Safe filtering includes isolating the transformer, controlling oil temperature, using grounded equipment, and preventing air ingress. The oil processing unit typically heats oil moderately, applies vacuum dehydration and degassing, then passes oil through fine particulate filters. Connections must be clean, dry, and sealed to avoid adding moisture and fibers. Sampling before and after treatment confirms improvement in moisture, breakdown voltage, acidity, and DGA trends. Operators also manage fire safety, spill containment, and waste handling for filters and sludge. Many utilities follow internal procedures aligned with IEC maintenance guidance for in service oil supervision.
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