Enhanced loss of life relationsfor IEEE thermal model for ageing assessment of running transformers in smart grid frameworks

Transformer insulation ageing has been extensively studied for past many decades as it is one of the major reasons for transformer failure which causes disturbance to the power system, interruption of power to consumers as well as loss of revenue. The estimation of elapsed life of transformer insulation is done by various methods like IEEE thermal model calculation or diagnostic test results. Though the ability of the thermal model to evaluate loss of life in any interval of time with typically available input data makes this technique acceptable, it slow accuracy due to consideration of temperature alone as the factor of degradation forces the operators to enhance accuracy by additionally performing the diagnostic test, i.e. measurement of the Degree of Polymerisation. This test gives a clear idea about the insulation condition as it involves chemical tests on insulation samples; however, performing this analysis for an operating transformer is impractical. Hence, in this paper we are proposing an enhanced IEEE thermal model to give a precise loss of life, using prior experimental data. Validation of the developed formula is performed on both power and distribution transformers and reported here.