HD 620 applies to cables with extruded insulation and for rated voltages Uo/U(Um) from 3,6/6 (7,2) kV up to 20,8/36(42) kV used in power distribution systems of voltages not exceeding the maximum r.m.s. value of the system voltage Um. This Part (Part 1) specifies the general requirements applicable to these cables, unless otherwise specified in the particular sections of this HD. Test methods specified are given EN 60228, EN 60229, EN 60332-1-2, EN 60811, EN 60885-3, HD 605 and HD 632. Attention should be drawn to the fact that a significant number of sections include references to long term tests which are collected in HD 605. These long-term tests are considered as necessary and reflect the best available knowledge for the existing cable design. They are related to specific designs and different philosophies concerning adequate measures against the influence of water. However, it is the firm intention to reduce this large number of different tests, but more experience should be gained before starting to rationalise this important matter. The particular types of cables are specified in Parts 9 to 12. NOTE – Parts 3, 4, 5, 6, 7 and 8 were withdrawn in HD 620 S2.