The invention discloses a new crosslinked low MFR polymer composition, a power cable insulation and a power cable, and relates to use thereof, a power cable insulation and a power cable, useful in high voltage (HV) and extra high voltage (EHV) cable applications direct current (DC) applications. The crosslinked polymer composition is obtained by crosslinking a polymer composition, which polymer composition has a melt flow rate (MFR) of at least 1.7 and comprises a polyolefin, peroxide and sulphur containing antioxidant, characterized by that the crosslinked polymer composition has an Oxidation Induction Time, determined according to ASTM-D3895, ISO / CD 11357 and EN 728 using a Differential Scanning Calorimeter (DSC), which Oxidation Induction Time corresponds to Z minutes, and comprises an amount of peroxide by-products which corresponds to W ppm determined according to BTM2222 using HPLC, wherein Z1 <= Z <= Z2, W1 <= W <= W2, and W <= p - 270 <x> Z, wherein Z1 is 0, Z2 is 60, W1 is 0 and W2 is 9500, and p is 18500.