Purification typically includes coarse filtration to remove solids, vacuum dehydration to remove moisture, degassing to remove dissolved gases and air, and fine filtration to improve cleanliness. Depending on condition, additional steps may include adsorption or clay treatment for oxidation byproducts, inhibitor adjustment, and final polishing filtration. The process is validated by post treatment tests such as BDV, moisture ppm, DDF, acidity, IFT, and sometimes DGA baseline checks. The goal is to restore dielectric and thermal performance while extending oil and transformer life.
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