Nanofluid and Transformer Oil Impregnated Aged Kraft Paper: Analysis of its Mechanical Strength

Transformer is a long run device in a power system network. When transformer oil comes in contact with cellulosic paper in the presence of heat, the paper undergoes polymerization. As a result, both dielectric and mechanical properties of the oil and kraft paper are affected. To understand the mechanism behind the decay in the properties of the kraft paper, thermal ageing study has been performed followed by mechanical strength analysis. Keeping the same kraft paper, a comparative study of mechanical strength has been carried out after thermal ageing in two different insulating oils namely: mineral oil (MO) and exfoliated hexagonal boron nitride (Eh-BN) based nanofluid (NF). Due to enhanced stability and superior thermophysical properties, 0.01 wt.% concentration is chosen to prepare Eh-BN/MO-NF for ageing study. It is also observed that thermophysical properties of 0.01wt.% of Eh-BN/MO-NF are far more superior to the existing MO. Ageing study of both MO/kraft paper and 0.01wt% Eh-BN/MO-NF/kraft paper are performed in two different ageing vessels at same parametric conditions and mechanical strength of the aged kraft paper are investigated in different ageing duration. It is observed from the experimental results that both modulus and tensile strength of the aged kraft paper in the Eh-BN/MO-NF are superior to the aged kraft paper in MO. Early polymerization in MO impregnated kraft paper is the reason for degradation in its mechanical strength. Eh-BN/MO-NF reduces the effect of early polymerization during ageing and hence provides better mechanical stability to the insulating kraft paper.