Epoxy composite with hBN fillers compatible with industrial application in electrical equipment

Abstract

Hexagonal Boron Nitride (hBN) has been used as secondary filler in an epoxy formulation in gas insulated substation (GIS) demonstrating higher electrical performance under HVAC stress, while being compatible with industrial process and constraints. A synergetic effect between hBN and alumina has been observed regarding thermal and electrical properties. A 500% increase in the thermal conductivity could be achieved with a limited impact on viscosity increase. Breakdown strength has been measured in flat sheets in oil and with embedded electrodes under divergent field simulating a defect. The breakdown strengths resulting from these different experimental setups show an interesting barrier effect from hBN even at low ratio in the formulation. Both results can be correlated with increased lifetime under thermoelectrical stress.