This International Standard is intended to give guidance in the selection of a.c. high-voltage cables and cable systems with extruded insulation and mainly to be used on three-phase alternating systems operating at voltages exceeding U = 1 kV (in this standard the term ‘high voltage’ is used to cover any cable above 1 kV). Submarine cables are not included in the scope. Guidance is given in the selection of the conductor size, insulation level and constructional requirements of cable to be used. In addition, information necessary to enable the appropriate selection to be made is summarized. Paper insulated power cables are not considered in this standard for their selection into cable systems. However, when selecting cables with extruded insulation to be connected together with existing paper insulated cables, particular consideration for their proper compatibility,accessories and operational characteristics should be made. Environmental aspects are mentioned at the level at which they may influence the selection of high-voltage cables and their application.