Cross linked poly ethylene used in high voltage cables insolation, has been studied to define its mechanical behavior. Time dependent deformation tests (stress relaxation) in three different strain levels and normal compressive and tensile tests were carried out. Result obtained from relaxation tests is compared to four basic visco elastic material models. The permanent deformation of specimens after relaxation test was measured and shows that higher strain level relaxation tests have higher permanent deformation. Modified two units Maxwell and Four element models correlate well to XLPE during relaxation tests. Higher strain level relaxation tests have larger reduction in stress and young modulus.