HD 621 applies to impregnated paper insulated cables for rated voltages U0/U(Um) from 3.6/6(7.2)kV up to 20.8/36(42)kV used in power distribution systems. Part 1 specifies the general requirements applicable to these cables, unless otherwise specified in the particular sections of this HD. Test methods are given in HD 605 EN 60811, HD 383 and HD 405 and in IEC 55-1and IEC 229. Part 2 covers all those test methods which are specified to paper insulated cables, and not included in HD 605. The particular types of cables are specified in Parts 3 and 4.