The present crosslinked polyethylene (XLPE) that is used in industry is not perfect for high voltage cable insulation due to the formation of space charge in the bulk of XLPE. This phenomenon is caused by the byproducts yielded from the cross-linking process, originating from the cross-linking agent, Dicumyl Peroxide (DCP). These byproducts also have other effects on other properties such as electrical breakdown strength, dielectric loss (tanô), permittivity, conduction current and so forth. To fully understand the role of these byproducts, we intend to investigate how these byproducts affect the electrical performance of LDPE.