Transformer Oil

Transformer oil is a highly refined mineral insulating oil used in power and distribution transformers, switchgear, tap changers and other oil-filled electrical equipment.

It has two jobs. First, it insulates, filling the gaps between windings and core so that the assembly withstands operating and surge voltages, which is measured as dielectric breakdown strength. Second, it cools, carrying heat from the windings out to the tank walls and radiators by convection. Both functions are destroyed by the same enemy: water. Even small amounts of dissolved moisture collapse dielectric strength, which is why sampling, drying and filtration are routine parts of transformer maintenance. Oxidation is the other concern, producing acids and sludge that foul cooling surfaces over years of service.

Handle and store transformer oil in clean, dry, sealed containers, and test dielectric strength before filling.