How does a dry type transformer differ from an oil type transformer?

A dry type transformer uses air and solid insulation systems, often with resin or varnish, while an oil type transformer uses insulating liquid for both cooling and dielectric strength. Oil types generally achieve higher MVA ratings and better heat removal, so they dominate outdoor HV and substation applications. Dry type units reduce spill and some fire hazards, making them popular indoors and in sensitive buildings, but they can be larger for the same rating and may have different thermal limits and maintenance profiles.