What is the ageing of cellulose in mineral-oil insulated transformers?

The ageing of cellulose in mineral-oil insulated transformers refers to the degradation process of the cellulose insulation material over time due to thermal, electrical, and chemical stresses. This ageing results in the formation of acids and other byproducts, which can compromise the insulation properties and lead to reduced dielectric strength. Monitoring the ageing of cellulose is crucial for assessing the health and longevity of the transformer, ensuring reliable operation.