Critical properties enhancement of oil-paper transformer insulation with turbostratic boron nitride

Recent research shows that a five-time enhancement in through-plane thermal conductivity of the oil-paper insulation in transformers can double their life by decreasing hotspot temperatures. This can be achieved by developing novel insulation paper with improved through-plane thermal conductivity without compromising other key paper attributes such as dielectric breakdown strength, tensile strength, and thermal degradation rate. The present study broadens the design space for advanced transformer insulation paper with improved and balanced thermal, mechanical, and dielectric properties by incorporating turbostratic boron nitride (BN) particles. A simulation model based on Scanning Electron Microscopic (SEM) imaging was used to explain the dielectric breakdown strength and through-plane thermal conductivity enhancement of the proposed material. Depending on the material formulation, the proposed BN insulation paper has 2 to 3 times greater through-plane thermal conductivity, 20 %–30 % higher dielectric strength, 25 %–50 % greater tensile strength and approximately 30 % smaller relative permittivity than the commercial insulation paper with similar thermal degradation rates. • Novel BN paper has three times better through-plane thermal conductivity. • Novel BN paper has 25 % higher dielectric strength and 30 % smaller relative permittivity. • Novel BN paper has 40 % higher tensile strength. • SEM-based model to assess the dielectric breakdown strength and thermal conductivity. • Doubles the transformer thermal life enabled by the novel BN paper.