AS/NZS IEC 60840:2020 pdf free.Power cables with extruded insulation and their accessories for rated voltages above 30 kV(Um=36kV)upto150kV(Um=170kV)一 Test methods and requirements.
4 Voltage designations, materials and rounding of numbers
4.1 Rated voltages
In this document, the symbols U0, U and Urn are used to designate the rated voltages of cables and accessories where these symbols have the meanings given in IEC 60183.
4.2 Cable insulating compounds
This document applies to cables insulated with one of the compounds listed in Table 1. which also specifies. for each type of insulating compound, the maximum operating conductor temperatures on which the specified test conditions are based.
It is recommended that cable cores with a crosslinked insulation system in accordance with this document should have been degassed.
4.3 Cable metal screens/sheaths
This document applies to the various designs in use. It covers designs providing a radial watertightness and designs that do not provide radial watertightness.
In all cases the metal screen/sheath shall be able to meet the screen short circuit rating.
Designs that provide radial watertightness mainly consist of:
• seamless metal sheaths;
• longitudinally applied metal tapes or foils bonded to the oversheath:
— CD: a metal screen design using a metal tape or foil, with either a welded or glued overlap, that carries part or all of the screen short circuit current with, if necessary, metal wires to carry part of the short circuit current;
— SD: a metal screen design using a laminated metal foil, coated on one or both sides for radial watertightness, and metal wires for carrying the full screen short circuit current;
— SscD: a metal screen design using a thin lead or Al toil coated with glue on the outer side and semi-conductive plastic on the underside, over a layer of semi-conductive tape, which is in turn over a layer of round copper wires. Typically, the aluminium foil and the semi•conductive plastic are each 0.05 mm thick;
NOTE 1 Definitions of CD, SD, and SscD are given in 3.3.3, 3.3.4 and 3.3.5
• composite screens, involving a layer of wires and either a metal sheath or a metal tape or foil bonded to the oversheath, acting as a radial water impermeable barrier (see Clause 5).
NOTE 2 During development of the cable and cable system, with a longitudinally applied metal tape or foil bonded to the oversheath. the tests as specified in IEC TR 61901 are preferred.
Designs which do not provide radial watertightness include:
• metal tapes or foils not bonded to the oversheath,
• a layer of metal wires only.
4.4 Cable oversheathing compounds
Tests are specified for five types of oversheath, as follows:
— ST1 and ST2 based on polyvinyl chloride (PVC);
— ST3 and ST7 based on polyethylene (PE):
— ST12 based on low smoke halogen free material (LSHF).
The choice of the type of oversheath depends on the design of the cable and the mechanical,
thermal and fire performance required during installation and operation.
The maximum conductor temperatures in normal operation for the different types of oversheathing compounds covered by this document are given in Table 2.
If there is concern that the oversheath will be deteriorated by UV radiation, the oversheath shall be protected against UV radiation, which will be mutually agreed with the client. Black PE oversheaths containing the required amount of a suitable and well-dispersed grade of carbon black (see Table 5) are protected against UV radiation.
NOTE I For installation in air, as for example in tunnels or buildings, it is preferable for the cable to have some tire performance and low smoke and zero halogen properties. For such applications, an ST12 (LSHF) oversheath can be applied.
NOTE 2 For some applications the oversheath can be covered by a functional layer (e.g. semi-conductive).
4.5 Rounding of numbers
The procedure given in Annex B shall be applied to all numbers and values employed or derived during the use of this document.AS/NZS IEC 60840 pdf download.