Scientific advancements in the field of high-power transmission and distribution of electrical energy revolutionized the field of high-performance polymer-based electrical insulation systems. Cross-linked polyethylene (XLPE) and its nanocomposites have gained substantial attention in the area of insulation, and these materials play a prodigious role in the arena of cable insulation. This paper includes various strategies for cross-linking PE coupled with different nanofillers to enhance the electrical insulation properties to attain high power transmission. It summarizes the significance of SiO2-, alumina-, TiO2-, and MgO-based XLPE nanocomposites as potential candidates for insulation in high voltage cables, electrical chips, and transistors and boron nitride-based XLPE nanocomposites for thermal insulation applications. Major challenges in dielectric insulation for cables, like partial discharge, space charge accumulation, water trees, volume resistivity, and DC breakdown strength, are addressed.