Why is viscosity of transformer oil in cSt important?

Viscosity in centistokes directly affects oil circulation and heat transfer inside a transformer. Low viscosity allows oil to flow easily through windings and cooling ducts, improving heat dissipation. Excessively high viscosity reduces convection, leading to hotspots and accelerated insulation aging. Viscosity must remain within specified limits across operating temperatures to ensure effective cooling during both normal load and peak conditions. It is a key parameter in oil selection for different climates and cooling designs.