be an alternative solution to the conventional monitoring methods.