On the life estimation of oil impregnated paper insulated transformer bushings

Oil impregnated paper (OIP) Bushings are indispensable parts in a power transformer, the failure of which accounts for the failure of power transformer, at least until the fault is detected and mitigated. Normal ageing of bushing insulation is generally independent of conditions within the transformer and therefore can be treated as a stand-alone component. Diagnostic Testing and Condition Monitoring (DTCM) of OIP bushing based on terminal measurements are often inconclusive and at times leads to hazardous conclusions being drawn. A quantitative estimation of remaining service life can be made using the results of specific tests on models. The authors propose controlled accelerated ageing experimental designs on pro-rated OIP bushings. The bushings are aged under different thermal and electrical stresses. Dielectric and other parameters are monitored, over the duration of ageing at different time windows.