Power transformer critical diagnostics for reliability and life extension

The power transformer has a significant role in the power delivery system. As it is a critical and expensive component, its safe operation with good reliability is always deemed important by the utilities. In many utilities, a transformer serves either close to or beyond its design life (25-30 years). The majority of ageing assets are operated on full load with no significant condition assessment. Due to the complexity of the asset, its insulation (chain) undergoes electrical, thermal, mechanical and chemical stresses. The asset fails when its insulation system cannot withstand the designed electrical and thermal stresses. Materials with different dielectric properties (solids and gases) within the insulation system discharge energy and may lead to breakdown. Many transformers are reported to fail before reaching to their design life. Technical assessment based on critical component monitoring and diagnostics is vital for both new and ageing assets. The paper presents transformer assessment criteria and a case study of a power transformer early failure.