Effects of the inhomogeneous microstructures on buffer layer ablation failure in high voltage cables

•The buffer layer is not treated as an ideal homogeneous material as previously researched.•The failure mechanism is investigated from a perspective of material inhomogeneous microstructures.•Small fiber protrusions are found on the buffer layer surface.•The geometric models for the fiber protrusions are proposed quantitatively.•Significant electric field distortion is observed at the fiber protrusion regions.