HD 621 applies to impregnated paper insulated cables for rated voltages Uo/U(Uml from 3,6/6(7,2)kV up to 20,8/36(42)kV used in power distribution systems.This part (Part 1) specifies the general requirements applicable to these cables, unless otherwise specified in the particular sections of this H D.Test methods specified are given in HD 605, EN 60811, HD 383 and HD 405 and in IEC 55-1 and IEC 229.Part 2 covers all those test methods which are specific to paper insulated cables, and not included in HD 605.The particular types of cables are specified in Parts 3 and 4.