Why are oil filled distribution transformers common in utility networks?

Oil filled distribution transformers are common because they provide a strong insulation system and efficient cooling at low cost per kVA, making them practical for outdoor pole mounted and pad mounted installations. Oil improves heat transfer, supports compact designs, and helps manage short term overloads. Utilities also have mature maintenance practices for leak control, oil sampling, and failure diagnostics, which supports long service life and predictable lifecycle costs across large fleets.