Selection starts with transformer design approval and required insulating liquid category, then considers voltage level, thermal loading, and cooling system capability. Site constraints drive choices such as higher fire point fluids for indoor or urban locations and biodegradable fluids for environmentally sensitive zones. Compatibility with paper insulation, seals, paints, and existing oil is checked, especially for retrofills. Standards compliance and utility specifications set minimum dielectric, moisture, acidity, and oxidation stability requirements. Finally, lifecycle factors are evaluated: monitoring strategy, filtration capability, spill containment, procurement availability, and total cost of ownership.
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