What is the pour point of transformer oil and why is it important for low temperatures?

Pour point is the lowest temperature at which the oil remains fluid enough to flow. In cold climates, a low pour point helps ensure circulation through radiators, pumps, and narrow passages during startup and winter operation. If oil becomes too viscous or stops flowing, cooling performance drops and hot spots can develop, accelerating insulation aging. Pour point is therefore a key selection parameter for outdoor transformers, along with viscosity at low temperature, density changes, and compatibility with seals and materials.