The insulated core quality of power cables is directly linked to the performance of the cable in its end-use. The high voltage distribution installations at 10 to 500 W range are large, expensive, and essential for community. Consequently, the most important quality properties are therefore the expected service life of the cable and its manufacturing costs. Standard cable constructions, with the exception of the extra high voltage (EHV) construction for over 385 W have substantial over-dimensioning in the insulation layer thickness. Medium voltage cables in the range 10 to 35 W (MV) are increasingly becoming commodity items and the cost function has become critical to the economic viability of cable production. Insulated core quality depends on the raw materials quality, e. g. the purity of the peroxide cross-linkable PE-LD. The extrusion process and insulation curing process should be considered as the major quality aspects. The total quality of the cable can be assured only if manufacturing is made correct at once. In the following is reviewed the good practice and related aspects based on marked field experience.